The default value for NullableString should be null (was ""). Mojo struct...

The default value for NullableString should be null (was ""). Mojo struct fields whose type is string? should be initialized to null, not "".

BUG=417039

Review URL: https://codereview.chromium.org/605443002

Cr-Commit-Position: refs/heads/master@{#296612}

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

@@ -20,4 +20,66 @@ struct RectPair {
 struct EmptyStruct {
 };
 
+// Used to verify that struct fields which don't specify a deafult are
+// initialized to: false for bool, 0 for numbers, and null for strings,
+// handles, and structs. The "?" nullable suffix shouldn't have any 
+// impact on initial field values.
+
+struct NoDefaultFieldValues {
+  bool f0;
+  int8 f1;
+  uint8 f2;
+  int16 f3;
+  uint16 f4;
+  int32 f5;
+  uint32 f6;
+  int64 f7;
+  uint64 f8;
+  float f9;
+  double f10;
+  string f11;
+  string? f12;
+  handle<message_pipe> f13;
+  handle<data_pipe_consumer> f14;
+  handle<data_pipe_producer> f15;
+  handle<message_pipe>? f16;
+  handle<data_pipe_consumer>? f17;
+  handle<data_pipe_producer>? f18;
+  handle f19;
+  handle? f20;
+  handle<shared_buffer> f21;
+  handle<shared_buffer>? f22;
+  string[] f23;
+  string?[] f24;
+  string[]? f25;
+  string?[]? f26;
+  EmptyStruct f27;
+  EmptyStruct? f28;
+};
+
+// Used to verify that struct fields with an explicit default value
+// are initialized correctly. The "?" nullable suffix shouldn't have any 
+// impact on initial field values.
+
+struct DefaultFieldValues {
+  const string kFoo = "foo";
+  bool f0 = true;
+  int8 f1 = 100;
+  uint8 f2 = 100;
+  int16 f3 = 100;
+  uint16 f4 = 100;
+  int32 f5 = 100;
+  uint32 f6 = 100;
+  int64 f7 = 100;
+  uint64 f8 = 100;
+  float f9 = 100;
+  float f10 = 100.0;
+  double f11 = 100;
+  double f12 = 100.0;
+  string f13 = kFoo;
+  string? f14 = kFoo;
+  Rect f15 = default;
+  Rect? f16 = default;
+};
+
 }

mojo/public/js/bindings/codec_unittests.js

@@ -188,6 +188,7 @@ define([
       expect(result).toEqual(expectedResult);
     }
     encodeDecode(codec.String, "banana", "banana", 24);
+    encodeDecode(codec.NullableString, null, null, 8);
     encodeDecode(codec.Int8, -1, -1);
     encodeDecode(codec.Int8, 0xff, -1);
     encodeDecode(codec.Int16, -1, -1);

mojo/public/js/bindings/struct_unittests.js

@@ -26,8 +26,7 @@ define([
     expect(new testStructs.RectPair({second: r}).first).toBeNull();
 
     var nr = new testStructs.NamedRegion();
-    // TODO(hansmuller): nr.name should be null, see crbug.com/417039.
-    expect(nr.name).toBe("");
+    expect(nr.name).toBeNull();
     expect(nr.rects).toBeNull();
     expect(nr).toEqual(new testStructs.NamedRegion({}));
 
@@ -42,6 +41,39 @@ define([
     expect(e).toEqual(new testStructs.EmptyStruct({foo:123}));
   }
 
+  function testNoDefaultFieldValues() {
+    var s = new testStructs.NoDefaultFieldValues();
+    expect(s.f0).toEqual(false);
+
+    // f1 - f10, number type fields
+    for (var i = 1; i <= 10; i++)
+      expect(s["f" + i]).toEqual(0);
+
+    // f11,12 strings, f13-22 handles, f23-f26 arrays, f27,28 structs
+    for (var i = 11; i <= 28; i++)
+      expect(s["f" + i]).toBeNull();
+  }
+
+  function testDefaultFieldValues() {
+    var s = new testStructs.DefaultFieldValues();
+    expect(s.f0).toEqual(true);
+
+    // f1 - f12, number type fields
+    for (var i = 1; i <= 12; i++)
+      expect(s["f" + i]).toEqual(100);
+
+    // f13,14 "foo"
+    for (var i = 13; i <= 14; i++)
+      expect(s["f" + i]).toEqual("foo");
+
+    // f15,16 a default instance of Rect
+    var r = new rect.Rect();
+    expect(s.f15).toEqual(r);
+    expect(s.f16).toEqual(r);
+  }
+
   testConstructors();
+  testNoDefaultFieldValues();
+  testDefaultFieldValues();
   this.result = "PASS";
 });
\ No newline at end of file

mojo/public/tools/bindings/generators/mojom_cpp_generator.py

@@ -233,6 +233,9 @@ def TranslateConstants(token, kind):
     if token.value == "double.NAN" or token.value == "float.NAN":
       return "NAN";
 
+  if (kind is not None and mojom.IsFloatKind(kind)):
+      return token if token.isdigit() else token + "f";
+
   return '%s%s' % (token, _kind_to_cpp_literal_suffix.get(kind, ''))
 
 def ExpressionToText(value, kind=None):

mojo/public/tools/bindings/generators/mojom_js_generator.py

@@ -31,8 +31,8 @@ _kind_to_javascript_default_value = {
   mojom.INT64:                 "0",
   mojom.UINT64:                "0",
   mojom.DOUBLE:                "0",
-  mojom.STRING:                '""',
-  mojom.NULLABLE_STRING:       '""'
+  mojom.STRING:                "null",
+  mojom.NULLABLE_STRING:       "null"
 }
 
 

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

@@ -334,6 +334,10 @@ def IsBoolKind(kind):
   return kind.spec == BOOL.spec
 
 
+def IsFloatKind(kind):
+  return kind.spec == FLOAT.spec
+
+
 def IsStringKind(kind):
   return kind.spec == STRING.spec or kind.spec == NULLABLE_STRING.spec