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A self-updating cross-platform application made as a coding challenge
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README.md

self-updating-program

A self-updating cross-platform application made as a coding challenge

Build Status

Getting Started

Installation

self-updating-app is a proper Python package: it can be installed via pip:

$ python3 -m venv env
(env) $ pip install git+https://github.com/BGR360/self-updating-program.git

To install a specific version, such as 1.0.0, specify it using @:

$ pip install git+https://github.com/BGR360/self-updating-program.git@1.0.0

This will also work with a branch name or a commit hash.

Updating

If your installed version of self-updating-app is out of date, it will prompt you to update the next time you start it:

$ self-updating-app
There is a new version available (v0.7.4).
Would you like to update? [Y/n]

If you select yes, then the app will invoke pip to upgrade your current installation, and the updated version will be available the next time you run the app. You could also run pip manually:

$ pip install --upgrade self-updating-app

Usage

Usage: self-updating-app [OPTIONS]

Options:
  --install-version TEXT  Install a specific version of the program (for
                          testing).
  -y, --yes-update        Automatically agree to any updates.
  -n, --no-update         Do not check for updates.
  --version               Show the version and exit.
  -h, --help              Show this message and exit.

Contributing

To contribute, fork the repository and make a pull request to the develop branch. Once your PR is merged, I will publish a new Release, and all installed instances will prompt their users to update the app the next time it is launched.

How it Works

Packaging and Distributing the Application

I use the python package PBR to handle packaging the application. PBR is a wrapper around python's setuptools that makes things a little cleaner to use and also offers nice features like automatic version detection.

Python's setuptools is what is used to publish and distribute PyPi (pip) packages. A really handy feature of pip that I utilized in this project is that you can install python packages from GitHub repositories.

Versions and Updating

Automatic Version Detection

Typically, when writing a setuptools package, one must explicitly code the version number into setup.py. Instead, PBR can automatically infer the package's version via git tags in the local/remote repository, and the detected version will be bundled into the package at installation time.

PBR is also included as a runtime dependency of self-updating-app so it can know its version at runtime and compare it to the latest version on GitHub.

Checking for Updates

self-updating-app makes a simple HTTP request to the GitHub API's /releases endpoint to grab the latest Release version from the GitHub repository. If the version is greater than the local version, it prompts the user to update the application.

Continuous Integration

I chose to use Cirrus CI for continuous integration testing. I originally chose Cirrus over Circle CI because Circle CI does not offer Mac OS testing for free. However, looking back, I think Circle CI may have been the better choice; I found Cirrus CI to be clunky and somewhat young, and didn't actually get around to running CI/CD on Mac instances.

CI Tasks

On every commit, Cirrus CI runs the Build and Run task, which simply packages the source tree up using setup.py and runs self-updating-application to see if it works.

On every Pull Request, an extra task runs: Install from GitHub. This attempts to pip install the package directly from GitHub using the latest commit hash, with no source code present (it skips the git clone step that all CI tasks have by default).

Finally, whenever a Release is published on GitHub, two more tasks run:

  • Install from GitHub and Check Version:
    • Runs pip install to install the latest released version from GitHub.
    • Runs self-updating-app --version and checks that it is the same as the tag_name of the Release that triggered the task.
  • Install Previous Version and Self-Update:
    • Queries the GitHub /releases API to detect what the second-to-latest released version is.
    • Runs pip install to install that version.
    • Runs self-updating-app --yes-update.
    • Ensures that the application actually updated itself to the most recent version by running self-updating-app --version.
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