[Fuchsia] Generate <test_target_name> Wrapper in Output Directory

Allow fuchsia_test_runner template to create an executable wrapper with
same name as test target itself.

When building a test target, in addition to the test component
<test_target_name>_component, three wrapper scripts are created:
1. deploy_<test_target_name>, for deploying the Fuchsia package onto a
   device
2. run_<test_target_name>, for running the Fuchsia package on the device
3. <test_target_name>, for running the Fuchsia package on the device
The first two executables will be found in ${OUTPUT_DIR}/bin whereas
%package% will be found directly in the output directory.

This change also allows ninja to identify which test target to build
in the case of duplicate target names (e.g. unit_tests) since ninja
prioritizes executable targets.

Bug: 1268956
Change-Id: I582ab0d22a1b19b0e8df1bb96e0c8d207b021a2c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3296401
Auto-Submit: Chong Gu <chonggu@google.com>
Reviewed-by: David Dorwin <ddorwin@chromium.org>
Commit-Queue: Chong Gu <chonggu@google.com>
Cr-Commit-Position: refs/heads/main@{#950169}

build/config/fuchsia/generate_runner_scripts.gni

@@ -151,6 +151,17 @@ template("fuchsia_run_script_with_packages") {
       ]
     }
   }
+
+  # Create a wrapper script rather than using a group() in order to ensure
+  # "ninja $target_name" always works.
+  if (defined(invoker.executable_wrapper)) {
+    generate_wrapper(invoker.executable_wrapper) {
+      forward_variables_from(invoker, TESTONLY_AND_VISIBILITY)
+      executable = _generated_script_path
+      wrapper_script = "$root_build_dir/${invoker.executable_wrapper}"
+      deps = [ ":${invoker._run_target}" ]
+    }
+  }
 }
 
 # Generates a script which deploys a package to the TUF repo of a Fuchsia
@@ -203,6 +214,7 @@ template("fuchsia_test_runner") {
       executable_args = []
     }
     output_name_format = "run_%package%"
+    executable_wrapper = invoker.target_name
 
     # Populate the arguments used by the test runner, defined at build-time.
     executable_args += [
@@ -251,14 +263,6 @@ template("fuchsia_test_runner") {
     testonly = invoker.testonly
     include_fuchsia_build_dir = true
   }
-
-  group(target_name) {
-    forward_variables_from(invoker, TESTONLY_AND_VISIBILITY)
-    deps = [
-      ":${_install_target}",
-      ":${_run_target}",
-    ]
-  }
 }
 
 # Transitional target that aliases "fuchsia_package_runner" to an installer

docs/fuchsia/build_instructions.md

@@ -268,13 +268,11 @@ that make working with both Fuchsia and Chromium checkouts easier.
 
 * `default_fuchsia_build_dir_for_installation`. Point this to an output
   directory in Fuchsia. For instance. `/path/to/src/fuchsia/out/qemu-x64`. This
-  will automatically add the `--fuchsia-out-dir` flag to most `run_*` and
-  `deploy_*` scripts.
+  will automatically add the `--fuchsia-out-dir` flag to wrapper scripts.
 * `default_fuchsia_device_node_name`. Set this to a Fuchsia device node name.
-  This will automatically add the `--node-name` flag to most `run_*` and
-  `deploy_*` scripts.
-* Finally, use the `-d` flag to `run_*` scripts to execute them on an already
-  running device or emulator, rather than starting an ephemeral emulator
-  instance. This speeds up subsequent runs since the runner script does not need
-  to wait for the emulator instance to boot and only differential changes are
-  pushed to the device.
+  This will automatically add the `--node-name` flag to most wrapper scripts.
+* Finally, use the `-d` flag when running the <test_target_name> wrappers to
+  execute them on an already running device or emulator, rather than starting an
+  ephemeral emulator instance. This speeds up subsequent runs since the runner
+  script does not need to wait for the emulator instance to boot and only
+  differential changes are pushed to the device.

docs/fuchsia/gtests.md

@@ -1,10 +1,19 @@
 # Deploying and running gtests on Fuchsia.
 
 Fuchsia gtest binaries are deployed and executed via scripts that are
-automatically generated by the `test()` GN target.
-The binaries can deploy to either emulators started by the runner script,
-an existing emulator instance, or a physical device. To build a gtest binary,
-check this [documentation](build_instructions.md).
+automatically generated by the `test()` GN target. For each test, three wrapper
+scripts are created:
+
+1. deploy_<test_target_name>, for deploying the Fuchsia package onto a device
+2. run_<test_target_name>, for running the Fuchsia package on the device
+3. <test_target_name>, for running the Fuchsia package on the device
+
+The first two executables are found in ${OUTPUT_DIR}/bin whereas the last one
+will be found directly in the output directory.
+
+The aforementioned devices can be either emulators started by the scripts
+themselves, an existing emulator instance, or a physical device. To build a
+gtest binary, check this [documentation](build_instructions.md).
 
 For the sake of this example, we will be using `base_unittests` as the package
 we wish to install and/or execute.
@@ -14,7 +23,7 @@ we wish to install and/or execute.
 The test script brings up an emulator, runs the tests on it, and
 shuts the emulator down when finished.
 ```bash
-$ out/fuchsia/bin/run_base_unittests
+$ out/fuchsia/base_unittests
 ```
 
 The flag `--custom-image` can be used to specify the Fuchsia boot image used
@@ -27,7 +36,7 @@ workstation image.
 Note the `-d` flag, which is an alias for `--device`.
 
 ```bash
-$ out/fuchsia/bin/run_base_unittests -d
+$ out/fuchsia/base_unittests -d
 ```
 
 ## Run on a device paved with Fuchsia built from source
@@ -36,7 +45,7 @@ Make sure that the CPU architecture of your Chromium output directory matches
 the architecture of the Fuchsia output directory (x64==x64, arm64==arm64, etc.).
 
 ```bash
-$ out/fuchsia/bin/run_base_unittests -d
+$ out/fuchsia/base_unittests -d
 --fuchsia-out-dir=/path/to/fuchsia/outdir
 ```
 
@@ -48,17 +57,17 @@ default_fuchsia_build_dir_for_installation = "/path/to/fuchsia/outdir"
 ```
 
 With this flag in place, the `--fuchsia-out-dir` flag will automatically be
-used whenever you `run_` or `install_` Fuchsia packages, making your command
-lines much shorter:
+used whenever you use the wrapper scripts to run or deploy Fuchsia packages,
+making your command lines much shorter:
 
 ```bash
-$ out/fuchsia/bin/run_base_unittests -d
+$ out/fuchsia/base_unittests -d
 ```
 
 ## Install on a device running Fuchsia built from source
 
 ```bash
-$ out/fuchsia/bin/install_base_unittests
+$ out/fuchsia/bin/deploy_base_unittests
 --fuchsia-out-dir=/path/to/fuchsia/outdir
 ```
 
@@ -75,7 +84,7 @@ Note the `--ssh-config` flag, which should point to the config file used to set
 up the connection between the host and the remote device.
 
 ```bash
-$ out/fuchsia/bin/run_base_unittests -d
+$ out/fuchsia/base_unittests -d
 --host=localhost --ssh-config=/path/to/ssh/config
 ```