Signal extension API schema corruption to the browser process.

extensions/common/extension_api.cc

Index: extensions/common/extension_api.cc
diff --git a/extensions/common/extension_api.cc b/extensions/common/extension_api.cc
index 4b49a83f8e5f70492f0aee34901739c1b85f1ce7..3425463d0f4ccbe538580db5832d21bd376bee21 100644
--- a/extensions/common/extension_api.cc
+++ b/extensions/common/extension_api.cc
@@ -55,15 +55,24 @@ std::unique_ptr<base::ListValue> LoadSchemaList(
       NULL,                                                   // error code
       &error_message));
 
-  // Tracking down http://crbug.com/121424
-  char buf[128];
-  base::snprintf(buf, arraysize(buf), "%s: (%d) '%s'",
-      name.c_str(),
-      result.get() ? result->GetType() : -1,
-      error_message.c_str());
-
-  CHECK(result.get()) << error_message << " for schema " << schema;
-  CHECK(result->IsType(base::Value::TYPE_LIST)) << " for schema " << schema;
+#if DCHECK_IS_ON()
+  // |schema| comes from JSON hard-coded to the Chrome binary, so in principle
+  // failure to parse indicates we generated corrupted JSON, but in practice
+  // corruption of the Chrome binary (e.g. disk errors) can also break it.
+  // See http://crbug.com/121424.
+  if (!result || !result->IsType(base::Value::TYPE_LIST)) {
+    char buf[128];
+    base::snprintf(buf, arraysize(buf), "%s: (%d) '%s'",
+                   name.c_str(),
+                   result.get() ? result->GetType() : -1,
+                   error_message.c_str());
+
+    DCHECK(result);
+    DCHECK(result->IsType(base::Value::TYPE_LIST));
+  }
+#endif // DCHECK_IS_ON()
+
+  // From() returns null if pass a null or non-list value.

[Devlin, 2016/08/19 15:02:32]

nit: "passed"

[Wez, 2016/08/19 18:22:15]

Done.

   return base::ListValue::From(std::move(result));
 }
 
@@ -214,6 +223,9 @@ ExtensionAPI::OverrideSharedInstanceForTest::~OverrideSharedInstanceForTest() {
 void ExtensionAPI::LoadSchema(const std::string& name,
                               const base::StringPiece& schema) {
   std::unique_ptr<base::ListValue> schema_list(LoadSchemaList(name, schema));
+  if (!schema_list)
+    return;
+
   std::string schema_namespace;
   extensions::ExtensionsClient* extensions_client =
       extensions::ExtensionsClient::Get();
@@ -331,7 +343,12 @@ const base::DictionaryValue* ExtensionAPI::GetSchema(
     }
 
     maybe_schema = schemas_.find(api_name);
-    CHECK(schemas_.end() != maybe_schema);
+    // If the schema failed to load then return null for it, rather than
+    // crashing, so that the browser can be notified of the problem.
+    // See http://crbug.com/121424.
+    if (schemas_.end() == maybe_schema)
+      return NULL;
+
     result = maybe_schema->second.get();
   }
 
@@ -341,6 +358,17 @@ const base::DictionaryValue* ExtensionAPI::GetSchema(
   return result;
 }
 
+void ExtensionAPI::LoadSchemaListOrDie(const std::string& api) {
+  std::string api_name = GetAPINameFromFullName(api, NULL);

[Devlin, 2016/08/19 15:02:32]

nullptr

[Wez, 2016/08/19 18:22:15]

Sticking with NULL for consistency with the rest of this file; we can migrate
NULL->nullptr as a follow-up.

[Devlin, 2016/08/19 18:40:57]

(Not blocking this change - feel free to ignore) I thought the decision was that
we preferred nullptr in all new code (even new code in existing files), but
didn't want to do mass updates (primarily for git-blame reasons)?  In which
case, putting nullptr here would be correct.

+  extensions::ExtensionsClient* extensions_client =
+      extensions::ExtensionsClient::Get();
+  // IsAPISchemaGenerated() will return false for invalid |api| names.
+  if (!extensions_client->IsAPISchemaGenerated(api))

[Devlin, 2016/08/19 15:02:32]

We aren't checking the unloaded schemas here.  That won't be a problem after
https://codereview.chromium.org/2257003002/ (done for orthogonal performance
reasons), but I don't plan to merge that back, so this should probably handle
that case.

[Wez, 2016/08/19 18:22:15]

Ah, OK, so we need to check for un-generated (why do we call them "unloaded,
BTW?) schemas, which are string resources in the binary.

Looking at the code for that, I notice that things are expecting that
InitDefaultConfiguration() has been called - I don't think we need to worry
about that here (it always will have been called, and if it hasn't been called
then things will safely no-op). Am I missing something?

[Devlin, 2016/08/19 18:40:57]

re unloaded, no idea - the whole concept doesn't make sense (which is why I'm
killing them :))
InitDefaultConfiguration is called when we create the ExtensionAPI, so we should
be good.

+    return;
+
+  CHECK(LoadSchemaList(api_name, extensions_client->GetAPISchema(api_name)));
+}
+
 Feature* ExtensionAPI::GetFeatureDependency(const std::string& full_name) {
   std::string feature_type;
   std::string feature_name;
@@ -390,7 +418,9 @@ std::string ExtensionAPI::GetAPINameFromFullName(const std::string& full_name,
     api_name_candidate = api_name_candidate.substr(0, last_dot_index);
   }
 
-  *child_name = "";
+  if (child_name)
+    *child_name = "";
+
   return std::string();
 }