Simplify Python code for running WPT tests

Combine `run.py` and `update.py` into `servowpt.py` in order to allow
them to share code. Import them directly into the mach script to avoid
having to call `compile` and `exec` on the code. This makes it clearer
how they are executed. In addition, move all of the setup into
`setupwpt.py` to avoid differences between tests executed via mach and
not. Finally, be more ambitious when detecting the build to use. If none
was specified, try to use the one that exists between "release" and
"debug."

tests/wpt/servowpt.py

@@ -0,0 +1,162 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+import os
+import sys
+
+import grouping_formatter
+import mozlog
+import multiprocessing
+
+SCRIPT_PATH = os.path.abspath(os.path.dirname(__file__))
+SERVO_ROOT = os.path.abspath(os.path.join(SCRIPT_PATH, "..", ".."))
+WPT_TOOLS_PATH = os.path.join(SCRIPT_PATH, "web-platform-tests", "tools")
+CERTS_PATH = os.path.join(WPT_TOOLS_PATH, "certs")
+
+sys.path.insert(0, WPT_TOOLS_PATH)
+import update  # noqa: F401,E402
+import localpaths  # noqa: F401,E402
+
+
+def determine_build_type(kwargs: dict, target_dir: str):
+    if kwargs["release"]:
+        return "release"
+    elif kwargs["debug"]:
+        return "debug"
+    elif os.path.exists(os.path.join(target_dir, "debug")):
+        return "debug"
+    elif os.path.exists(os.path.join(target_dir, "release")):
+        return "release"
+    return "debug"
+
+
+def set_if_none(args: dict, key: str, value):
+    if key not in args or args[key] is None:
+        args[key] = value
+
+
+def update_args_for_layout_2020(kwargs: dict):
+    if kwargs.pop("layout_2020"):
+        kwargs["test_paths"]["/"]["metadata_path"] = os.path.join(
+            SCRIPT_PATH, "metadata-layout-2020"
+        )
+        kwargs["test_paths"]["/_mozilla/"]["metadata_path"] = os.path.join(
+            SCRIPT_PATH, "mozilla", "meta-layout-2020"
+        )
+        kwargs["include_manifest"] = os.path.join(
+            SCRIPT_PATH, "include-layout-2020.ini"
+        )
+
+
+def run_tests(**kwargs):
+    from wptrunner import wptrunner
+    from wptrunner import wptcommandline
+
+    # By default, Rayon selects the number of worker threads based on the
+    # available CPU count. This doesn't work very well when running tests on CI,
+    # since we run so many Servo processes in parallel. The result is a lot of
+    # extra timeouts. Instead, force Rayon to assume we are running on a 2 CPU
+    # environment.
+    os.environ["RAYON_RS_NUM_CPUS"] = "2"
+    os.environ["RUST_BACKTRACE"] = "1"
+    os.environ["HOST_FILE"] = os.path.join(SERVO_ROOT, "tests", "wpt", "hosts")
+
+    set_if_none(kwargs, "product", "servo")
+    set_if_none(kwargs, "config", os.path.join(SCRIPT_PATH, "config.ini"))
+    set_if_none(kwargs, "include_manifest", os.path.join(SCRIPT_PATH, "include.ini"))
+    set_if_none(kwargs, "manifest_update", False)
+    set_if_none(kwargs, "processes", multiprocessing.cpu_count())
+
+    set_if_none(kwargs, "ca_cert_path", os.path.join(CERTS_PATH, "cacert.pem"))
+    set_if_none(
+        kwargs, "host_key_path", os.path.join(CERTS_PATH, "web-platform.test.key")
+    )
+    set_if_none(
+        kwargs, "host_cert_path", os.path.join(CERTS_PATH, "web-platform.test.pem")
+    )
+
+    kwargs["user_stylesheets"].append(os.path.join(SERVO_ROOT, "resources", "ahem.css"))
+
+    if "CARGO_TARGET_DIR" in os.environ:
+        target_dir = os.path.join(os.environ["CARGO_TARGET_DIR"])
+    else:
+        target_dir = os.path.join(SERVO_ROOT, "target")
+    default_binary_path = os.path.join(
+        target_dir, determine_build_type(kwargs, target_dir), "servo"
+    )
+    if sys.platform == "win32":
+        target_dir += ".exe"
+
+    set_if_none(kwargs, "binary", default_binary_path)
+    set_if_none(kwargs, "webdriver_binary", default_binary_path)
+
+    if kwargs.pop("rr_chaos"):
+        kwargs["debugger"] = "rr"
+        kwargs["debugger_args"] = "record --chaos"
+        kwargs["repeat_until_unexpected"] = True
+        # TODO: Delete rr traces from green test runs?
+
+    prefs = kwargs.pop("prefs")
+    if prefs:
+        kwargs["binary_args"] = ["--pref=" + pref for pref in prefs]
+
+    if not kwargs.get("no_default_test_types"):
+        test_types = {
+            "servo": ["testharness", "reftest", "wdspec"],
+            "servodriver": ["testharness", "reftest"],
+        }
+        product = kwargs.get("product") or "servo"
+        kwargs["test_types"] = test_types[product]
+
+    wptcommandline.check_args(kwargs)
+    update_args_for_layout_2020(kwargs)
+
+    mozlog.commandline.log_formatters["servo"] = (
+        grouping_formatter.ServoFormatter,
+        "Servo's grouping output formatter",
+    )
+    mozlog.commandline.log_formatters["servojson"] = (
+        grouping_formatter.ServoJsonFormatter,
+        "Servo's JSON logger of unexpected results",
+    )
+
+    use_mach_logging = False
+    if len(kwargs["test_list"]) == 1:
+        file_ext = os.path.splitext(kwargs["test_list"][0])[1].lower()
+        if file_ext in [".htm", ".html", ".js", ".xhtml", ".xht", ".py"]:
+            use_mach_logging = True
+
+    if use_mach_logging:
+        wptrunner.setup_logging(kwargs, {"mach": sys.stdout})
+    else:
+        wptrunner.setup_logging(kwargs, {"servo": sys.stdout})
+
+    success = wptrunner.run_tests(**kwargs)
+    return 0 if success else 1
+
+
+def update_tests(**kwargs):
+    from update import updatecommandline
+
+    set_if_none(kwargs, "product", "servo")
+    set_if_none(kwargs, "config", os.path.join(SCRIPT_PATH, "config.ini"))
+    kwargs["store_state"] = False
+
+    updatecommandline.check_args(kwargs)
+
+    logger = update.setup_logging(kwargs, {"mach": sys.stdout})
+    return_value = update.run_update(logger, **kwargs)
+    return 1 if return_value is update.exit_unclean else 0
+
+
+def main():
+    from wptrunner import wptcommandline
+
+    parser = wptcommandline.create_parser()
+    kwargs = vars(parser.parse_args())
+    return run_tests(**kwargs)
+
+
+if __name__ == "__main__":
+    sys.exit(0 if main() else 1)