chore: add test-legacy build env

.github/workflows/ci.yml

@@ -30,7 +30,7 @@ jobs:
         uses: actions/setup-node@v2-beta # Build Babel on latest node versions
       - name: Build
         run: |
-          BABEL_ENV=production make -j bootstrap
+          BABEL_ENV=test-legacy make -j bootstrap
       - name: Use Node.js ${{ matrix.node-version }}
         uses: actions/setup-node@v2-beta
         with:

babel.config.js

@@ -17,7 +17,8 @@ module.exports = function (api) {
   };
   const envOpts = Object.assign({}, envOptsNoTargets);
 
-  const compileDynamicImport = env === "test" || env === "development";
+  const compileDynamicImport =
+    env === "test" || env === "development" || env === "test-legacy";
 
   let convertESM = true;
   let ignoreLib = true;
@@ -55,6 +56,7 @@ module.exports = function (api) {
       );
       if (env === "rollup") envOpts.targets = { node: nodeVersion };
       break;
+    case "test-legacy": // In test-legacy environment, we build babel on latest node but test on minimum supported legacy versions
     case "production":
       // Config during builds before publish.
       envOpts.targets = {
@@ -109,7 +111,7 @@ module.exports = function (api) {
         "@babel/proposal-object-rest-spread",
         { useBuiltIns: true, loose: true },
       ],
-      dynamicImportUrlToPath,
+      compileDynamicImport ? dynamicImportUrlToPath : null,
       compileDynamicImport ? "@babel/plugin-proposal-dynamic-import" : null,
 
       convertESM ? "@babel/transform-modules-commonjs" : null,
@@ -170,9 +172,9 @@ module.exports = function (api) {
 // NOTE: This plugin must run before @babel/plugin-transform-modules-commonjs,
 // and assumes that the target is the current node version.
 function dynamicImportUrlToPath({ template, env }) {
-  const currentNodeSupportsURL = !!require("url").pathToFileURL;
-
-  if (currentNodeSupportsURL && env() !== "production") {
+  const currentNodeSupportsURL =
+    !!require("url").pathToFileURL && env() !== "test-legacy"; // test-legacy is run on legacy node versions without pathToFileURL support
+  if (currentNodeSupportsURL) {
     return {
       visitor: {
         CallExpression(path) {