Mojo JS Bindings: Prevent issues with method parameter names.

- Append '_' to parameter names which are also reserved keywords in
  JavaScript. Struct field names remain unchanged as such keywords
  still work there.

- Rename "params" variable in generated Proxy.prototype.{{method.name}}
  to prevent a parameter named "params" from breaking the bindings.

Bug: 826070
Change-Id: I29046179929df18e14f63ff4d1cc3a74c1ef71e0
Reviewed-on: https://chromium-review.googlesource.com/1009347Reviewed-by: Ken Rockot <rockot@chromium.org>
Commit-Queue: Oliver Chang <ochang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#550420}

mojo/public/tools/bindings/generators/js_templates/externs/interface_definition.tmpl

@@ -3,7 +3,7 @@
 {%  for method in interface.methods %}
   /**
 {%-   for parameter in method.parameters %}
-   * @param { {{parameter.kind|closure_type_with_nullability}} } {{parameter.name}}
+   * @param { {{parameter.kind|closure_type_with_nullability}} } {{parameter.name|sanitize_identifier}}
 {%-   endfor -%}
 {%-   if method.response_parameters != None %}
    * @return {Promise}
@@ -11,7 +11,7 @@
    */
    {{method.name}}(
 {%-   for parameter in method.parameters -%}
-{{parameter.name}}{% if not loop.last %}, {% endif %}
+{{parameter.name|sanitize_identifier}}{% if not loop.last %}, {% endif %}
 {%-   endfor -%}
 ) {}
 {%- endfor %}

mojo/public/tools/bindings/generators/js_templates/interface_definition.tmpl

@@ -33,12 +33,12 @@
 
   {{interface.name}}Proxy.prototype.{{method.name}} = function(
 {%- for parameter in method.parameters -%}
-{{parameter.name}}{% if not loop.last %}, {% endif %}
+{{parameter.name|sanitize_identifier}}{% if not loop.last %}, {% endif %}
 {%- endfor -%}
 ) {
-    var params = new {{interface_method_id}}_Params();
+    var params_ = new {{interface_method_id}}_Params();
 {%- for parameter in method.parameters %}
-    params.{{parameter.name}} = {{parameter.name}};
+    params_.{{parameter.name}} = {{parameter.name|sanitize_identifier}};
 {%- endfor %}
 
 {%- if method.response_parameters == None %}
@@ -46,12 +46,12 @@
     var builder = new codec.MessageV2Builder(
         k{{interface_method_id}}_Name,
         codec.align({{interface_method_id}}_Params.encodedSize));
-    builder.setPayload({{interface_method_id}}_Params, params);
+    builder.setPayload({{interface_method_id}}_Params, params_);
 {%-   else %}
     var builder = new codec.MessageV0Builder(
         k{{interface_method_id}}_Name,
         codec.align({{interface_method_id}}_Params.encodedSize));
-    builder.encodeStruct({{interface_method_id}}_Params, params);
+    builder.encodeStruct({{interface_method_id}}_Params, params_);
 {%-   endif %}
     var message = builder.finish();
     this.receiver_.accept(message);
@@ -62,13 +62,13 @@
           k{{interface_method_id}}_Name,
           codec.align({{interface_method_id}}_Params.encodedSize),
           codec.kMessageExpectsResponse, 0);
-      builder.setPayload({{interface_method_id}}_Params, params);
+      builder.setPayload({{interface_method_id}}_Params, params_);
 {%-   else %}
       var builder = new codec.MessageV1Builder(
           k{{interface_method_id}}_Name,
           codec.align({{interface_method_id}}_Params.encodedSize),
           codec.kMessageExpectsResponse, 0);
-      builder.encodeStruct({{interface_method_id}}_Params, params);
+      builder.encodeStruct({{interface_method_id}}_Params, params_);
 {%-   endif %}
       var message = builder.finish();
       this.receiver_.acceptAndExpectResponse(message).then(function(message) {
@@ -89,8 +89,8 @@
   }
 
 {%- for method in interface.methods %}
-  {{interface.name}}Stub.prototype.{{method.name}} = function({{method.parameters|map(attribute='name')|join(', ')}}) {
-    return this.delegate_ && this.delegate_.{{method.name}} && this.delegate_.{{method.name}}({{method.parameters|map(attribute='name')|join(', ')}});
+  {{interface.name}}Stub.prototype.{{method.name}} = function({{method.parameters|map(attribute='name')|map('sanitize_identifier')|join(', ')}}) {
+    return this.delegate_ && this.delegate_.{{method.name}} && this.delegate_.{{method.name}}({{method.parameters|map(attribute='name')|map('sanitize_identifier')|join(', ')}});
   }
 {%- endfor %}
 

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

@@ -89,6 +89,54 @@ _kind_to_closure_type = {
   mojom.NULLABLE_SHAREDBUFFER: "mojo.MojoHandle",
 }
 
+_js_reserved_keywords = [
+    'arguments',
+    'await',
+    'break'
+    'case',
+    'catch',
+    'class',
+    'const',
+    'continue',
+    'debugger',
+    'default',
+    'delete',
+    'do',
+    'else',
+    'enum',
+    'export',
+    'extends',
+    'finally',
+    'for',
+    'function',
+    'if',
+    'implements',
+    'import',
+    'in',
+    'instanceof',
+    'interface',
+    'let',
+    'new',
+    'package',
+    'private',
+    'protected',
+    'public',
+    'return',
+    'static',
+    'super',
+    'switch',
+    'this',
+    'throw',
+    'try',
+    'typeof',
+    'var',
+    'void',
+    'while',
+    'with',
+    'yield',
+]
+
+
 def JavaScriptPayloadSize(packed):
   packed_fields = packed.packed_fields
   if not packed_fields:
@@ -204,6 +252,7 @@ class Generator(generator.Generator):
       "validate_nullable_params": self._JavaScriptNullableParam,
       "validate_struct_params": self._JavaScriptValidateStructParams,
       "validate_union_params": self._JavaScriptValidateUnionParams,
+      "sanitize_identifier": self._JavaScriptSanitizeIdentifier,
     }
     return js_filters
 
@@ -449,6 +498,12 @@ class Generator(generator.Generator):
     return "%s, %s, %s, %s" % \
         (nullable, keys_type, values_type, values_nullable)
 
+  def _JavaScriptSanitizeIdentifier(self, identifier):
+    if identifier in _js_reserved_keywords:
+      return identifier + '_'
+
+    return identifier
+
   def _TranslateConstants(self, token):
     if isinstance(token, (mojom.EnumValue, mojom.NamedValue)):
       # Both variable and enum constants are constructed like: