From 1b2b71ea1cffe3f8810e89b7362a324cbb2e9133 Mon Sep 17 00:00:00 2001
From: Mike Moore <mike@blowmage.com>
Date: Sat, 10 Dec 2022 13:54:39 -0700
Subject: [PATCH] Remove method_source dependency

Replace with Rails' TestParser using Ripper.
---
 lib/m/test_method.rb | 22 ++----------
 lib/m/test_parser.rb | 86 ++++++++++++++++++++++++++++++++++++++++++++
 m.gemspec            |  1 -
 3 files changed, 89 insertions(+), 20 deletions(-)
 create mode 100644 lib/m/test_parser.rb

diff --git a/lib/m/test_method.rb b/lib/m/test_method.rb
index 0601072..56a5364 100644
--- a/lib/m/test_method.rb
+++ b/lib/m/test_method.rb
@@ -1,4 +1,4 @@
-require "method_source"
+require "m/test_parser"
 
 module M
   ### Simple data structure for what a test method contains.
@@ -9,26 +9,10 @@ module M
   # Includes the name of this method, what line on the file it begins on,
   # and where it ends.
   TestMethod = Struct.new :name, :start_line, :end_line do
-    # Set up a new test method for this test suite class
     def self.create suite_class, test_method
-      # Hopefully it's been defined as an instance method, so we'll need to
-      # look up the ruby Method instance for it
       method = suite_class.instance_method test_method
-
-      # Ruby can find the starting line for us, so pull that out of the array
-      start_line = method.source_location.last
-
-      # Ruby can't find the end line however, and I'm too lazy to write
-      # a parser. Instead, `method_source` adds `Method#source` so we can
-      # deduce this ourselves.
-      #
-      # The end line should be the number of line breaks in the method source,
-      # added to the starting line and subtracted by one.
-
-      end_line = method.source.split("\n").size + start_line - 1
-
-      # Shove the given attributes into a new databag
-      new test_method, start_line, end_line
+      _file, line_range = TestParser.definition_for method
+      new test_method, line_range.begin, line_range.end
     end
   end
 end
diff --git a/lib/m/test_parser.rb b/lib/m/test_parser.rb
new file mode 100644
index 0000000..f1da28f
--- /dev/null
+++ b/lib/m/test_parser.rb
@@ -0,0 +1,86 @@
+require "ripper"
+
+module M
+  # Parse a test file to extract the line ranges of all tests in both
+  # method-style (def test_foo) and declarative-style (test "foo" do)
+  class TestParser < Ripper
+    # Brazenly stolen from Rails::TestUnit::TestParser by Carl Brasic @brasic
+
+    # Helper to translate a method object into the path and line range where
+    # the method was defined.
+    def self.definition_for(method_obj)
+      path, begin_line = method_obj.source_location
+      begins_to_ends = new(File.read(path), path).parse
+      return unless (end_line = begins_to_ends[begin_line])
+      [path, (begin_line..end_line)]
+    end
+
+    def initialize(*)
+      # A hash mapping the 1-indexed line numbers that tests start on to where they end.
+      @begins_to_ends = {}
+      super
+    end
+
+    def parse
+      super
+      @begins_to_ends
+    end
+
+    # method test e.g. `def test_some_description`
+    # This event's first argument gets the `ident` node containing the method
+    # name, which we have overridden to return the line number of the ident
+    # instead.
+    def on_def(begin_line, *)
+      @begins_to_ends[begin_line] = lineno
+    end
+
+    # Everything past this point is to support declarative tests, which
+    # require more work to get right because of the many different ways
+    # methods can be invoked in ruby, all of which are parsed differently.
+    #
+    # The approach is just to store the current line number when the
+    # "test" method is called and pass it up the tree so it's available at
+    # the point when we also know the line where the associated block ends.
+
+    def on_method_add_block(begin_line, end_line)
+      if begin_line && end_line
+        @begins_to_ends[begin_line] = end_line
+      end
+    end
+
+    def on_command_call(*, begin_lineno, _args)
+      begin_lineno
+    end
+
+    def first_arg(arg, *)
+      arg
+    end
+
+    def just_lineno(*)
+      lineno
+    end
+
+    alias_method :on_method_add_arg, :first_arg
+    alias_method :on_command, :first_arg
+    alias_method :on_stmts_add, :first_arg
+    alias_method :on_arg_paren, :first_arg
+    alias_method :on_bodystmt, :first_arg
+
+    alias_method :on_ident, :just_lineno
+    alias_method :on_do_block, :just_lineno
+    alias_method :on_stmts_new, :just_lineno
+    alias_method :on_brace_block, :just_lineno
+
+    def on_args_new
+      []
+    end
+
+    def on_args_add(parts, part)
+      parts << part
+    end
+
+    def on_args_add_block(args, *rest)
+      args.first
+    end
+  end
+end
diff --git a/m.gemspec b/m.gemspec
index befb11c..a13f43d 100644
--- a/m.gemspec
+++ b/m.gemspec
@@ -12,7 +12,6 @@ Gem::Specification.new do |gem|
   gem.require_paths = ["lib"]
   gem.version = M::VERSION
 
-  gem.add_runtime_dependency "method_source", ">= 0.6.7"
   gem.add_runtime_dependency "rake", ">= 0.9.2.2"
 
   gem.add_development_dependency "activesupport"