Mojom: allow attributes that are not assigned a value.

For example, with this CL you can use [Extensible], which is the same as [Extensible=true].

This CL also fixes the issue that boolean attribute values are not correctly evaluated: if you use the mojom keywords "true"/"false" there is parsing error; if you use "True"/"False" they are actually considered as strings.

BUG=None

Review URL: https://codereview.chromium.org/1671613002

Cr-Commit-Position: refs/heads/master@{#373707}

components/arc/common/ime.mojom

@@ -5,7 +5,7 @@
 module arc;
 
 // Represents the type of text input field currently focused.
-[Extensible=True]
+[Extensible]
 enum TextInputType {
   NONE,
   TEXT,

components/arc/common/net.mojom

@@ -4,7 +4,7 @@
 
 module arc;
 
-[Extensible=True]
+[Extensible]
 enum NetworkResult {
   SUCCESS = 0,
   FAILURE = 1,

components/arc/common/power.mojom

@@ -6,7 +6,7 @@ module arc;
 
 // Enumerates the types of wake lock the ARC instance can request from the
 // host.
-[Extensible=True]
+[Extensible]
 enum DisplayWakeLockType {
   // Does not allow the screen to dim, turn off, or lock; prevents
   // idle suspend.

components/mus/public/interfaces/input_key_codes.mojom

@@ -8,7 +8,7 @@ module mus.mojom;
 //
 // Because the web has standardized on Win32 keyboard codes, so does mojo.
 // TODO: shouldn't need extensible, see http://crbug.com/582279
-[Extensible=True]
+[Extensible]
 enum KeyboardCode {
   BACK                      = 0x08,
   TAB                       = 0x09,

mojo/public/interfaces/bindings/tests/test_native_types.mojom

@@ -8,7 +8,7 @@ import "mojo/public/interfaces/bindings/tests/rect.mojom";
 
 // Used to verify that structs can be declared with no body in mojom.
 
-[Native=True]
+[Native]
 struct PickledStruct;
 
 struct PickleContainer {

mojo/public/interfaces/bindings/tests/test_unions.mojom

@@ -8,7 +8,7 @@ enum AnEnum {
   FIRST, SECOND
 };
 
-[Extensible=True]
+[Extensible]
 enum AnExtensibleEnum {
   FIRST, SECOND, THIRD
 };

mojo/public/interfaces/bindings/tests/validation_test_interfaces.mojom

@@ -49,7 +49,7 @@ enum EnumA {
   ENUM_A_1
 };
 
-[Extensible=True]
+[Extensible]
 enum EnumB {
   ENUM_B_0,
   ENUM_B_1,

mojo/public/tools/bindings/pylib/mojom/generate/data.py

@@ -225,12 +225,12 @@ def StructFromData(module, data):
     struct.fields_data = data['fields']
   struct.attributes = data.get('attributes')
 
-  # Enforce that a [Native=True] attribute is set to make native-only struct
+  # Enforce that a [Native] attribute is set to make native-only struct
   # declarations more explicit.
   if struct.native_only:
     if not struct.attributes or not struct.attributes.get('Native', False):
       raise Exception("Native-only struct declarations must include a " +
-                      "Native=True attribute.")
+                      "Native attribute.")
 
   return struct
 

mojo/public/tools/bindings/pylib/mojom/parse/parser.py

@@ -145,15 +145,26 @@ def p_nonempty_attribute_list_2(self, p):
     p[0] = p[1]
     p[0].Append(p[3])
 
-  def p_attribute(self, p):
+  def p_attribute_1(self, p):
     """attribute : NAME EQUALS evaled_literal
                  | NAME EQUALS NAME"""
     p[0] = ast.Attribute(p[1], p[3], filename=self.filename, lineno=p.lineno(1))
 
+  def p_attribute_2(self, p):
+    """attribute : NAME"""
+    p[0] = ast.Attribute(p[1], True, filename=self.filename, lineno=p.lineno(1))
+
   def p_evaled_literal(self, p):
     """evaled_literal : literal"""
-    # 'eval' the literal to strip the quotes.
-    p[0] = eval(p[1])
+    # 'eval' the literal to strip the quotes. Handle keywords "true" and "false"
+    # specially since they cannot directly be evaluated to python boolean
+    # values.
+    if p[1] == "true":
+      p[0] = True
+    elif p[1] == "false":
+      p[0] = False
+    else:
+      p[0] = eval(p[1])
 
   def p_struct_1(self, p):
     """struct : attribute_section STRUCT NAME LBRACE struct_body RBRACE SEMI"""