Bazel is an amazing tool for building and managing software projects, but sometimes you might need to use a Python package that’s not available on PyPI or another package manager. Fear not, dear reader! In this article, we’ll take you by the hand and guide you through the process of adding a Python package from Git as a dependency in Bazel.
Why Use Git as a Dependency?
There are several reasons why you might want to use a Python package from Git as a dependency:
- The package is not available on PyPI or another package manager.
- You need to use a specific version of the package that’s not available on PyPI.
- You want to use a package that’s still in development and not yet released.
- You want to customize the package for your specific use case.
Prerequisites
Before we dive into the process, make sure you have the following:
A Bazel project set up and running.
Git installed on your system.
A Python package hosted on Git that you want to use as a dependency.
Step 1: Create a WORKSPACE File
The first step is to create a WORKSPACE file in the root of your Bazel project. This file tells Bazel where to find your dependencies.
touch WORKSPACEAdd the following code to the WORKSPACE file:
workspace(name = "my_project")
load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
http_archive(
name = "my_git_dependency",
urls = ["https://github.com/username/repository.git"],
sha256 = "commit_sha256_here",
strip_prefix = "repository-branch",
type = "git",
branch = "main",
)This code tells Bazel to download the Git repository at the specified URL and use it as a dependency. Make sure to replace username, repository, commit_sha256_here, and branch with the actual values for your Git repository.
Step 2: Create a BUILD File
Next, create a BUILD file in the same directory as the WORKSPACE file. This file tells Bazel how to build your project.
touch BUILDAdd the following code to the BUILD file:
load("@rules_python//python:defs.bzl", "py_library")
py_library(
name = "my_library",
srcs = ["my_file.py"],
deps = ["@my_git_dependency//:my_module"],
)This code tells Bazel to build a Python library called my_library that depends on the my_module module from the Git repository.
Step 3: Add the Dependency to Your BUILD File
In the BUILD file, add the following code to include the Git repository as a dependency:
load("@//my_git_dependency:my_module.bzl", "my_module")
py_binary(
name = "my_binary",
main = "my_file.py",
deps = [":my_library"],
)This code tells Bazel to build a Python binary called my_binary that depends on the my_library library, which in turn depends on the my_module module from the Git repository.
Step 4: Build and Run Your Project
Finally, build and run your project using the following command:
bazel build //:my_binaryThis will build your project and create an executable file called my_binary. You can then run the executable using the following command:
bazel run //:my_binaryTroubleshooting Common Issues
If you encounter any issues during the process, here are some common solutions:
| Error | Solution |
|---|---|
Error: Unable to find repository |
Make sure the Git repository URL is correct and the repository exists. |
Error: Invalid SHA256 checksum |
Make sure the SHA256 checksum is correct for the commit you’re trying to use. |
Error: Unable to build project |
Make sure the BUILD file is correctly formatted and the dependencies are correctly specified. |
Conclusion
In this article, we’ve shown you how to add a Python package from Git as a dependency in Bazel. By following these steps, you can easily use custom Python packages in your Bazel projects. Remember to replace the placeholders with the actual values for your Git repository and project.
If you have any further questions or need more assistance, feel free to ask in the comments below!
Happy building!
Frequently Asked Question
Got stuck with adding a Python package from Git as a dependency in Bazel? Don’t worry, we’ve got you covered!
Why can’t I just use pip to install the package from Git?
Bazel doesn’t use pip to install packages, instead, it relies on its own dependency management system. This allows for more control and reproducibility in the build process. To add a Python package from Git, you need to use Bazel’s `http_archive` rule.
How do I specify the Git repository and commit hash in the BUILD file?
You can use the `http_archive` rule to specify the Git repository and commit hash. For example: `http_archive(name = “my_package”, urls = [“https://github.com/user/my_package.git”], commit = “43697bd”)`. This tells Bazel to fetch the repository from the specified URL and use the specified commit hash.
What if I want to use a specific branch or tag instead of a commit hash?
You can use the `strip_prefix` and `type` attributes to specify a branch or tag. For example: `http_archive(name = “my_package”, urls = [“https://github.com/user/my_package.git”], type = “git”, strip_prefix = “main”)`. This tells Bazel to fetch the `main` branch from the repository.
How do I make the package available as a dependency in my Bazel project?
Once you’ve defined the `http_archive` rule, you can use the `requirements` attribute to specify the package as a dependency in your `BUILD` file. For example: `python_library(name = “my_target”, srcs = [“my_file.py”], requirements = [“@my_package//:my_package”])`. This makes the `my_package` package available as a dependency for your `my_target` target.
What if I encounter errors or issues when adding the package as a dependency?
If you encounter errors or issues, check the Bazel documentation and the package’s documentation for troubleshooting tips. You can also try using the `–verbose` flag when running Bazel to get more detailed error messages. Additionally, make sure you’re using the correct syntax and formatting in your `BUILD` file.
