feat: Adding code samples and tests for them (#55)

* feat: Adding code samples and tests for them

* chore: Remove unused import.

* Update .github/CODEOWNERS

Co-authored-by: Bu Sun Kim <8822365+busunkim96@users.noreply.github.com>

* chore: Updating samples to meet reviewers suggestions.

* chore: Fixing regions.

* chore: Adjusting the testing scripts in .kokoro/samples.

* Revert "chore: Adjusting the testing scripts in .kokoro/samples."

This reverts commit 6d0b427

* chore: Moving samples tests to dedicated noxfile.py.

* chore: Adding 3.6 and 3.7 Python versions to samples noxfile.py

* chore: Updating the Samples section to reflect new testing setup.

* chore: Updating the Samples README.

* chore: add standardized samples noxfile

* chore: uncomment sections in synth.py

* chore: Changing the waiting for operation part.

* chore: Minor changes based on review.

* README suggests using `gcloud auth application-default login` which is safer than Service Account key.
* The name of created instance now starts with "quickstart-".
* Changed one variable name.

Co-authored-by: Bu Sun Kim <8822365+busunkim96@users.noreply.github.com>
Co-authored-by: Bu Sun Kim <busunkim@google.com>
Co-authored-by: Dina Graves Portman <dinagraves@google.com>

.github/CODEOWNERS

@@ -8,4 +8,4 @@
 *               @googleapis/yoshi-python
 
 
-/samples/   @googleapis/python-samples-owners
+/samples/   @m-strzelczyk @googleapis/python-samples-owners

CONTRIBUTING.rst

@@ -182,6 +182,30 @@ Build the docs via:
 
    $ nox -s docs
 
+*************************
+Samples and code snippets
+*************************
+
+Code samples and snippets live in the `samples/` catalogue. Feel free to
+provide more examples, but make sure to write tests for those examples.
+Each folder containing example code requires its own `noxfile.py` script
+which automates testing. If you decide to create a new folder, you can
+base it on the `samples/snippets` folder (providing `noxfile.py` and
+the requirements files).
+
+The tests will run against a real Google Cloud Project, so you should
+configure them just like the System Tests.
+
+- To run sample tests, you can execute::
+
+   # Run all tests in a folder
+   $ cd samples/snippets
+   $ nox -s py-3.8
+
+   # Run a single sample test
+   $ cd samples/snippets
+   $ nox -s py-3.8 -- -k <name of test>
+
 ********************************************
 Note About ``README`` as it pertains to PyPI
 ********************************************

samples/snippets/README.md

@@ -0,0 +1,31 @@
+# google-cloud-compute library samples
+
+These samples demonstrate usage of the google-cloud-compute library to interact
+with the Google Compute Engine API.
+
+## Running the quickstart script
+
+### Before you begin
+
+1. If you haven't already, set up a Python Development Environment by following the [python setup guide](https://cloud.google.com/python/setup) and 
+[create a project](https://cloud.google.com/resource-manager/docs/creating-managing-projects#creating_a_project).
+
+1. Use `gcloud auth application-default login` to allow the script to authenticate using
+your credentials to the Google Cloud APIs.
+
+### Install requirements
+
+Create a new virtual environment and install the required libraries.
+```bash
+virtualenv --python python3 name-of-your-virtualenv
+source name-of-your-virtualenv/bin/activate
+pip install -r requirements.txt
+```
+
+### Run the demo
+
+Run the quickstart script, it will create and destroy a `n1-standard-1` 
+type machine in the `europe-central2-b` zone.
+```bash
+python quickstart.py
+```

samples/snippets/noxfile.py

@@ -0,0 +1,259 @@
+# Copyright 2019 Google LLC
+#
+# 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.
+
+from __future__ import print_function
+
+import os
+from pathlib import Path
+import sys
+from typing import Callable, Dict, List, Optional
+
+import nox
+
+
+# WARNING - WARNING - WARNING - WARNING - WARNING
+# WARNING - WARNING - WARNING - WARNING - WARNING
+#           DO NOT EDIT THIS FILE EVER!
+# WARNING - WARNING - WARNING - WARNING - WARNING
+# WARNING - WARNING - WARNING - WARNING - WARNING
+
+# Copy `noxfile_config.py` to your directory and modify it instead.
+
+
+# `TEST_CONFIG` dict is a configuration hook that allows users to
+# modify the test configurations. The values here should be in sync
+# with `noxfile_config.py`. Users will copy `noxfile_config.py` into
+# their directory and modify it.
+
+TEST_CONFIG = {
+    # You can opt out from the test for specific Python versions.
+    'ignored_versions': ["2.7"],
+
+    # Old samples are opted out of enforcing Python type hints
+    # All new samples should feature them
+    'enforce_type_hints': False,
+
+    # An envvar key for determining the project id to use. Change it
+    # to 'BUILD_SPECIFIC_GCLOUD_PROJECT' if you want to opt in using a
+    # build specific Cloud project. You can also use your own string
+    # to use your own Cloud project.
+    'gcloud_project_env': 'GOOGLE_CLOUD_PROJECT',
+    # 'gcloud_project_env': 'BUILD_SPECIFIC_GCLOUD_PROJECT',
+    # If you need to use a specific version of pip,
+    # change pip_version_override to the string representation
+    # of the version number, for example, "20.2.4"
+    "pip_version_override": None,
+    # A dictionary you want to inject into your test. Don't put any
+    # secrets here. These values will override predefined values.
+    'envs': {},
+}
+
+
+try:
+    # Ensure we can import noxfile_config in the project's directory.
+    sys.path.append('.')
+    from noxfile_config import TEST_CONFIG_OVERRIDE
+except ImportError as e:
+    print("No user noxfile_config found: detail: {}".format(e))
+    TEST_CONFIG_OVERRIDE = {}
+
+# Update the TEST_CONFIG with the user supplied values.
+TEST_CONFIG.update(TEST_CONFIG_OVERRIDE)
+
+
+def get_pytest_env_vars() -> Dict[str, str]:
+    """Returns a dict for pytest invocation."""
+    ret = {}
+
+    # Override the GCLOUD_PROJECT and the alias.
+    env_key = TEST_CONFIG['gcloud_project_env']
+    # This should error out if not set.
+    ret['GOOGLE_CLOUD_PROJECT'] = os.environ[env_key]
+
+    # Apply user supplied envs.
+    ret.update(TEST_CONFIG['envs'])
+    return ret
+
+
+# DO NOT EDIT - automatically generated.
+# All versions used to tested samples.
+ALL_VERSIONS = ["2.7", "3.6", "3.7", "3.8", "3.9"]
+
+# Any default versions that should be ignored.
+IGNORED_VERSIONS = TEST_CONFIG['ignored_versions']
+
+TESTED_VERSIONS = sorted([v for v in ALL_VERSIONS if v not in IGNORED_VERSIONS])
+
+INSTALL_LIBRARY_FROM_SOURCE = bool(os.environ.get("INSTALL_LIBRARY_FROM_SOURCE", False))
+#
+# Style Checks
+#
+
+
+def _determine_local_import_names(start_dir: str) -> List[str]:
+    """Determines all import names that should be considered "local".
+
+    This is used when running the linter to insure that import order is
+    properly checked.
+    """
+    file_ext_pairs = [os.path.splitext(path) for path in os.listdir(start_dir)]
+    return [
+        basename
+        for basename, extension in file_ext_pairs
+        if extension == ".py"
+        or os.path.isdir(os.path.join(start_dir, basename))
+        and basename not in ("__pycache__")
+    ]
+
+
+# Linting with flake8.
+#
+# We ignore the following rules:
+#   E203: whitespace before ‘:’
+#   E266: too many leading ‘#’ for block comment
+#   E501: line too long
+#   I202: Additional newline in a section of imports
+#
+# We also need to specify the rules which are ignored by default:
+# ['E226', 'W504', 'E126', 'E123', 'W503', 'E24', 'E704', 'E121']
+FLAKE8_COMMON_ARGS = [
+    "--show-source",
+    "--builtin=gettext",
+    "--max-complexity=20",
+    "--import-order-style=google",
+    "--exclude=.nox,.cache,env,lib,generated_pb2,*_pb2.py,*_pb2_grpc.py",
+    "--ignore=E121,E123,E126,E203,E226,E24,E266,E501,E704,W503,W504,I202",
+    "--max-line-length=88",
+]
+
+
+@nox.session
+def lint(session: nox.sessions.Session) -> None:
+    if not TEST_CONFIG['enforce_type_hints']:
+        session.install("flake8", "flake8-import-order")
+    else:
+        session.install("flake8", "flake8-import-order", "flake8-annotations")
+
+    local_names = _determine_local_import_names(".")
+    args = FLAKE8_COMMON_ARGS + [
+        "--application-import-names",
+        ",".join(local_names),
+        "."
+    ]
+    session.run("flake8", *args)
+#
+# Black
+#
+
+
+@nox.session
+def blacken(session: nox.sessions.Session) -> None:
+    session.install("black")
+    python_files = [path for path in os.listdir(".") if path.endswith(".py")]
+
+    session.run("black", *python_files)
+
+#
+# Sample Tests
+#
+
+
+PYTEST_COMMON_ARGS = ["--junitxml=sponge_log.xml"]
+
+
+def _session_tests(session: nox.sessions.Session, post_install: Callable = None) -> None:
+    if TEST_CONFIG["pip_version_override"]:
+        pip_version = TEST_CONFIG["pip_version_override"]
+        session.install(f"pip=={pip_version}")
+    """Runs py.test for a particular project."""
+    if os.path.exists("requirements.txt"):
+        if os.path.exists("constraints.txt"):
+            session.install("-r", "requirements.txt", "-c", "constraints.txt")
+        else:
+            session.install("-r", "requirements.txt")
+
+    if os.path.exists("requirements-test.txt"):
+        if os.path.exists("constraints-test.txt"):
+            session.install("-r", "requirements-test.txt", "-c", "constraints-test.txt")
+        else:
+            session.install("-r", "requirements-test.txt")
+
+    if INSTALL_LIBRARY_FROM_SOURCE:
+        session.install("-e", _get_repo_root())
+
+    if post_install:
+        post_install(session)
+
+    session.run(
+        "pytest",
+        *(PYTEST_COMMON_ARGS + session.posargs),
+        # Pytest will return 5 when no tests are collected. This can happen
+        # on travis where slow and flaky tests are excluded.
+        # See http://doc.pytest.org/en/latest/_modules/_pytest/main.html
+        success_codes=[0, 5],
+        env=get_pytest_env_vars()
+    )
+
+
+@nox.session(python=ALL_VERSIONS)
+def py(session: nox.sessions.Session) -> None:
+    """Runs py.test for a sample using the specified version of Python."""
+    if session.python in TESTED_VERSIONS:
+        _session_tests(session)
+    else:
+        session.skip("SKIPPED: {} tests are disabled for this sample.".format(
+            session.python
+        ))
+
+
+#
+# Readmegen
+#
+
+
+def _get_repo_root() -> Optional[str]:
+    """ Returns the root folder of the project. """
+    # Get root of this repository. Assume we don't have directories nested deeper than 10 items.
+    p = Path(os.getcwd())
+    for i in range(10):
+        if p is None:
+            break
+        if Path(p / ".git").exists():
+            return str(p)
+        # .git is not available in repos cloned via Cloud Build
+        # setup.py is always in the library's root, so use that instead
+        # https://github.com/googleapis/synthtool/issues/792
+        if Path(p / "setup.py").exists():
+            return str(p)
+        p = p.parent
+    raise Exception("Unable to detect repository root.")
+
+
+GENERATED_READMES = sorted([x for x in Path(".").rglob("*.rst.in")])
+
+
+@nox.session
+@nox.parametrize("path", GENERATED_READMES)
+def readmegen(session: nox.sessions.Session, path: str) -> None:
+    """(Re-)generates the readme for a sample."""
+    session.install("jinja2", "pyyaml")
+    dir_ = os.path.dirname(path)
+
+    if os.path.exists(os.path.join(dir_, "requirements.txt")):
+        session.install("-r", os.path.join(dir_, "requirements.txt"))
+
+    in_file = os.path.join(dir_, "README.rst.in")
+    session.run(
+        "python", _get_repo_root() + "/scripts/readme-gen/readme_gen.py", in_file
+    )