Run Danger with GitHub Actions

.github/workflows/danger.yml

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+name: Danger
+
+on: [pull_request]
+
+jobs:
+  danger:
+    name: Danger JS
+    runs-on: ubuntu-latest
+    steps:
+    - name: Checkout the Git repository
+      uses: actions/checkout@v1
+    # Danger JS would fail because of the below missing module.
+    # TODO: Report to Danger JS
+    - name: Install missing module
+      run: yarn add -D @babel/plugin-transform-flow-strip-types
+    # TODO: Figure out why GITHUB_TOKEN isn't enough for Danger JS to create a comment.
+    # Our dangerfile.js escalates any warnings as failures to get more attention.
+    #
+    # Here is the error response from GitHub API:
+    #
+    # Request failed [403]: https://api.github.com/repos/TextureGroup/Texture/issues/1635/comments
+    # Response: {
+    #   "message": "Resource not accessible by integration",
+    #   "documentation_url": "https://developer.github.com/v3/issues/comments/#create-a-comment"
+    # }
+    #
+    # https://github.com/TextureGroup/Texture/pull/1635/checks?check_run_id=200541353
+    - name: Danger
+      uses: danger/[email protected]
+      env:
+        GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}

dangerfile.js

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+const { danger, fail, warn, schedule } = require('danger');
+const { readFileSync } = require('fs');
+
+const source_pattern = /(\.m|\.mm|\.h)$/;
+const modified_source_files = danger.git.modified_files.filter(f => source_pattern.test(f));
+const has_modified_source_files = (Array.isArray(modified_source_files) && modified_source_files.length > 0);
+const added_source_files = danger.git.created_files.filter(f => source_pattern.test(f));
+const has_added_source_files = (Array.isArray(added_source_files) && added_source_files.length > 0);
+
+// Make it more obvious that a PR is a work in progress and shouldn't be merged yet
+if (danger.github.pr.title.includes("[WIP]")) {
+  const msg = "PR is classed as Work in Progress";
+  console.error("FAIL: " + msg);
+  fail(msg);
+}
+
+// Warn when there is a big PR
+if (danger.github.pr.additions + danger.github.pr.deletions > 500) {
+  const msg = "This is a big PR, please consider splitting it up to ease code review.";
+  console.error("WARN: "+ msg);
+  warn(msg);
+}
+
+// Modifying the changelog will probably get overwritten.
+if (danger.git.modified_files.includes("CHANGELOG.md")) {
+  if (danger.github.pr.title.includes("#changelog")) {
+    const msg = "PR modifies CHANGELOG.md, which is a generated file. #changelog added to the title to suppress this warning.";
+    console.error("WARN: "+ msg);
+    warn(msg);
+  } else {
+    const msg = "PR modifies CHANGELOG.md, which is a generated file. Add #changelog to the title to suppress this failure.";
+    console.error("FAIL: " + msg);
+    fail(msg);
+  }
+}
+
+// Reference: http://a32.me/2014/03/heredoc-multiline-variable-with-javascript/
+function hereDoc(f) {
+  return f.toString().
+  replace(/^[^\/]+\/\*!?/, '').
+  replace(/\*\/[^\/]+$/, '');
+}
+
+function full_license(partial_license, filename) {
+  var license_header = hereDoc(function() {/*!
+//
+*/});
+  license_header += "//  " + filename;
+  license_header += hereDoc(function() {/*!
+//  Texture
+//*/});
+  license_header += partial_license;
+  return license_header;
+}
+
+function check_file_header(files_to_check, license) {
+  for (let file of files_to_check) {
+    const filename = file.replace(/^.*[\\\/]/, '');
+    schedule(async () => {
+      const content = await danger.github.utils.fileContents(file);
+      if (!content.includes("Pinterest, Inc.")) {
+        const msg = "Please ensure license is correct for " + filename +":\n```" + full_license(license, filename) + "\n```";
+        console.error("FAIL: " + msg);
+        fail(msg);
+      }  
+    });
+  }   
+}
+
+const new_source_license_header = hereDoc(function() {/*!
+//  Copyright (c) Pinterest, Inc.  All rights reserved.
+//  Licensed under Apache 2.0: http://www.apache.org/licenses/LICENSE-2.0
+//*/});
+
+const modified_source_license_header = hereDoc(function() {/*!
+//  Copyright (c) Facebook, Inc. and its affiliates.  All rights reserved.
+//  Changes after 4/13/2017 are: Copyright (c) Pinterest, Inc.  All rights reserved.
+//  Licensed under Apache 2.0: http://www.apache.org/licenses/LICENSE-2.0
+//*/});
+
+// Ensure new files have proper header
+if (has_added_source_files) {
+  check_file_header(added_source_files, new_source_license_header);
+}
+
+// Ensure modified files have proper header
+if (has_modified_source_files) {
+  check_file_header(modified_source_files, modified_source_license_header);
+}