Rule dsl

src/ameba/rule.cr

@@ -4,6 +4,16 @@ module Ameba
     Rules::TrailingWhitespace,
   ]
 
+  macro rule(name, &block)
+    module Ameba::Rules
+      struct {{name.id}} < Rule
+        def test(source)
+          {{block.body}}
+        end
+      end
+    end
+  end
+
   abstract struct Rule
     abstract def test(source : Source)
 

src/ameba/rules/line_length.cr

@@ -1,14 +1,8 @@
-module Ameba::Rules
-  # A rule that checks the size of lines in sources.
-  #
-  # This rule will report an error if there is at least
-  # one line 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)"
-      end
-    end
+# A rule that disallows lines longer than 79 symbols.
+
+Ameba.rule LineLength do |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)"
   end
 end

src/ameba/rules/trailing_whitespace.cr

@@ -1,11 +1,8 @@
-module Ameba::Rules
-  # A rule that disallows trailing whitespace at the end of a line.
-  struct TrailingWhitespace < Rule
-    def test(source)
-      source.lines.each_with_index do |line, index|
-        next unless line =~ /\s$/
-        source.error self, index + 1, "Trailing whitespace detected"
-      end
-    end
+# A rule that disallows trailing whitespace at the end of a line.
+
+Ameba.rule TrailingWhitespace do |source|
+  source.lines.each_with_index do |line, index|
+    next unless line =~ /\s$/
+    source.error self, index + 1, "Trailing whitespace detected"
   end
 end