Lint changesets

.github/contributing.md

@@ -93,6 +93,11 @@ yarn changeset add
 
 Follow the prompts to select which package(s) are affected by your change, and whether the change is a major, minor or patch change. This will create a file in the `.changesets` directory of the repo. This change should be committed and included with your PR.
 
+Considerations:
+
+- You can use markdown in your changeset to include code examples, headings, and more. However, **please use plain text for the first line of your changeset**. The formatting of the GitHub release notes does not support headings as the first line of the changeset.
+- When selecting packages for the changesets, only select packages which are published. Do not include private packages, as it will cause the build to fail. _Hopefully these are removed from the list of options in a [future Changesets release](https://github.com/changesets/changesets/issues/436)_.
+
 > **Important**: Until our official release, we will only release `minor` and `patch` updates. This means that breaking changes will be included in minor releases. Once we officially launch Hydrogen, we'll switch to `1.0.0` and follow a normal semantic release pattern.
 
 ## Contributing Examples

.github/workflows/changesets_linter.yml

@@ -0,0 +1,12 @@
+on:
+  pull_request:
+
+name: Changelog Linter
+jobs:
+  lint:
+    name: Lint Changelog
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - name: Lint changesets
+        run: node scripts/lint-changesets.mjs

scripts/lint-changesets.mjs

@@ -0,0 +1,64 @@
+import fs from 'fs';
+
+function lint() {
+  // Get the list of ignored packages from .changeset/config.json
+  const config = JSON.parse(fs.readFileSync('.changeset/config.json', 'utf8'));
+  const ignoredPackages = config.ignore;
+
+  // Iterate through all the .md files in the .changeset directory
+  var changesetFiles = fs.readdirSync('.changeset');
+  changesetFiles.forEach(function (file) {
+    if (file.indexOf('.md') < 0) return;
+
+    var filePath = '.changeset/' + file;
+    var fileContents = fs.readFileSync(filePath, 'utf8');
+
+    // Check to see if any of the ignored packages exist in the frontmatter
+    const frontmatter = fileContents.match(/^---\n([\s\S]*?)\n---/m);
+    if (!frontmatter) return;
+
+    let foundPackage;
+
+    /**
+     * We have to manually lint for this due to an issue with changesets:
+     * @see https://github.com/changesets/changesets/issues/436
+     */
+    if (
+      (foundPackage = ignoredPackages.find((ignoredPackage) =>
+        frontmatter[1].includes(ignoredPackage)
+      ))
+    ) {
+      throw new Error(
+        `The changeset ${filePath} contains an ignored package: ${foundPackage}. ` +
+          `Please remove it from the changeset. If it is the only package in the changeset, ` +
+          `remove the changeset entirely.`
+      );
+    }
+
+    /**
+     * Ensure the first line of the changeset is NOT a markdown header:
+     */
+    const fileContentsWithoutFrontmatter = fileContents
+      .replace(/^---\n([\s\S]*?)\n---/m, '')
+      .trim();
+
+    if (fileContentsWithoutFrontmatter.startsWith('#')) {
+      throw new Error(
+        `The first line of changeset ${filePath} begins with a header: \n\n${
+          fileContentsWithoutFrontmatter.split('\n')[0]
+        }\n\n` +
+          `Changesets must begin with plain text. You may use markdown headers later in the body if desired.`
+      );
+    }
+  });
+
+  console.log('No ignored packages found in changesets.');
+}
+
+try {
+  lint();
+} catch (e) {
+  console.error(e.message);
+  // eslint-disable-next-line no-process-exit
+  process.exit(1);
+}