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FIDL

FIDL targets generate implicit Dart bindings targets. To use the bindings generated for:

//foo/bar
//foo/bar:blah

add a dependencies in BUILD.gn:

deps = [
   ...
   "//foo/bar",
   "//foo/bar:blah",
   ...
]

There are 3 files generated for dart from FIDL. These are found in out/default/dartlang/gen/<path-to-target>/<fidl-servicename>_package/lib

  • fidl.dart - the synchronous bindings
  • fidl_async.dart - the asynchronous bindings
  • fidl_test.dart - the stubbed out implementation of the service.
import "package:fidl_foo_bar/fidl.dart";
import "package:fidl_foo_bar_blah/fidl_async.dart";

Known issues

Multiple FIDL targets in a single BUILD file

If two FIDL targets coexist in a single BUILD file:

  • Their respective, generated files will currently be placed in the same subdirectory of the output directory. This means that files belonging to one target will be available to clients of the other target, and this will likely confuse the analyzer. This should not be a build issue now but could become one once the generated Dart files are placed in separate directories if clients do not correctly set up their dependencies.
  • Depending on one of these targets from another FIDL target that is used by a Dart package leads to a Unable to read Dart source ... error. The bindings generator for FIDL builds Dart package names based on the directory structure containing the included FIDL file, while GN (used to compute dependencies for the Dart package) does so using the full GN target name. For example: depending on lib/foo/fidl:bar generates a package like lib.foo.fidl._bar. Depending on the top-level target lib/foo/fidl generates the package lib.foo.fidl, which coincides with the Dart FIDL binding's assumptions.

Calling a FIDL service

The generated bindings for Dart require the importing of fuchsia_services.

import 'package:fuchsia_services/services.dart';

In order to use the Launcher service to start services that implement a FIDL interface, you need to have the fuchsia.sys.Launcher service declared in the .cmx