Converting Python's requirements.txt into Homebrew formula resources

For developers who maintain both Python and Homebrew packages, you've likely found that managing dependencies between the two ecosystems can be a bit challenging. Today, I am going to share a Python function that I wrote that automates the conversion of a Python requirements.txt file into Homebrew resource blocks. This can be a real time-saver, ensuring you have the correct dependencies for your Homebrew formula.

In Python, requirements.txt is the standard way to specify package dependencies with their corresponding versions. In a Homebrew formula, dependencies can be listed as 'resources'. Each resource block defines a package dependency, including its download URL and a SHA256 hash for verification.

The script uses the PyPI (Python Package Index) JSON API to fetch information about each package listed in your requirements.txt file. For each package, it generates a resource block with the package's download URL and SHA256 hash.

import requests
 
def generate_resource_blocks(requirements_file="requirements.txt"):
    pypi_base_url = "https://pypi.org/pypi"
 
    resource_blocks = ""
 
    with open(requirements_file, "r") as file:
        for line in file:
            line = line.strip()
 
            if line.startswith("-e") or line.startswith("#") or line == '':
                continue
 
            try:
                pkg_name, version = line.split("==")
            except ValueError:
                print(f"Skipping invalid line: {line}")
                continue
 
            pkg_info_url = f"{pypi_base_url}/{pkg_name}/{version}/json"
            response = requests.get(pkg_info_url)
 
            if response.status_code != 200:
                print(f"Failed to fetch package info for {pkg_name}=={version}")
                continue
 
            pkg_info = response.json()
            # Select the tar.gz distribution URL
            selected_url = next((url_info for url_info in pkg_info["urls"]
                                 if url_info["url"].endswith(".tar.gz")), None)
 
            if not selected_url:
                print(f"No .tar.gz distribution found for {pkg_name}=={version}")
                continue
 
            download_url = selected_url["url"]
            sha256 = selected_url["digests"]["sha256"]
 
            resource_block = (
                f'resource "{pkg_name}" do\n'
                f'  url "{download_url}"\n'
                f'  sha256 "{sha256}"\n'
                "end\n\n"
            )
 
            resource_blocks += resource_block
 
    return resource_blocks
 
 
if __name__ == "__main__":
    resources_text = generate_resource_blocks()
    print(resources_text)

This function skips lines in requirements.txt that start with -e (editable installs) or # (comments). It also provides error handling for ill-formatted lines in the requirements file, cases where fetching package information fails, and cases where no tar.gz distribution is found for a package.

Here's an example of what a generated Homebrew resource block looks like for the package 'requests':

resource "requests" do
  url "https://files.pythonhosted.org/packages/29/c1/24814557f1d22c56d50280771a17307e6bf87b70727d975fd6b2ce6b014a/requests-2.25.1.tar.gz"
  sha256 "27973dd6a34a5f11a9c95637757764ef5b3a8c33fe6e2e5e88b6fc93dd1d3a6f"
end

You can then paste these resource blocks into your Homebrew formula file to define the dependencies. This way, when the formula is installed with brew install, Homebrew will fetch and install these Python packages.

Remember, the idea here is to facilitate the conversion process, but always review the output to make sure it meets your exact needs!

This script should be a great help for developers looking to streamline their Homebrew formula creation process. Please feel free to adjust it according to your specific needs. Happy brewing!