Add support for tracing mojo structs

Add helper to trace mojo autogenerated struct parameters. Thus provide
more information for local debugging.

Bug: 1103623
Change-Id: I4729a92dff39670f1d88136fb0c2f7887b2d334b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2302892
Commit-Queue: Karel Král <karelkral@google.com>
Reviewed-by: Alexander Timin <altimin@chromium.org>
Reviewed-by: Oksana Zhuravlova <oksamyt@chromium.org>
Cr-Commit-Position: refs/heads/master@{#790289}

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

@@ -120,7 +120,7 @@ bool {{proxy_name}}::{{method.name}}(
     {{interface_macros.declare_sync_method_params("param_", method)}}) {
 #if BUILDFLAG(MOJO_TRACE_ENABLED)
 {%-     set qualified_method_name = "%s::%s::%s" % (namespace_as_string,
-                                                    class_name, method_name) %}
+                                                    class_name, method.name) %}
   {{interface_macros.trace_event("param_", method.parameters,
                                  qualified_method_name)}}
 #endif
@@ -163,7 +163,7 @@ void {{proxy_name}}::{{method.name}}(
     {{interface_macros.declare_request_params("in_", method)}}) {
 #if BUILDFLAG(MOJO_TRACE_ENABLED)
 {%- set qualified_method_name = "%s::%s::%s" % (namespace_as_string, class_name,
-                                                method_name) %}
+                                                method.name) %}
   {{interface_macros.trace_event("in_", method.parameters,
                                  qualified_method_name)}}
 #endif

mojo/public/tools/bindings/generators/cpp_templates/interface_macros.tmpl

@@ -24,8 +24,7 @@ base::OnceCallback<void(
 {%-   endif -%}
 {%- endmacro -%}
 
-{%- macro trace_event(prefix, method_parameters, qualified_method_name,
-                      value="input_params_for_tracing") -%}
+{%- macro trace_event(prefix, method_parameters, qualified_method_name) -%}
 {#- This macro assumes that the argument names are the ones declared by -#}
 {#- |declare_request_params|. Namely the |prefix| should be the same here as -#}
 {#- in |declare_request_params|. -#}
@@ -33,15 +32,17 @@ base::OnceCallback<void(
   TRACE_EVENT1(
     "mojom", "{{qualified_method_name}}", "input_parameters",
     [&](){
-      auto {{value}} = std::make_unique<base::trace_event::TracedValue>();
+      auto value = std::make_unique<base::trace_event::TracedValue>();
+      base::trace_event::TracedValue* raw_value = value.get();
 {%-     for param in method_parameters %}
-{%-       for line in param.kind|write_input_param_for_tracing(prefix,
-                                                               param.name,
-                                                               value) %}
+{%-       for line in param.kind|write_input_param_for_tracing(
+                                   parameter_name=param.name,
+                                   cpp_parameter_name=prefix+param.name,
+                                   value='raw_value') %}
       {{line}}
 {%-       endfor -%}
 {%-     endfor %}
-      return {{value}};
+      return value;
     }());
 {%-   else -%}
   TRACE_EVENT0("mojom", "{{qualified_method_name}}");

mojo/public/tools/bindings/generators/cpp_templates/wrapper_class_declaration.tmpl

@@ -128,6 +128,19 @@ class {{export_attribute}} {{struct.name}} {
   {{type}} {{name}};
 {%- endfor %}
 
+#if BUILDFLAG(MOJO_TRACE_ENABLED)
+  // Write this structure into |value|. The members are represented as a
+  // dictionary |member name|: |member value|.
+  //
+  // |value| The TracedValue to be written into.
+  // |parameter_name| Name of the variable holding this structure,
+  //   used as the name of the dictionary representing this structure.
+  //   If nullptr, then the dictionary representing this structure has no name
+  //   (used in arrays of structures).
+  void ToTracedValue(base::trace_event::TracedValue* value,
+    const char* parameter_name = nullptr);
+#endif  // BUILDFLAG(MOJO_TRACE_ENABLED)
+
  private:
   static bool Validate(const void* data,
                        mojo::internal::ValidationContext* validation_context);

mojo/public/tools/bindings/generators/cpp_templates/wrapper_class_definition.tmpl

@@ -32,6 +32,26 @@ size_t {{struct.name}}::Hash(size_t seed) const {
 }
 {%- endif %}
 
+#if BUILDFLAG(MOJO_TRACE_ENABLED)
+void {{struct.name}}::ToTracedValue(base::trace_event::TracedValue* value,
+    const char* parameter_name) {
+  if (parameter_name) {
+    value->BeginDictionary(parameter_name);
+  } else {
+    value->BeginDictionary();
+  }
+{%-  for field in struct.fields %}
+{%-    for line in field.kind|write_input_param_for_tracing(
+                                parameter_name=field.name,
+                                cpp_parameter_name='this->'+field.name,
+                                value='value') %}
+  {{line}}
+{%-    endfor -%}
+{%-  endfor %}
+  value->EndDictionary();
+}
+#endif  // BUILDFLAG(MOJO_TRACE_ENABLED)
+
 bool {{struct.name}}::Validate(
     const void* data,
     mojo::internal::ValidationContext* validation_context) {

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

@@ -670,22 +670,21 @@ class Generator(generator.Generator):
         GetCppPodType(constant.kind), constant.name,
         self._ConstantValue(constant))
 
-  def _WriteInputParamForTracing(self, kind, mojo_prefix, parameter_name,
+  def _WriteInputParamForTracing(self, kind, parameter_name, cpp_parameter_name,
                                  value):
     """Generates lines of C++ to log parameter |parameter_name| into TracedValue
     |value|.
 
     Args:
       kind: {Kind} The kind of the parameter (corresponds to its C++ type).
-      mojo_prefix: {string} The prefix of the auto-generated parameter.
-      parameter_name: {string} The mojom parameter name to be logged
-        (auto-generated C++ parameter name is |mojo_prefix+parameter_name|).
+      parameter_name: {string} The name of the mojom parameter to be logged.
+      cpp_parameter_name: {string} The actual C++ variable name corresponding to
+        the mojom parameter |parameter_name|.
       value: {string} The C++ TracedValue* variable name to be logged into.
 
     Yields:
       {string} C++ lines of code that trace |parameter_name| into |value|.
     """
-    cpp_parameter_name = mojo_prefix + parameter_name
     value_name_cppname = (value, parameter_name, cpp_parameter_name)
     # TODO(crbug.com/1103623): Support more involved types.
     if mojom.IsEnumKind(kind):
@@ -729,6 +728,15 @@ class Generator(generator.Generator):
     if mojom.IsFloatKind(kind) or mojom.IsDoubleKind(kind):
       yield '%s->SetDouble("%s", %s);' % value_name_cppname
       return
+    if (mojom.IsStructKind(kind) and not self._IsTypemappedKind(kind)
+        and not IsNativeOnlyKind(kind)):
+      yield 'if (%s.is_null()) {' % cpp_parameter_name
+      yield '  %s->SetString("%s", "nullptr");' % (value, parameter_name)
+      yield '} else {'
+      yield '  %s->ToTracedValue(%s, "%s");' % (cpp_parameter_name, value,
+                                                parameter_name)
+      yield '}'
+      return
     yield '%s->SetString("%s", "<value of type %s>");' % (
         value, parameter_name, self._GetCppWrapperParamType(kind))