Remove dsl & refactor ast visitors

closes #4

src/ameba/ast.cr

@@ -0,0 +1,27 @@
+require "compiler/crystal/syntax/*"
+
+module Ameba
+  NODE_VISITORS = [
+    Unless,
+    Call,
+  ]
+
+  {% for name in NODE_VISITORS %}
+    class {{name}}Visitor < Crystal::Visitor
+      @rule : Rule
+      @source : Source
+
+      def initialize(@rule, @source)
+        @source.ast.accept self
+      end
+
+      def visit(node : Crystal::ASTNode)
+        true
+      end
+
+      def visit(node : Crystal::{{name}})
+        @rule.test @source, node
+      end
+    end
+  {% end %}
+end

src/ameba/dsl.cr

@@ -1,32 +0,0 @@
-module Ameba
-  macro rule(name, &block)
-    module Ameba::Rules
-      struct {{name.id}} < Rule
-        def test(source)
-          {{block.body}}
-        end
-      end
-    end
-  end
-
-  macro visitor(name, node, &block)
-    module Ameba::Rules
-      class {{name.id}}Visitor < Crystal::Visitor
-        @rule : Rule
-        @source : Source
-
-        def initialize(@rule, @source)
-          @source.ast.accept self
-        end
-
-        def visit(node : Crystal::ASTNode)
-          true
-        end
-
-        def visit(node : {{node.id}})
-          {{block.body}}
-        end
-      end
-    end
-  end
-end

src/ameba/rule.cr

@@ -10,6 +10,10 @@ module Ameba
   abstract struct Rule
     abstract def test(source : Source)
 
+    def test(source : Source, node : Crystal::ASTNode)
+      raise "Unimplemented"
+    end
+
     def catch(source : Source)
       source.tap { |s| test s }
     end

src/ameba/rules/comparison_to_boolean.cr

@@ -1,26 +1,29 @@
-# A rule that disallows comparison to booleans.
-#
-# For example, these are considered invalid:
-#
-# ```
-# foo == true
-# bar != false
-# false === baz
-# ```
-# This is because these expressions evaluate to `true` or `false`, so you
-# could get the same result by using either the variable directly, or negating
-# the variable.
+module Ameba::Rules
+  # A rule that disallows comparison to booleans.
+  #
+  # For example, these are considered invalid:
+  #
+  # ```
+  # foo == true
+  # bar != false
+  # false === baz
+  # ```
+  # This is because these expressions evaluate to `true` or `false`, so you
+  # could get the same result by using either the variable directly, or negating
+  # the variable.
+  struct ComparisonToBoolean < Rule
+    def test(source)
+      CallVisitor.new self, source
+    end
 
-Ameba.rule ComparisonToBoolean do |source|
-  ComparisonToBooleanVisitor.new self, source
-end
-
-Ameba.visitor ComparisonToBoolean, Crystal::Call do |node|
+    def test(source, node : Crystal::Call)
       if %w(== != ===).includes?(node.name) && (
            node.args.first?.try &.is_a?(Crystal::BoolLiteral) ||
            node.obj.is_a?(Crystal::BoolLiteral)
          )
-    @source.error @rule, node.location.try &.line_number,
+        source.error self, node.location.try &.line_number,
           "Comparison to a boolean is pointless"
       end
+    end
+  end
 end

src/ameba/rules/line_length.cr

@@ -1,8 +1,12 @@
-# A rule that disallows lines longer than 79 symbols.
-
-Ameba.rule LineLength do |source|
+module Ameba::Rules
+  # A rule that disallows lines longer than 79 symbols.
+  struct LineLength < Rule
+    def test(source)
       source.lines.each_with_index do |line, index|
         next unless line.size > 79
-    source.error self, index + 1, "Line too long (#{line.size} symbols)"
+        source.error self, index + 1,
+          "Line too long (#{line.size} symbols)"
+      end
+    end
   end
 end

src/ameba/rules/trailing_blank_lines.cr

@@ -1,8 +1,11 @@
-# A rule that disallows trailing blank lines at the end of the source file.
-
-Ameba.rule TrailingBlankLines do |source|
+module Ameba::Rules
+  # A rule that disallows trailing blank lines at the end of the source file.
+  struct TrailingBlankLines < Rule
+    def test(source)
       if source.lines.size > 1 && source.lines[-2, 2].join.strip.empty?
         source.error self, source.lines.size,
           "Blank lines detected at the end of the file"
       end
+    end
+  end
 end

src/ameba/rules/trailing_whitespace.cr

@@ -1,8 +1,12 @@
-# A rule that disallows trailing whitespace at the end of a line.
-
-Ameba.rule TrailingWhitespace do |source|
+module Ameba::Rules
+  # A rule that disallows trailing whitespaces.
+  struct TrailingWhitespace < Rule
+    def test(source)
       source.lines.each_with_index do |line, index|
         next unless line =~ /\s$/
-    source.error self, index + 1, "Trailing whitespace detected"
+        source.error self, index + 1,
+          "Trailing whitespace detected"
+      end
+    end
   end
 end

src/ameba/rules/unless_else.cr

@@ -1,47 +1,50 @@
-# A rule that disallows the use of an `else` block with the `unless`.
-#
-# For example, the rule considers these valid:
-#
-# ```
-# unless something
-#   :ok
-# end
-#
-# if something
-#   :one
-# else
-#   :two
-# end
-# ```
-#
-# But it considers this one invalid as it is an `unless` with an `else`:
-#
-# ```
-# unless something
-#   :one
-# else
-#   :two
-# end
-# ```
-#
-# The solution is to swap the order of the blocks, and change the `unless` to
-# an `if`, so the previous invalid example would become this:
-#
-# ```
-# if something
-#   :two
-# else
-#   :one
-# end
-# ```
+module Ameba::Rules
+  # A rule that disallows the use of an `else` block with the `unless`.
+  #
+  # For example, the rule considers these valid:
+  #
+  # ```
+  # unless something
+  #   :ok
+  # end
+  #
+  # if something
+  #   :one
+  # else
+  #   :two
+  # end
+  # ```
+  #
+  # But it considers this one invalid as it is an `unless` with an `else`:
+  #
+  # ```
+  # unless something
+  #   :one
+  # else
+  #   :two
+  # end
+  # ```
+  #
+  # The solution is to swap the order of the blocks, and change the `unless` to
+  # an `if`, so the previous invalid example would become this:
+  #
+  # ```
+  # if something
+  #   :two
+  # else
+  #   :one
+  # end
+  # ```
+  struct UnlessElse < Rule
+    def test(source)
+      UnlessVisitor.new self, source
+    end
 
-Ameba.rule UnlessElse do |source|
-  UnlessElseVisitor.new self, source
-end
-
-Ameba.visitor UnlessElse, Crystal::Unless do |node|
+    def test(source, node : Crystal::Unless)
       unless node.else.is_a?(Crystal::Nop)
-    @source.error @rule, node.location.try &.line_number,
+        source.error self, node.location.try &.line_number,
           "Favour if over unless with else"
       end
+    end
+  end
 end

src/ameba/source.cr

@@ -1,5 +1,3 @@
-require "compiler/crystal/syntax/*"
-
 module Ameba
   # An entity that represents a Crystal source file.
   # Has path, lines of code and errors reported by rules.
@@ -13,13 +11,13 @@ module Ameba
       pos : Int32?,
       message : String
 
-    getter lines : Array(String)
+    getter lines : Array(String)?
     getter errors = [] of Error
     getter path : String?
     getter content : String
+    getter ast : Crystal::ASTNode?
 
     def initialize(@content : String, @path = nil)
-      @lines = @content.split("\n")
     end
 
     def error(rule : Rule, line_number : Int32?, message : String)
@@ -30,8 +28,14 @@ module Ameba
       errors.empty?
     end
 
+    def lines
+      @lines ||= @content.split("\n")
+    end
+
     def ast
-      Crystal::Parser.new(@content).tap { |p| p.filename = @path }.parse
+      @ast ||= Crystal::Parser.new(@content)
+                              .tap { |p| p.filename = @path }
+                              .parse
     end
   end
 end