Aliases for Ripper Translation

bin/prism

@@ -220,7 +220,7 @@ module Prism
       source, filepath = read_source(argv)
 
       ripper = Ripper.sexp_raw(source)
-      prism = Prism::RipperCompat.sexp_raw(source)
+      prism = Prism::Translation::Ripper.sexp_raw(source) rescue :parse_error
 
       puts "Ripper:"
       pp ripper

lib/prism/translation/ripper.rb

@@ -222,6 +222,44 @@ def visit_break_node(node)
         on_break(on_args_add_block(args_val, false))
       end
 
+      # Visit an AliasMethodNode.
+      def visit_alias_method_node(node)
+        # For both the old and new name, if there is a colon in the symbol
+        # name (e.g. 'alias :foo :bar') then we do *not* emit the [:symbol] wrapper around
+        # the lexer token (e.g. :@ident) inside [:symbol_literal]. But if there
+        # is no colon (e.g. 'alias foo bar') then we *do* still emit the [:symbol] wrapper.
+
+        if node.new_name.is_a?(SymbolNode) && !node.new_name.opening
+          new_name_val = visit_symbol_literal_node(node.new_name, no_symbol_wrapper: true)
+        else
+          new_name_val = visit(node.new_name)
+        end
+        if node.old_name.is_a?(SymbolNode) && !node.old_name.opening
+          old_name_val = visit_symbol_literal_node(node.old_name, no_symbol_wrapper: true)
+        else
+          old_name_val = visit(node.old_name)
+        end
+
+        on_alias(new_name_val, old_name_val)
+      end
+
+      # Visit an AliasGlobalVariableNode.
+      def visit_alias_global_variable_node(node)
+        on_var_alias(visit(node.new_name), visit(node.old_name))
+      end
+
+      # Visit a GlobalVariableReadNode.
+      def visit_global_variable_read_node(node)
+        bounds(node.location)
+        on_gvar(node.name.to_s)
+      end
+
+      # Visit a BackReferenceReadNode.
+      def visit_back_reference_read_node(node)
+        bounds(node.location)
+        on_backref(node.name.to_s)
+      end
+
       # Visit an AndNode.
       def visit_and_node(node)
         visit_binary_operator(node)
@@ -326,23 +364,7 @@ def visit_x_string_node(node)
 
       # Visit an InterpolatedStringNode node.
       def visit_interpolated_string_node(node)
-        parts = node.parts.map do |part|
-          case part
-          when StringNode
-            bounds(part.content_loc)
-            on_tstring_content(part.content)
-          when EmbeddedStatementsNode
-            on_string_embexpr(visit(part))
-          else
-            raise NotImplementedError, "Unexpected node type in InterpolatedStringNode"
-          end
-        end
-
-        string_list = parts.inject(on_string_content) do |items, item|
-          on_string_add(items, item)
-        end
-
-        on_string_literal(string_list)
+        on_string_literal(visit_enumerated_node(node))
       end
 
       # Visit an EmbeddedStatementsNode node.
@@ -352,15 +374,12 @@ def visit_embedded_statements_node(node)
 
       # Visit a SymbolNode node.
       def visit_symbol_node(node)
-        if (opening = node.opening) && (['"', "'"].include?(opening[-1]) || opening.start_with?("%s"))
-          bounds(node.value_loc)
-          tstring_val = on_tstring_content(node.value.to_s)
-          return on_dyna_symbol(on_string_add(on_string_content, tstring_val))
-        end
+        visit_symbol_literal_node(node)
+      end
 
-        bounds(node.value_loc)
-        ident_val = on_ident(node.value.to_s)
-        on_symbol_literal(on_symbol(ident_val))
+      # Visit an InterpolatedSymbolNode node.
+      def visit_interpolated_symbol_node(node)
+        on_dyna_symbol(visit_enumerated_node(node))
       end
 
       # Visit a StatementsNode node.
@@ -459,6 +478,25 @@ def visit_elements(elements)
         end
       end
 
+      # Visit an InterpolatedStringNode or an InterpolatedSymbolNode node.
+      def visit_enumerated_node(node)
+        parts = node.parts.map do |part|
+          case part
+          when StringNode
+            bounds(part.content_loc)
+            on_tstring_content(part.content)
+          when EmbeddedStatementsNode
+            on_string_embexpr(visit(part))
+          else
+            raise NotImplementedError, "Unexpected node type in visit_enumerated_node"
+          end
+        end
+
+        parts.inject(on_string_content) do |items, item|
+          on_string_add(items, item)
+        end
+      end
+
       # Visit an operation-and-assign node, such as +=.
       def visit_binary_op_assign(node, operator: node.operator)
         bounds(node.name_loc)
@@ -487,6 +525,87 @@ def visit_aref_field_node(node)
         on_assign(on_aref_field(visit(node.receiver), args_val), assign_val)
       end
 
+      # In an alias statement Ripper will emit @kw instead of @ident if the object
+      # being aliased is a Ruby keyword. For instance, in the line "alias :foo :if",
+      # the :if is treated as a lexer keyword. So we need to know what symbols are
+      # also keywords.
+      RUBY_KEYWORDS = [
+        "alias",
+        "and",
+        "begin",
+        "BEGIN",
+        "break",
+        "case",
+        "class",
+        "def",
+        "defined?",
+        "do",
+        "else",
+        "elsif",
+        "end",
+        "END",
+        "ensure",
+        "false",
+        "for",
+        "if",
+        "in",
+        "module",
+        "next",
+        "nil",
+        "not",
+        "or",
+        "redo",
+        "rescue",
+        "retry",
+        "return",
+        "self",
+        "super",
+        "then",
+        "true",
+        "undef",
+        "unless",
+        "until",
+        "when",
+        "while",
+        "yield",
+        "__ENCODING__",
+        "__FILE__",
+        "__LINE__",
+      ]
+
+      # Ripper has several methods of emitting a symbol literal. Inside an alias
+      # sometimes it suppresses the [:symbol] wrapper around ident. If the symbol
+      # is also the name of a keyword (e.g. :if) it will emit a :@kw wrapper, not
+      # an :@ident wrapper, with similar treatment for constants and operators.
+      def visit_symbol_literal_node(node, no_symbol_wrapper: false)
+        if (opening = node.opening) && (['"', "'"].include?(opening[-1]) || opening.start_with?("%s"))
+          bounds(node.value_loc)
+          str_val = node.value.to_s
+          if str_val == ""
+            return on_dyna_symbol(on_string_content)
+          else
+            tstring_val = on_tstring_content(str_val)
+            return on_dyna_symbol(on_string_add(on_string_content, tstring_val))
+          end
+        end
+
+        bounds(node.value_loc)
+        node_name = node.value.to_s
+        if RUBY_KEYWORDS.include?(node_name)
+          token_val = on_kw(node_name)
+        elsif node_name.length == 0
+          raise NotImplementedError
+        elsif /[[:upper:]]/.match(node_name[0])
+          token_val = on_const(node_name)
+        elsif /[[:punct:]]/.match(node_name[0])
+          token_val = on_op(node_name)
+        else
+          token_val = on_ident(node_name)
+        end
+        sym_val = no_symbol_wrapper ? token_val : on_symbol(token_val)
+        on_symbol_literal(sym_val)
+      end
+
       # Visit a node that represents a number. We need to explicitly handle the
       # unary - operator.
       def visit_number(node)

test/prism/ripper_test.rb

@@ -4,6 +4,50 @@
 
 module Prism
   class RipperTest < TestCase
+    def truffleruby?
+      RUBY_ENGINE == "truffleruby"
+    end
+
+    def windows?
+      Gem.win_platform?
+    end
+
+    # Ripper produces certain ambiguous structures. For instance, it often
+    # adds an :args_add_block with "false" as the block meaning there is
+    # no block call. It can be hard to tell which of multiple equivalent
+    # structures it will produce. This method attempts to return a normalized
+    # comparable structure.
+    def normalized_sexp(parsed)
+      if parsed.is_a?(Array)
+        # For args_add_block, if the third entry is nil or false, remove it.
+        # Note that CRuby Ripper uses false for no block, while older JRuby
+        # uses nil. We need to do this for both.
+        return normalized_sexp(parsed[1]) if parsed[0] == :args_add_block && !parsed[2]
+
+        parsed.each.with_index do |item, idx|
+          if item.is_a?(Array)
+            parsed[idx] = normalized_sexp(parsed[idx])
+          end
+        end
+      end
+
+      parsed
+    end
+
+    def assert_ripper_equivalent(source, path: "inline source code")
+      expected = Ripper.sexp_raw(source)
+
+      refute_nil expected, "Could not parse #{path} with Ripper!"
+      expected = normalized_sexp(expected)
+      actual = Prism::Translation::Ripper.sexp_raw(source)
+      refute_nil actual, "Could not parse #{path} with Prism!"
+      actual = normalized_sexp(actual)
+      assert_equal expected, actual, "Expected Ripper and Prism to give equivalent output for #{path}!"
+    end
+
+  end
+
+  class RipperShortSourceTest < RipperTest
     def test_binary
       assert_equivalent("1 + 2")
       assert_equivalent("3 - 4 * 5")
@@ -36,7 +80,7 @@ def test_method_calls_with_variable_names
       assert_equivalent("foo.bar")
 
       # TruffleRuby prints emoji symbols differently in a way that breaks here.
-      if RUBY_ENGINE != "truffleruby"
+      unless truffleruby?
         assert_equivalent("🗻")
         assert_equivalent("🗻.location")
         assert_equivalent("foo.🗻")
@@ -57,9 +101,9 @@ def test_method_calls_with_variable_names
     def test_method_call_blocks
       assert_equivalent("foo { |a| a }")
 
-      # assert_equivalent("foo(bar 1)")
-      # assert_equivalent("foo bar 1")
-      # assert_equivalent("foo(bar 1) { 7 }")
+      assert_equivalent("foo(bar 1)")
+      assert_equivalent("foo bar 1")
+      assert_equivalent("foo(bar 1) { 7 }")
     end
 
     def test_method_calls_on_immediate_values
@@ -69,7 +113,7 @@ def test_method_calls_on_immediate_values
       assert_equivalent("7 and 7")
       assert_equivalent("7 || 7")
       assert_equivalent("7 or 7")
-      #assert_equivalent("'racecar'.reverse")
+      assert_equivalent("'racecar'.reverse")
     end
 
     def test_range
@@ -142,20 +186,49 @@ def test_assign
       assert_equivalent("a = 1")
     end
 
+    def test_alias
+      assert_equivalent("alias :foo :bar")
+      assert_equivalent("alias $a $b")
+      assert_equivalent("alias $a $'")
+      assert_equivalent("alias foo bar")
+      assert_equivalent("alias foo if")
+      assert_equivalent("alias :'def' :\"abc\#{1}\"")
+      assert_equivalent("alias :\"abc\#{1}\" :'def'")
+
+      unless truffleruby?
+        assert_equivalent("alias :foo :Ę") # Uppercase Unicode character is a constant
+        assert_equivalent("alias :Ę :foo")
+      end
+
+      assert_equivalent("alias foo +")
+      assert_equivalent("alias foo :+")
+      assert_equivalent("alias :foo :''")
+      assert_equivalent("alias :'' :foo")
+    end
+
+    # This is *exactly* the kind of thing where Ripper would have a weird
+    # special case we didn't handle correctly. We're still testing with
+    # a leading colon since putting random keywords there will often get
+    # parse errors. Mostly we want to know that Ripper will use :@kw
+    # instead of :@ident for the lexer symbol for all of these.
+    def test_keyword_aliases
+      Prism::Translation::Ripper::RUBY_KEYWORDS.each do |keyword|
+        assert_equivalent("alias :foo :#{keyword}")
+      end
+    end
+
     private
 
     def assert_equivalent(source)
-      expected = Ripper.sexp_raw(source)
-
-      refute_nil expected
-      assert_equal expected, Prism::Translation::Ripper.sexp_raw(source)
+      assert_ripper_equivalent(source)
     end
   end
 
-  class RipperFixturesTest < TestCase
+  class RipperFixturesTest < RipperTest
     #base = File.join(__dir__, "fixtures")
     #relatives = ENV["FOCUS"] ? [ENV["FOCUS"]] : Dir["**/*.txt", base: base]
     relatives = [
+      "alias.txt",
       "arithmetic.txt",
       "booleans.txt",
       "boolean_operators.txt",
@@ -172,14 +245,8 @@ class RipperFixturesTest < TestCase
         # and explicitly set the external encoding to UTF-8 to override the binmode default.
         source = File.read(path, binmode: true, external_encoding: Encoding::UTF_8)
 
-        expected = Ripper.sexp_raw(source)
-        if expected.nil?
-          puts "Could not parse #{path.inspect}!"
-        end
-        refute_nil expected
-        assert_equal expected, Translation::Ripper.sexp_raw(source)
+        assert_ripper_equivalent(source, path: path)
       end
     end
-
   end
 end