Makes descriptors hold nullptr for properties not implemented in API.

third_party/WebKit/Source/build/scripts/templates/CSSPropertyDescriptor.cpp.tmpl

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 #include "core/css/properties/CSSPropertyDescriptor.h"
 
 {% for api_class in api_classes %}
 #include "core/css/properties/{{api_class.classname}}.h"
 {% endfor %}
 
 namespace blink {
 
 static_assert(
     std::is_pod<CSSPropertyDescriptor>::value,
     "CSSPropertyDescriptor must be a POD to support using initializer lists.");
 
 static CSSPropertyDescriptor cssPropertyDescriptors[] = {
-    // An invalid CSSPropertyDescriptor. When functions are added to
-    // CSSPropertyAPI, add a nullptr to represent their function pointers in the
-    // struct initaliser.
-    { nullptr, false },
-    // When functions are added to CSSPropertyAPI, also add them to the struct
-    // initaliser below.
+    // An invalid CSSPropertyDescriptor.
+    {

[sashab, 2017/02/01 17:50:20]

YAY getting rid of code dependencies!! \o/

+      {% for valid_api_method in valid_api_methods %}
+        nullptr,
+      {% endfor %}
+    },
+    // CSSPropertyDescriptors for all valid properties.
     {% for api_class in api_classes %}
-    { {{api_class.classname}}::parseSingleValue, true },
+    {
+      {% for api_method in api_methods %}
+        {% if api_method in api_class.api_methods %}

[sashab, 2017/02/01 17:50:20]

You can merge these:

{% for foo in bar if baz %}

Also be careful with your indenting -- see other tmpl files -- the indenting
needs to match C++, not Jinja2, so don't indent {%'s unless the C++ should be
indented :)

[aazzam, 2017/02/01 22:33:16]

done :) that makes things look a bit nicer!

+          {{api_class.classname}}::{{api_method}},
+        {% else %}
+           nullptr,

[sashab, 2017/02/01 17:50:20]

One thing I'm worried about here is ordering. Since the descriptor is not
generated, we don't know the order these APIs will appear in, e.g if valid
values is [parseShorthand, parseSingleValue] all this code will fail.

This is OK for now because we can just add a comment to CSSProperties.json5, but
yet another reason to move to IDL. :)

[aazzam, 2017/02/01 22:33:15]

ahhh I didn't even notice the ordering issue! that is a bit annoying

+        {% endif %}
+      {% endfor %}
+    },
     {% endfor %}
 };
 
 const CSSPropertyDescriptor& CSSPropertyDescriptor::get(CSSPropertyID id) {
   // TODO(aazzam): We are currently using hard-coded indexes for
   // cssPropertyDescriptor since we have only implemented a few properties.
   // Later, generate this switch statement, or alternatively return
   // cssPropertyDescriptors[id], and generate the cssPropertyDescriptors array
   // to hold invalid descriptors for methods which haven't been implemented yet.
   switch (id) {
   {% for api_class in api_classes %}
     {% for property_id in api_class.property_ids %}
     case {{property_id}}:
     {% endfor %}
       return cssPropertyDescriptors[{{api_class.index}}];
   {% endfor %}
     default:
       return cssPropertyDescriptors[0];
   }
 }
 
 }  // namespace blink