Add checkHybrid job

.github/workflows/main_ci.yml

@@ -37,6 +37,16 @@ jobs:
           registry-url: https://registry.npmjs.org/
       - run: npm ci
       - run: npm run format:ci
+  check-hybrid:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 18
+          registry-url: https://registry.npmjs.org/
+      - run: npm ci
+      - run: npm run checkHybrid
   gitdiff:
     runs-on: ubuntu-latest
     steps:

package.json

@@ -24,7 +24,7 @@
   },
   "scripts": {
     "build": "tsc -p ./tsconfig.json && tsc -p ./tsconfig.cjs.json",
-    "postbuild": "find src/cjs -type f -name \"*.js\" -exec bash -c 'mv \"$0\" \"${0%.js}.cjs\"' {} \\; && chmod +x fixup.cjs && node fixup.cjs",
+    "checkHybrid": "chmod +x test.cjs && node test.cjs",
     "coverage-report": "npm run build && npm run nobuild:coverage-report",
     "coverage": "npm run build && npm run nobuild:coverage",
     "format": "npm run prettier -- --write",
@@ -34,6 +34,7 @@
     "nobuild:coverage-report": "c8 report --reporter=lcov",
     "nobuild:coverage": "c8 --check-coverage --branches 90 --functions 90 npm run nobuild:unit",
     "nobuild:unit": "tape test/*.js",
+    "postbuild": "find src/cjs -type f -name \"*.js\" -exec bash -c 'mv \"$0\" \"${0%.js}.cjs\"' {} \\; && chmod +x fixup.cjs && node fixup.cjs",
     "prettier": "prettier 'ts-src/**/*.ts' --ignore-path ./.prettierignore",
     "test": "npm run build && npm run format:ci && npm run lint && npm run nobuild:coverage",
     "unit": "npm run build && npm run nobuild:unit"

test.cjs

@@ -0,0 +1,39 @@
+const fs = require('fs');
+const childProcess = require('child_process');
+
+let mainFile = JSON.parse(fs.readFileSync('./package.json').toString()).module;
+if (!mainFile.startsWith('.')) {
+  // ESM imports of files must start with ./
+  mainFile = `./${mainFile}`;
+}
+const cjsFile = './tmp.cjs';
+const esmFile = './tmp.mjs';
+const cjs = `const x = require('.')\nconsole.log(x)`;
+const esm = `import * as x from '${mainFile}';\nconsole.log(x)`;
+
+fs.writeFileSync(cjsFile, cjs);
+fs.writeFileSync(esmFile, esm);
+
+const result1 = childProcess.spawnSync('node', [cjsFile], {
+  cwd: __dirname,
+});
+const result2 = childProcess.spawnSync('node', [esmFile], {
+  cwd: __dirname,
+});
+
+fs.unlinkSync(cjsFile);
+fs.unlinkSync(esmFile);
+
+const errors = [];
+if (result1.status !== 0) {
+  errors.push(result1.stderr.toString());
+}
+if (result2.status !== 0) {
+  errors.push(result2.stderr.toString());
+}
+if (errors.length > 0) {
+  console.error(
+    `Failed to run this library under CJS or ESM. Errors:\n${errors.join('\n')}`,
+  );
+  process.exit(1);
+}