Improve dynamic import spec compliance

packages/babel-plugin-proposal-dynamic-import/test/fixtures/amd/module/output.js

@@ -1,5 +1,5 @@
 define(["require"], function (_require) {
   "use strict";
 
-  var modP = new Promise((_resolve, _reject) => _require(["mod"], imported => _resolve(babelHelpers.interopRequireWildcard(imported)), _reject));
+  var modP = Promise.resolve().then(() => new Promise((_resolve, _reject) => _require(["mod"], imported => _resolve(babelHelpers.interopRequireWildcard(imported)), _reject)));
 });

packages/babel-plugin-proposal-dynamic-import/test/fixtures/amd/no-interop/output.js

@@ -1,3 +1,3 @@
 define(["require"], function (_require) {
-  var modP = new Promise((_resolve, _reject) => _require(["mod"], imported => _resolve(imported), _reject));
+  var modP = Promise.resolve().then(() => new Promise((_resolve, _reject) => _require(["mod"], imported => _resolve(imported), _reject)));
 });

packages/babel-plugin-proposal-dynamic-import/test/fixtures/amd/script/output.js

@@ -1,3 +1,3 @@
 define(["require"], function (_require) {
-  var modP = new Promise((_resolve, _reject) => _require(["mod"], imported => _resolve(babelHelpers.interopRequireWildcard(imported)), _reject));
+  var modP = Promise.resolve().then(() => new Promise((_resolve, _reject) => _require(["mod"], imported => _resolve(babelHelpers.interopRequireWildcard(imported)), _reject)));
 });

packages/babel-plugin-proposal-dynamic-import/test/fixtures/amd/to-string/input.js

@@ -0,0 +1 @@
+import(2);

packages/babel-plugin-proposal-dynamic-import/test/fixtures/amd/to-string/output.js

@@ -0,0 +1,3 @@
+define(["require"], function (_require) {
+  new Promise(r => r(`${2}`)).then(s => new Promise((_resolve, _reject) => _require([s], imported => _resolve(babelHelpers.interopRequireWildcard(imported)), _reject)));
+});

packages/babel-plugin-proposal-dynamic-import/test/fixtures/amd/with-other-import-export/output.js

@@ -8,5 +8,5 @@ define(["require", "exports", "foo"], function (_require, _exports, _foo) {
   _foo = babelHelpers.interopRequireDefault(_foo);
   var mod;
   _exports.mod = mod;
-  new Promise((_resolve, _reject) => _require(["mod"], imported => _resolve(babelHelpers.interopRequireWildcard(imported)), _reject)).then(m => _exports.mod = mod = m);
+  Promise.resolve().then(() => new Promise((_resolve, _reject) => _require(["mod"], imported => _resolve(babelHelpers.interopRequireWildcard(imported)), _reject))).then(m => _exports.mod = mod = m);
 });

packages/babel-plugin-proposal-dynamic-import/test/fixtures/commonjs/exec-to-string-order/1.js

@@ -0,0 +1 @@
+module.exports = 1;

packages/babel-plugin-proposal-dynamic-import/test/fixtures/commonjs/exec-to-string-order/exec.js

@@ -0,0 +1,7 @@
+let i = 0;
+const promise = expect(import({ toString: () => `./${++i}.js` }))
+  .resolves.toHaveProperty("default", 1);
+expect(i).toBe(1);
+++i;
+expect(i).toBe(2);
+return promise;

packages/babel-plugin-proposal-dynamic-import/test/fixtures/commonjs/exec-to-string-order/options.json

@@ -0,0 +1,5 @@
+{
+  "parserOpts": {
+    "allowReturnOutsideFunction": true
+  }
+}

packages/babel-plugin-proposal-dynamic-import/test/fixtures/commonjs/exec-to-string-throw/exec.js

@@ -0,0 +1,2 @@
+return expect(import({ toString: () => { throw "toString failed"; } }))
+  .rejects.toBe("toString failed");

packages/babel-plugin-proposal-dynamic-import/test/fixtures/commonjs/exec-to-string-throw/options.json

@@ -0,0 +1,5 @@
+{
+  "parserOpts": {
+    "allowReturnOutsideFunction": true
+  }
+}

packages/babel-plugin-proposal-dynamic-import/test/fixtures/commonjs/to-string/output.js

@@ -1 +1 @@
-Promise.resolve(`${2}`).then(s => babelHelpers.interopRequireWildcard(require(s)));
+new Promise(r => r(`${2}`)).then(s => babelHelpers.interopRequireWildcard(require(s)));

packages/babel-plugin-proposal-dynamic-import/test/fixtures/systemjs/to-string/input.js

@@ -0,0 +1 @@
+import(2);

packages/babel-plugin-proposal-dynamic-import/test/fixtures/systemjs/to-string/output.js

@@ -0,0 +1,10 @@
+System.register([], function (_export, _context) {
+  "use strict";
+
+  return {
+    setters: [],
+    execute: function () {
+      new Promise(r => r(`${2}`)).then(s => _context.import(s));
+    }
+  };
+});

packages/babel-plugin-transform-modules-amd/src/index.ts

@@ -98,15 +98,31 @@ export default declare<State>((api, options: Options) => {
         let result: t.Node = t.identifier("imported");
         if (!noInterop) result = wrapInterop(path, result, "namespace");
 
+        const source = getDynamicImportSource(path.node);
+
         path.replaceWith(
-          template.expression.ast`
-            new Promise((${resolveId}, ${rejectId}) =>
-              ${requireId}(
-                [${getDynamicImportSource(path.node)}],
-                imported => ${t.cloneNode(resolveId)}(${result}),
-                ${t.cloneNode(rejectId)}
-              )
-            )`,
+          t.isStringLiteral(source) ||
+            (t.isTemplateLiteral(source) && source.quasis.length === 0)
+            ? template.expression.ast`
+              Promise.resolve()
+                .then(() => new Promise((${resolveId}, ${rejectId}) =>
+                  ${requireId}(
+                    [${source}],
+                    imported => ${t.cloneNode(resolveId)}(${result}),
+                    ${t.cloneNode(rejectId)}
+                  )
+                ))
+            `
+            : template.expression.ast`
+              new Promise(r => r(${source}))
+                .then(s => new Promise((${resolveId}, ${rejectId}) =>
+                  ${requireId}(
+                    [s],
+                    imported => ${t.cloneNode(resolveId)}(${result}),
+                    ${t.cloneNode(rejectId)}
+                  )
+                ))
+            `,
         );
       },
 

packages/babel-plugin-transform-modules-commonjs/src/dynamic-import.ts

@@ -29,9 +29,8 @@ export function transformDynamicImport(
         Promise.resolve().then(() => ${buildRequire(source, file)})
       `
       : template.expression.ast`
-        Promise.resolve(${source}).then(
-          s => ${buildRequire(t.identifier("s"), file)}
-        )
+        new Promise(r => r(${source}))
+          .then(s => ${buildRequire(t.identifier("s"), file)})
       `;
 
   path.replaceWith(replacement);

packages/babel-plugin-transform-modules-systemjs/src/index.ts

@@ -273,14 +273,23 @@ export default declare<PluginState>((api, options: Options) => {
             }
           }
 
+          const source = getDynamicImportSource(path.node);
+          const context = t.identifier(state.contextIdent);
+
           path.replaceWith(
-            t.callExpression(
-              t.memberExpression(
-                t.identifier(state.contextIdent),
-                t.identifier("import"),
-              ),
-              [getDynamicImportSource(path.node)],
-            ),
+            t.isStringLiteral(source) ||
+              (t.isTemplateLiteral(source) && source.quasis.length === 0)
+              ? t.callExpression(
+                  t.memberExpression(
+                    t.identifier(state.contextIdent),
+                    t.identifier("import"),
+                  ),
+                  [source],
+                )
+              : template.expression.ast`
+                new Promise(r => r(${source}))
+                  .then(s => ${context}.import(s))
+              `,
           );
         }
       },

packages/babel-preset-env/test/fixtures/dynamic-import-babel-7/modules-amd/output.js

@@ -1,7 +1,9 @@
 define(["require"], function (_require) {
-  new Promise(function (_resolve, _reject) {
-    return _require(["foo"], function (imported) {
-      return _resolve(babelHelpers.interopRequireWildcard(imported));
-    }, _reject);
+  Promise.resolve().then(function () {
+    return new Promise(function (_resolve, _reject) {
+      return _require(["foo"], function (imported) {
+        return _resolve(babelHelpers.interopRequireWildcard(imported));
+      }, _reject);
+    });
   });
 });

packages/babel-preset-env/test/fixtures/dynamic-import/modules-amd/output.js

@@ -1,3 +1,3 @@
 define(["require"], function (_require) {
-  new Promise((_resolve, _reject) => _require(["foo"], imported => _resolve(babelHelpers.interopRequireWildcard(imported)), _reject));
+  Promise.resolve().then(() => new Promise((_resolve, _reject) => _require(["foo"], imported => _resolve(babelHelpers.interopRequireWildcard(imported)), _reject)));
 });