Mojo: separate generation of MojoLPM and JS fuzzing bindings.

This CL replaces the enable_fuzzing mojom buildrule parameter with two
flags, enable_js_fuzzing and enable_mojolpm_fuzzing, which allow
independently controlling the generation of the MojoLPM and JS fuzzing
bindings.

This means that MojoLPM fuzzers don't need to require the generation
of legacy JS bindings, and allows cleaning up some of the WebUI and
ChromeOS specific interfaces which currently need to generate unused
legacy bindings.

Bug: 1413182
Change-Id: I426f40a96c8ba15898c78a30d235d26e0c23fc4b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4225396
Reviewed-by: Rebekah Potter <rbpotter@chromium.org>
Reviewed-by: Alex Gough <ajgo@chromium.org>
Reviewed-by: Jack Hsieh <chengweih@chromium.org>
Reviewed-by: Michael van Ouwerkerk <mvanouwerkerk@chromium.org>
Reviewed-by: Austin Sullivan <asully@chromium.org>
Commit-Queue: Mark Brand <markbrand@google.com>
Reviewed-by: Andrew Paseltiner <apaseltiner@chromium.org>
Reviewed-by: Roland Bock <rbock@google.com>
Cr-Commit-Position: refs/heads/main@{#1111488}

chromeos/ash/services/nearby/public/mojom/BUILD.gn

@@ -48,6 +48,8 @@ mojom("mojom") {
     "//url/mojom:url_mojom_gurl",
   ]
 
+  enable_js_fuzzing = false
+
   cpp_only = true
 
   cpp_typemaps = [

chromeos/crosapi/mojom/BUILD.gn

@@ -109,6 +109,7 @@ mojom("mojom") {
     "web_page_info.mojom",
   ]
   disable_variants = true
+  enable_js_fuzzing = false
   cpp_only = true
 
   public_deps = [

components/attribution_reporting/BUILD.gn

@@ -16,8 +16,7 @@ mojom("mojom") {
   webui_module_path = "/"
   use_typescript_sources = true
 
-  # The 3 legacy JS bindings types are required by Blink and by the fuzzer
-  # targets below.
+  # Used by Blink, so requires legacy JS bindings.
   generate_legacy_js_bindings = true
   generate_java = true
 }
@@ -305,9 +304,4 @@ mojom("source_type_mojom") {
   sources = [ "source_type.mojom" ]
   webui_module_path = "/"
   use_typescript_sources = true
-
-  # Fuzzers use the 3 legacy JS bindings types. This mojom is a dependency of
-  # the attribution_reporting component, which is used by the fuzzer tests
-  # above.
-  generate_legacy_js_bindings = enable_mojom_fuzzer
 }

components/services/storage/privileged/mojom/BUILD.gn

@@ -15,9 +15,6 @@ mojom("mojom_bucket") {
 
   webui_module_path = "/"
   use_typescript_sources = true
-
-  # Fuzzers require legacy bindings.
-  generate_legacy_js_bindings = enable_mojom_fuzzer
 }
 
 mojom("mojom") {
@@ -26,8 +23,13 @@ mojom("mojom") {
     "indexed_db_control.mojom",
     "indexed_db_control_test.mojom",
   ]
+
   cpp_only = true
 
+  # The interfaces defined here are privileged, and not vended to a renderer, so
+  # they are not fuzzable by javascript-based fuzzers.
+  enable_js_fuzzing = false
+
   public_deps = [
     ":mojom_bucket",
     "//components/services/storage/public/mojom",

components/services/storage/public/mojom/BUILD.gn

@@ -7,6 +7,10 @@ import("//mojo/public/tools/bindings/mojom.gni")
 mojom("mojom") {
   cpp_only = true
 
+  # The interfaces defined here are privileged, and not vended to a renderer, so
+  # they are not fuzzable by javascript-based fuzzers.
+  enable_js_fuzzing = false
+
   sources = [
     "blob_storage_context.mojom",
     "cache_storage_control.mojom",

components/services/storage/public/mojom/buckets/BUILD.gn

@@ -48,7 +48,4 @@ mojom("buckets") {
 
   webui_module_path = "/"
   use_typescript_sources = true
-
-  # Fuzzers use legacy bindings.
-  generate_legacy_js_bindings = enable_mojom_fuzzer
 }

gpu/ipc/common/BUILD.gn

@@ -665,11 +665,11 @@ mojom("gpu_preferences_interface") {
 mojom("vulkan_interface") {
   generate_java = true
 
-  # TODO(crbug.com/1062364): This interface code is used by some javascript targets even
-  # when vulkan isn't enabled, but the C++ fuzzer code will fail to compile if
-  # the headers aren't available.
+  # TODO(crbug.com/1062364): This interface code is used by some javascript
+  # targets even when vulkan isn't enabled, but the C++ fuzzer code will fail
+  # to compile if the headers aren't available.
   if (!enable_vulkan) {
-    enable_fuzzing = false
+    enable_mojolpm_fuzzing = false
   }
 
   sources = [

mojo/public/tools/bindings/mojom.gni

@@ -262,12 +262,16 @@ if (enable_scrambled_message_ids) {
 #       |cpp_only| is set to true, it overrides this to prevent generation of
 #       Java bindings.
 #
-#   enable_fuzzing (optional)
+#   enable_js_fuzzing (optional)
+#       Enables generation of javascript fuzzing sources for the target if the
+#       global build arg |enable_mojom_fuzzer| is also set to |true|.
+#       Defaults to |true|. If JS fuzzing generation is enabled for a target,
+#       the target will always generate JS bindings even if |cpp_only| is set to
+#       |true|. See note above.
+#
+#   enable_mojolpm_fuzzing (optional)
 #       Enables generation of fuzzing sources for the target if the global build
-#       arg |enable_mojom_fuzzer| is also set to |true|. Defaults to |true|. If
-#       fuzzing generation is enabled for a target, the target will always
-#       generate JS bindings even if |cpp_only| is set to |true|. See note
-#       above.
+#       arg |enable_mojom_fuzzer| is also set to |true|. Defaults to |true|.
 #
 #   support_lazy_serialization (optional)
 #       If set to |true|, generated C++ bindings will effectively prefer to
@@ -667,10 +671,15 @@ template("mojom") {
   }
   write_file(build_metadata_filename, build_metadata, "json")
 
-  generate_fuzzing =
-      (!defined(invoker.enable_fuzzing) || invoker.enable_fuzzing) &&
+  generate_js_fuzzing =
+      (!defined(invoker.enable_js_fuzzing) || invoker.enable_js_fuzzing) &&
       enable_mojom_fuzzer && (!defined(invoker.testonly) || !invoker.testonly)
 
+  generate_mojolpm_fuzzing =
+      (!defined(invoker.enable_mojolpm_fuzzing) ||
+       invoker.enable_mojolpm_fuzzing) && enable_mojom_fuzzer &&
+      (!defined(invoker.testonly) || !invoker.testonly)
+
   parser_target_name = "${target_name}__parser"
   parser_deps = []
   foreach(dep, all_deps) {
@@ -1036,7 +1045,7 @@ template("mojom") {
     }
   }
 
-  if (generate_fuzzing) {
+  if (generate_mojolpm_fuzzing) {
     # This block generates the proto files used for the MojoLPM fuzzer,
     # and the corresponding proto targets that will be linked in the fuzzer
     # targets. These are independent of the typemappings, and can be done
@@ -1317,7 +1326,8 @@ template("mojom") {
               "$root_gen_dir/mojo/public/tools/bindings/cpp_templates.zip",
               type_mappings_path,
             ]
-        if (generate_fuzzing && !defined(bindings_configuration.variant)) {
+        if (generate_mojolpm_fuzzing &&
+            !defined(bindings_configuration.variant)) {
           sources += [
             "$root_gen_dir/mojo/public/tools/bindings/mojolpm_templates.zip",
           ]
@@ -1349,7 +1359,8 @@ template("mojom") {
             "$root_gen_dir/${base_path}${variant_dash_suffix}.cc",
             "$root_gen_dir/${base_path}${variant_dash_suffix}.h",
           ]
-          if (generate_fuzzing && !defined(bindings_configuration.variant)) {
+          if (generate_mojolpm_fuzzing &&
+              !defined(bindings_configuration.variant)) {
             outputs += [
               "$root_gen_dir/${base_path}${variant_dash_suffix}-mojolpm.cc",
               "$root_gen_dir/${base_path}${variant_dash_suffix}-mojolpm.h",
@@ -1366,7 +1377,8 @@ template("mojom") {
           "-g",
         ]
 
-        if (generate_fuzzing && !defined(bindings_configuration.variant)) {
+        if (generate_mojolpm_fuzzing &&
+            !defined(bindings_configuration.variant)) {
           args += [ "c++,mojolpm" ]
         } else {
           args += [ "c++" ]
@@ -1644,7 +1656,7 @@ template("mojom") {
       }
     }
 
-    if (generate_fuzzing && !defined(variant)) {
+    if (generate_mojolpm_fuzzing && !defined(variant)) {
       # This block contains the C++ targets for the MojoLPM fuzzer, we need to
       # do this here so that we can use the typemap configuration for the
       # empty-variant Mojo target.
@@ -1896,8 +1908,8 @@ template("mojom") {
   # targets when generate_legacy_js_bindings is true. This option is provided
   # since the legacy bindings are needed by Blink tests and non-Chromium users,
   # which are not expected to migrate to modules or TypeScript.
-  if (generate_legacy_js &&
-      (generate_fuzzing || !defined(invoker.cpp_only) || !invoker.cpp_only)) {
+  if (generate_legacy_js && (generate_js_fuzzing ||
+                             !defined(invoker.cpp_only) || !invoker.cpp_only)) {
     if (sources_list != []) {
       generator_js_target_name = "${target_name}_js__generator"
 
@@ -1951,7 +1963,7 @@ template("mojom") {
           args += message_scrambling_args
         }
 
-        if (generate_fuzzing) {
+        if (generate_js_fuzzing) {
           args += [ "--generate_fuzzing" ]
         }
       }
@@ -2078,8 +2090,8 @@ template("mojom") {
       }
     }
   }
-  if ((generate_fuzzing || !defined(invoker.cpp_only) || !invoker.cpp_only) &&
-      use_typescript_for_target) {
+  if ((generate_js_fuzzing || !defined(invoker.cpp_only) ||
+       !invoker.cpp_only) && use_typescript_for_target) {
     if (sources_list != []) {
       source_filelist = []
       foreach(source, sources_list) {

services/device/public/mojom/BUILD.gn

@@ -92,6 +92,10 @@ mojom("device_service") {
   disable_variants = true
   cpp_only = true
 
+  # The interfaces defined here are privileged, and not vended to a renderer, so
+  # they are not fuzzable by javascript-based fuzzers.
+  enable_js_fuzzing = false
+
   enabled_features = []
   if ((is_linux || is_chromeos) && use_udev) {
     enabled_features += [ "enable_input_device_manager" ]
@@ -208,8 +212,4 @@ mojom("usb_test") {
   public_deps = [ "//url/mojom:url_mojom_gurl" ]
   webui_module_path = "/"
   use_typescript_sources = true
-
-  # Generate legacy JS bindings in addition to WebUI bindings for fuzzers,
-  # since fuzzers still use the 3 legacy bindings types.
-  generate_legacy_js_bindings = enable_mojom_fuzzer
 }