How to build a .mojom target with ninja

[Chacha Marwa]

Hi,

Noob here  i was learning to use mojom interface and got stuck for four days now with this error here.

ninja: error: unknown target '/home/user_name/chromium/src/example/public/mojom'

i was following this documentation here (https://chromium.googlesource.com/chromium/src.git/+/master/docs/mojo_and_services.md), and am sure that i am missing out a certain step while following up the illustrations on the page.

what i did:

1. ~/chromium/src$ mkdir -p example/public/mojom

2. ~/chromium/src/example/public/mojom$ touch ping_responder.mojom && nano ping_responder.mojom

pasted this interface data in  ping_responder.mojom

module example.mojom;

interface PingResponder {

  // Receives a "Ping" and responds with a random integer.

  Ping() => (int32 random);

};

3. ~/chromium/src/example/public/mojom$ touch BUILD.gn && nano BUILD.gn

pasted this details in BUILD.gn

import("//mojo/public/tools/bindings/mojom.gni")

mojom("mojom") {

  sources = [ "ping_responder.mojom" ]

}

4. ~/chromium/src/example/public/mojom$ gn gen out/r

i did this because of step 5 threw an error of not finding the out/r directory while excuting the command on step 5 (am not sure if this i right)

5.~/chromium/src/example/public/mojom$ ninja -C out/r ~/chromium/src/example/public/mojom

hope one you guys can spot my mistake there. also on top of that i would like to ask these questions here

1. is it right to create a BUILD.gn manualy like how i did on step 3 there.

(i asked because i was thinking that BUILD.gn is suposed

 to be automatically genreated from a certain command that i don't know like (ie. gn gen args.gn)

2. i get comfused by the ending line of this ninja statement while building js bingings and c++ bindings because the former (js) adds a colon and the other doesn't.

for c++ 

ninja -C out/r ~/chromium/src/example/public/mojom

for js

ninja -C out/r services/echo/public/interfaces:interfaces_js

NB; just stabed this group while searching for solution am not as well sure if its a right place to post this, in any case if this is not an apropriate place for this i present my apologies in advance in respect to ever one annoyed by my post thanks.

[Joe Mason]

GN starts at one top-level target and then searches all its dependencies for other targets to build. So even though you added an //example/public/mojom target, GN can't find it unless some other target references it.

As a quick test, try adding "//example/public/mojom" to the gn_all deps in chromium/src/BUILD.gn:

group("gn_all") {

testonly = true

deps = [

":gn_visibility",

"//base:base_perftests",

(etc)

(There's a comment at the top of that BUILD.gn file explaining how this works a bit more.)

deps = [ "//example/public/mojom" ]

To 

--
You received this message because you are subscribed to the Google Groups "chromium-mojo" group.
To unsubscribe from this group and stop receiving emails from it, send an email to chromium-moj...@chromium.org.
To view this discussion on the web visit https://groups.google.com/a/chromium.org/d/msgid/chromium-mojo/1ba33897-7eaf-48b6-b196-fb54047f0db2n%40chromium.org.

[Chacha Marwa]

Thanks for the reply Joe, that is what i was missing.

but after i added the that the generation proces started and threw this exception 

[1/1] Regenerating ninja files
[5/7] ACTION //services/echo/public/interfaces:interfaces_js__generator(//build/toolchain/linux:clang_x64)
FAILED: gen/services/echo/public/interfaces/echo.mojom.js gen/services/echo/public/interfaces/echo.mojom.externs.js gen/services/echo/public/interfaces/echo.mojom-lite.js gen/services/echo/public/interfaces/echo.mojom.html gen/services/echo
/public/interfaces/echo.mojom-lite-for-compile.js  
python ../../../../../../mojo/public/tools/bindings/mojom_bindings_generator.py --use_bundled_pylibs -o gen generate -d ../../../../../../ -I ../../../../../../ --bytecode_path gen/mojo/public/tools/bindings --filelist=__services_echo_publi
c_interfaces_interfaces_js__generator___build_toolchain_linux_clang_x64__rule..rsp -g javascript --js_bindings_mode=new --scrambled_message_id_salt_path ../../../../../../chrome/VERSION
Traceback (most recent call last):
 File "../../../../../../mojo/public/tools/bindings/mojom_bindings_generator.py", line 390, in <module>
   sys.exit(main())
 File "../../../../../../mojo/public/tools/bindings/mojom_bindings_generator.py", line 385, in main
   return args.func(args, remaining_args)
 File "../../../../../../mojo/public/tools/bindings/mojom_bindings_generator.py", line 250, in _Generate
   RelativePath(filename, args.depth, args.output_dir), [])
 File "../../../../../../mojo/public/tools/bindings/mojom_bindings_generator.py", line 95, in __init__
   raise Exception("Invalid input path %s" % path)
Exception: Invalid input path ../../echo.mojom
ninja: build stopped: subcommand failed.

what am i missing there?

[Chacha Marwa]

OKey so  imanaged to solve the error above after reading the bindings generator script mojo_bindings_generator.py

it turns out that i was running ninja inside a wrong directory

like this.

~/chromium/src/example/public/mojom$ ninja -C out/r example/public/mojom

there fore ninja couldn't determine a relative path from the directory where i was (current working directory) this one (example/public/mojom)

so i had to switch/go back to the root dir  "src/" and GN a new output dir from there and run ninja from there and everthing went well .

Thanks Joe Mason for helping me out with the first issue.

[Joe Mason]

Glad you got it working!

[Bharani Tharan]

I'm also facing the ninja: error: unknown target '/home/user_name/repo/chromium/src/chrome/services/math/public/mojom'

After I have added below code in BUILD.gn in src folder

+++++++++++++++++++

group("gn_all") {

testonly = true

deps = [

":gn_visibility",

"//base:base_perftests",

+++++++++++++++++++

Then Build the particular service(math) using ninja -C out/r ~/chromium/src/example/public/mojom . This case I have observed below error.

Error:

ninja: Entering directory `out/r'
[0/1] Regenerating ninja files
ERROR Unresolved dependencies.
//:gn_all(//build/toolchain/linux:clang_x64)
  needs //:gn_visibility(//build/toolchain/linux:clang_x64)

FAILED: build.ninja.stamp
../../../../../../../buildtools/linux64/gn --root=../../../../../../.. -q --regeneration gen .
ninja: error: rebuilding 'build.ninja': subcommand failed

Kindly support me to solve the error. Also kindly share the example source code for better understanding about client server communication for browser and render process.