Changed Lines

This GitHub action returns the file names and modified lines of each file in a pull request. This action is intended for custom linters, where you want to compare log lines against modified lines in your PR.

The action uses the patch data returned from the Git API PR endpoint to collect the modified file names and lines. Changes in your PR are compared against the target branch and line numbers in the output are relative to the modified file. If the entire file is new, all lines appear in the output.

Note

This action only works with pull requests. This action only works on Linux runners.

The action outputs a JSON formatted string. For example:

{"test_file_1.py": [13, 30, 39], "test_file_2.md": [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33], "test_file_3.txt": [14, 18, 19]}

Using Changed Lines

on: [ pull_request ]

jobs:
  find_changed_lines:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - name: Find changed lines
        id: changed_lines
        uses: hestonhoffman/changed-lines@v1
      - name: Print changed lines
        run: echo ${{ steps.changed_lines.outputs.changed_lines }}

Return only a list of changed files

The outputs.changed_files output gives you only the changed filenames in a space-delimited list. For example:

test_file_1.py test_file_2.md test_file_3.txt

File delimiter

To change the delimiter, use the delimiter input. The following example outputs filenames separated by commas:

[...]
    steps:
      - uses: actions/checkout@v4
      - name: Find changed lines
        id: changed_lines
        uses: hestonhoffman/changed-lines@v1
        with:
          delimiter: ','
      - name: Print changed files
        run: echo ${{ steps.changed_lines.outputs.changed_files }}

Filter by file type

To return the output for only certain file types, use the file_filter input and specify a comma-separated list of file extensions. The following example only returns markdown and text files:

[...]
    steps:
      - uses: actions/checkout@v4
      - name: Find changed lines
        id: changed_lines
        uses: hestonhoffman/changed-lines@v1
        with:
          file_filter: '.md, .txt'
      - name: Print changed files
        run: echo ${{ steps.changed_lines.outputs.changed_files }}

Use an alternate GitHub API URL

Use the api_url input if you need to use a custom GitHub API URL. This is useful if you're a GitHub Enterprise user.

[...]
    steps:
      - uses: actions/checkout@v4
      - name: Find changed lines
        id: changed_lines
        uses: hestonhoffman/changed-lines@v1
        with:
          api_url: https://example.com
      - name: Print changed files
        run: echo ${{ steps.changed_lines.outputs.changed_files }}

Thanks to Jacob Tomlinson for a helpful tutorial.

Local development

You can use the instructions below to load some environment variables so you can run the script locally. You'll need a GitHub personal access token with repo privileges.

If you want to run the script locally:

1. (Optional) Set up a virtual environment using your preferred method.

2. Install the python modules:

   pip install -r requirements.txt

3. Make a copy of example.env and change the environment variables to point to a PR you want to test against:

   Note: This file (.env) is ignored by git, but make sure you don't accidentally commit it somehow, as it stores your git token.

   cp example.env .env

4. Source the environment variables:

   source .env

5. Run the script:

   python main.py

6. Check the generated text file for the results. The environment GITHUB_OUTPUT variable sets this to temp.txt by default.

Deleted files and lines

Deleted files and lines don't show up in the output. This is intentional because the main use case for the action is to pass changed lines to a linter for GitHub command annotations. The GitHub API doesn't allow annotations on deleted lines.