[3.14] gh-131531: Android test fixes (GH-136845) (#136962)

Modifies the test runner script to no longer export the the HOST environment
variable, and to allow for tests that produce no Python output (output from the
Android console is still expected and required). These changes stem from
knowledge gained during developing a PR for Android support in cibuildwheel.
(cherry picked from commit 149bddcc21)

Co-authored-by: Malcolm Smith <smith@chaquo.com>

Android/android.py

@@ -50,7 +50,19 @@
     + (".bat" if os.name == "nt" else "")
 )
 
-logcat_started = False
+# Whether we've seen any output from Python yet.
+python_started = False
+
+# Buffer for verbose output which will be displayed only if a test fails and
+# there has been no output from Python.
+hidden_output = []
+
+
+def log_verbose(context, line, stream=sys.stdout):
+    if context.verbose:
+        stream.write(line)
+    else:
+        hidden_output.append((stream, line))
 
 
 def delete_glob(pattern):
@@ -118,7 +130,7 @@ def android_env(host):
     env_script = ANDROID_DIR / "android-env.sh"
     env_output = subprocess.run(
         f"set -eu; "
-        f"export HOST={host}; "
+        f"HOST={host}; "
         f"PREFIX={prefix}; "
         f". {env_script}; "
         f"export",
@@ -453,17 +465,19 @@ async def logcat_task(context, initial_devices):
 
     # `--pid` requires API level 24 or higher.
     args = [adb, "-s", serial, "logcat", "--pid", pid,  "--format", "tag"]
-    hidden_output = []
+    logcat_started = False
     async with async_process(
         *args, stdout=subprocess.PIPE, stderr=subprocess.STDOUT,
     ) as process:
         while line := (await process.stdout.readline()).decode(*DECODE_ARGS):
             if match := re.fullmatch(r"([A-Z])/(.*)", line, re.DOTALL):
+                logcat_started = True
                 level, message = match.groups()
             else:
-                # If the regex doesn't match, this is probably the second or
+                # If the regex doesn't match, this is either a logcat startup
-                # subsequent line of a multi-line message. Python won't produce
+                # error, or the second or subsequent line of a multi-line
-                # such messages, but other components might.
+                # message. Python won't produce multi-line messages, but other
+                # components might.
                 level, message = None, line
 
             # Exclude high-volume messages which are rarely useful.
@@ -483,25 +497,22 @@ async def logcat_task(context, initial_devices):
             # tag indicators from Python's stdout and stderr.
             for prefix in ["python.stdout: ", "python.stderr: "]:
                 if message.startswith(prefix):
-                    global logcat_started
+                    global python_started
-                    logcat_started = True
+                    python_started = True
                     stream.write(message.removeprefix(prefix))
                     break
             else:
-                if context.verbose:
+                # Non-Python messages add a lot of noise, but they may
-                    # Non-Python messages add a lot of noise, but they may
+                # sometimes help explain a failure.
-                    # sometimes help explain a failure.
+                log_verbose(context, line, stream)
-                    stream.write(line)
-                else:
-                    hidden_output.append(line)
 
         # If the device disconnects while logcat is running, which always
         # happens in --managed mode, some versions of adb return non-zero.
         # Distinguish this from a logcat startup error by checking whether we've
-        # received a message from Python yet.
+        # received any logcat messages yet.
         status = await wait_for(process.wait(), timeout=1)
         if status != 0 and not logcat_started:
-            raise CalledProcessError(status, args, "".join(hidden_output))
+            raise CalledProcessError(status, args)
 
 
 def stop_app(serial):
@@ -516,16 +527,6 @@ async def gradle_task(context):
         task_prefix = "connected"
         env["ANDROID_SERIAL"] = context.connected
 
-    hidden_output = []
-
-    def log(line):
-        # Gradle may take several minutes to install SDK packages, so it's worth
-        # showing those messages even in non-verbose mode.
-        if context.verbose or line.startswith('Preparing "Install'):
-            sys.stdout.write(line)
-        else:
-            hidden_output.append(line)
-
     if context.command:
         mode = "-c"
         module = context.command
@@ -550,7 +551,7 @@ def log(line):
     ]
     if context.verbose >= 2:
         args.append("--info")
-    log("> " + join_command(args))
+    log_verbose(context, f"> {join_command(args)}\n")
 
     try:
         async with async_process(
@@ -558,7 +559,12 @@ def log(line):
             stdout=subprocess.PIPE, stderr=subprocess.STDOUT,
         ) as process:
             while line := (await process.stdout.readline()).decode(*DECODE_ARGS):
-                log(line)
+                # Gradle may take several minutes to install SDK packages, so
+                # it's worth showing those messages even in non-verbose mode.
+                if line.startswith('Preparing "Install'):
+                    sys.stdout.write(line)
+                else:
+                    log_verbose(context, line)
 
             status = await wait_for(process.wait(), timeout=1)
             if status == 0:
@@ -566,11 +572,6 @@ def log(line):
             else:
                 raise CalledProcessError(status, args)
     finally:
-        # If logcat never started, then something has gone badly wrong, so the
-        # user probably wants to see the Gradle output even in non-verbose mode.
-        if hidden_output and not logcat_started:
-            sys.stdout.write("".join(hidden_output))
-
         # Gradle does not stop the tests when interrupted.
         if context.connected:
             stop_app(context.connected)
@@ -600,6 +601,12 @@ async def run_testbed(context):
     except* MySystemExit as e:
         raise SystemExit(*e.exceptions[0].args) from None
     except* CalledProcessError as e:
+        # If Python produced no output, then the user probably wants to see the
+        # verbose output to explain why the test failed.
+        if not python_started:
+            for stream, line in hidden_output:
+                stream.write(line)
+
         # Extract it from the ExceptionGroup so it can be handled by `main`.
         raise e.exceptions[0]