Implement the prepare_bazel_test_env script am: 2178bb2de9 am: 8eb6bb443e am: 0fa3de4e84 am: 33631428e8

Original change: https://android-review.googlesource.com/c/platform/build/pesto/+/1677135

Change-Id: Ia199349aff514f07be49051f3e762c8da901b47a

2 files changed, 734 insertions, 0 deletions

diff --git a/experiments/prepare_bazel_test_env/bazelenv.py b/experiments/prepare_bazel_test_env/bazelenv.py
new file mode 100644
index 0000000..e42e767
--- /dev/null
+++ b/experiments/prepare_bazel_test_env/bazelenv.py
@@ -0,0 +1,643 @@
+# Copyright (C) 2021 The Android Open Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+"""Core logic for generating, syncing, and cleaning up a Bazel environment."""
+import abc
+import datetime
+import logging
+import os
+import pathlib
+import re
+import shutil
+import subprocess
+from typing import Set, Dict, List
+
+# Regex for BUILD files used to identify them since they can be named
+# BUILD or BUILD.bazel.
+BUILD_FILENAME_REGEX = re.compile("(BUILD|BUILD.bazel)")
+
+
+class Error(Exception):
+    """Base Error that all other errors the system throws are descendants of."""
+    pass
+
+
+class SoongExecutionError(Error):
+    """Raised when Soong fails to build provided targets."""
+    pass
+
+
+class Soong:
+    """Interface for the Soong build system.
+
+    Attributes:
+        soong_workspace: the top of the Android workspace that Soong
+        will be operating in.
+        soong_executable: the path to the executable for the soong_ui.bash
+        launcher.
+    """
+    soong_workspace: pathlib.Path
+    soong_executable: pathlib.Path
+
+    def __init__(self, soong_workspace: pathlib.Path):
+        self.soong_workspace = soong_workspace
+
+        self.soong_executable = self.soong_workspace.joinpath(
+            "build/soong/soong_ui.bash")
+        if not self.soong_executable.exists():
+            raise SoongExecutionError(
+                "Unable to find Soong executable, expected location: %s" %
+                self.soong_executable)
+
+    def build(self, build_targets: Set[str]) -> None:
+        """Builds the provided set of targets with Soong.
+
+        Of note, there is no verification for the targets that get passed in,
+        rather that responsibility passes to Soong which will fail to build if a
+        target is invalid.
+
+        Args:
+            build_targets: a set of targets to build with Soong.
+        """
+        cmd_args = [
+            str(self.soong_executable), "--build-mode", "--all-modules",
+            f"--dir={self.soong_workspace}"
+        ]
+        cmd_args.extend(build_targets)
+
+        logging.info("Building targets with Soong: %s", build_targets)
+        logging.info("Please be patient, this may take a while...")
+        logging.debug("Soong Command is: %s", " ".join(cmd_args))
+
+        try:
+            subprocess.run(cmd_args,
+                           cwd=self.soong_workspace,
+                           check=True,
+                           stdout=subprocess.PIPE,
+                           stderr=subprocess.STDOUT)
+        except subprocess.CalledProcessError as cpe:
+            raise SoongExecutionError(
+                "There was an error during the Soong build process. Please "
+                "correct the error with Soong, and try running this script "
+                "again. Soong output follows:\n\n"
+                f"{cpe.stdout.decode('utf-8')}") from cpe
+
+        logging.info("Soong command completed successfully.")
+
+
+class Resource(abc.ABC):
+    """
+    Represents a resource file that is used for scaffolding the Bazel env.
+
+    Resource is an abstract class. Inheriting classes must provide the following
+    attributes which are used by the default method implementations below.
+
+    Attributes:
+        stage_path: the path where this resource should be written when staged.
+        workspace_path: the path where this resource should be synced to in the
+        workspace.
+    """
+    stage_path: pathlib.Path
+    workspace_path: pathlib.Path
+
+    def build_targets(self) -> set:
+        return set()
+
+    @abc.abstractmethod
+    def stage(self, _):
+        """Writes a resource to its stage location."""
+        pass
+
+    @abc.abstractmethod
+    def sync(self):
+        """Syncs a resource to its workspace location."""
+
+        # Overwrite any existing file in the workspace when synced.
+        self.workspace_path.unlink(missing_ok=True)
+        self.workspace_path.symlink_to(self.stage_path)
+
+    @abc.abstractmethod
+    def clean(self):
+        """Cleans a resource from its workspace location."""
+        self.workspace_path.unlink(missing_ok=True)
+
+
+class StaticResource(Resource):
+    """Resource representing a static file to be copied.
+
+    Attributes:
+        resource_path: path to the resource on disk.
+    """
+    def __init__(self, stage_path: pathlib.Path, workspace_path: pathlib.Path,
+                 resource_path: pathlib.Path):
+        self.stage_path = stage_path
+        self.workspace_path = workspace_path
+        self._resource_path = resource_path
+
+    def stage(self, _):
+        _verify_directory(self.stage_path.parent)
+        shutil.copy(self._resource_path, self.stage_path)
+        _make_executable_if_script(self.stage_path)
+
+    def sync(self):
+        super().sync()
+
+    def clean(self):
+        super().sync()
+
+    def __repr__(self):
+        return (f"StaticResource(stage_path={self.stage_path}, "
+                f"workspace_path={self.workspace_path}, "
+                f"resource_path={self._resource_path})")
+
+
+class TemplateError(Error):
+    """Raised when there is an issue while templating a template file."""
+    pass
+
+
+class TemplateResource(Resource):
+    """Resource that represents a file to be templated.
+
+    When staged, the resource is templated using the "mapping" provided
+    to the stage function.
+
+    Attributes:
+        resource_path: path to the resource on disk.
+    """
+    resource_path: pathlib.Path
+
+    # Key within templates that identifies a Soong target to build for a
+    # provided template.
+    SOONG_TARGET_KEY = "SOONG_TARGET"
+    _KEY_VALUE_SEP = ":"
+
+    # For a provided template, lines matching this regex are ignored when
+    # loading the template.
+    #
+    # This enables to contain metadata that, while visible to the script, is
+    # not visible in the generated templates. This is currently used with the
+    # SOONG_TARGET key/value pairs in templates.
+    _IGNORE_LINE_REGEX = re.compile(f"({SOONG_TARGET_KEY})")
+
+    def __init__(self, stage_path: pathlib.Path, workspace_path: pathlib.Path,
+                 resource_path: pathlib.Path):
+        self.stage_path = stage_path
+        self.workspace_path = workspace_path
+        self.resource_path = resource_path
+
+    def __repr__(self):
+        return (f"TemplateResource(stage_path={self.stage_path}, "
+                f"workspace_path={self.workspace_path}, "
+                f"resource_path={self.resource_path})")
+
+    def stage(self, mapping: Dict[str, str]):
+        _verify_directory(self.stage_path.parent)
+        lines = self.resource_path.open().readlines()
+        lines = [
+            line for line in lines if not self._IGNORE_LINE_REGEX.search(line)
+        ]
+
+        try:
+            output = "".join(lines).format_map(mapping)
+        except KeyError as ke:
+            raise TemplateError(
+                f"Malformed template file: {self.resource_path}") from ke
+
+        with self.stage_path.open("w") as output_file:
+            output_file.write(output)
+        _make_executable_if_script(self.stage_path)
+
+    def sync(self):
+        super().sync()
+
+    def clean(self):
+        super().clean()
+
+    @classmethod
+    def read_value_from_template_var(cls, line: str) -> str:
+        value = line.split(cls._KEY_VALUE_SEP)[-1]
+        return value.strip()
+
+
+class BuildTemplateResource(Resource):
+    """Resource that represents a BUILD file.
+
+    This operates in the same way as a TemplateResource, however also
+    sets up the prebuilts directory needed by BUILD files.
+
+    Attributes:
+        _template_resource: underlying TemplateResource for this resource.
+        global_prebuilts_dir: the directory in the filesystem where prebuilts
+        live, this directory is symlinked to by a directory adjacent
+        to the BUILD file represented by this Resource.
+        prebuilts_stage_path: the path of the staged prebuilts directory
+        which is a symlink to the global_prebuilts_dir.
+        prebuilts_workspace_path: the path of the workspace prebuilts directory,
+        which is a symlink to the global_prebuilts_dir.
+    """
+    _template_resource: TemplateResource
+    global_prebuilts_dir: pathlib.Path
+    prebuilts_stage_path: pathlib.Path
+    prebuilts_workspace_path: pathlib.Path
+
+    def __init__(self, stage_path: pathlib.Path, workspace_path: pathlib.Path,
+                 resource_path: pathlib.Path,
+                 global_prebuilts_dir: pathlib.Path, prebuilts_dir_name: str):
+        self.stage_path = stage_path
+        self.workspace_path = workspace_path
+
+        self._template_resource = TemplateResource(stage_path, workspace_path,
+                                                   resource_path)
+        self.global_prebuilts_dir = global_prebuilts_dir
+        self.prebuilts_stage_path = self.stage_path.parent.joinpath(
+            prebuilts_dir_name)
+        self.prebuilts_workspace_path = self.workspace_path.parent.joinpath(
+            prebuilts_dir_name)
+
+    def __repr__(self):
+        return ("BuildTemplateResource("
+                f"template_resource={self._template_resource}, "
+                f"global_prebuilts_dir={self.global_prebuilts_dir}, "
+                f"prebuilts_stage_path={self.prebuilts_stage_path}, "
+                f"prebuilts_workspace_path={self.prebuilts_workspace_path})")
+
+    def build_targets(self) -> set:
+        """Overrides build_targets() to read targets from the BUILD template."""
+        targets = set()
+        with self._template_resource.resource_path.open() as build_file:
+            while line := build_file.readline():
+                if self._template_resource.SOONG_TARGET_KEY in line:
+                    targets.add(
+                        self._template_resource.read_value_from_template_var(
+                            line))
+
+        return targets
+
+    def stage(self, mapping: Dict[str, str]):
+        """Overrides stage() to stage a BUILD resource.
+
+        Delegates most actions to the _template_resource, while ensuring that
+        a generated prebuilts directory is also staged.
+        """
+        self._template_resource.stage(mapping)
+        self.prebuilts_stage_path.symlink_to(self.global_prebuilts_dir,
+                                             target_is_directory=True)
+
+    def sync(self):
+        """Overrides sync() to sync a BUILD resource with prebuilts.
+
+        Delegates to the _template_resource while also ensuring that the
+        generated prebuilts directory is written to the workspace.
+        """
+        self._template_resource.sync()
+
+        # Overwrite the existing prebuilts directory, if it exists.
+        self.prebuilts_workspace_path.unlink(missing_ok=True)
+        self.prebuilts_workspace_path.symlink_to(self.global_prebuilts_dir,
+                                                 target_is_directory=True)
+
+    def clean(self):
+        """Overrides clean() to clean a BUILD resource.
+
+        Delegates most actions to the _template_resource, while also ensuring
+        that the generated prebuilts directory is removed from the workspace.
+        """
+        self._template_resource.clean()
+        self.prebuilts_workspace_path.unlink(missing_ok=True)
+
+
+def _make_executable_if_script(path: pathlib.Path) -> None:
+    """Makes the provided path executable if it is a script.
+    Args:
+        path: the path to check and conditionally make executable.
+    """
+    if path.name.endswith(".sh"):
+        # Grant full permissions (read/write/execute) for current user and
+        # read/write permissions for group.
+        path.chmod(mode=0o750)
+
+
+class ResourcesNotFoundError(Error):
+    """Raised when the required resources are not found."""
+    pass
+
+
+class Resources:
+    """Manages and loads resources from disk.
+
+    Attributes:
+        workspace_base_path: the path to the root of the workspace where
+        staged files will be synced to.
+        gendir_base_path: the path to the root of the staging directory.
+        global_prebuilts_dir_path: the path to the root of the global
+        prebuilts directory to which all generated prebuilts directories will
+        symlink to.
+        prebuilts_dir_name: the name to use for generated prebuilts
+        directories.
+        static_path: the path to the static resources directory.
+        template_path: the path to the template resources directory.
+    """
+    workspace_base_path: pathlib.Path
+    gendir_base_path: pathlib.Path
+    global_prebuilts_dir_path: pathlib.Path
+    prebuilts_dir_name: str
+    static_path: pathlib.Path
+    template_path: pathlib.Path
+
+    # Name of the directory where script runfiles are located.
+    _DATA_DIRNAME = "data"
+
+    # Name of the directory where the templates should be located.
+    _TEMPLATES_DIRNAME = "templates"
+
+    # Name of the directory where static files (to be copied to the environment)
+    # should be located.
+    _STATIC_DIRNAME = "static"
+
+    # If the script is executed from the root of the runfiles directory, this is
+    # where the data should be.
+    _RESOURCES_RUNFILES_BASEPATH = pathlib.Path(
+        "build/pesto/experiments/prepare_bazel_test_env", _DATA_DIRNAME)
+
+    # File extension for templates, determining whether or not a given file is a
+    # template.
+    _TEMPLATE_FILE_EXT = ".template"
+
+    def __init__(self,
+                 workspace_base_path: pathlib.Path,
+                 gendir_base_path: pathlib.Path,
+                 global_prebuilts_dir_path: pathlib.Path,
+                 prebuilts_dir_name: str,
+                 path: pathlib.Path = _RESOURCES_RUNFILES_BASEPATH):
+        logging.debug("Resources(path=%s)", path)
+
+        self.workspace_base_path = workspace_base_path
+        self.gendir_base_path = gendir_base_path
+        self.global_prebuilts_dir_path = global_prebuilts_dir_path
+        self.prebuilts_dir_name = prebuilts_dir_name
+
+        path = path.resolve()
+
+        self.template_path = path.joinpath(Resources._TEMPLATES_DIRNAME)
+        self.static_path = path.joinpath(Resources._STATIC_DIRNAME)
+
+        if not self.template_path.exists() or not self.static_path.exists():
+            raise ResourcesNotFoundError("Unable to find resources at path "
+                                         f"{path}, expected the following "
+                                         "directories: "
+                                         f"{Resources._TEMPLATES_DIRNAME}, "
+                                         f"{Resources._STATIC_DIRNAME}")
+
+    def __repr__(self):
+        return ("Resources("
+                f"template_path={self.template_path}"
+                f"static_path={self.static_path})")
+
+    def stage(self, mapping: Dict[str, str]) -> None:
+        for resource in self.load():
+            logging.debug("Staging resource: %s", resource)
+            resource.stage(mapping)
+
+    def sync(self) -> None:
+        for resource in self.load():
+            logging.debug("Syncing resource: %s", resource)
+            resource.sync()
+
+    def clean(self) -> None:
+        for resource in self.load():
+            logging.debug("Cleaning resource: %s", resource)
+            resource.clean()
+
+    def build_targets(self) -> Set[str]:
+        return {
+            t
+            for resource in self.load() for t in resource.build_targets()
+        }
+
+    def load(self) -> List[Resource]:
+        """Loads the Resources used to scaffold the Bazel env.
+
+        Returns:
+            a list of Resource objects representing the files
+            that should be used to template the environment.
+        """
+        resources = []
+
+        # Add all templates.
+        for p in self._template_resource_paths():
+            template_relpath = Resources._strip_template_identifier_from_path(
+                p.relative_to(self.template_path))
+            stage_path = self.gendir_base_path.joinpath(template_relpath)
+            workspace_path = self.workspace_base_path.joinpath(
+                template_relpath)
+
+            if BUILD_FILENAME_REGEX.match(template_relpath.name):
+                resources.append(
+                    BuildTemplateResource(
+                        stage_path=stage_path,
+                        workspace_path=workspace_path,
+                        resource_path=p,
+                        global_prebuilts_dir=self.global_prebuilts_dir_path,
+                        prebuilts_dir_name=self.prebuilts_dir_name))
+            else:
+                resources.append(
+                    TemplateResource(stage_path=stage_path,
+                                     workspace_path=workspace_path,
+                                     resource_path=p))
+
+        # Add all static files.
+        for p in self._static_resource_paths():
+            static_relpath = p.relative_to(self.static_path)
+            stage_path = self.gendir_base_path.joinpath(static_relpath)
+            workspace_path = self.workspace_base_path.joinpath(static_relpath)
+            resources.append(
+                StaticResource(stage_path=stage_path,
+                               workspace_path=workspace_path,
+                               resource_path=p))
+
+        return resources
+
+    def _static_resource_paths(self) -> List[pathlib.Path]:
+        return [p for p in self.static_path.glob("**/*") if p.is_file()]
+
+    def _template_resource_paths(self) -> List[pathlib.Path]:
+        return [p for p in self.template_path.glob("**/*") if p.is_file()]
+
+    @staticmethod
+    def _strip_template_identifier_from_path(p: pathlib.Path):
+        """Strips the template file extension from a provided path."""
+        if p.name.endswith(Resources._TEMPLATE_FILE_EXT):
+            p = p.with_name(p.name[:len(p.name) -
+                                   len(Resources._TEMPLATE_FILE_EXT)])
+        return p
+
+
+class AndroidBuildEnvironmentError(Error):
+    """Raised when the Android Build Environment is not properly set."""
+    pass
+
+
+class BazelTestEnvGenerator:
+    """Context for the Bazel environment generation.
+
+  This class provides access to locations within the filesystem pertinent to the
+  current execution as members that can be accessed by users of the class.
+
+  Attributes:
+      workspace_top: the top of the codebase, which also serves as the top of
+      the Bazel WORKSPACE.
+      host_out: Host artifact staging directory location.
+      host_testcases: Host testcase staging directory location.
+      product_out: Product/Target artifact staging directory location.
+      target_testcases: Product/Target testcase staging directory location.
+      staging_dir: Staging directory for generated Bazel artifacts.
+      prebuilts_dir_name: Name of the directory that should be used for the
+      directories that prebuilts are placed into when synced into the source
+      tree.
+      global_prebuilts_dir_path: The absolute path to the global prebuilts
+      directory.
+      year: the current calendar year.
+      gen_dir: Subdirectory of the staging dir where the Bazel environment
+      should be generated to.
+  """
+    workspace_top: pathlib.Path
+    host_out: pathlib.Path
+    host_testcases: pathlib.Path
+    product_out: pathlib.Path
+    target_testcases: pathlib.Path
+    staging_dir: pathlib.Path
+    prebuilts_dir_name: str = ".soong_prebuilts"
+    prebuilts_dir_path: pathlib.Path
+    gen_dir: pathlib.Path
+    year: str
+    _resources: Resources
+    _soong: Soong
+
+    # Name of the subdirectory, within the output directory, where the
+    # prebuilts directory is scaffolded.
+    #
+    # This directory then serves as the target of symlinks from across the
+    # source tree that gives any Bazel target access to the Soong staging
+    # directories.
+    GLOBAL_PREBUILTS_DIR_PATH = "prebuilts"
+
+    def __init__(self, env_dict: Dict[str, str] = os.environ):
+        try:
+            self.workspace_top = pathlib.Path(env_dict["ANDROID_BUILD_TOP"])
+            self.host_out = pathlib.Path(env_dict["ANDROID_HOST_OUT"])
+            self.host_testcases = pathlib.Path(
+                env_dict["ANDROID_HOST_OUT_TESTCASES"])
+            self.product_out = pathlib.Path(env_dict["ANDROID_PRODUCT_OUT"])
+            self.target_testcases = pathlib.Path(
+                env_dict["ANDROID_TARGET_OUT_TESTCASES"])
+        except KeyError as e:
+            raise AndroidBuildEnvironmentError(
+                "Missing expected environment variable.") from e
+
+        self.staging_dir = pathlib.Path(self.workspace_top,
+                                        "out/pesto-environment")
+        self.prebuilts_dir_name = BazelTestEnvGenerator.prebuilts_dir_name
+        self.global_prebuilts_dir_path = self.staging_dir.joinpath(
+            self.GLOBAL_PREBUILTS_DIR_PATH)
+        self.year = str(datetime.date.today().year)
+        self.gen_dir = pathlib.Path(self.staging_dir, "gen")
+
+        self._resources = Resources(self.workspace_top, self.gen_dir,
+                                    self.global_prebuilts_dir_path,
+                                    self.prebuilts_dir_name)
+        self._soong = Soong(self.workspace_top)
+
+    def __repr__(self):
+        return "GenerationContext(%s)" % vars(self)
+
+    def generate(self):
+        logging.info("Starting generation of Bazel environment.")
+
+        self._soong.build(self._resources.build_targets())
+
+        logging.debug("Creating fresh staging dir at: %s", self.staging_dir)
+        _verify_directory(self.staging_dir, clean=True)
+
+        logging.debug("Creating fresh gen dir at: %s", self.gen_dir)
+        _verify_directory(self.gen_dir, clean=True)
+
+        logging.debug("Creating global prebuilts directory at: %s",
+                      self.global_prebuilts_dir_path)
+        _verify_directory(self.global_prebuilts_dir_path, clean=True)
+
+        # Symlink the build system provided staging directories to the
+        # global prebuilts directory.
+        self.global_prebuilts_dir_path.joinpath("host").symlink_to(
+            self.host_out)
+        self.global_prebuilts_dir_path.joinpath("host_testcases").symlink_to(
+            self.host_testcases)
+        self.global_prebuilts_dir_path.joinpath("product").symlink_to(
+            self.product_out)
+        self.global_prebuilts_dir_path.joinpath("target_testcases").symlink_to(
+            self.target_testcases)
+
+        # Load and process each resource into the gen directory.
+        self._resources.stage(mapping=vars(self))
+
+        logging.info(
+            "Generation of Bazel environment to staging directory "
+            "(%s) completed successfully.", self.staging_dir)
+
+    def sync(self):
+        logging.info(
+            "Starting synchronization of generated environment to source tree."
+        )
+
+        if not self.staging_dir.exists():
+            raise FileNotFoundError("Staging directory does not exist, "
+                                    "the generate function should be called "
+                                    " to create this directory.")
+
+        self._resources.sync()
+
+        logging.info(
+            "Successfully synchronized generated Bazel environment from "
+            "%s to %s", self.gen_dir, self.workspace_top)
+
+    def clean(self):
+        logging.info("Starting clean of generated environment.")
+
+        logging.info("Cleaning up synchronized files from the source tree.")
+        # For all of our configured templates, attempt to find the corresponding
+        # location in the source tree and remove them.
+        self._resources.clean()
+
+        logging.info("Cleaning up staging directory: %s", self.staging_dir)
+        try:
+            shutil.rmtree(self.staging_dir)
+        except FileNotFoundError:
+            logging.debug("Staging directory not found during cleanup "
+                          "and may have already been removed.")
+        logging.info("Successfully cleaned up generated environment.")
+
+
+def _verify_directory(directory: pathlib.Path, clean: bool = False) -> None:
+    """Verifies that the provided directory exists, creating it if it does not.
+
+    Args:
+      directory: path to the directory to create.
+      clean: whether or not the existing directory should be removed if found or
+        reused.
+    """
+    if directory.exists() and clean:
+        logging.debug("Cleaning existing directory %s", directory)
+        shutil.rmtree(directory)
+
+    logging.debug("Verifying directory exists at %s", directory)
+    directory.mkdir(parents=True, exist_ok=True)
diff --git a/experiments/prepare_bazel_test_env/prepare_bazel_test_env.py b/experiments/prepare_bazel_test_env/prepare_bazel_test_env.py
new file mode 100644
index 0000000..b086b00
--- /dev/null
+++ b/experiments/prepare_bazel_test_env/prepare_bazel_test_env.py
@@ -0,0 +1,91 @@
+# Copyright (C) 2021 The Android Open Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+"""Binary that generates a simulated Bazel environment in the Android source.
+
+The script utilizes an internal repository of templates to determine the targets
+to build, builds them via Soong, then imports them into a Bazel environment
+all relying on templated BUILD files. These files can then be placed
+directly within the Android source tree to simulate what a real Bazel
+environment would look like.
+"""
+import argparse
+import logging
+
+import bazelenv
+
+_LOG_PRINT_FORMAT = ("%(asctime)s %(filename)s:%(lineno)s:%(levelname)s: "
+                     "%(message)s")
+_LOG_DATE_FORMAT = "%Y-%m-%d %H:%M:%S"
+
+
+def _configure_logging(verbose: bool) -> None:
+    """Configures logging for the application.
+
+  Args:
+    verbose: if True, all messages are logged, otherwise only INFO and above
+    are logged.
+  """
+    logging.basicConfig(format=_LOG_PRINT_FORMAT, datefmt=_LOG_DATE_FORMAT)
+    level = logging.DEBUG if verbose else logging.INFO
+    logging.root.setLevel(level)
+
+
+def _create_arg_parser():
+    parser = argparse.ArgumentParser(description=(
+        "Prepares a simulated Bazel environment that can be used to "
+        "execute tests in a Bazel environment based on Soong "
+        "produced artifacts."))
+
+    parser.add_argument("-v",
+                        "--verbose",
+                        help="Enables verbose logging.",
+                        action="store_true")
+
+    subparsers = parser.add_subparsers(dest="action", required=True)
+
+    # For each subparser, provide a default 'func' argument that calls the
+    # corresponding method on the generator instance.
+    subparsers.add_parser(
+        "generate",
+        help="Generates the Bazel environment to the staging directory."
+    ).set_defaults(func=lambda g: g.generate())
+
+    subparsers.add_parser(
+        "sync",
+        help="Synchronizes the staged Bazel environment to the source tree."
+    ).set_defaults(func=lambda g: g.sync())
+
+    subparsers.add_parser(
+        "clean",
+        help=
+        ("Cleans up the Bazel environment by clearing anything that has been "
+         "synced to the source tree as well as the staging directory itself."
+         )).set_defaults(func=lambda g: g.clean())
+
+    return parser
+
+
+if __name__ == "__main__":
+    args = _create_arg_parser().parse_args()
+    logging.debug("prepare_bazel_test_env(%s)", args)
+
+    _configure_logging(args.verbose)
+
+    try:
+        generator = bazelenv.BazelTestEnvGenerator()
+        args.func(generator)
+    except bazelenv.Error:
+        logging.exception(
+            "A known error occurred, check the error description "
+            "or logs for more details.")