From b5bd76dfa8f4229aab30f9cf1ed57b40d035b3f9 Mon Sep 17 00:00:00 2001
From: Vitalii Elenhaupt <velenhaupt@gmail.com>
Date: Thu, 20 Aug 2020 21:15:58 +0300
Subject: [PATCH 1/2] Useless Assign: ignore variables with '_' prefix

closes #164
---
 spec/ameba/ast/variabling/variable_spec.cr  | 17 +++++++++++++++++
 spec/ameba/rule/lint/useless_assign_spec.cr |  8 ++++++++
 src/ameba/ast/variabling/variable.cr        |  5 +++++
 src/ameba/rule/lint/useless_assign.cr       |  2 +-
 4 files changed, 31 insertions(+), 1 deletion(-)

diff --git a/spec/ameba/ast/variabling/variable_spec.cr b/spec/ameba/ast/variabling/variable_spec.cr
index 6f7f1c7b..fc39ef0d 100644
--- a/spec/ameba/ast/variabling/variable_spec.cr
+++ b/spec/ameba/ast/variabling/variable_spec.cr
@@ -140,6 +140,23 @@ module Ameba::AST
       end
     end
 
+    describe "#ignored?" do
+      it "is true if variable is ignored" do
+        variable = Variable.new(Crystal::Var.new("_var"), scope)
+        variable.ignored?.should be_true
+      end
+
+      it "is false if variable is not ignored" do
+        variable = Variable.new(Crystal::Var.new("v_ar"), scope)
+        variable.ignored?.should be_false
+      end
+
+      it "is true if variable is a black hole" do
+        variable = Variable.new(Crystal::Var.new("_"), scope)
+        variable.ignored?.should be_true
+      end
+    end
+
     describe "#eql?" do
       var = Crystal::Var.new("foo").at(Crystal::Location.new(nil, 1, 2))
       variable = Variable.new var, scope
diff --git a/spec/ameba/rule/lint/useless_assign_spec.cr b/spec/ameba/rule/lint/useless_assign_spec.cr
index 34b50451..bd5fdb2d 100644
--- a/spec/ameba/rule/lint/useless_assign_spec.cr
+++ b/spec/ameba/rule/lint/useless_assign_spec.cr
@@ -54,6 +54,14 @@ module Ameba::Rule::Lint
       subject.catch(s).should_not be_valid
     end
 
+    it "does not report ignored assigments" do
+      s = Source.new %(
+        payload, _header = decode
+        puts payload
+      )
+      subject.catch(s).should be_valid
+    end
+
     it "reports a useless assignment in a proc inside a block" do
       s = Source.new %(
         def method
diff --git a/src/ameba/ast/variabling/variable.cr b/src/ameba/ast/variabling/variable.cr
index 7e8d9af2..1a7eab42 100644
--- a/src/ameba/ast/variabling/variable.cr
+++ b/src/ameba/ast/variabling/variable.cr
@@ -143,6 +143,11 @@ module Ameba::AST
       end
     end
 
+    # Returns true if the name starts with '_', false if not.
+    def ignored?
+      name.starts_with? '_'
+    end
+
     # Returns true if the `node` represents exactly
     # the same Crystal node as `@node`.
     def eql?(node)
diff --git a/src/ameba/rule/lint/useless_assign.cr b/src/ameba/rule/lint/useless_assign.cr
index 7c6c4b79..bff18188 100644
--- a/src/ameba/rule/lint/useless_assign.cr
+++ b/src/ameba/rule/lint/useless_assign.cr
@@ -39,7 +39,7 @@ module Ameba::Rule::Lint
 
     def test(source, node, scope : AST::Scope)
       scope.variables.each do |var|
-        next if var.captured_by_block? || var.used_in_macro?
+        next if var.captured_by_block? || var.used_in_macro? || var.ignored?
 
         var.assignments.each do |assign|
           next if assign.referenced? || assign.transformed?

From 5ee54293a8f08bf39f5deb6cbdbd7c919eb71da6 Mon Sep 17 00:00:00 2001
From: Vitalii Elenhaupt <velenhaupt@gmail.com>
Date: Wed, 26 Aug 2020 22:42:29 +0300
Subject: [PATCH 2/2] Upgrade alpine img

refs #166
---
 Dockerfile | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/Dockerfile b/Dockerfile
index bb8a924e..cb448078 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,11 +1,11 @@
-FROM alpine:3.8 as builder
+FROM alpine:3.12 as builder
 RUN apk add --update crystal shards openssl-dev yaml-dev musl-dev make
 RUN mkdir /ameba
 WORKDIR /ameba
 COPY . /ameba/
 RUN make clean && make
 
-FROM alpine:3.8
+FROM alpine:3.12
 RUN apk add --update openssl yaml pcre gc libevent libgcc
 RUN mkdir /src
 WORKDIR /src