[mojo] introduce mojo forwarding header

This CL introduce mojom-forward.h and mojom-import-headers.h

mojo-forward.h is introduced for forward enum/class/struct declaration with some using aliases.
I replaced some mojom.h includes with mojom-foward.h in mojom.h except files using inlined struct.

mojom-import-headers.h is used to include all mojom.h of all (indirectly) imported header for mojo's cc files.

Bug: 922875
Change-Id: I386528b1059516dc1d52b18a4778a79a2289c063
Reviewed-on: https://chromium-review.googlesource.com/c/1438975
Commit-Queue: Takuto Ikuta <tikuta@chromium.org>
Reviewed-by: Ken Rockot <rockot@google.com>
Cr-Commit-Position: refs/heads/master@{#628544}

mojo/public/tools/bindings/BUILD.gn

@@ -17,6 +17,8 @@ action("precompile_templates") {
     "$mojom_generator_root/generators/cpp_templates/interface_request_validator_declaration.tmpl",
     "$mojom_generator_root/generators/cpp_templates/interface_response_validator_declaration.tmpl",
     "$mojom_generator_root/generators/cpp_templates/interface_stub_declaration.tmpl",
+    "$mojom_generator_root/generators/cpp_templates/module-forward.h.tmpl",
+    "$mojom_generator_root/generators/cpp_templates/module-import-headers.h.tmpl",
     "$mojom_generator_root/generators/cpp_templates/module-params-data.h.tmpl",
     "$mojom_generator_root/generators/cpp_templates/module-shared-internal.h.tmpl",
     "$mojom_generator_root/generators/cpp_templates/module-shared-message-ids.h.tmpl",

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

@@ -2,8 +2,14 @@
   Macro for enum definition, and the declaration of associated functions.
 ---#}
 
+{%- macro enum_forward(enum) %}
+{%-   set enum_name = enum|get_name_for_kind(flatten_nested_kind=True) %}
+enum class {{enum_name}} : int32_t;
+{%- endmacro %}
+
 {%- macro enum_decl(enum, export_attribute) %}
 {%-   set enum_name = enum|get_name_for_kind(flatten_nested_kind=True) %}
+
 enum class {{enum_name}} : int32_t {
 {%-   for field in enum.fields %}
 {%-     if field.value %}

mojo/public/tools/bindings/generators/cpp_templates/module-forward.h.tmpl

+// Copyright 2019 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.
+
+{%- if variant -%}
+{%-   set variant_path = "%s-%s"|format(module.path, variant) -%}
+{%- else -%}
+{%-   set variant_path = module.path -%}
+{%- endif -%}
+
+{%- set header_guard = "%s_FORWARD_H_"|format(
+        variant_path|upper|replace("/","_")|replace(".","_")|
+            replace("-", "_")) %}
+
+{%- macro namespace_begin() %}
+{%-   for namespace in namespaces_as_array %}
+namespace {{namespace}} {
+{%-   endfor %}
+{%-   if variant %}
+namespace {{variant}} {
+{%-   endif %}
+{%- endmacro %}
+
+{%- macro namespace_end() %}
+{%-   if variant %}
+}  // namespace {{variant}}
+{%-   endif %}
+{%-   for namespace in namespaces_as_array|reverse %}
+}  // namespace {{namespace}}
+{%-   endfor %}
+{%- endmacro %}
+
+#ifndef {{header_guard}}
+#define {{header_guard}}
+
+#include "mojo/public/cpp/bindings/struct_ptr.h"
+
+{% if not disallow_interfaces -%}
+#include "mojo/public/cpp/bindings/associated_interface_ptr.h"
+#include "mojo/public/cpp/bindings/associated_interface_ptr_info.h"
+#include "mojo/public/cpp/bindings/associated_interface_request.h"
+#include "mojo/public/cpp/bindings/interface_ptr.h"
+#include "mojo/public/cpp/bindings/interface_request.h"
+#include "mojo/public/cpp/bindings/lib/control_message_handler.h"
+#include "mojo/public/cpp/bindings/raw_ptr_impl_ref_traits.h"
+#include "mojo/public/cpp/bindings/thread_safe_interface_ptr.h"
+{%-   if for_blink %}
+#include "third_party/blink/renderer/platform/mojo/revocable_interface_ptr.h"
+{%-   endif %}
+{%- endif %}
+
+{% if not disallow_native_types %}
+#include "mojo/public/cpp/bindings/lib/native_enum_serialization.h"
+#include "mojo/public/cpp/bindings/lib/native_struct_serialization.h"
+{%- endif %}
+
+{%- if export_header %}
+#include "{{export_header}}"
+{%- endif %}
+
+{{namespace_begin()}}
+
+{#- These are non-variant header only. #}
+{%- if not variant %}
+
+{#--- Struct Forward Declarations -#}
+{%- for struct in structs %}
+{%-   if struct|is_native_only_kind %}
+using {{struct.name}}DataView = mojo::native::NativeStructDataView;
+{%-   else %}
+class {{struct.name}}DataView;
+{%-   endif %}
+{%  endfor %}
+
+{#--- Union Forward Declarations -#}
+{%- for union in unions %}
+class {{union.name}}DataView;
+{%- endfor %}
+
+{#--- Enums #}
+{%- from "enum_macros.tmpl" import enum_forward%}
+{%- for enum in all_enums %}
+{%-   if enum|is_native_only_kind %}
+using {{enum|get_name_for_kind(flatten_nested_kind=True)}} = mojo::NativeEnum;
+{%-   else %}
+{{enum_forward(enum)}}
+{%-   endif %}
+{%- endfor %}
+
+{%- endif %}
+
+{#--- Enums #}
+{%- if variant %}
+{%-   for enum in enums %}
+using {{enum.name}} = {{enum.name}};  // Alias for definition in the parent namespace.
+{%-   endfor %}
+{%- endif %}
+
+{#--- Constants #}
+{%- for constant in module.constants %}
+{{constant|format_constant_declaration}};
+{%- endfor %}
+
+{#--- Struct Forward Declarations -#}
+{%  for struct in structs %}
+{%-   if struct|is_native_only_kind %}
+using {{struct.name}} = mojo::native::NativeStruct;
+using {{struct.name}}Ptr = mojo::native::NativeStructPtr;
+{%-   else %}
+class {{struct.name}};
+{%-     if struct|should_inline %}
+using {{struct.name}}Ptr = mojo::InlinedStructPtr<{{struct.name}}>;
+{%-     else %}
+using {{struct.name}}Ptr = mojo::StructPtr<{{struct.name}}>;
+{%-     endif %}
+{%-   endif %}
+{%  endfor %}
+
+{#--- Union Forward Declarations -#}
+{%  for union in unions %}
+class {{union.name}};
+{%    if union|should_inline_union %}
+typedef mojo::InlinedStructPtr<{{union.name}}> {{union.name}}Ptr;
+{%    else %}
+typedef mojo::StructPtr<{{union.name}}> {{union.name}}Ptr;
+{%    endif %}
+{%- endfor %}
+
+
+{#--- Interface Forward Declarations -#}
+{%  for interface in interfaces %}
+class {{interface.name}};
+using {{interface.name}}Ptr = mojo::InterfacePtr<{{interface.name}}>;
+{%-   if for_blink %}
+using Revocable{{interface.name}}Ptr = ::blink::RevocableInterfacePtr<{{interface.name}}>;
+{%-   endif %}
+using {{interface.name}}PtrInfo = mojo::InterfacePtrInfo<{{interface.name}}>;
+using ThreadSafe{{interface.name}}Ptr =
+    mojo::ThreadSafeInterfacePtr<{{interface.name}}>;
+using {{interface.name}}Request = mojo::InterfaceRequest<{{interface.name}}>;
+using {{interface.name}}AssociatedPtr =
+    mojo::AssociatedInterfacePtr<{{interface.name}}>;
+using ThreadSafe{{interface.name}}AssociatedPtr =
+    mojo::ThreadSafeAssociatedInterfacePtr<{{interface.name}}>;
+using {{interface.name}}AssociatedPtrInfo =
+    mojo::AssociatedInterfacePtrInfo<{{interface.name}}>;
+using {{interface.name}}AssociatedRequest =
+    mojo::AssociatedInterfaceRequest<{{interface.name}}>;
+{%  endfor %}
+
+
+{{namespace_end()}}
+
+{#- TODO(tikuta): Use forward declaration of native enum/struct here. #}
+
+{%- for header in extra_public_headers %}
+#include "{{header}}"
+{%- endfor %}
+
+#endif  // {{header_guard}}

mojo/public/tools/bindings/generators/cpp_templates/module-import-headers.h.tmpl

+// Copyright 2019 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.
+
+{%- if variant -%}
+{%-   set variant_path = "%s-%s"|format(module.path, variant) -%}
+{%- else -%}
+{%-   set variant_path = module.path -%}
+{%- endif -%}
+
+{%- set header_guard = "%s_IMPORT_HEADERS_H_"|format(
+        variant_path|upper|replace("/","_")|replace(".","_")|
+            replace("-", "_")) %}
+
+#ifndef {{header_guard}}
+#define {{header_guard}}
+
+{%- for import in imports %}
+{%-   if variant %}
+#include "{{"%s-%s.h"|format(import.path, variant)}}"
+#include "{{"%s-%s-import-headers.h"|format(import.path, variant)}}"
+{%-   else %}
+#include "{{import.path}}.h"
+#include "{{import.path}}-import-headers.h"
+{%-   endif %}
+{%- endfor %}
+
+#endif  // {{header_guard}}

mojo/public/tools/bindings/generators/cpp_templates/module-test-utils.cc.tmpl

@@ -52,6 +52,14 @@ namespace {{variant}} {
 #include "mojo/public/cpp/bindings/lib/wtf_serialization.h"
 {%- endif %}
 
+{%- for import in imports %}
+{%-   if variant %}
+#include "{{"%s-%s.h"|format(import.path, variant)}}"
+{%-   else %}
+#include "{{import.path}}.h"
+{%-   endif %}
+{%- endfor %}
+
 {# This is include guard for jumbo build. #}
 #ifndef {{header_guard_for_jumbo}}
 #define {{header_guard_for_jumbo}}

mojo/public/tools/bindings/generators/cpp_templates/module.cc.tmpl

@@ -41,6 +41,8 @@
 #include "{{module.path}}-params-data.h"
 #include "{{module.path}}-shared-message-ids.h"
 
+#include "{{variant_path}}-import-headers.h"
+
 {%- if for_blink %}
 #include "mojo/public/cpp/bindings/lib/wtf_serialization.h"
 {%- endif %}

mojo/public/tools/bindings/generators/cpp_templates/module.h.tmpl

@@ -54,13 +54,35 @@ namespace {{variant}} {
 #include "mojo/public/cpp/bindings/struct_traits.h"
 #include "mojo/public/cpp/bindings/union_traits.h"
 #include "{{module.path}}-shared.h"
+#include "{{variant_path}}-forward.h"
+
+{#- Imported struct and union types must be fully defined if used in this
+    mojom. #}
+{%- set import_definition_header = namespace(need=false) %}
+{%- for struct in structs %}
+{%-   for field in struct.fields %}
+{%-     if field.kind|is_object_kind or field.kind|is_union_kind %}
+{%-       set import_definition_header.need = true %}
+{%-     endif %}
+{%-   endfor %}
+{%- endfor %}
+
 {%- for import in imports %}
-{%-   if variant %}
+{%-   if import_definition_header.need %}
+{%-     if variant %}
 #include "{{"%s-%s.h"|format(import.path, variant)}}"
-{%-   else %}
+{%-     else %}
 #include "{{import.path}}.h"
+{%-     endif %}
+{%-   else %}
+{%-     if variant %}
+#include "{{"%s-%s-forward.h"|format(import.path, variant)}}"
+{%-     else %}
+#include "{{import.path}}-forward.h"
+{%-     endif %}
 {%-   endif %}
 {%- endfor %}
+
 {%- if not for_blink %}
 #include <string>
 #include <vector>
@@ -113,64 +135,6 @@ namespace {{variant}} {
 
 {{namespace_begin()}}
 
-{#--- Enums #}
-{%- if variant %}
-{%-   for enum in enums %}
-using {{enum.name}} = {{enum.name}};  // Alias for definition in the parent namespace.
-{%-   endfor %}
-{%- endif %}
-
-{#--- Constants #}
-{%- for constant in module.constants %}
-{{constant|format_constant_declaration}};
-{%- endfor %}
-
-{#--- Interface Forward Declarations -#}
-{%  for interface in interfaces %}
-class {{interface.name}};
-using {{interface.name}}Ptr = mojo::InterfacePtr<{{interface.name}}>;
-{%-   if for_blink %}
-using Revocable{{interface.name}}Ptr = ::blink::RevocableInterfacePtr<{{interface.name}}>;
-{%-   endif %}
-using {{interface.name}}PtrInfo = mojo::InterfacePtrInfo<{{interface.name}}>;
-using ThreadSafe{{interface.name}}Ptr =
-    mojo::ThreadSafeInterfacePtr<{{interface.name}}>;
-using {{interface.name}}Request = mojo::InterfaceRequest<{{interface.name}}>;
-using {{interface.name}}AssociatedPtr =
-    mojo::AssociatedInterfacePtr<{{interface.name}}>;
-using ThreadSafe{{interface.name}}AssociatedPtr =
-    mojo::ThreadSafeAssociatedInterfacePtr<{{interface.name}}>;
-using {{interface.name}}AssociatedPtrInfo =
-    mojo::AssociatedInterfacePtrInfo<{{interface.name}}>;
-using {{interface.name}}AssociatedRequest =
-    mojo::AssociatedInterfaceRequest<{{interface.name}}>;
-{%  endfor %}
-
-{#--- Struct Forward Declarations -#}
-{%  for struct in structs %}
-{%-   if struct|is_native_only_kind %}
-using {{struct.name}} = mojo::native::NativeStruct;
-using {{struct.name}}Ptr = mojo::native::NativeStructPtr;
-{%-   else %}
-class {{struct.name}};
-{%-     if struct|should_inline %}
-using {{struct.name}}Ptr = mojo::InlinedStructPtr<{{struct.name}}>;
-{%-     else %}
-using {{struct.name}}Ptr = mojo::StructPtr<{{struct.name}}>;
-{%-     endif %}
-{%-   endif %}
-{%  endfor %}
-
-{#--- Union Forward Declarations -#}
-{%  for union in unions %}
-class {{union.name}};
-{%    if union|should_inline_union %}
-typedef mojo::InlinedStructPtr<{{union.name}}> {{union.name}}Ptr;
-{%    else %}
-typedef mojo::StructPtr<{{union.name}}> {{union.name}}Ptr;
-{%    endif %}
-{%- endfor %}
-
 {#--- Interfaces -#}
 {%  for interface in interfaces %}
 {%    include "interface_declaration.tmpl" %}

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

@@ -376,10 +376,18 @@ class Generator(generator.Generator):
   def _GenerateModuleHeader(self):
     return self._GetJinjaExports()
 
+  @UseJinja("module-forward.h.tmpl")
+  def _GenerateModuleForwardHeader(self):
+    return self._GetJinjaExports()
+
   @UseJinja("module.cc.tmpl")
   def _GenerateModuleSource(self):
     return self._GetJinjaExports()
 
+  @UseJinja("module-import-headers.h.tmpl")
+  def _GenerateModuleImportHeadersHeader(self):
+    return self._GetJinjaExports()
+
   @UseJinja("module-shared.h.tmpl")
   def _GenerateModuleSharedHeader(self):
     return self._GetJinjaExports()
@@ -428,8 +436,12 @@ class Generator(generator.Generator):
       suffix = "-%s" % self.variant if self.variant else ""
       self.Write(self._GenerateModuleHeader(),
                  "%s%s.h" % (self.module.path, suffix))
+      self.Write(self._GenerateModuleForwardHeader(),
+                 "%s%s-forward.h" % (self.module.path, suffix))
       self.Write(self._GenerateModuleSource(),
                  "%s%s.cc" % (self.module.path, suffix))
+      self.Write(self._GenerateModuleImportHeadersHeader(),
+                 "%s%s-import-headers.h" % (self.module.path, suffix))
       self.Write(self._GenerateModuleTestUtilsHeader(),
                  "%s%s-test-utils.h" % (self.module.path, suffix))
       self.Write(self._GenerateModuleTestUtilsSource(),

mojo/public/tools/bindings/mojom.gni

@@ -754,10 +754,12 @@ template("mojom") {
         variant_dash_suffix = "-${variant}"
       }
       generator_cpp_outputs += [
-        "{{source_gen_dir}}/{{source_file_part}}${variant_dash_suffix}.cc",
-        "{{source_gen_dir}}/{{source_file_part}}${variant_dash_suffix}.h",
+        "{{source_gen_dir}}/{{source_file_part}}${variant_dash_suffix}-forward.h",
+        "{{source_gen_dir}}/{{source_file_part}}${variant_dash_suffix}-import-headers.h",
         "{{source_gen_dir}}/{{source_file_part}}${variant_dash_suffix}-test-utils.cc",
         "{{source_gen_dir}}/{{source_file_part}}${variant_dash_suffix}-test-utils.h",
+        "{{source_gen_dir}}/{{source_file_part}}${variant_dash_suffix}.cc",
+        "{{source_gen_dir}}/{{source_file_part}}${variant_dash_suffix}.h",
       ]
       enabled_sources = []
       if (defined(bindings_configuration.blacklist)) {
@@ -830,10 +832,12 @@ template("mojom") {
         foreach(source, invoker.sources) {
           filelist += [ rebase_path("$source", root_build_dir) ]
           outputs += [
-            "$target_gen_dir/${source}${variant_dash_suffix}.cc",
-            "$target_gen_dir/${source}${variant_dash_suffix}.h",
+            "$target_gen_dir/${source}${variant_dash_suffix}-forward.h",
+            "$target_gen_dir/${source}${variant_dash_suffix}-import-headers.h",
             "$target_gen_dir/${source}${variant_dash_suffix}-test-utils.cc",
             "$target_gen_dir/${source}${variant_dash_suffix}-test-utils.h",
+            "$target_gen_dir/${source}${variant_dash_suffix}.cc",
+            "$target_gen_dir/${source}${variant_dash_suffix}.h",
           ]
         }