Use esm package locally when testing to use ESM syntax from CJS code

phillipj · phillipj · commit d4a50420c5fc · 2021-03-05T21:30:49.000+01:00
These changes are primarily aiming for having an acceptable developer experience when working on changes locally and want to run the test suite. By using `esm` as a required package to be executed *before* the individual test files are executed, `esm` allows CommonJS/`require()` based code to use code written with ES Modules syntax. In practise that means our existing CommonJS based test suite that is `require()`ing the source code witten in ES Modules, is seamless and totally transparent. It just works without any build or transpiling pipeline like `babel` involved. Caveat: the `esm` package only support Node.js 6.x and above. That is more than okey, as we've got continous integration to verify how our changes works on different versions of Node.js, browsers & deno. Refs https://www.npmjs.com/package/esm
diff --git a/.esmrc b/.esmrc
@@ -0,0 +1,8 @@
+{
+  cjs: {
+    // Ensure ESM `export default` ends up as the root, e.g. `module.exports` when
+    // being `require()`d from CJS code. This is not spec compliant, but that does
+    // not matter because only use this `esm` package trickery locally while testing
+    dedefault: true
+  }
+}
diff --git a/package-lock.json b/package-lock.json
diff --git a/package.json b/package.json
@@ -31,7 +31,7 @@
     "build": "cp mustache.js mustache.mjs && rollup mustache.mjs --file mustache.js --format umd --name Mustache && uglifyjs mustache.js > mustache.min.js",
     "test": "npm run test-lint && npm run test-unit",
     "test-lint": "eslint mustache.js bin/mustache test/**/*.js",
-    "test-unit": "mocha --reporter spec test/*-test.js",
+    "test-unit": "mocha --reporter spec --require esm test/*-test.js",
     "test-render": "mocha  --reporter spec test/render-test",
     "pre-test-browser": "node test/create-browser-suite.js",
     "test-browser": "npm run pre-test-browser && zuul -- test/context-test.js test/parse-test.js test/scanner-test.js test/render-test-browser.js",
@@ -41,6 +41,7 @@
   "devDependencies": {
     "chai": "^3.4.0",
     "eslint": "^6.5.1",
+    "esm": "^3.2.25",
     "jshint": "^2.9.5",
     "mocha": "^3.0.2",
     "puppeteer": "^2.0.0",
diff --git a/test/cli-test.js b/test/cli-test.js
@@ -9,10 +9,10 @@ var cliPartialsTxt = path.resolve(_files, 'cli_with_partials.txt');
 var moduleVersion = require('../package').version;
 
 function changeForOS (command) {
+  command = command.replace('bin/mustache', 'node --require esm bin/mustache')
 
   if (process.platform === 'win32') {
     return command
-      .replace(/bin\/mustache/g, 'node bin\\mustache')
       .replace(/\bcat\b/g, 'type')
       .replace(/\//g, '\\');
   }
