From 742b723237866a22e72b68f558f789555a483f99 Mon Sep 17 00:00:00 2001
From: Sijawusz Pur Rahnama <sija@sija.pl>
Date: Mon, 28 Dec 2020 22:17:23 +0100
Subject: [PATCH 01/23] Add Backtracer.configure

---
 src/backtracer.cr | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/backtracer.cr b/src/backtracer.cr
index e11a616..6d0f507 100644
--- a/src/backtracer.cr
+++ b/src/backtracer.cr
@@ -1,6 +1,10 @@
 module Backtracer
   class_getter(configuration) { Configuration.new }
 
+  def self.configure : Nil
+    yield configuration
+  end
+
   def self.parse(backtrace : Array(String) | String, **options) : Backtrace
     Backtrace::Parser.parse(backtrace, **options)
   end

From 8ad814c7c141097dc645e47b8a37087821250516 Mon Sep 17 00:00:00 2001
From: Sijawusz Pur Rahnama <sija@sija.pl>
Date: Tue, 29 Dec 2020 18:45:29 +0100
Subject: [PATCH 02/23] Add documentation

---
 src/backtracer/backtrace/frame.cr        | 44 +++++++++++++++++++++++-
 src/backtracer/backtrace/frame/parser.cr |  8 +++--
 src/backtracer/backtrace/parser.cr       |  8 +++++
 src/backtracer/configuration.cr          | 17 +++++++--
 4 files changed, 72 insertions(+), 5 deletions(-)

diff --git a/src/backtracer/backtrace/frame.cr b/src/backtracer/backtrace/frame.cr
index c7fd0fd..ad9ae5a 100644
--- a/src/backtracer/backtrace/frame.cr
+++ b/src/backtracer/backtrace/frame.cr
@@ -21,7 +21,7 @@ module Backtracer
 
     def_equals_and_hash @method, @path, @lineno, @column
 
-    # Reconstructs the frame in a readable fashion
+    # Reconstructs the frame in a readable fashion.
     def to_s(io : IO) : Nil
       io << '`' << @method << '`'
       if @path
@@ -37,11 +37,24 @@ module Backtracer
       io << ')'
     end
 
+    # Returns `true` if `path` of this frame is within
+    # the `configuration.src_path`, `false` otherwise.
+    #
+    # See `Configuration#src_path`
     def under_src_path? : Bool
       return false unless src_path = configuration.src_path
       !!path.try(&.starts_with?(src_path))
     end
 
+    # Returns:
+    #
+    # - `path` as is, unless it's absolute - i.e. starts with `/`
+    # - `path` relative to `configuration.src_path` when `under_src_path?` is `true`
+    # - `nil` otherwise
+    #
+    # NOTE: returned path is not required to be `under_src_path?` - see point no. 1
+    #
+    # See `Configuration#src_path`
     def relative_path : String?
       return unless path = @path
       return path unless path.starts_with?('/')
@@ -51,6 +64,13 @@ module Backtracer
       end
     end
 
+    # Returns:
+    #
+    # - `path` as is, if it's absolute - i.e. starts with `/`
+    # - `path` appended to `configuration.src_path`
+    # - `nil` otherwise
+    #
+    # See `Configuration#src_path`
     def absolute_path : String?
       return unless path = @path
       return path if path.starts_with?('/')
@@ -59,16 +79,31 @@ module Backtracer
       end
     end
 
+    # Returns name of the shard from which this frame originated.
+    #
+    # See `Configuration#modules_path_pattern`
     def shard_name : String?
       relative_path
         .try(&.match(configuration.modules_path_pattern))
         .try(&.["name"])
     end
 
+    # Returns `true` if this frame originated from the app source code,
+    # `false` otherwise.
+    #
+    # See `Configuration#in_app_pattern`
     def in_app? : Bool
       !!(path.try(&.matches?(configuration.in_app_pattern)))
     end
 
+    # Returns a tuple consisting of 3 elements - an array of context lines
+    # before the `lineno`, line at `lineno`, and an array of context lines
+    # after the `lineno`. In case of failure it returns `nil`.
+    #
+    # Amount of returned context lines is taken from the *context_lines*
+    # argument if given, or `configuration.context_lines` otherwise.
+    #
+    # See `Configuration#context_lines`
     def context(context_lines : Int32? = nil) : {Array(String), String, Array(String)}?
       context_lines ||= configuration.context_lines
 
@@ -86,6 +121,13 @@ module Backtracer
       end
     end
 
+    # Returns hash with context lines, where line numbers are keys and
+    # the lines itself are values. In case of failure it returns `nil`.
+    #
+    # Amount of returned context lines is taken from the *context_lines*
+    # argument if given, or `configuration.context_lines` otherwise.
+    #
+    # See `Configuration#context`, `Configuration#context_lines`
     def context_hash(context_lines : Int32? = nil) : Hash(Int32, String)?
       return unless context = self.context(context_lines)
       return unless lineno = @lineno
diff --git a/src/backtracer/backtrace/frame/parser.cr b/src/backtracer/backtrace/frame/parser.cr
index f771639..427d79d 100644
--- a/src/backtracer/backtrace/frame/parser.cr
+++ b/src/backtracer/backtrace/frame/parser.cr
@@ -2,10 +2,13 @@ module Backtracer
   module Backtrace::Frame::Parser
     extend self
 
-    # Parses a single line of a given backtrace, where *unparsed_line* is
+    # Parses a single line of a given backtrace, where *line* is
     # the raw line from `caller` or some backtrace.
     #
-    # Returns the parsed backtrace frame on success or `nil` otherwise.
+    # Accepts options:
+    # - `configuration`: `Configuration` object - uses `Backtracer.configuration` if `nil`
+    #
+    # Returns parsed `Backtrace::Frame` on success or `nil` otherwise.
     def parse?(line : String, **options) : Backtrace::Frame?
       return unless Configuration::LINE_PATTERNS.any? &.match(line)
 
@@ -20,6 +23,7 @@ module Backtracer
         configuration: options[:configuration]?
     end
 
+    # Same as `parse` but raises `ArgumentError` on error.
     def parse(line : String, **options) : Backtrace::Frame
       parse?(line, **options) ||
         raise ArgumentError.new("Error parsing line: #{line.inspect}")
diff --git a/src/backtracer/backtrace/parser.cr b/src/backtracer/backtrace/parser.cr
index ade656e..30d6744 100644
--- a/src/backtracer/backtrace/parser.cr
+++ b/src/backtracer/backtrace/parser.cr
@@ -2,6 +2,14 @@ module Backtracer
   module Backtrace::Parser
     extend self
 
+    # Parses *backtrace* (possibly obtained as a return value
+    # from `caller` or `Exception#backtrace` methods).
+    #
+    # Accepts options:
+    # - `configuration`: `Configuration` object - uses `Backtracer.configuration` if `nil`
+    # - `filters`: additional line filters - see `Configuration#line_filters`
+    #
+    # Returns parsed `Backtrace` object or raises `ArgumentError` otherwise.
     def parse(backtrace : Array(String), **options) : Backtrace
       configuration = options[:configuration]? || Backtracer.configuration
 
diff --git a/src/backtracer/configuration.cr b/src/backtracer/configuration.cr
index c944188..19fcd47 100644
--- a/src/backtracer/configuration.cr
+++ b/src/backtracer/configuration.cr
@@ -54,23 +54,36 @@ module Backtracer
     }
 
     # Used in `#in_app_pattern`.
+    #
+    # See `Frame#under_src_path?`
     property src_path : String? = {{ Process::INITIAL_PWD }}
 
     # Directories to be recognized as part of your app. e.g. if you
     # have an `engines` dir at the root of your project, you may want
     # to set this to something like `/(src|engines)/`
+    #
+    # See `Frame#in_app?`
     property app_dirs_pattern = /src/
 
-    # `Regex` pattern matched against `Backtrace::Frame#file`.
+    # `Regex` pattern matched against `Backtrace::Frame#path`.
+    #
+    # See `Frame#in_app?`
     property in_app_pattern : Regex { /^(#{src_path}\/)?(#{app_dirs_pattern})/ }
 
     # Path pattern matching directories to be recognized as your app modules.
     # Defaults to standard Shards setup (`lib/shard-name/...`).
+    #
+    # See `Frame#shard_name`
     property modules_path_pattern = /^lib\/(?<name>[^\/]+)\/(?:.+)/
 
-    # Number of lines of code context to capture, or `nil` for none.
+    # Number of lines of code context to return by default, or `nil` for none.
+    #
+    # See `Frame#context`
     property context_lines : Int32? = 5
 
+    # Array of procs used for filtering backtrace lines before parsing.
+    # Each filter is expected to return a string, which is then passed
+    # onto the next filter, or ignored althoghether if `nil` is returned.
     getter(line_filters) {
       [
         ->(line : String) { line unless line.matches?(IGNORED_LINES_PATTERN) },

From c41fcb5d282699938f9ae34c58d59eb58c6d9f5d Mon Sep 17 00:00:00 2001
From: Sijawusz Pur Rahnama <sija@sija.pl>
Date: Wed, 30 Dec 2020 22:13:51 +0100
Subject: [PATCH 03/23] Remove redundant Configuration#in_app_pattern

---
 src/backtracer/backtrace/frame.cr | 4 ++--
 src/backtracer/configuration.cr   | 9 ++-------
 2 files changed, 4 insertions(+), 9 deletions(-)

diff --git a/src/backtracer/backtrace/frame.cr b/src/backtracer/backtrace/frame.cr
index ad9ae5a..e99aed2 100644
--- a/src/backtracer/backtrace/frame.cr
+++ b/src/backtracer/backtrace/frame.cr
@@ -91,9 +91,9 @@ module Backtracer
     # Returns `true` if this frame originated from the app source code,
     # `false` otherwise.
     #
-    # See `Configuration#in_app_pattern`
+    # See `Configuration#app_dirs_pattern`
     def in_app? : Bool
-      !!(path.try(&.matches?(configuration.in_app_pattern)))
+      !!(relative_path.try(&.matches?(configuration.app_dirs_pattern)))
     end
 
     # Returns a tuple consisting of 3 elements - an array of context lines
diff --git a/src/backtracer/configuration.cr b/src/backtracer/configuration.cr
index 19fcd47..39184fe 100644
--- a/src/backtracer/configuration.cr
+++ b/src/backtracer/configuration.cr
@@ -53,7 +53,7 @@ module Backtracer
       /^(?<method>.+?)$/,
     }
 
-    # Used in `#in_app_pattern`.
+    # Path considered as "root" of your project.
     #
     # See `Frame#under_src_path?`
     property src_path : String? = {{ Process::INITIAL_PWD }}
@@ -63,12 +63,7 @@ module Backtracer
     # to set this to something like `/(src|engines)/`
     #
     # See `Frame#in_app?`
-    property app_dirs_pattern = /src/
-
-    # `Regex` pattern matched against `Backtrace::Frame#path`.
-    #
-    # See `Frame#in_app?`
-    property in_app_pattern : Regex { /^(#{src_path}\/)?(#{app_dirs_pattern})/ }
+    property app_dirs_pattern = /^src\//
 
     # Path pattern matching directories to be recognized as your app modules.
     # Defaults to standard Shards setup (`lib/shard-name/...`).

From 57f5746d6e034e703a76d14d5b46a3d2a9b81c33 Mon Sep 17 00:00:00 2001
From: Sijawusz Pur Rahnama <sija@sija.pl>
Date: Fri, 1 Jan 2021 16:12:57 +0100
Subject: [PATCH 04/23] Extend specs coverage

---
 .../backtracer/backtrace/frame/parser_spec.cr | 202 +++++++++++++++++
 spec/backtracer/backtrace/frame_spec.cr       | 207 +-----------------
 spec/backtracer/backtrace/parser_spec.cr      |  33 +++
 spec/backtracer/backtrace_spec.cr             |  25 ++-
 spec/backtracer/configuration_spec.cr         |   4 -
 spec/spec_helper.cr                           |  34 +++
 6 files changed, 287 insertions(+), 218 deletions(-)
 create mode 100644 spec/backtracer/backtrace/frame/parser_spec.cr
 create mode 100644 spec/backtracer/backtrace/parser_spec.cr

diff --git a/spec/backtracer/backtrace/frame/parser_spec.cr b/spec/backtracer/backtrace/frame/parser_spec.cr
new file mode 100644
index 0000000..7df2f9e
--- /dev/null
+++ b/spec/backtracer/backtrace/frame/parser_spec.cr
@@ -0,0 +1,202 @@
+require "../../../spec_helper"
+
+describe Backtracer::Backtrace::Frame::Parser do
+  describe ".parse" do
+    it "fails to parse an empty string" do
+      expect_raises(ArgumentError) { with_frame("", &.itself) }
+    end
+
+    context "when --no-debug flag is set" do
+      it "parses frame with any value as method" do
+        backtrace_line = "__crystal_main"
+
+        with_frame(backtrace_line) do |frame|
+          frame.lineno.should be_nil
+          frame.column.should be_nil
+          frame.method.should eq(backtrace_line)
+          frame.path.should be_nil
+          frame.relative_path.should be_nil
+          frame.under_src_path?.should be_false
+          frame.shard_name.should be_nil
+          frame.in_app?.should be_false
+        end
+      end
+    end
+
+    context "with ~proc signature" do
+      it "parses absolute path outside of src/ dir" do
+        path = "/usr/local/Cellar/crystal/0.27.2/src/fiber.cr"
+        backtrace_line = "~proc2Proc(Fiber, (IO::FileDescriptor | Nil))@#{path}:72"
+
+        with_frame(backtrace_line) do |frame|
+          frame.lineno.should eq(72)
+          frame.column.should be_nil
+          frame.method.should eq("~proc2Proc(Fiber, (IO::FileDescriptor | Nil))")
+          frame.path.should eq(path)
+          frame.absolute_path.should eq(frame.path)
+          frame.relative_path.should be_nil
+          frame.under_src_path?.should be_false
+          frame.shard_name.should be_nil
+          frame.in_app?.should be_false
+        end
+      end
+
+      it "parses relative path inside of lib/ dir" do
+        with_configuration do |configuration|
+          path = "lib/kemal/src/kemal/route.cr"
+          backtrace_line = "~procProc(HTTP::Server::Context, String)@#{path}:11"
+
+          with_frame(backtrace_line) do |frame|
+            frame.lineno.should eq(11)
+            frame.column.should be_nil
+            frame.method.should eq("~procProc(HTTP::Server::Context, String)")
+            frame.path.should eq(path)
+            frame.absolute_path.should eq(
+              File.join(configuration.src_path.not_nil!, path)
+            )
+            frame.relative_path.should eq(frame.path)
+            frame.under_src_path?.should be_false
+            frame.shard_name.should eq("kemal")
+            frame.in_app?.should be_false
+          end
+        end
+      end
+    end
+
+    it "parses absolute path outside of configuration.src_path" do
+      path = "/some/absolute/path/to/foo.cr"
+
+      with_foo_frame(path: path) do |frame|
+        frame.lineno.should eq(1)
+        frame.column.should eq(7)
+        frame.method.should eq("foo_bar?")
+        frame.path.should eq(path)
+        frame.absolute_path.should eq(frame.path)
+        frame.relative_path.should be_nil
+        frame.under_src_path?.should be_false
+        frame.shard_name.should be_nil
+        frame.in_app?.should be_false
+      end
+    end
+
+    context "with in_app? = false" do
+      it "parses absolute path outside of src/ dir" do
+        with_foo_frame(path: "#{__DIR__}/foo.cr") do |frame|
+          frame.lineno.should eq(1)
+          frame.column.should eq(7)
+          frame.method.should eq("foo_bar?")
+          frame.path.should eq("#{__DIR__}/foo.cr")
+          frame.absolute_path.should eq(frame.path)
+          frame.relative_path.should eq("spec/backtracer/backtrace/frame/foo.cr")
+          frame.under_src_path?.should be_true
+          frame.shard_name.should be_nil
+          frame.in_app?.should be_false
+        end
+      end
+
+      it "parses relative path outside of src/ dir" do
+        with_configuration do |configuration|
+          path = "some/relative/path/to/foo.cr"
+
+          with_foo_frame(path: path) do |frame|
+            frame.lineno.should eq(1)
+            frame.column.should eq(7)
+            frame.method.should eq("foo_bar?")
+            frame.path.should eq(path)
+            frame.absolute_path.should eq(
+              File.join(configuration.src_path.not_nil!, path)
+            )
+            frame.relative_path.should eq(frame.path)
+            frame.under_src_path?.should be_false
+            frame.shard_name.should be_nil
+            frame.in_app?.should be_false
+          end
+        end
+      end
+    end
+
+    context "with in_app? = true" do
+      it "parses absolute path inside of src/ dir" do
+        src_path = File.expand_path("../../../../src", __DIR__)
+        path = "#{src_path}/foo.cr"
+
+        with_foo_frame(path: path) do |frame|
+          frame.lineno.should eq(1)
+          frame.column.should eq(7)
+          frame.method.should eq("foo_bar?")
+          frame.path.should eq(path)
+          frame.absolute_path.should eq(frame.path)
+          frame.relative_path.should eq("src/foo.cr")
+          frame.under_src_path?.should be_true
+          frame.shard_name.should be_nil
+          frame.in_app?.should be_true
+        end
+      end
+
+      it "parses relative path inside of src/ dir" do
+        with_configuration do |configuration|
+          path = "src/foo.cr"
+
+          with_foo_frame(path: path) do |frame|
+            frame.lineno.should eq(1)
+            frame.column.should eq(7)
+            frame.method.should eq("foo_bar?")
+            frame.path.should eq(path)
+            frame.absolute_path.should eq(
+              File.join(configuration.src_path.not_nil!, path)
+            )
+            frame.relative_path.should eq(path)
+            frame.under_src_path?.should be_false
+            frame.shard_name.should be_nil
+            frame.in_app?.should be_true
+          end
+        end
+      end
+    end
+
+    context "with shard path" do
+      it "parses absolute path inside of lib/ dir" do
+        lib_path = File.expand_path("../../../../lib/bar", __DIR__)
+        path = "#{lib_path}/src/bar.cr"
+
+        with_foo_frame(path: path) do |frame|
+          frame.lineno.should eq(1)
+          frame.column.should eq(7)
+          frame.method.should eq("foo_bar?")
+          frame.path.should eq(path)
+          frame.absolute_path.should eq(frame.path)
+          frame.relative_path.should eq("lib/bar/src/bar.cr")
+          frame.under_src_path?.should be_true
+          frame.shard_name.should eq "bar"
+          frame.in_app?.should be_false
+        end
+      end
+
+      it "parses relative path inside of lib/ dir" do
+        with_configuration do |configuration|
+          path = "lib/bar/src/bar.cr"
+
+          with_foo_frame(path: path) do |frame|
+            frame.lineno.should eq(1)
+            frame.column.should eq(7)
+            frame.method.should eq("foo_bar?")
+            frame.path.should eq(path)
+            frame.absolute_path.should eq(
+              File.join(configuration.src_path.not_nil!, path)
+            )
+            frame.relative_path.should eq(path)
+            frame.under_src_path?.should be_false
+            frame.shard_name.should eq "bar"
+            frame.in_app?.should be_false
+          end
+        end
+      end
+
+      it "uses only folders for shard names" do
+        with_foo_frame(path: "lib/bar.cr") do |frame|
+          frame.shard_name.should be_nil
+        end
+      end
+    end
+  end
+end
diff --git a/spec/backtracer/backtrace/frame_spec.cr b/spec/backtracer/backtrace/frame_spec.cr
index 5f6032c..ac355da 100644
--- a/spec/backtracer/backtrace/frame_spec.cr
+++ b/spec/backtracer/backtrace/frame_spec.cr
@@ -1,207 +1,6 @@
 require "../../spec_helper"
 
-private def parse_frame(line)
-  Backtracer::Backtrace::Frame::Parser.parse(line)
-end
-
-private def with_frame(method, path = nil, lineno = nil, column = nil)
-  line = String.build do |io|
-    if path
-      io << path
-      io << ':' << lineno if lineno
-      io << ':' << column if column
-      io << " in '" << method << '\''
-    else
-      io << method
-    end
-  end
-  yield parse_frame(line)
-end
-
-private def with_foo_frame(
-  method = "foo_bar?",
-  path = "#{__DIR__}/foo.cr",
-  lineno = 1,
-  column = 7
-)
-  with_frame(method, path, lineno, column) do |frame|
-    yield frame
-  end
-end
-
 describe Backtracer::Backtrace::Frame do
-  describe ".parse" do
-    it "fails to parse an empty string" do
-      expect_raises(ArgumentError) { parse_frame("") }
-    end
-
-    context "when --no-debug flag is set" do
-      it "parses frame with any value as method" do
-        backtrace_line = "__crystal_main"
-
-        with_frame(backtrace_line) do |frame|
-          frame.lineno.should be_nil
-          frame.column.should be_nil
-          frame.method.should eq(backtrace_line)
-          frame.path.should be_nil
-          frame.relative_path.should be_nil
-          frame.under_src_path?.should be_false
-          frame.shard_name.should be_nil
-          frame.in_app?.should be_false
-        end
-      end
-    end
-
-    context "with ~proc signature" do
-      it "parses absolute path outside of src/ dir" do
-        backtrace_line = "~proc2Proc(Fiber, (IO::FileDescriptor | Nil))@/usr/local/Cellar/crystal/0.27.2/src/fiber.cr:72"
-
-        with_frame(backtrace_line) do |frame|
-          frame.lineno.should eq(72)
-          frame.column.should be_nil
-          frame.method.should eq("~proc2Proc(Fiber, (IO::FileDescriptor | Nil))")
-          frame.path.should eq("/usr/local/Cellar/crystal/0.27.2/src/fiber.cr")
-          frame.relative_path.should be_nil
-          frame.under_src_path?.should be_false
-          frame.shard_name.should be_nil
-          frame.in_app?.should be_false
-        end
-      end
-
-      it "parses relative path inside of lib/ dir" do
-        backtrace_line = "~procProc(HTTP::Server::Context, String)@lib/kemal/src/kemal/route.cr:11"
-
-        with_frame(backtrace_line) do |frame|
-          frame.lineno.should eq(11)
-          frame.column.should be_nil
-          frame.method.should eq("~procProc(HTTP::Server::Context, String)")
-          frame.path.should eq("lib/kemal/src/kemal/route.cr")
-          frame.relative_path.should eq("lib/kemal/src/kemal/route.cr")
-          frame.under_src_path?.should be_false
-          frame.shard_name.should eq("kemal")
-          frame.in_app?.should be_false
-        end
-      end
-    end
-
-    it "parses absolute path outside of configuration.src_path" do
-      path = "/some/absolute/path/to/foo.cr"
-
-      with_foo_frame(path: path) do |frame|
-        frame.lineno.should eq(1)
-        frame.column.should eq(7)
-        frame.method.should eq("foo_bar?")
-        frame.path.should eq(path)
-        frame.relative_path.should be_nil
-        frame.under_src_path?.should be_false
-        frame.shard_name.should be_nil
-        frame.in_app?.should be_false
-      end
-    end
-
-    context "with in_app? = false" do
-      it "parses absolute path outside of src/ dir" do
-        with_foo_frame do |frame|
-          frame.lineno.should eq(1)
-          frame.column.should eq(7)
-          frame.method.should eq("foo_bar?")
-          frame.path.should eq("#{__DIR__}/foo.cr")
-          frame.relative_path.should eq("spec/backtracer/backtrace/foo.cr")
-          frame.under_src_path?.should be_true
-          frame.shard_name.should be_nil
-          frame.in_app?.should be_false
-        end
-      end
-
-      it "parses relative path outside of src/ dir" do
-        path = "some/relative/path/to/foo.cr"
-
-        with_foo_frame(path: path) do |frame|
-          frame.lineno.should eq(1)
-          frame.column.should eq(7)
-          frame.method.should eq("foo_bar?")
-          frame.path.should eq(path)
-          frame.relative_path.should eq(path)
-          frame.under_src_path?.should be_false
-          frame.shard_name.should be_nil
-          frame.in_app?.should be_false
-        end
-      end
-    end
-
-    context "with in_app? = true" do
-      it "parses absolute path inside of src/ dir" do
-        src_path = File.expand_path("../../../src", __DIR__)
-        path = "#{src_path}/foo.cr"
-
-        with_foo_frame(path: path) do |frame|
-          frame.lineno.should eq(1)
-          frame.column.should eq(7)
-          frame.method.should eq("foo_bar?")
-          frame.path.should eq(path)
-          frame.relative_path.should eq("src/foo.cr")
-          frame.under_src_path?.should be_true
-          frame.shard_name.should be_nil
-          frame.in_app?.should be_true
-        end
-      end
-
-      it "parses relative path inside of src/ dir" do
-        path = "src/foo.cr"
-
-        with_foo_frame(path: path) do |frame|
-          frame.lineno.should eq(1)
-          frame.column.should eq(7)
-          frame.method.should eq("foo_bar?")
-          frame.path.should eq(path)
-          frame.relative_path.should eq(path)
-          frame.under_src_path?.should be_false
-          frame.shard_name.should be_nil
-          frame.in_app?.should be_true
-        end
-      end
-    end
-
-    context "with shard path" do
-      it "parses absolute path inside of lib/ dir" do
-        lib_path = File.expand_path("../../../lib/bar", __DIR__)
-        path = "#{lib_path}/src/bar.cr"
-
-        with_foo_frame(path: path) do |frame|
-          frame.lineno.should eq(1)
-          frame.column.should eq(7)
-          frame.method.should eq("foo_bar?")
-          frame.path.should eq(path)
-          frame.relative_path.should eq("lib/bar/src/bar.cr")
-          frame.under_src_path?.should be_true
-          frame.shard_name.should eq "bar"
-          frame.in_app?.should be_false
-        end
-      end
-
-      it "parses relative path inside of lib/ dir" do
-        path = "lib/bar/src/bar.cr"
-
-        with_foo_frame(path: path) do |frame|
-          frame.lineno.should eq(1)
-          frame.column.should eq(7)
-          frame.method.should eq("foo_bar?")
-          frame.path.should eq(path)
-          frame.relative_path.should eq(path)
-          frame.under_src_path?.should be_false
-          frame.shard_name.should eq "bar"
-          frame.in_app?.should be_false
-        end
-      end
-
-      it "uses only folders for shard names" do
-        with_foo_frame(path: "lib/bar.cr") do |frame|
-          frame.shard_name.should be_nil
-        end
-      end
-    end
-  end
-
   it "#inspect" do
     with_foo_frame do |frame|
       frame.inspect.should match(/Backtrace::Frame(.*)$/)
@@ -209,7 +8,7 @@ describe Backtracer::Backtrace::Frame do
   end
 
   it "#to_s" do
-    with_foo_frame do |frame|
+    with_foo_frame(path: "#{__DIR__}/foo.cr") do |frame|
       frame.to_s.should eq "`foo_bar?` at #{__DIR__}/foo.cr:1:7"
     end
   end
@@ -219,8 +18,8 @@ describe Backtracer::Backtrace::Frame do
       with_foo_frame do |frame2|
         frame.should eq(frame2)
       end
-      with_foo_frame(method: "other_method") do |frame2|
-        frame.should_not eq(frame2)
+      with_foo_frame(method: "other_method") do |frame3|
+        frame.should_not eq(frame3)
       end
     end
   end
diff --git a/spec/backtracer/backtrace/parser_spec.cr b/spec/backtracer/backtrace/parser_spec.cr
new file mode 100644
index 0000000..8ebbe75
--- /dev/null
+++ b/spec/backtracer/backtrace/parser_spec.cr
@@ -0,0 +1,33 @@
+require "../../spec_helper"
+
+describe Backtracer::Backtrace::Parser do
+  describe ".parse" do
+    it "handles `caller` as an input" do
+      with_backtrace(caller) do |backtrace|
+        backtrace.frames.should_not be_empty
+
+        backtrace.frames.first
+          .tap(&.absolute_path.should eq(__FILE__))
+          .tap(&.path.should eq("spec/backtracer/backtrace/parser_spec.cr"))
+
+        backtrace.frames.last.method.should eq("main")
+      end
+    end
+
+    it "handles `Exception#backtrace` as an input" do
+      begin
+        raise "Oh, no!"
+      rescue ex
+        with_backtrace(ex.backtrace) do |backtrace|
+          backtrace.frames.should_not be_empty
+
+          backtrace.frames.first
+            .tap(&.absolute_path.should eq(__FILE__))
+            .tap(&.path.should eq("spec/backtracer/backtrace/parser_spec.cr"))
+
+          backtrace.frames.last.method.should eq("main")
+        end
+      end
+    end
+  end
+end
diff --git a/spec/backtracer/backtrace_spec.cr b/spec/backtracer/backtrace_spec.cr
index 36bc340..3948c3e 100644
--- a/spec/backtracer/backtrace_spec.cr
+++ b/spec/backtracer/backtrace_spec.cr
@@ -1,24 +1,29 @@
 require "../spec_helper"
 
 describe Backtracer::Backtrace do
-  backtrace = Backtracer.parse(caller)
-
   it "#frames" do
-    backtrace.frames.should be_a(Array(Backtracer::Backtrace::Frame))
+    with_backtrace(caller) do |backtrace|
+      backtrace.frames.should be_a(Array(Backtracer::Backtrace::Frame))
+      backtrace.frames.should_not be_empty
+    end
   end
 
   it "#inspect" do
-    backtrace.inspect.should match(/#<Backtrace: .*>$/)
+    with_backtrace(caller) do |backtrace|
+      backtrace.inspect.should match(/#<Backtrace: .+>$/)
+    end
   end
 
-  {% unless flag?(:release) || !flag?(:debug) %}
-    it "#to_s" do
-      backtrace.to_s.should match(/backtrace_spec.cr:4/)
+  it "#to_s" do
+    with_backtrace(caller) do |backtrace|
+      backtrace.to_s.should match(/backtrace_spec.cr/)
     end
-  {% end %}
+  end
 
   it "#==" do
-    backtrace2 = Backtracer::Backtrace.new(backtrace.frames)
-    backtrace2.should eq(backtrace)
+    with_backtrace(caller) do |backtrace|
+      backtrace2 = Backtracer::Backtrace.new(backtrace.frames)
+      backtrace2.should eq(backtrace)
+    end
   end
 end
diff --git a/spec/backtracer/configuration_spec.cr b/spec/backtracer/configuration_spec.cr
index 76284c6..c192860 100644
--- a/spec/backtracer/configuration_spec.cr
+++ b/spec/backtracer/configuration_spec.cr
@@ -1,9 +1,5 @@
 require "../spec_helper"
 
-private def with_configuration
-  yield Backtracer::Configuration.new
-end
-
 describe Backtracer::Configuration do
   it "should set #src_path to current dir from default" do
     with_configuration do |configuration|
diff --git a/spec/spec_helper.cr b/spec/spec_helper.cr
index e0c7f38..11c6c86 100644
--- a/spec/spec_helper.cr
+++ b/spec/spec_helper.cr
@@ -1,2 +1,36 @@
 require "spec"
 require "../src/backtracer"
+
+def with_configuration(shared = true)
+  yield shared ? Backtracer.configuration : Backtracer::Configuration.new
+end
+
+def with_backtrace(backtrace, **options)
+  yield Backtracer::Backtrace::Parser.parse(backtrace, **options)
+end
+
+def with_frame(method, path = nil, lineno = nil, column = nil, **options)
+  line = String.build do |io|
+    if path
+      io << path
+      io << ':' << lineno if lineno
+      io << ':' << column if column
+      io << " in '" << method << '\''
+    else
+      io << method
+    end
+  end
+  yield Backtracer::Backtrace::Frame::Parser.parse(line, **options)
+end
+
+def with_foo_frame(
+  method = "foo_bar?",
+  path = "#{__DIR__}/foo.cr",
+  lineno = 1,
+  column = 7,
+  **options
+)
+  with_frame(method, path, lineno, column, **options) do |frame|
+    yield frame
+  end
+end

From 45b9cefe7356818f441dd734ad87a16901883db4 Mon Sep 17 00:00:00 2001
From: Sijawusz Pur Rahnama <sija@sija.pl>
Date: Fri, 1 Jan 2021 23:53:55 +0100
Subject: [PATCH 05/23] Remove unreliable specs

---
 spec/backtracer/backtrace/parser_spec.cr | 12 ------------
 spec/backtracer/backtrace_spec.cr        | 10 ++++++----
 2 files changed, 6 insertions(+), 16 deletions(-)

diff --git a/spec/backtracer/backtrace/parser_spec.cr b/spec/backtracer/backtrace/parser_spec.cr
index 8ebbe75..7713983 100644
--- a/spec/backtracer/backtrace/parser_spec.cr
+++ b/spec/backtracer/backtrace/parser_spec.cr
@@ -5,12 +5,6 @@ describe Backtracer::Backtrace::Parser do
     it "handles `caller` as an input" do
       with_backtrace(caller) do |backtrace|
         backtrace.frames.should_not be_empty
-
-        backtrace.frames.first
-          .tap(&.absolute_path.should eq(__FILE__))
-          .tap(&.path.should eq("spec/backtracer/backtrace/parser_spec.cr"))
-
-        backtrace.frames.last.method.should eq("main")
       end
     end
 
@@ -20,12 +14,6 @@ describe Backtracer::Backtrace::Parser do
       rescue ex
         with_backtrace(ex.backtrace) do |backtrace|
           backtrace.frames.should_not be_empty
-
-          backtrace.frames.first
-            .tap(&.absolute_path.should eq(__FILE__))
-            .tap(&.path.should eq("spec/backtracer/backtrace/parser_spec.cr"))
-
-          backtrace.frames.last.method.should eq("main")
         end
       end
     end
diff --git a/spec/backtracer/backtrace_spec.cr b/spec/backtracer/backtrace_spec.cr
index 3948c3e..c8d58f2 100644
--- a/spec/backtracer/backtrace_spec.cr
+++ b/spec/backtracer/backtrace_spec.cr
@@ -14,11 +14,13 @@ describe Backtracer::Backtrace do
     end
   end
 
-  it "#to_s" do
-    with_backtrace(caller) do |backtrace|
-      backtrace.to_s.should match(/backtrace_spec.cr/)
+  {% unless flag?(:release) || !flag?(:debug) %}
+    it "#to_s" do
+      with_backtrace(caller) do |backtrace|
+        backtrace.to_s.should match(/backtrace_spec.cr/)
+      end
     end
-  end
+  {% end %}
 
   it "#==" do
     with_backtrace(caller) do |backtrace|

From 7d7192ec09bb1d9b0b64e7eeb5a4e9c47e348b65 Mon Sep 17 00:00:00 2001
From: Sijawusz Pur Rahnama <sija@sija.pl>
Date: Fri, 1 Jan 2021 23:53:59 +0100
Subject: [PATCH 06/23] Fix doc comments

---
 src/backtracer/backtrace/frame/parser.cr | 2 +-
 src/backtracer/configuration.cr          | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/backtracer/backtrace/frame/parser.cr b/src/backtracer/backtrace/frame/parser.cr
index 427d79d..37f77ff 100644
--- a/src/backtracer/backtrace/frame/parser.cr
+++ b/src/backtracer/backtrace/frame/parser.cr
@@ -23,7 +23,7 @@ module Backtracer
         configuration: options[:configuration]?
     end
 
-    # Same as `parse` but raises `ArgumentError` on error.
+    # Same as `parse?` but raises `ArgumentError` on error.
     def parse(line : String, **options) : Backtrace::Frame
       parse?(line, **options) ||
         raise ArgumentError.new("Error parsing line: #{line.inspect}")
diff --git a/src/backtracer/configuration.cr b/src/backtracer/configuration.cr
index 39184fe..1b91465 100644
--- a/src/backtracer/configuration.cr
+++ b/src/backtracer/configuration.cr
@@ -60,7 +60,7 @@ module Backtracer
 
     # Directories to be recognized as part of your app. e.g. if you
     # have an `engines` dir at the root of your project, you may want
-    # to set this to something like `/(src|engines)/`
+    # to set this to something like `/^(src|engines)\//`
     #
     # See `Frame#in_app?`
     property app_dirs_pattern = /^src\//

From e3ee3a494df98dc9971f22349d881bb5a46010dc Mon Sep 17 00:00:00 2001
From: Sijawusz Pur Rahnama <sija@sija.pl>
Date: Sat, 2 Jan 2021 19:22:18 +0100
Subject: [PATCH 07/23] Bump to v1.1.0

---
 shard.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/shard.yml b/shard.yml
index 20cf883..3a9956d 100644
--- a/shard.yml
+++ b/shard.yml
@@ -1,5 +1,5 @@
 name: backtracer
-version: 1.0.0
+version: 1.1.0
 
 authors:
   - Sijawusz Pur Rahnama <sija@sija.pl>

From 0300476813b5e311dd477aeef13e359969f0bff3 Mon Sep 17 00:00:00 2001
From: Sijawusz Pur Rahnama <sija@sija.pl>
Date: Sun, 3 Jan 2021 17:04:34 +0100
Subject: [PATCH 08/23] Refactor context tuple into a dedicated `Context`
 struct

---
 .../backtrace/frame/context_spec.cr           | 33 +++++++++++++++
 src/backtracer/backtrace/frame.cr             | 41 +++++--------------
 src/backtracer/backtrace/frame/context.cr     | 36 ++++++++++++++++
 3 files changed, 80 insertions(+), 30 deletions(-)
 create mode 100644 spec/backtracer/backtrace/frame/context_spec.cr
 create mode 100644 src/backtracer/backtrace/frame/context.cr

diff --git a/spec/backtracer/backtrace/frame/context_spec.cr b/spec/backtracer/backtrace/frame/context_spec.cr
new file mode 100644
index 0000000..2ee0a82
--- /dev/null
+++ b/spec/backtracer/backtrace/frame/context_spec.cr
@@ -0,0 +1,33 @@
+require "../../../spec_helper"
+
+describe Backtracer::Backtrace::Frame::Context do
+  describe ".to_h" do
+    it "works with empty #pre and #post" do
+      context = Backtracer::Backtrace::Frame::Context.new(
+        lineno: 1,
+        pre: %w[],
+        line: "violent offender!",
+        post: %w[],
+      )
+      context.to_h.should eq({1 => "violent offender!"})
+    end
+
+    it "returns hash with #pre, #line and #post strings" do
+      context = Backtracer::Backtrace::Frame::Context.new(
+        lineno: 10,
+        pre: %w[foo bar baz],
+        line: "violent offender!",
+        post: %w[boo far faz],
+      )
+      context.to_h.should eq({
+         7 => "foo",
+         8 => "bar",
+         9 => "baz",
+        10 => "violent offender!",
+        11 => "boo",
+        12 => "far",
+        13 => "faz",
+      })
+    end
+  end
+end
diff --git a/src/backtracer/backtrace/frame.cr b/src/backtracer/backtrace/frame.cr
index e99aed2..cd44cfc 100644
--- a/src/backtracer/backtrace/frame.cr
+++ b/src/backtracer/backtrace/frame.cr
@@ -96,15 +96,18 @@ module Backtracer
       !!(relative_path.try(&.matches?(configuration.app_dirs_pattern)))
     end
 
-    # Returns a tuple consisting of 3 elements - an array of context lines
+    # Returns `Context` record consisting of 3 elements - an array of context lines
     # before the `lineno`, line at `lineno`, and an array of context lines
     # after the `lineno`. In case of failure it returns `nil`.
     #
     # Amount of returned context lines is taken from the *context_lines*
     # argument if given, or `configuration.context_lines` otherwise.
     #
+    # NOTE: amount of returned context lines might be lower than given
+    # in cases where `lineno` is near the start or the end of the file.
+    #
     # See `Configuration#context_lines`
-    def context(context_lines : Int32? = nil) : {Array(String), String, Array(String)}?
+    def context(context_lines : Int32? = nil) : Context?
       context_lines ||= configuration.context_lines
 
       return unless context_lines && (context_lines > 0)
@@ -117,35 +120,13 @@ module Backtracer
       if context_line = lines[lineidx]?
         pre_context = lines[Math.max(0, lineidx - context_lines), context_lines]
         post_context = lines[Math.min(lines.size, lineidx + 1), context_lines]
-        {pre_context, context_line, post_context}
-      end
-    end
 
-    # Returns hash with context lines, where line numbers are keys and
-    # the lines itself are values. In case of failure it returns `nil`.
-    #
-    # Amount of returned context lines is taken from the *context_lines*
-    # argument if given, or `configuration.context_lines` otherwise.
-    #
-    # See `Configuration#context`, `Configuration#context_lines`
-    def context_hash(context_lines : Int32? = nil) : Hash(Int32, String)?
-      return unless context = self.context(context_lines)
-      return unless lineno = @lineno
-
-      pre_context, context_line, post_context = context
-
-      ({} of Int32 => String).tap do |hash|
-        pre_context.each_with_index do |code, index|
-          line = (lineno - pre_context.size) + index
-          hash[line] = code
-        end
-
-        hash[lineno] = context_line
-
-        post_context.each_with_index do |code, index|
-          line = lineno + (index + 1)
-          hash[line] = code
-        end
+        Context.new(
+          lineno: lineno,
+          pre: pre_context,
+          line: context_line,
+          post: post_context,
+        )
       end
     end
   end
diff --git a/src/backtracer/backtrace/frame/context.cr b/src/backtracer/backtrace/frame/context.cr
new file mode 100644
index 0000000..12a9e1b
--- /dev/null
+++ b/src/backtracer/backtrace/frame/context.cr
@@ -0,0 +1,36 @@
+module Backtracer
+  struct Backtrace::Frame::Context
+    # The line number this `Context` refers to.
+    getter lineno : Int32
+
+    # An array of lines before `lineno`.
+    getter pre : Array(String)
+
+    # The line at `lineno`.
+    getter line : String
+
+    # An array of lines after `lineno`.
+    getter post : Array(String)
+
+    def initialize(@lineno, @pre, @line, @post)
+    end
+
+    # Returns hash with context lines, where line numbers are
+    # the keys and the lines itself are the values.
+    def to_h : Hash(Int32, String)
+      ({} of Int32 => String).tap do |hash|
+        base_index = lineno - pre.size
+        pre.each_with_index do |code, index|
+          hash[base_index + index] = code
+        end
+
+        hash[lineno] = line
+
+        base_index = lineno + 1
+        post.each_with_index do |code, index|
+          hash[base_index + index] = code
+        end
+      end
+    end
+  end
+end

From d88a17f3e646cb901dcd6cfd09232f373ad7b052 Mon Sep 17 00:00:00 2001
From: Sijawusz Pur Rahnama <sija@sija.pl>
Date: Sun, 3 Jan 2021 17:04:59 +0100
Subject: [PATCH 09/23] Cache Frame#context results

---
 src/backtracer/backtrace/frame.cr | 20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

diff --git a/src/backtracer/backtrace/frame.cr b/src/backtracer/backtrace/frame.cr
index cd44cfc..eea7a47 100644
--- a/src/backtracer/backtrace/frame.cr
+++ b/src/backtracer/backtrace/frame.cr
@@ -1,6 +1,8 @@
 module Backtracer
   # An object representation of a stack frame.
   struct Backtrace::Frame
+    @context_cache = {} of Int32 => Context
+
     # The method of this frame (such as `User.find`).
     getter method : String
 
@@ -109,8 +111,11 @@ module Backtracer
     # See `Configuration#context_lines`
     def context(context_lines : Int32? = nil) : Context?
       context_lines ||= configuration.context_lines
-
       return unless context_lines && (context_lines > 0)
+
+      cached = @context_cache[context_lines]?
+      return cached if cached
+
       return unless (lineno = @lineno) && (lineno > 0)
       return unless (path = @path) && File.readable?(path)
 
@@ -121,12 +126,13 @@ module Backtracer
         pre_context = lines[Math.max(0, lineidx - context_lines), context_lines]
         post_context = lines[Math.min(lines.size, lineidx + 1), context_lines]
 
-        Context.new(
-          lineno: lineno,
-          pre: pre_context,
-          line: context_line,
-          post: post_context,
-        )
+        @context_cache[context_lines] =
+          Context.new(
+            lineno: lineno,
+            pre: pre_context,
+            line: context_line,
+            post: post_context,
+          )
       end
     end
   end

From 0663fbfa01b7a91ff3901d91d3f30d87943036d3 Mon Sep 17 00:00:00 2001
From: Sijawusz Pur Rahnama <sija@sija.pl>
Date: Sun, 3 Jan 2021 17:56:44 +0100
Subject: [PATCH 10/23] Add specs for Frame#context

---
 spec/backtracer/backtrace/frame_spec.cr | 35 +++++++++++++++++++++++++
 1 file changed, 35 insertions(+)

diff --git a/spec/backtracer/backtrace/frame_spec.cr b/spec/backtracer/backtrace/frame_spec.cr
index ac355da..53c3766 100644
--- a/spec/backtracer/backtrace/frame_spec.cr
+++ b/spec/backtracer/backtrace/frame_spec.cr
@@ -23,4 +23,39 @@ describe Backtracer::Backtrace::Frame do
       end
     end
   end
+
+  {% unless flag?(:release) || !flag?(:debug) %}
+    describe "#context" do
+      it "returns proper lines" do
+        with_configuration do |configuration|
+          with_backtrace(caller) do |backtrace|
+            backtrace.frames.first.tap do |first_frame|
+              context_lines = configuration.context_lines.should_not be_nil
+              context = first_frame.context.should_not be_nil
+
+              lines = File.read_lines(__FILE__)
+              lineidx = context.lineno - 1
+
+              context.pre
+                .should eq(lines[Math.max(0, lineidx - context_lines), context_lines]?)
+              context.line
+                .should eq(lines[lineidx]?)
+              context.post
+                .should eq(lines[Math.min(lines.size, lineidx + 1), context_lines]?)
+            end
+          end
+        end
+      end
+
+      it "returns given amount of lines" do
+        with_backtrace(caller) do |backtrace|
+          backtrace.frames.first.tap do |first_frame|
+            context = first_frame.context(3).should_not be_nil
+            context.pre.size.should eq(3)
+            context.post.size.should eq(3)
+          end
+        end
+      end
+    end
+  {% end %}
 end

From 521bf7ff28a71c6e015ab7b2fff221e2e0b18cf9 Mon Sep 17 00:00:00 2001
From: Sijawusz Pur Rahnama <sija@sija.pl>
Date: Mon, 4 Jan 2021 03:24:44 +0100
Subject: [PATCH 11/23] Add Context#to_a

---
 .../backtrace/frame/context_spec.cr           | 57 ++++++++++++++-----
 src/backtracer/backtrace/frame/context.cr     | 10 ++++
 2 files changed, 52 insertions(+), 15 deletions(-)

diff --git a/spec/backtracer/backtrace/frame/context_spec.cr b/spec/backtracer/backtrace/frame/context_spec.cr
index 2ee0a82..1ec0a74 100644
--- a/spec/backtracer/backtrace/frame/context_spec.cr
+++ b/spec/backtracer/backtrace/frame/context_spec.cr
@@ -1,6 +1,37 @@
 require "../../../spec_helper"
 
+def with_foo_context
+  yield Backtracer::Backtrace::Frame::Context.new(
+    lineno: 10,
+    pre: %w[foo bar baz],
+    line: "violent offender!",
+    post: %w[boo far faz],
+  )
+end
+
 describe Backtracer::Backtrace::Frame::Context do
+  describe ".to_a" do
+    it "works with empty #pre and #post" do
+      context = Backtracer::Backtrace::Frame::Context.new(
+        lineno: 1,
+        pre: %w[],
+        line: "violent offender!",
+        post: %w[],
+      )
+      context.to_a.should eq(["violent offender!"])
+    end
+
+    it "returns array with #pre, #line and #post strings" do
+      with_foo_context do |context|
+        context.to_a.should eq([
+          "foo", "bar", "baz",
+          "violent offender!",
+          "boo", "far", "faz",
+        ])
+      end
+    end
+  end
+
   describe ".to_h" do
     it "works with empty #pre and #post" do
       context = Backtracer::Backtrace::Frame::Context.new(
@@ -13,21 +44,17 @@ describe Backtracer::Backtrace::Frame::Context do
     end
 
     it "returns hash with #pre, #line and #post strings" do
-      context = Backtracer::Backtrace::Frame::Context.new(
-        lineno: 10,
-        pre: %w[foo bar baz],
-        line: "violent offender!",
-        post: %w[boo far faz],
-      )
-      context.to_h.should eq({
-         7 => "foo",
-         8 => "bar",
-         9 => "baz",
-        10 => "violent offender!",
-        11 => "boo",
-        12 => "far",
-        13 => "faz",
-      })
+      with_foo_context do |context|
+        context.to_h.should eq({
+           7 => "foo",
+           8 => "bar",
+           9 => "baz",
+          10 => "violent offender!",
+          11 => "boo",
+          12 => "far",
+          13 => "faz",
+        })
+      end
     end
   end
 end
diff --git a/src/backtracer/backtrace/frame/context.cr b/src/backtracer/backtrace/frame/context.cr
index 12a9e1b..d5d22aa 100644
--- a/src/backtracer/backtrace/frame/context.cr
+++ b/src/backtracer/backtrace/frame/context.cr
@@ -15,6 +15,16 @@ module Backtracer
     def initialize(@lineno, @pre, @line, @post)
     end
 
+    # Returns an array composed of context lines from `pre`,
+    # `line` and `post`.
+    def to_a : Array(String)
+      ([] of String).tap do |ary|
+        ary.concat(pre)
+        ary << line
+        ary.concat(post)
+      end
+    end
+
     # Returns hash with context lines, where line numbers are
     # the keys and the lines itself are the values.
     def to_h : Hash(Int32, String)

From 63ca71ba5648fa0597d62c27169ca96472773fbe Mon Sep 17 00:00:00 2001
From: Sijawusz Pur Rahnama <sija@sija.pl>
Date: Mon, 4 Jan 2021 03:26:40 +0100
Subject: [PATCH 12/23] Bump to v1.2.0

---
 shard.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/shard.yml b/shard.yml
index 3a9956d..f815ea3 100644
--- a/shard.yml
+++ b/shard.yml
@@ -1,5 +1,5 @@
 name: backtracer
-version: 1.1.0
+version: 1.2.0
 
 authors:
   - Sijawusz Pur Rahnama <sija@sija.pl>

From 1ff793f00b413903e9e4740dc17198b43248d8a1 Mon Sep 17 00:00:00 2001
From: Sijawusz Pur Rahnama <sija@sija.pl>
Date: Sun, 10 Jan 2021 14:29:29 +0100
Subject: [PATCH 13/23] Fix edge case where lineno <= context_lines

---
 src/backtracer/backtrace/frame.cr | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/backtracer/backtrace/frame.cr b/src/backtracer/backtrace/frame.cr
index eea7a47..9e0c8a7 100644
--- a/src/backtracer/backtrace/frame.cr
+++ b/src/backtracer/backtrace/frame.cr
@@ -123,8 +123,11 @@ module Backtracer
       lineidx = lineno - 1
 
       if context_line = lines[lineidx]?
-        pre_context = lines[Math.max(0, lineidx - context_lines), context_lines]
-        post_context = lines[Math.min(lines.size, lineidx + 1), context_lines]
+        pre_context_lines =
+          (lineno <= context_lines) ? lineidx : context_lines
+
+        pre_context = lines[(lineidx - context_lines).clamp(0..), pre_context_lines]
+        post_context = lines[(lineidx + 1).clamp(..lines.size), context_lines]
 
         @context_cache[context_lines] =
           Context.new(

From 5e1ea0bd781bb7593aa4bd7e7acaee40aa85af6c Mon Sep 17 00:00:00 2001
From: Sijawusz Pur Rahnama <sija@sija.pl>
Date: Sun, 10 Jan 2021 15:02:20 +0100
Subject: [PATCH 14/23] Refactor Frame#context to avoid reading whole file at
 once

---
 src/backtracer/backtrace/frame.cr | 22 ++++++++++++++--------
 1 file changed, 14 insertions(+), 8 deletions(-)

diff --git a/src/backtracer/backtrace/frame.cr b/src/backtracer/backtrace/frame.cr
index 9e0c8a7..5826422 100644
--- a/src/backtracer/backtrace/frame.cr
+++ b/src/backtracer/backtrace/frame.cr
@@ -119,16 +119,22 @@ module Backtracer
       return unless (lineno = @lineno) && (lineno > 0)
       return unless (path = @path) && File.readable?(path)
 
-      lines = File.read_lines(path)
-      lineidx = lineno - 1
+      context_line = nil
+      pre_context, post_context = %w[], %w[]
 
-      if context_line = lines[lineidx]?
-        pre_context_lines =
-          (lineno <= context_lines) ? lineidx : context_lines
-
-        pre_context = lines[(lineidx - context_lines).clamp(0..), pre_context_lines]
-        post_context = lines[(lineidx + 1).clamp(..lines.size), context_lines]
+      i = 0
+      File.each_line(path) do |line|
+        case i += 1
+        when lineno - context_lines...lineno
+          pre_context << line
+        when lineno
+          context_line = line
+        when lineno + 1..lineno + context_lines
+          post_context << line
+        end
+      end
 
+      if context_line
         @context_cache[context_lines] =
           Context.new(
             lineno: lineno,

From f18b0546f8d781af630a9ee39c2c2559c44cc9da Mon Sep 17 00:00:00 2001
From: Sijawusz Pur Rahnama <sija@sija.pl>
Date: Sun, 10 Jan 2021 15:09:49 +0100
Subject: [PATCH 15/23] Bump to v1.2.1

---
 shard.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/shard.yml b/shard.yml
index f815ea3..89b3887 100644
--- a/shard.yml
+++ b/shard.yml
@@ -1,5 +1,5 @@
 name: backtracer
-version: 1.2.0
+version: 1.2.1
 
 authors:
   - Sijawusz Pur Rahnama <sija@sija.pl>

From 5649a04adf66d7b90acf613817814e120eeed627 Mon Sep 17 00:00:00 2001
From: Sijawusz Pur Rahnama <sija@sija.pl>
Date: Mon, 1 Mar 2021 14:47:39 +0100
Subject: [PATCH 16/23] Bump ameba dependency

---
 shard.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/shard.yml b/shard.yml
index 89b3887..b08af20 100644
--- a/shard.yml
+++ b/shard.yml
@@ -7,7 +7,7 @@ authors:
 development_dependencies:
   ameba:
     github: crystal-ameba/ameba
-    version: ~> 0.13.0
+    version: ~> 0.14.0
 
 crystal: ">= 0.35.0"
 

From 14f5d77cdd7e656b89c7c0fefe44a1038e1920a8 Mon Sep 17 00:00:00 2001
From: Sijawusz Pur Rahnama <sija@sija.pl>
Date: Wed, 10 Mar 2021 15:32:36 +0100
Subject: [PATCH 17/23] Migrate from Travis CI to GitHub Actions

---
 .github/workflows/ci.yml | 46 ++++++++++++++++++++++++++++++++++++++++
 .travis.yml              | 20 -----------------
 README.md                |  2 +-
 3 files changed, 47 insertions(+), 21 deletions(-)
 create mode 100644 .github/workflows/ci.yml
 delete mode 100644 .travis.yml

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
new file mode 100644
index 0000000..ac9ac2f
--- /dev/null
+++ b/.github/workflows/ci.yml
@@ -0,0 +1,46 @@
+name: CI
+
+on:
+  push:
+  pull_request:
+  schedule:
+    - cron: "0 3 * * 1" # Every monday at 3 AM
+
+jobs:
+  test:
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest, macos-latest]
+        crystal: [latest, nightly]
+    runs-on: ${{ matrix.os }}
+
+    steps:
+      - name: Install Crystal
+        uses: oprypin/install-crystal@v1
+        with:
+          crystal: ${{ matrix.crystal }}
+
+      - name: Download source
+        uses: actions/checkout@v2
+
+      - name: Install dependencies
+        run: shards install
+        env:
+          SHARDS_OPTS: --ignore-crystal-version
+
+      - name: Run specs
+        run: |
+          crystal spec
+          crystal spec --no-debug
+
+      - name: Run specs (release)
+        run: |
+          crystal spec --release
+          crystal spec --release --no-debug
+
+      - name: Check formatting
+        run: crystal tool format --check
+
+      - name: Run ameba linter
+        run: bin/ameba
diff --git a/.travis.yml b/.travis.yml
deleted file mode 100644
index 7521934..0000000
--- a/.travis.yml
+++ /dev/null
@@ -1,20 +0,0 @@
-language: crystal
-
-crystal:
-  - latest
-  - nightly
-
-jobs:
-  allow_failures:
-    - crystal: nightly
-
-install:
-  - shards install
-
-script:
-  - crystal spec
-  - crystal spec --no-debug
-  - crystal spec --release
-  - crystal spec --release --no-debug
-  - crystal tool format --check
-  - bin/ameba
diff --git a/README.md b/README.md
index 03ca6ae..8d17ade 100644
--- a/README.md
+++ b/README.md
@@ -1,4 +1,4 @@
-# backtracer.cr [![Build Status](https://travis-ci.com/Sija/backtracer.cr.svg?branch=master)](https://travis-ci.com/Sija/backtracer.cr) [![Releases](https://img.shields.io/github/release/Sija/backtracer.cr.svg)](https://github.com/Sija/backtracer.cr/releases) [![License](https://img.shields.io/github/license/Sija/backtracer.cr.svg)](https://github.com/Sija/backtracer.cr/blob/master/LICENSE)
+# backtracer.cr [![CI](https://github.com/Sija/backtracer.cr/actions/workflows/ci.yml/badge.svg)](https://github.com/Sija/backtracer.cr/actions/workflows/ci.yml) [![Releases](https://img.shields.io/github/release/Sija/backtracer.cr.svg)](https://github.com/Sija/backtracer.cr/releases) [![License](https://img.shields.io/github/license/Sija/backtracer.cr.svg)](https://github.com/Sija/backtracer.cr/blob/master/LICENSE)
 
 Crystal shard aiming to assist with parsing backtraces into a structured form.
 

From 30287e3025e7a3409a772254c96fa722bd3391a7 Mon Sep 17 00:00:00 2001
From: Sijawusz Pur Rahnama <sija@sija.pl>
Date: Sat, 13 Aug 2022 23:30:25 +0200
Subject: [PATCH 18/23] Bump ameba to ~> 1.0.0

---
 shard.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/shard.yml b/shard.yml
index b08af20..201bbd6 100644
--- a/shard.yml
+++ b/shard.yml
@@ -7,7 +7,7 @@ authors:
 development_dependencies:
   ameba:
     github: crystal-ameba/ameba
-    version: ~> 0.14.0
+    version: ~> 1.0.0
 
 crystal: ">= 0.35.0"
 

From 07d6dc43817d16c7fb7f0ab51d7d67325a469534 Mon Sep 17 00:00:00 2001
From: Sijawusz Pur Rahnama <sija@sija.pl>
Date: Sat, 13 Aug 2022 23:31:37 +0200
Subject: [PATCH 19/23] Bump to v1.2.2

---
 shard.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/shard.yml b/shard.yml
index 201bbd6..4c89914 100644
--- a/shard.yml
+++ b/shard.yml
@@ -1,5 +1,5 @@
 name: backtracer
-version: 1.2.1
+version: 1.2.2
 
 authors:
   - Sijawusz Pur Rahnama <sija@sija.pl>

From 8410b1147869e5b902c76eb5dffeb4c552deb502 Mon Sep 17 00:00:00 2001
From: Sijawusz Pur Rahnama <sija@sija.pl>
Date: Wed, 26 Oct 2022 02:19:07 +0200
Subject: [PATCH 20/23]  Bump ameba dependency

---
 shard.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/shard.yml b/shard.yml
index 4c89914..2266835 100644
--- a/shard.yml
+++ b/shard.yml
@@ -7,7 +7,7 @@ authors:
 development_dependencies:
   ameba:
     github: crystal-ameba/ameba
-    version: ~> 1.0.0
+    version: ~> 1.2.0
 
 crystal: ">= 0.35.0"
 

From a7eed4b2304376a4be8e87d142cd3c85e6709ae1 Mon Sep 17 00:00:00 2001
From: Sijawusz Pur Rahnama <sija@sija.pl>
Date: Mon, 6 Mar 2023 05:58:15 +0100
Subject: [PATCH 21/23] Bump ameba dependency and fix found issues

---
 .ameba.yml                                      | 3 +++
 shard.yml                                       | 2 +-
 spec/backtracer/backtrace/frame/context_spec.cr | 2 +-
 spec/spec_helper.cr                             | 9 +++++----
 src/backtracer.cr                               | 2 +-
 5 files changed, 11 insertions(+), 7 deletions(-)
 create mode 100644 .ameba.yml

diff --git a/.ameba.yml b/.ameba.yml
new file mode 100644
index 0000000..399b108
--- /dev/null
+++ b/.ameba.yml
@@ -0,0 +1,3 @@
+Lint/NotNil:
+  Excluded:
+    - spec/backtracer/backtrace/frame/parser_spec.cr
diff --git a/shard.yml b/shard.yml
index 2266835..c718818 100644
--- a/shard.yml
+++ b/shard.yml
@@ -7,7 +7,7 @@ authors:
 development_dependencies:
   ameba:
     github: crystal-ameba/ameba
-    version: ~> 1.2.0
+    version: ~> 1.4.0
 
 crystal: ">= 0.35.0"
 
diff --git a/spec/backtracer/backtrace/frame/context_spec.cr b/spec/backtracer/backtrace/frame/context_spec.cr
index 1ec0a74..b6fc3aa 100644
--- a/spec/backtracer/backtrace/frame/context_spec.cr
+++ b/spec/backtracer/backtrace/frame/context_spec.cr
@@ -1,6 +1,6 @@
 require "../../../spec_helper"
 
-def with_foo_context
+def with_foo_context(&)
   yield Backtracer::Backtrace::Frame::Context.new(
     lineno: 10,
     pre: %w[foo bar baz],
diff --git a/spec/spec_helper.cr b/spec/spec_helper.cr
index 11c6c86..ed152bb 100644
--- a/spec/spec_helper.cr
+++ b/spec/spec_helper.cr
@@ -1,15 +1,15 @@
 require "spec"
 require "../src/backtracer"
 
-def with_configuration(shared = true)
+def with_configuration(shared = true, &)
   yield shared ? Backtracer.configuration : Backtracer::Configuration.new
 end
 
-def with_backtrace(backtrace, **options)
+def with_backtrace(backtrace, **options, &)
   yield Backtracer::Backtrace::Parser.parse(backtrace, **options)
 end
 
-def with_frame(method, path = nil, lineno = nil, column = nil, **options)
+def with_frame(method, path = nil, lineno = nil, column = nil, **options, &)
   line = String.build do |io|
     if path
       io << path
@@ -28,7 +28,8 @@ def with_foo_frame(
   path = "#{__DIR__}/foo.cr",
   lineno = 1,
   column = 7,
-  **options
+  **options,
+  &
 )
   with_frame(method, path, lineno, column, **options) do |frame|
     yield frame
diff --git a/src/backtracer.cr b/src/backtracer.cr
index 6d0f507..c507a2d 100644
--- a/src/backtracer.cr
+++ b/src/backtracer.cr
@@ -1,7 +1,7 @@
 module Backtracer
   class_getter(configuration) { Configuration.new }
 
-  def self.configure : Nil
+  def self.configure(&) : Nil
     yield configuration
   end
 

From 7e92356a508682f1062a368a4c208ebecfea61ee Mon Sep 17 00:00:00 2001
From: Sijawusz Pur Rahnama <sija@sija.pl>
Date: Wed, 11 Oct 2023 04:10:23 +0200
Subject: [PATCH 22/23] Bump ameba to ~> 1.5.0

---
 shard.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/shard.yml b/shard.yml
index c718818..96ff072 100644
--- a/shard.yml
+++ b/shard.yml
@@ -7,7 +7,7 @@ authors:
 development_dependencies:
   ameba:
     github: crystal-ameba/ameba
-    version: ~> 1.4.0
+    version: ~> 1.5.0
 
 crystal: ">= 0.35.0"
 

From abdac766c5106cf5e39068d7795beaf13116d14e Mon Sep 17 00:00:00 2001
From: Sijawusz Pur Rahnama <sija@sija.pl>
Date: Thu, 12 Oct 2023 17:33:12 +0200
Subject: [PATCH 23/23] Bump ameba version to ~> 1.5.0

---
 shard.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/shard.yml b/shard.yml
index c718818..96ff072 100644
--- a/shard.yml
+++ b/shard.yml
@@ -7,7 +7,7 @@ authors:
 development_dependencies:
   ameba:
     github: crystal-ameba/ameba
-    version: ~> 1.4.0
+    version: ~> 1.5.0
 
 crystal: ">= 0.35.0"