Improve jinja2 templates to support build on python3

Summary: Python3 doesn't support comparison between NoneType objects. Jinja uses sort function within 'groupby' and that leads to
"TypeError: '<' not supported between instances of 'NoneType' and 'NoneType'" when template tries to group by attribute that is empty.
This commit adds 'stringifykeygroupby' which mimics jinja's groupby but converts keys to string during sort, so comparison always succeeds.

Bug: 1138872
Change-Id: If604b4b8c405b5d924c934a04ffc763132b72061
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2495062Reviewed-by: Yuki Shiino <yukishiino@chromium.org>
Commit-Queue: Raphael Kubo da Costa <raphael.kubo.da.costa@intel.com>
Cr-Commit-Position: refs/heads/master@{#821196}

third_party/blink/renderer/bindings/scripts/code_generator.py

@@ -13,6 +13,7 @@ import re
 import sys
 
 from idl_types import set_ancestors, IdlType
+from itertools import groupby
 from v8_globals import includes
 from v8_interface import constant_filters
 from v8_types import set_component_dirs
@@ -43,6 +44,7 @@ TEMPLATES_DIR = os.path.normpath(
 # after path[0] == invoking script dir
 sys.path.insert(1, THIRD_PARTY_DIR)
 import jinja2
+from jinja2.filters import make_attrgetter, environmentfilter
 
 
 def generate_indented_conditional(code, conditional):
@@ -88,6 +90,13 @@ def runtime_enabled_if(code, name):
     return generate_indented_conditional(code, function)
 
 
+@environmentfilter
+def do_stringify_key_group_by(environment, value, attribute):
+    expr = make_attrgetter(environment, attribute)
+    key = lambda item: '' if expr(item) is None else str(expr(item))
+    return groupby(sorted(value, key=key), expr)
+
+
 def initialize_jinja_env(cache_dir):
     jinja_env = jinja2.Environment(
         loader=jinja2.FileSystemLoader(TEMPLATES_DIR),
@@ -117,6 +126,7 @@ def initialize_jinja_env(cache_dir):
     })
     jinja_env.filters.update(constant_filters())
     jinja_env.filters.update(method_filters())
+    jinja_env.filters["stringifykeygroupby"] = do_stringify_key_group_by
     return jinja_env
 
 

third_party/blink/renderer/bindings/templates/dictionary_v8.cc.tmpl

@@ -59,9 +59,9 @@ void {{v8_class}}::ToImpl(v8::Isolate* isolate, v8::Local<v8::Value> v8_value, {
   DCHECK(executionContext);
   {% endif %}{# has_origin_trial_members #}
   {% endif %}{# members #}
-  {% for origin_trial_test, origin_trial_member_list in members | groupby('origin_trial_feature_name') %}
+  {% for origin_trial_test, origin_trial_member_list in members | stringifykeygroupby('origin_trial_feature_name') %}
   {% filter origin_trial_enabled(origin_trial_test, "executionContext") %}
-  {% for feature_name, member_list in origin_trial_member_list | groupby('runtime_enabled_feature_name') %}
+  {% for feature_name, member_list in origin_trial_member_list | stringifykeygroupby('runtime_enabled_feature_name') %}
   {% filter runtime_enabled(feature_name) %}
   {% for member in member_list %}
   v8::Local<v8::Value> {{member.v8_value}};
@@ -147,9 +147,9 @@ bool toV8{{cpp_class}}(const {{cpp_class}}* impl, v8::Local<v8::Object> dictiona
   DCHECK(executionContext);
   {% endif %}{# has_origin_trial_members #}
   {% endif %}{# members #}
-  {% for origin_trial_test, origin_trial_member_list in members | groupby('origin_trial_feature_name') %}
+  {% for origin_trial_test, origin_trial_member_list in members | stringifykeygroupby('origin_trial_feature_name') %}
   {% filter origin_trial_enabled(origin_trial_test, "executionContext") %}
-  {% for feature_name, member_list in origin_trial_member_list | groupby('runtime_enabled_feature_name') %}
+  {% for feature_name, member_list in origin_trial_member_list | stringifykeygroupby('runtime_enabled_feature_name') %}
   {% filter runtime_enabled(feature_name) %}
   {% for member in member_list %}
   v8::Local<v8::Value> {{member.v8_value}};