This GitHub action posts comments on a PR that can vary depending on which files are being changed in the PR.

Create your workflow file .github/workflows/pr-commenter.yml as follows.

name: "PR Commenter"
on:
  - pull_request_target

jobs:
  pr-comment:
    runs-on: ubuntu-latest
    steps:
      - uses: exercism/[email protected]
        with:
          github-token: "${{ github.token }}"
          config-file: ".github/pr-commenter.yml"

Create your action configuration file .github/pr-commenter.yml as follows.

comment:
  on-update: recreate
  header: |
    Thank you for contributing to this repository :tada:.

  footer: |
    ---
    Automated comment created by [PR Commenter](https://github.com/exercism/pr-commenter-action) :robot:.

  snippets:
    - id: any-markdown-file-changed
      files:
        - '*.md'
        - '**/*.md'
      body: |
        It looks like you're changing a Markdown file.
        Make sure your changes follow our [language guidelines](some-link) when writing documentation.

Auth token used to manage issues or pull requests.

Required: true

Default: ${{ github.token }}

Required: true

Default: .github/pr-commenter.yml

To reference a config file in another repo use the format: <owner>/<repo>@<ref>:<path>, for example someuser/my-repo@v1:.github/pr-commenter.yml. NOTE: make sure that "my-repo" is public and has "Workflow permissions" allowing files to be read.

Dictates what should happen if there is no comment on this PR yet. For almost all use cases, you want to keep the default behavior. The custom nothing option makes sense if you're using this action twice on the same PR, and you want the second execution not to create a new comment, but only edit it if it already exists from the first execution.

• create - create a new comment
• nothing - do not create a new comment

Also accepts a Mustache template that evaluates to one of the above values.

Required: false

Default: create

Dictates what should happen if a comment was already created on this PR, but more changes were pushed to the PR and the comment needs to change.

• recreate - delete the old comment and create a new one
• edit - edit the old comment
• nothing - leave the old comment unchanged

Also accepts a Mustache template that evaluates to one of the above values.

Required: true

Default: recreate

An optional text to be included at the beginning of each comment.

Required: false

An optional text to be included at the end of each comment.

Required: false

A list of comment snippet configurations. At least one snippet is required. Note that a PR comment will only be created if at least one of the snippets match, even if comment.header and/or comment.footer are given.

Required: true

A string consisting of letters, numbers, -, and _ or a Mustache template that evaluates to such a string.

Snippet ids are used to check whether a comment's content changed. If you're using a template variable in the snippets's body and you want to recreate the whole comment when that variable changes value, use it in the snippet's id too.

Required: true

The text to be included in the PR comment.

Required: true

Comment snippet bodies and ids (as well as comment.on-create, comment.on-update, comment.header, and comment.footer) are Mustache templates.

Variables for the template can be provided via the template-variables input which should be a string containing a valid JSON.

You can use the context and expression syntax to assemble the JSON and set-output to calculate data for the template in separate steps.

name: "PR Commenter"
on:
  - pull_request_target

jobs:
  pr-comment:
    runs-on: ubuntu-latest
    steps:
      - name: Calculate some template variables
        id: vars
        run: |
          echo ::set-output name=today::"$(date +%d-%m-%Y)"

      - uses: exercism/[email protected]
        with:
          template-variables: |
            {
              "today": "${{ steps.vars.outputs.today }}",
              "prAuthor": "${{ github.event.pull_request.user.login }}",
              "branchNamePrefix": ${{ startsWith(github.event.pull_request.head.ref, 'ref-') }}
            }

comment:
  header: |
    Hi {{ prAuthor }}! Thank you for your contribution.

    {{^branchNamePrefix}}Your branch name doesn't start with the required prefix 'ref-'.{{/branchNamePrefix}}

Note that values such as the PR's title, body, or branch name should be considered unsafe user input.

Here's a more complex example of using template variables. Let's say you have a multiline file that changes often, and you want to always include the newest content of the file in the snippet.

To ensure the comment will be recreated when the file changes, use the file's hash in the snippet's id.

To ensure that newline characters are handled correctly, use environment variables instead of job outputs and toJSON.

name: "PR Commenter"
on:
  - pull_request_target

jobs:
  pr-comment:
    runs-on: ubuntu-latest
    steps:
      - name: Set environment variables
        run: |
          IMPORTANT_FILE_CONTENT=$(cat important_file)
          echo "IMPORTANT_FILE_CONTENT<<EOF" >> $GITHUB_ENV
          echo "$IMPORTANT_FILE_CONTENT" >> $GITHUB_ENV
          echo "EOF" >> $GITHUB_ENV

      - uses: exercism/[email protected]
        with:
          template-variables: |
            {
              "importantFileContent": ${{ toJSON(env.IMPORTANT_FILE_CONTENT) }},
              "importnatFileHash": ${{ toJSON(hashFiles('important_file.txt')) }}
            }

comment:
  snippets:
    - id: snippet_{{ importnatFileHash }}}
    - files:
      - 'important_file.txt'
    - body: |
        This is very important:
        {{ importantFileContent }}

A list of globs (strings) and/or match objects. If at least one file changed in the PR matches at least one of the globs or match objects, this snippet's body will be included in the comment.

Example:

# any markdown file changed in any directory
comment:
  snippets:
    - id: any-markdown-file-changed
      files:
        - '*.md'
        - '**/*.md'

A match object contains the keys any and/or all with a list of globs.

• all - every file changed in this PR must match every glob in this list
• any - at least one file changed in this PR must match every glob in this list

Example:

# at least one root-level markdown file changed
# and none of the changed files is the README.md
comment:
  snippets:
    - id: any-markdown-file-changed-but-readme
      files:
        - any: ['*.md']
          all: ['!README.md']

Required: true

This GitHub action uses the minimatch library for glob matching. A object with options can be provided under comment.glob-options to modify the behavior of this library. See the list of minimatch options for the list of supported options.

Example:

# Make all globs also match hidden files and directories
comment:
  glob-options:
    dot: true

• Install the required NodeJS version as specified in .tool-versions. The recommended way to manage multiple NodeJS versions is to use asdf.
• Install the dependencies with npm install.
• Run the tests with npm run test and the linter with npm run lint.

This library was originally created by @angelikatyborska. It is maintained by @angelikatyborska and the Exercism team. See the GitHub contributors graph for a full list of contributors.