Populate Rule::Base+.parsed_doc on compile time

src/ameba/rule/base.cr

@@ -138,13 +138,15 @@ module Ameba::Rule
       end
     end
 
-    macro inherited
-      protected def self.path_to_source_file
-        __FILE__
-      end
+    private macro read_rule_doc(filepath = __FILE__)
+      {{ run("../../read_rule_doc",
+           @type.name.split("::").last,
+           filepath
+         ).chomp.stringify }}.presence
     end
 
-    # Returns documentation for this rule if any.
+    macro inherited
+      # Returns documentation for this rule, if there is any.
       #
       # ```
       # module Ameba
@@ -158,37 +160,7 @@ module Ameba::Rule
       #
       # MyRule.parsed_doc # => "This is a test rule.\nDoes nothing."
       # ```
-    def self.parsed_doc
-      source = File.read(path_to_source_file)
-      nodes = Crystal::Parser.new(source)
-        .tap(&.wants_doc = true)
-        .parse
-      type_name = rule_name.split('/').last?
-
-      DocFinder.new(nodes, type_name).doc
-    end
-
-    # :nodoc:
-    private class DocFinder < Crystal::Visitor
-      getter doc : String?
-      getter type_name : String?
-
-      def initialize(nodes, @type_name)
-        self.accept(nodes)
-      end
-
-      def visit(node : Crystal::ASTNode)
-        return false if @doc
-
-        if node.responds_to?(:name) &&
-           (name = node.name) &&
-           name.is_a?(Crystal::Path) &&
-           name.names.last? == @type_name
-          @doc = node.doc
-        end
-
-        true
-      end
+      class_getter parsed_doc : String? = read_rule_doc
     end
   end
 

src/read_rule_doc.cr

@@ -0,0 +1,32 @@
+require "compiler/crystal/syntax/*"
+
+private class DocFinder < Crystal::Visitor
+  getter type_name : String?
+  getter doc : String?
+
+  def initialize(nodes, @type_name)
+    self.accept(nodes)
+  end
+
+  def visit(node : Crystal::ASTNode)
+    return false if @doc
+
+    if node.responds_to?(:name) &&
+       (name = node.name) &&
+       name.is_a?(Crystal::Path) &&
+       name.names.last? == @type_name
+      @doc = node.doc
+    end
+
+    true
+  end
+end
+
+type_name, path_to_source_file = ARGV
+
+source = File.read(path_to_source_file)
+nodes = Crystal::Parser.new(source)
+  .tap(&.wants_doc = true)
+  .parse
+
+puts DocFinder.new(nodes, type_name).doc