[run host script] update stderr output for host script.

- Use subprocess.PIPE for subprocess in order to show subprocess error
  in stdout correctly.
- Formate stderr with .decode("utf-8")
- Remove the if statements that checks if host_script is defined. The
  template currently fails if host_script is not defined.
- Add an else statement in src/testing/system-validaion/ui/BUILD.gn for
  when building with asan variant. It seems that GN will error with
  unresolved target for flatland_view_provider_with_host_script.

Bug: 116493
Change-Id: I6a7e2aa218af7bdd6d6070f84e13acbf2fc25b35
Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/774007
Reviewed-by: Oliver Newman <olivernewman@google.com>
Reviewed-by: Satsuki Ueno <satsukiu@google.com>
Reviewed-by: Marc-Antoine Ruel <maruel@google.com>
Commit-Queue: Yuan Zhi <yuanzhi@google.com>

Author: yz-zhi

build/testing/run_target_test_and_host_script.gni

@@ -93,20 +93,18 @@ template("run_target_test_and_host_script") {
     }
   }
 
-  if (defined(invoker.host_script)) {
-    _script_bin_name =
-        get_path_info(get_label_info(invoker.host_script, "target_out_dir"),
-                      "file")
-    host_test_data("host_script_for_${target_name}") {
-      sources = [ "${root_out_dir}/${_script_bin_name}" ]
-      deps = [ invoker.host_script ]
-    }
-    _data_deps += [ ":host_script_for_${target_name}" ]
-    _args += [
-      "--host-script-bin",
-      rebase_path("${root_out_dir}/${_script_bin_name}", root_build_dir),
-    ]
+  _script_bin_name =
+      get_path_info(get_label_info(invoker.host_script, "target_out_dir"),
+                    "file")
+  host_test_data("host_script_for_${target_name}") {
+    sources = [ "${root_out_dir}/${_script_bin_name}" ]
+    deps = [ invoker.host_script ]
   }
+  _data_deps += [ ":host_script_for_${target_name}" ]
+  _args += [
+    "--host-script-bin",
+    rebase_path("${root_out_dir}/${_script_bin_name}", root_build_dir),
+  ]
 
   if (defined(invoker.host_script_args)) {
     foreach(_host_script_arg, invoker.host_script_args) {

build/testing/run_target_test_and_host_script.py

@@ -42,7 +42,7 @@ def run_target_test(
         outdir
     ]
     args += ffx_test_args
-    return subprocess.run(args, stderr=sys.stdout)
+    return subprocess.run(args, text=True, stderr=subprocess.PIPE)
 
 
 def get_test_suite_artifact_dir(
@@ -78,7 +78,8 @@ def run_host_script(
     substituted_args = []
     for arg in script_args:
         substituted_args.append(do_variable_substitution(arg))
-    return subprocess.run([script_bin] + substituted_args, stderr=sys.stdout)
+    return subprocess.run(
+        [script_bin] + substituted_args, text=True, stderr=subprocess.PIPE)
 
 
 class RunTargetTestWithHostScript(unittest.TestCase):
@@ -97,7 +98,7 @@ def runTest(self):
             self.args.ffx_test_args)
         self.assertEqual(
             self.test_status.returncode, 0,
-            "test returned non-zero status, error: %s" %
+            "test returned non-zero status, stderr: %s" %
             self.test_status.stderr)
 
     def tearDown(self):
@@ -111,7 +112,7 @@ def tearDown(self):
                 self.args.host_script_bin, self.args.host_script_args)
             self.assertEqual(
                 script_status.returncode, 0,
-                "host script returned non-zero status, error: %s" %
+                "host script returned non-zero status, stderr: %s" %
                 script_status.stderr)
 
 

src/testing/system-validation/ui/BUILD.gn

@@ -96,4 +96,7 @@ if (is_host && target_cpu == "x64" && !is_asan) {
     ]
     environments = [ emu_env ]
   }
+} else {
+  group("flatland_view_provider_with_host_script") {
+  }
 }