1 files changed, 110 insertions, 0 deletions
diff --git a/test/prism/magic_comment_test.rb b/test/prism/magic_comment_test.rb
new file mode 100644
index 0000000000..14653fb0f8
--- /dev/null
+++ b/test/prism/magic_comment_test.rb
@@ -0,0 +1,110 @@
+# frozen_string_literal: true
+
+require_relative "test_helper"
+
+module Prism
+  class MagicCommentTest < TestCase
+    if RUBY_ENGINE == "ruby"
+      class MagicCommentRipper < Ripper
+        attr_reader :magic_comments
+
+        def initialize(*)
+          super
+          @magic_comments = []
+        end
+
+        def on_magic_comment(key, value)
+          @magic_comments << [key, value]
+          super
+        end
+      end
+
+      Fixture.each do |fixture|
+        define_method(fixture.test_name) { assert_magic_comments(fixture) }
+      end
+    end
+
+    def test_encoding
+      assert_magic_encoding(Encoding::US_ASCII, "# encoding: ascii")
+    end
+
+    def test_coding
+      assert_magic_encoding(Encoding::US_ASCII, "# coding: ascii")
+    end
+
+    def test_eNcOdInG
+      assert_magic_encoding(Encoding::US_ASCII, "# eNcOdInG: ascii")
+    end
+
+    def test_CoDiNg
+      assert_magic_encoding(Encoding::US_ASCII, "# CoDiNg: ascii")
+    end
+
+    def test_encoding_whitespace
+      assert_magic_encoding(Encoding::US_ASCII, "# \s\t\v encoding \s\t\v : \s\t\v ascii \s\t\v")
+    end
+
+    def test_emacs_encoding
+      assert_magic_encoding(Encoding::US_ASCII, "# -*- encoding: ascii -*-")
+    end
+
+    def test_emacs_coding
+      assert_magic_encoding(Encoding::US_ASCII, "# -*- coding: ascii -*-")
+    end
+
+    def test_emacs_eNcOdInG
+      assert_magic_encoding(Encoding::US_ASCII, "# -*- eNcOdInG: ascii -*-")
+    end
+
+    def test_emacs_CoDiNg
+      assert_magic_encoding(Encoding::US_ASCII, "# -*- CoDiNg: ascii -*-")
+    end
+
+    def test_emacs_whitespace
+      assert_magic_encoding(Encoding::US_ASCII, "# -*- \s\t\v encoding \s\t\v : \s\t\v ascii \s\t\v -*-")
+    end
+
+    def test_emacs_multiple
+      assert_magic_encoding(Encoding::US_ASCII, "# -*- foo: bar; encoding: ascii -*-")
+    end
+
+    def test_coding_whitespace
+      assert_magic_encoding(Encoding::ASCII_8BIT, "# coding \t \r  \v   :     \t \v    \r   ascii-8bit")
+    end
+
+    def test_vim
+      assert_magic_encoding(Encoding::Windows_31J, "# vim: filetype=ruby, fileencoding=windows-31j, tabsize=3, shiftwidth=3")
+    end
+
+    private
+
+    def assert_magic_encoding(expected, line)
+      source = %Q{#{line}\n""}
+      actual = Prism.parse(source).encoding
+
+      # Compare against our expectation.
+      assert_equal expected, actual
+
+      # Compare against Ruby's expectation.
+      if defined?(RubyVM::InstructionSequence)
+        expected = RubyVM::InstructionSequence.compile(source).eval.encoding
+        assert_equal expected, actual
+      end
+    end
+
+    def assert_magic_comments(fixture)
+      source = fixture.read
+
+      # Check that we get the correct number of magic comments when lexing with
+      # ripper.
+      expected = MagicCommentRipper.new(source).tap(&:parse).magic_comments
+      actual = Prism.parse(source).magic_comments
+
+      assert_equal expected.length, actual.length
+      expected.zip(actual).each do |(expected_key, expected_value), magic_comment|
+        assert_equal expected_key, magic_comment.key
+        assert_equal expected_value, magic_comment.value
+      end
+    end
+  end
+end