Contributing

Please sign one of the contributor license agreements below.
Fork the repo, develop and test your code changes, add docs.
Make sure that your commit messages clearly describe the changes.
Send a pull request.

Here are some guidelines for hacking on google-cloud-python.

Using a Development Checkout

You'll have to create a development environment to hack on google-cloud-python, using a Git checkout:

While logged into your GitHub account, navigate to the google-cloud-python repo on GitHub.

https://github.com/GoogleCloudPlatform/google-cloud-python
Fork and clone the google-cloud-python repository to your GitHub account by clicking the "Fork" button.

Clone your fork of google-cloud-python from your GitHub account to your local computer, substituting your account username and specifying the destination as "hack-on-google-cloud-python". E.g.:

$ cd ~
$ git clone git@github.com:USERNAME/google-cloud-python.git hack-on-google-cloud-python
$ cd hack-on-google-cloud-python
# Configure remotes such that you can pull changes from the google-cloud-python
# repository into your local repository.
$ git remote add upstream https://github.com:GoogleCloudPlatform/google-cloud-python
# fetch and merge changes from upstream into master
$ git fetch upstream
$ git merge upstream/master

Now your local repo is set up such that you will push changes to your GitHub repo, from which you can submit a pull request.

Create a virtualenv in which to install google-cloud-python:
```
$ cd ~/hack-on-google-cloud-python
$ virtualenv --python python2.7 env
```
Note that very old versions of virtualenv (virtualenv versions below, say, 1.10 or thereabouts) require you to pass a --no-site-packages flag to get a completely isolated environment.

You can choose which Python version you want to use by passing a --python flag to virtualenv. For example, virtualenv --python python2.7 chooses the Python 2.7 interpreter to be installed.

From here on in within these instructions, the ~/hack-on-google-cloud-python/env virtual environment you created above will be referred to as $VENV. To use the instructions in the steps that follow literally, use the export VENV=~/hack-on-google-cloud-python/env command.
Install google-cloud-python from the checkout into the virtualenv using setup.py develop. Running setup.py develop must be done while the current working directory is the google-cloud-python checkout directory:
```
$ cd ~/hack-on-google-cloud-python
$ $VENV/bin/python setup.py develop
```

I'm getting weird errors... Can you help?

If the error mentions Python.h not being found, install python-dev and try again. On Debian/Ubuntu:

$ sudo apt-get install python-dev

Adding Features

In order to add a feature to google-cloud-python:

The feature must be documented in both the API and narrative documentation (in docs/).
The feature must work fully on the following CPython versions: 2.7, 3.4, and 3.5 on both UNIX and Windows.
The feature must not add unnecessary dependencies (where "unnecessary" is of course subjective, but new dependencies should be discussed).

Coding Style

PEP8 compliance, with exceptions defined in tox.ini. If you have tox installed, you can test that you have not introduced any non-compliant code via:
```
$ tox -e lint
```
In order to make tox -e lint run faster, you can set some environment variables:
```
export GOOGLE_CLOUD_REMOTE_FOR_LINT="upstream"
export GOOGLE_CLOUD_BRANCH_FOR_LINT="master"
```
By doing this, you are specifying the location of the most up-to-date version of google-cloud-python. The the suggested remote name upstream should point to the official GoogleCloudPlatform checkout and the the branch should be the main branch on that remote (master).

Exceptions to PEP8:

Many unit tests use a helper method, _callFUT ("FUT" is short for "Function-Under-Test"), which is PEP8-incompliant, but more readable. Some also use a local variable, MUT (short for "Module-Under-Test").

Running Tests

To run all tests for google-cloud-python on a single Python version, run py.test from your development virtualenv (See Using a Development Checkout above).
To run the full set of google-cloud-python tests on all platforms, install tox (https://testrun.org/tox/) into a system Python. The tox console script will be installed into the scripts location for that Python. While cd'ed to the google-cloud-python checkout root directory (it contains tox.ini), invoke the tox console script. This will read the tox.ini file and execute the tests on multiple Python versions and platforms; while it runs, it creates a virtualenv for each version/platform combination. For example:
```
$ sudo /usr/bin/pip install tox
$ cd ~/hack-on-google-cloud-python/
$ /usr/bin/tox
```

Running System Tests

To run system tests you can execute:
```
$ tox -e system-tests
```
or run only system tests for a particular package via:
```
$ python system_tests/run_system_test.py --package {package}
```
This alone will not run the tests. You'll need to change some local auth settings and change some configuration in your project to run all the tests.
System tests will be run against an actual project and so you'll need to provide some environment variables to facilitate authentication to your project:
- GOOGLE_CLOUD_TESTS_PROJECT_ID: Developers Console project ID (e.g. bamboo-shift-455).
- GOOGLE_APPLICATION_CREDENTIALS: The path to a JSON key file; see system_tests/app_credentials.json.sample as an example. Such a file can be downloaded directly from the developer's console by clicking "Generate new JSON key". See private key docs for more details. In order for Logging system tests to work, the Service Account will also have to be made a project Owner. This can be changed under "IAM & Admin".
Examples of these can be found in system_tests/local_test_setup.sample. We recommend copying this to system_tests/local_test_setup, editing the values and sourcing them into your environment:
```
$ source system_tests/local_test_setup
```

For datastore tests, you'll need to create composite indexes with the gcloud command line tool:

# Install the app (App Engine Command Line Interface) component.
$ gcloud components update app

# See https://cloud.google.com/sdk/crypto for details on PyOpenSSL and
# http://stackoverflow.com/a/25067729/1068170 for why we must persist.
$ export CLOUDSDK_PYTHON_SITEPACKAGES=1

# Authenticate the gcloud tool with your account.
$ JSON_CREDENTIALS_FILE="path/to/app_credentials.json"
$ gcloud auth activate-service-account --key-file=$JSON_CREDENTIALS_FILE

# Create the indexes
$ gcloud preview datastore create-indexes system_tests/data/index.yaml \
> --project=$GOOGLE_CLOUD_TESTS_PROJECT_ID

# Restore your environment to its previous state.
$ unset CLOUDSDK_PYTHON_SITEPACKAGES

For datastore query tests, you'll need stored data in your dataset. To populate this data, run:
```
$ python system_tests/populate_datastore.py
```
If you make a mistake during development (i.e. a failing test that prevents clean-up) you can clear all system test data from your datastore instance via:
```
$ python system_tests/clear_datastore.py
```

System tests can also be run against local emulators that mock the production services. To run the system tests with the datastore emulator:

$ tox -e datastore-emulator
$ GOOGLE_CLOUD_DISABLE_GRPC=true tox -e datastore-emulator

This also requires that the gcloud command line tool is installed. If you'd like to run them directly (outside of a tox environment), first start the emulator and take note of the process ID:

$ gcloud beta emulators datastore start --no-legacy 2>&1 > log.txt &
[1] 33333

then determine the environment variables needed to interact with the emulator:

$ gcloud beta emulators datastore env-init
export DATASTORE_LOCAL_HOST=localhost:8417
export DATASTORE_HOST=http://localhost:8417
export DATASTORE_DATASET=google-cloud-settings-app-id
export DATASTORE_PROJECT_ID=google-cloud-settings-app-id

using these environment variables run the emulator:

$ DATASTORE_HOST=http://localhost:8471 \
>   DATASTORE_DATASET=google-cloud-settings-app-id \
>   GOOGLE_CLOUD_NO_PRINT=true \
>   python system_tests/run_system_test.py \
>   --package=datastore --ignore-requirements

and after completion stop the emulator and any child processes it spawned:

$ kill -- -33333

To run the system tests with the pubsub emulator:
```
$ tox -e pubsub-emulator
```
If you'd like to run them directly (outside of a tox environment), first start the emulator and take note of the process ID:
```
$ gcloud beta emulators pubsub start 2>&1 > log.txt &
[1] 44444
```
then determine the environment variables needed to interact with the emulator:
```
$ gcloud beta emulators pubsub env-init
export PUBSUB_EMULATOR_HOST=localhost:8897
```
using these environment variables run the emulator:
```
$ PUBSUB_EMULATOR_HOST=localhost:8897 \
>   python system_tests/run_system_test.py \
>   --package=pubsub
```
and after completion stop the emulator and any child processes it spawned:
```
$ kill -- -44444
```

Test Coverage

The codebase must have 100% test statement coverage after each commit. You can test coverage via tox -e cover.

Documentation Coverage and Building HTML Documentation

If you fix a bug, and the bug requires an API or behavior modification, all documentation in this package which references that API or behavior must be changed to reflect the bug fix, ideally in the same commit that fixes the bug or adds the feature.

To build and review docs (where $VENV refers to the virtualenv you're using to develop google-cloud-python):

After following the steps above in "Using a Development Checkout", install Sphinx and all development requirements in your virtualenv:
```
$ cd ~/hack-on-google-cloud-python
$ $VENV/bin/pip install Sphinx
```
Change into the docs directory within your google-cloud-python checkout and execute the make command with some flags:
```
$ cd ~/hack-on-google-cloud-python/google-cloud-python/docs
$ make clean html SPHINXBUILD=$VENV/bin/sphinx-build
```
The SPHINXBUILD=... argument tells Sphinx to use the virtualenv Python, which will have both Sphinx and google-cloud-python (for API documentation generation) installed.
Open the docs/_build/html/index.html file to see the resulting HTML rendering.

As an alternative to 1. and 2. above, if you have tox installed, you can build the docs via:

$ tox -e docs

In addition, to build a preview of the readthedocs theme, you can build via:

$ tox -e docs-rtd

Note About `README` as it pertains to PyPI

The description on PyPI for the project comes directly from the README. Due to the reStructuredText (rst) parser used by PyPI, relative links which will work on GitHub (e.g. CONTRIBUTING.rst instead of https://github.com/GoogleCloudPlatform/google-cloud-python/blob/master/CONTRIBUTING.rst) may cause problems creating links or rendering the description.

Travis Configuration and Build Optimizations

All build scripts in the .travis.yml configuration file which have Python dependencies are specified in the tox.ini configuration. They are executed in the Travis build via tox -e {ENV} where {ENV} is the environment being tested.

If new tox environments are added to be run in a Travis build, they should be listed in [tox].envlist as a default environment.

We speed up builds by using the Travis caching feature.

We intentionally do not cache the .tox/ directory. Instead, we allow the tox environments to be re-built for every build. This way, we'll always get the latest versions of our dependencies and any caching or wheel optimization to be done will be handled automatically by pip.

Supported Python Versions

We support:

Python 2.7
Python 3.4
Python 3.5

Supported versions can be found in our tox.ini config.

We explicitly decided not to support Python 2.5 due to decreased usage and lack of continuous integration support.

We have dropped 2.6 as a supported version as well since Python 2.6 is no longer supported by the core development team.

We also explicitly decided to support Python 3 beginning with version 3.4. Reasons for this include:

Encouraging use of newest versions of Python 3
Taking the lead of prominent open-source projects
Unicode literal support which allows for a cleaner codebase that works in both Python 2 and Python 3

Versioning

This library follows Semantic Versioning.

It is currently in major version zero (0.y.z), which means that anything may change at any time and the public API should not be considered stable.

Contributor License Agreements

Before we can accept your pull requests you'll need to sign a Contributor License Agreement (CLA):

If you are an individual writing original source code and you own the intellectual property, then you'll need to sign an individual CLA.
If you work for a company that wants to allow you to contribute your work, then you'll need to sign a corporate CLA.

You can sign these electronically (just scroll to the bottom). After that, we'll be able to accept your pull requests.

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