Test out idempotency against shipped Ruby files

Author: kddnewton

lib/syntax_tree.rb

@@ -294,6 +294,19 @@ def self.format(source)
     output.join
   end
 
+  # Returns the source from the given filepath taking into account any potential
+  # magic encoding comments.
+  def self.read(filepath)
+    encoding =
+      File.open(filepath, "r") do |file|
+        header = file.readline
+        header += file.readline if header.start_with?("#!")
+        Ripper.new(header).tap(&:parse).encoding
+      end
+
+    File.read(filepath, encoding: encoding)
+  end
+
   private
 
   # ----------------------------------------------------------------------------
@@ -7357,7 +7370,12 @@ def on_in(pattern, statements, consequent)
     beginning = find_token(Kw, "in")
     ending = consequent || find_token(Kw, "end")
 
-    statements_start = find_token(Kw, "then", consume: false) || pattern
+    statements_start = pattern
+    if token = find_token(Kw, "then", consume: false)
+      tokens.delete(token)
+      statements_start = token
+    end
+
     statements.bind(
       find_next_statement_start(statements_start.location.end_char),
       ending.location.start_char
@@ -7900,6 +7918,10 @@ def initialize(value:, location:, comments: [])
       @comments = comments
     end
 
+    def child_nodes
+      []
+    end
+
     def format(q)
       q.text(value)
     end
@@ -13071,7 +13093,12 @@ def on_when(arguments, statements, consequent)
     beginning = find_token(Kw, "when")
     ending = consequent || find_token(Kw, "end")
 
-    statements_start = find_token(Kw, "then", consume: false) || arguments
+    statements_start = arguments
+    if token = find_token(Kw, "then", consume: false)
+      tokens.delete(token)
+      statements_start = token
+    end
+
     statements.bind(
       find_next_statement_start(statements_start.location.end_char),
       ending.location.start_char

lib/syntax_tree/cli.rb

@@ -174,7 +174,7 @@ def run(argv)
         patterns.each do |pattern|
           Dir.glob(pattern).each do |filepath|
             next unless File.file?(filepath)
-            source = source_for(filepath)
+            source = SyntaxTree.read(filepath)
 
             begin
               action.run(filepath, source)
@@ -210,19 +210,6 @@ def run(argv)
 
       private
 
-      # Returns the source from the given filepath taking into account any
-      # potential magic encoding comments.
-      def source_for(filepath)
-        encoding =
-          File.open(filepath, "r") do |file|
-            header = file.readline
-            header += file.readline if header.start_with?("#!")
-            Ripper.new(header).tap(&:parse).encoding
-          end
-
-        File.read(filepath, encoding: encoding)
-      end
-
       # Highlights a snippet from a source and parse error.
       def highlight_error(error, source)
         lines = source.lines

test/behavior_test.rb

@@ -0,0 +1,36 @@
+# frozen_string_literal: true
+
+require_relative "test_helper"
+
+class SyntaxTree
+  class BehaviorTest < Minitest::Test
+    def test_empty
+      void_stmt = SyntaxTree.parse("").statements.body.first
+      assert_kind_of(VoidStmt, void_stmt)
+    end
+
+    def test_multibyte
+      assign = SyntaxTree.parse("🎉 + 🎉").statements.body.first
+      assert_equal(5, assign.location.end_char)
+    end
+
+    def test_parse_error
+      assert_raises(ParseError) { SyntaxTree.parse("<>") }
+    end
+
+    def test_next_statement_start
+      source = <<~SOURCE
+        def method # comment
+          expression
+        end
+      SOURCE
+
+      bodystmt = SyntaxTree.parse(source).statements.body.first.bodystmt
+      assert_equal(20, bodystmt.location.start_char)
+    end
+
+    def test_version
+      refute_nil(VERSION)
+    end
+  end
+end

test/idempotency_test.rb

@@ -0,0 +1,17 @@
+# frozen_string_literal: true
+
+return if ENV["FAST"]
+require_relative "test_helper"
+
+class SyntaxTree
+  class IdempotencyTest < Minitest::Test
+    Dir[File.join(RbConfig::CONFIG["libdir"], "**/*.rb")].each do |filepath|
+      define_method(:"test_#{filepath}") do
+        source = SyntaxTree.read(filepath)
+        formatted = SyntaxTree.format(source)
+
+        assert_equal(formatted, SyntaxTree.format(formatted), "expected #{filepath} to be formatted idempotently")
+      end
+    end
+  end
+end

test/syntax_tree_test.rb renamed to test/node_test.rb

@@ -1,54 +1,9 @@
 # frozen_string_literal: true
 
-require "simplecov"
-SimpleCov.start { add_filter("prettyprint.rb") }
-
-$LOAD_PATH.unshift(File.expand_path("../lib", __dir__))
-require "syntax_tree"
-
-require "json"
-require "pp"
-require "minitest/autorun"
+require_relative "test_helper"
 
 class SyntaxTree
-  class SyntaxTreeTest < Minitest::Test
-    # --------------------------------------------------------------------------
-    # Tests for behavior
-    # --------------------------------------------------------------------------
-
-    def test_empty
-      void_stmt = SyntaxTree.parse("").statements.body.first
-      assert_kind_of(VoidStmt, void_stmt)
-    end
-
-    def test_multibyte
-      assign = SyntaxTree.parse("🎉 + 🎉").statements.body.first
-      assert_equal(5, assign.location.end_char)
-    end
-
-    def test_parse_error
-      assert_raises(ParseError) { SyntaxTree.parse("<>") }
-    end
-
-    def test_next_statement_start
-      source = <<~SOURCE
-        def method # comment
-          expression
-        end
-      SOURCE
-
-      bodystmt = SyntaxTree.parse(source).statements.body.first.bodystmt
-      assert_equal(20, bodystmt.location.start_char)
-    end
-
-    def test_version
-      refute_nil(VERSION)
-    end
-
-    # --------------------------------------------------------------------------
-    # Tests for nodes
-    # --------------------------------------------------------------------------
-
+  class NodeTest < Minitest::Test
     def test_BEGIN
       assert_node(BEGINBlock, "BEGIN", "BEGIN {}")
     end

test/test_helper.rb

@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+require "simplecov"
+SimpleCov.start { add_filter("prettyprint.rb") }
+
+$LOAD_PATH.unshift(File.expand_path("../lib", __dir__))
+require "syntax_tree"
+
+require "json"
+require "pp"
+require "minitest/autorun"