Feat: Allow repo specific dangerfile.

.github/test-dangerfile.js

@@ -0,0 +1,37 @@
+// Test dangerfile for exercising extra-dangerfile feature
+// This demonstrates how repositories can add custom Danger checks
+
+module.exports = async function ({ fail, warn, message, markdown, danger }) {
+  console.log('::notice::Running custom dangerfile checks...');
+
+  // Test that we have access to the danger API
+  if (!danger || !danger.github || !danger.github.pr) {
+    fail('Custom dangerfile cannot access danger API');
+    return;
+  }
+
+  // Example check: Verify PR has a description
+  const prBody = danger.github.pr.body;
+  if (!prBody || prBody.trim().length === 0) {
+    warn('PR description is empty. Consider adding a description to help reviewers.');
+  } else {
+    message('✅ Custom dangerfile check: PR has a description');
+  }
+
+  // Example check: Verify PR title is not too short
+  const prTitle = danger.github.pr.title;
+  if (prTitle && prTitle.length < 10) {
+    warn('PR title is quite short. Consider making it more descriptive.');
+  } else {
+    message('✅ Custom dangerfile check: PR title length is reasonable');
+  }
+
+  // Show that we can access git information
+  const modifiedFiles = danger.git.modified_files || [];
+  const createdFiles = danger.git.created_files || [];
+  const totalChangedFiles = modifiedFiles.length + createdFiles.length;
+
+  message(`📊 Custom check: This PR changes ${totalChangedFiles} file(s)`);
+
+  console.log('::notice::Custom dangerfile checks completed successfully');
+};

.github/workflows/danger-workflow-tests.yml

@@ -34,3 +34,70 @@ jobs:
 
           Write-Host "✅ Danger PR analysis completed successfully!"
           Write-Host "ℹ️  Check the PR comments for any Danger findings"
+
+  # Test extra-dangerfile feature
+  extra-dangerfile-test:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Run danger with extra dangerfile
+        id: danger-extra
+        uses: ./danger
+        with:
+          extra-dangerfile: '.github/test-dangerfile.js'
+
+      - name: Validate danger with extra-dangerfile outputs
+        env:
+          DANGER_OUTCOME: ${{ steps.danger-extra.outputs.outcome }}
+        shell: pwsh
+        run: |
+          Write-Host "🔍 Validating Danger action with extra-dangerfile..."
+          Write-Host "Danger Outcome: '$env:DANGER_OUTCOME'"
+
+          # Validate that Danger ran successfully
+          $env:DANGER_OUTCOME | Should -Be "success"
+
+          Write-Host "✅ Danger with extra-dangerfile completed successfully!"
+
+  # Test extra-install-packages feature
+  extra-packages-test:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      # Create a test dangerfile that requires curl
+      - name: Create test dangerfile requiring curl
+        shell: bash
+        run: |
+          cat > .github/test-dangerfile-curl.js << 'EOF'
+          module.exports = async function ({ message, danger }) {
+            const { execSync } = require('child_process');
+            try {
+              const curlVersion = execSync('curl --version', { encoding: 'utf-8' });
+              message('✅ curl is available: ' + curlVersion.split('\n')[0]);
+            } catch (err) {
+              throw new Error('curl command not found - extra-install-packages failed');
+            }
+          };
+          EOF
+
+      - name: Run danger with extra packages
+        id: danger-packages
+        uses: ./danger
+        with:
+          extra-dangerfile: '.github/test-dangerfile-curl.js'
+          extra-install-packages: 'curl'
+
+      - name: Validate danger with extra-install-packages outputs
+        env:
+          DANGER_OUTCOME: ${{ steps.danger-packages.outputs.outcome }}
+        shell: pwsh
+        run: |
+          Write-Host "🔍 Validating Danger action with extra-install-packages..."
+          Write-Host "Danger Outcome: '$env:DANGER_OUTCOME'"
+
+          # Validate that Danger ran successfully
+          $env:DANGER_OUTCOME | Should -Be "success"
+
+          Write-Host "✅ Danger with extra-install-packages completed successfully!"

danger/README.md

@@ -30,6 +30,16 @@ jobs:
   * required: false
   * default: `${{ github.token }}`
 
+* `extra-dangerfile`: Path to an additional dangerfile to run custom checks.
+  * type: string
+  * required: false
+  * default: ""
+
+* `extra-install-packages`: Additional packages that are required by the extra-dangerfile, you can find a list of packages here: https://packages.debian.org/search?suite=bookworm&keywords=curl.
+  * type: string
+  * required: false
+  * default: ""
+
 ## Outputs
 
 * `outcome`: Whether the Danger run finished successfully. Possible values are `success`, `failure`, `cancelled`, or `skipped`.
@@ -52,4 +62,18 @@ The Danger action runs the following checks:
 - **Conventional commits**: Validates commit message format and PR title conventions
 - **Cross-repo links**: Checks for proper formatting of links in changelog entries
 
-For detailed rule implementations, see [dangerfile.js](dangerfile.js).
+For detailed rule implementations, see [dangerfile.js](dangerfile.js).
+
+## Extra Danger File
+
+When using an extra dangerfile, the file must be inside the repository and written in CommonJS syntax. You can use the following snippet to export your dangerfile:
+
+```JavaScript
+module.exports = async function ({ fail, warn, message, markdown, danger }) {
+  ...
+  const gitUrl = danger.github.pr.head.repo.git_url;
+  ...
+  warn('...');
+}
+
+```

danger/action.yml

@@ -7,6 +7,14 @@ inputs:
     description: 'Token for the repo. Can be passed in using {{ secrets.GITHUB_TOKEN }}'
     required: false
     default: ${{ github.token }}
+  extra-dangerfile:
+    description: 'Path to additional dangerfile to run after the main checks'
+    type: string
+    required: false
+  extra-install-packages:
+    description: 'Additional apt packages to install in the DangerJS container (space-separated package names)'
+    type: string
+    required: false
 
 outputs:
   outcome:
@@ -28,19 +36,62 @@ runs:
       shell: pwsh
       run: Get-Content '${{ github.action_path }}/danger.properties' | Tee-Object $env:GITHUB_OUTPUT -Append
 
+    # Validate extra-install-packages to prevent code injection
+    - name: Validate package names
+      if: ${{ inputs.extra-install-packages }}
+      shell: pwsh
+      env:
+        EXTRA_INSTALL_PACKAGES: ${{ inputs.extra-install-packages }}
+      run: |
+        # Validate against Debian package naming rules: must start with alphanumeric,
+        # contain only lowercase letters, digits, hyphens, plus signs, periods
+        # Package names cannot start with hyphen or period, and must be reasonable length
+        foreach ($pkg in $env:EXTRA_INSTALL_PACKAGES -split '\s+') {
+          if ($pkg -notmatch '^[a-z0-9][a-z0-9.+-]{0,100}$') {
+            Write-Host "::error::Invalid package name '$pkg'. Debian packages must start with lowercase letter or digit and contain only lowercase letters, digits, hyphens, periods, and plus signs."
+            exit 1
+          }
+        }
+
     # Using a pre-built docker image in GitHub container registry instead of NPM to reduce possible attack vectors.
-    - name: Run DangerJS
-      id: danger
+    - name: Setup container
       shell: bash
+      env:
+        GITHUB_TOKEN: ${{ inputs.api-token }}
+        EXTRA_DANGERFILE_INPUT: ${{ inputs.extra-dangerfile }}
       run: |
-        docker run \
+        # Start a detached container with all necessary volumes and environment variables
+        docker run -td --name danger \
+          --entrypoint /bin/bash \
           --volume ${{ github.workspace }}:/github/workspace \
           --volume ${{ github.action_path }}:${{ github.action_path }} \
           --volume ${{ github.event_path }}:${{ github.event_path }} \
           --workdir /github/workspace \
           --user $(id -u) \
           -e "INPUT_ARGS" -e "GITHUB_JOB" -e "GITHUB_REF" -e "GITHUB_SHA" -e "GITHUB_REPOSITORY" -e "GITHUB_REPOSITORY_OWNER" -e "GITHUB_RUN_ID" -e "GITHUB_RUN_NUMBER" -e "GITHUB_RETENTION_DAYS" -e "GITHUB_RUN_ATTEMPT" -e "GITHUB_ACTOR" -e "GITHUB_TRIGGERING_ACTOR" -e "GITHUB_WORKFLOW" -e "GITHUB_HEAD_REF" -e "GITHUB_BASE_REF" -e "GITHUB_EVENT_NAME" -e "GITHUB_SERVER_URL" -e "GITHUB_API_URL" -e "GITHUB_GRAPHQL_URL" -e "GITHUB_REF_NAME" -e "GITHUB_REF_PROTECTED" -e "GITHUB_REF_TYPE" -e "GITHUB_WORKSPACE" -e "GITHUB_ACTION" -e "GITHUB_EVENT_PATH" -e "GITHUB_ACTION_REPOSITORY" -e "GITHUB_ACTION_REF" -e "GITHUB_PATH" -e "GITHUB_ENV" -e "GITHUB_STEP_SUMMARY" -e "RUNNER_OS" -e "RUNNER_ARCH" -e "RUNNER_NAME" -e "RUNNER_TOOL_CACHE" -e "RUNNER_TEMP" -e "RUNNER_WORKSPACE" -e "ACTIONS_RUNTIME_URL" -e "ACTIONS_RUNTIME_TOKEN" -e "ACTIONS_CACHE_URL" -e GITHUB_ACTIONS=true -e CI=true \
-          -e GITHUB_TOKEN="${{ inputs.api-token }}" \
+          -e "GITHUB_TOKEN" \
           -e DANGER_DISABLE_TRANSPILATION="true" \
+          -e "EXTRA_DANGERFILE_INPUT" \
           ghcr.io/danger/danger-js:${{ steps.config.outputs.version }} \
-          --failOnErrors --dangerfile ${{ github.action_path }}/dangerfile.js
+          -c "sleep infinity"
+
+    - name: Setup additional packages
+      if: ${{ inputs.extra-install-packages }}
+      shell: bash
+      env:
+        EXTRA_INSTALL_PACKAGES: ${{ inputs.extra-install-packages }}
+      run: |
+        echo "Installing packages: $EXTRA_INSTALL_PACKAGES"
+        docker exec --user root danger sh -c "set -e && apt-get update && apt-get install -y --no-install-recommends $EXTRA_INSTALL_PACKAGES"
+        echo "All additional packages installed successfully."
+
+    - name: Run DangerJS
+      id: danger
+      shell: bash
+      run: |
+        docker exec --user $(id -u) danger danger ci --fail-on-errors --dangerfile ${{ github.action_path }}/dangerfile.js
+
+    - name: Cleanup container
+      if: always()
+      shell: bash
+      run: docker rm -f danger || true

danger/dangerfile.js

@@ -186,10 +186,52 @@ async function checkActionsArePinned() {
   }
 }
 
+async function checkFromExternalChecks() {
+  // Get the external dangerfile path from environment variable (passed via workflow input)
+  // Priority: EXTRA_DANGERFILE (absolute path) -> EXTRA_DANGERFILE_INPUT (relative path)
+  const extraDangerFilePath = process.env.EXTRA_DANGERFILE || process.env.EXTRA_DANGERFILE_INPUT;
+  console.log(`::debug:: Checking from external checks: ${extraDangerFilePath}`);
+  if (extraDangerFilePath) {
+    try {
+      const workspaceDir = '/github/workspace';
+
+      const path = require('path');
+      const fs = require('fs');
+      const customPath = path.join(workspaceDir, extraDangerFilePath);
+      // Ensure the resolved path is within workspace
+      const resolvedPath = fs.realpathSync(customPath);
+      if (!resolvedPath.startsWith(workspaceDir)) {
+        fail(`Invalid dangerfile path: ${extraDangerFilePath}. Must be within workspace.`);
+        throw new Error('Security violation: dangerfile path outside workspace');
+      }
+
+      const extraModule = require(customPath);
+      if (typeof extraModule !== 'function') { 
+        warn(`EXTRA_DANGERFILE must export a function at ${customPath}`); 
+        return; 
+      }
+      await extraModule({
+        fail: fail, 
+        warn: warn,
+        message: message, 
+        markdown: markdown,
+        danger: danger,
+      });
+    } catch (err) {
+      if (err.message && err.message.includes('Cannot use import statement outside a module')) {
+        warn(`External dangerfile uses ES6 imports. Please convert to CommonJS syntax (require/module.exports) or use .mjs extension with proper module configuration.\nFile: ${extraDangerFilePath}`);
+      } else {
+        warn(`Could not load custom Dangerfile: ${extraDangerFilePath}\n${err}`);
+      }
+    }
+  }
+}
+
 async function checkAll() {
   await checkDocs();
   await checkChangelog();
   await checkActionsArePinned();
+  await checkFromExternalChecks();
 }
 
 schedule(checkAll);