Add Danger changelog checker (#34)

Author: marandaneto

.github/workflows/danger.yml

@@ -0,0 +1,16 @@
+name: "Danger"
+on:
+  pull_request:
+    types: [opened, synchronize, reopened, edited, ready_for_review]
+
+jobs:
+  build:
+    name: Changelog
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+      - run: npx danger ci
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}

dangerfile.js

@@ -0,0 +1,60 @@
+async function checkChangelog() {
+  const changelogFile = "CHANGELOG.md";
+
+  // Check if skipped
+  const skipChangelog =
+    danger.github && (danger.github.pr.body + "").includes("#skip-changelog");
+
+  if (skipChangelog) {
+    return;
+  }
+
+  // Check if current PR has an entry in changelog
+  const changelogContents = await danger.github.utils.fileContents(
+    changelogFile
+  );
+
+  const hasChangelogEntry = RegExp(`#${danger.github.pr.number}\\b`).test(
+    changelogContents
+  );
+
+  if (hasChangelogEntry) {
+    return;
+  }
+
+  // Report missing changelog entry
+  fail(
+    "Please consider adding a changelog entry for the next release.",
+    changelogFile
+  );
+
+  const prTitleFormatted = danger.github.pr.title
+    .split(": ")
+    .slice(-1)[0]
+    .trim()
+    .replace(/\.+$/, "");
+
+  markdown(
+    `
+### Instructions and example for changelog
+Please add an entry to \`CHANGELOG.md\` to the "Next" section. Make sure the entry includes this PR's number.
+Example:
+\`\`\`markdown
+## Next
+- ${prTitleFormatted} ([#${danger.github.pr.number}](${danger.github.pr.html_url}))
+\`\`\`
+If none of the above apply, you can opt out of this check by adding \`#skip-changelog\` to the PR description.`.trim()
+  );
+}
+
+async function checkAll() {
+  const isDraft = danger.github.pr.mergeable_state === "draft";
+
+  if (isDraft) {
+    return;
+  }
+
+  await checkChangelog();
+}
+
+schedule(checkAll);