Make tests pass

babel.config.js

@@ -12,6 +12,8 @@ module.exports = function(api) {
   };
   const envOpts = Object.assign({}, envOptsNoTargets);
 
+  const compileDynamicImport = env === "test" || env === "development";
+
   let convertESM = true;
   let ignoreLib = true;
   let includeRegeneratorRuntime = false;
@@ -107,10 +109,6 @@ module.exports = function(api) {
       ["@babel/plugin-proposal-nullish-coalescing-operator", { loose: true }],
 
       convertESM ? "@babel/transform-modules-commonjs" : null,
-      // Until Jest supports native mjs, we must simulate it 🤷
-      env === "test" || env === "development"
-        ? "@babel/plugin-proposal-dynamic-import"
-        : null,
     ].filter(Boolean),
     overrides: [
       {
@@ -141,6 +139,15 @@ module.exports = function(api) {
         exclude: /regenerator-runtime/,
         plugins: [["@babel/transform-runtime", transformRuntimeOptions]],
       },
+      compileDynamicImport && {
+        // Until Jest supports native mjs, we must simulate it 🤷
+
+        test: "./packages/babel-core/src/config/files/import.js",
+        plugins: [
+          dynamicImportUrlToPath,
+          "@babel/plugin-proposal-dynamic-import",
+        ],
+      },
     ].filter(Boolean),
   };
 
@@ -152,3 +159,28 @@ module.exports = function(api) {
 
   return config;
 };
+
+// import() uses file:// URLs for absolute imports, while require() uses
+// file paths.
+// Since this isn't handled by @babel/plugin-transform-modules-commonjs,
+// we must handle it here.
+// NOTE: This plugin must run before @babel/plugin-transform-modules-commonjs
+function dynamicImportUrlToPath({ template }) {
+  return {
+    visitor: {
+      Program(path) {
+        path.traverse({
+          CallExpression(path) {
+            if (path.get("callee").isImport()) {
+              path.get("arguments.0").replaceWith(
+                template.expression.ast`
+                  require("url").fileURLToPath(${path.node.arguments[0]})
+                `
+              );
+            }
+          },
+        });
+      },
+    },
+  };
+}