Fixed buildExternalHelpers tool for var and module output types (#6260)

packages/babel-core/src/tools/build-external-helpers.js

@@ -66,36 +66,41 @@ function buildModule(namespace, builder) {
   const body = [];
   builder(body);
 
-  const module = body
-    .map(helper => {
-      const originalIdentifier = helper.expression.left.property.name;
-      const isKeywordHelper = keywordHelpers.indexOf(originalIdentifier) !== -1;
-      const helperIndentifier = isKeywordHelper
-        ? `_${originalIdentifier}`
-        : originalIdentifier;
+  const module = body.map(helperNode => {
+    const possibleAssignment = t.isExpressionStatement(helperNode)
+      ? helperNode.expression
+      : helperNode;
 
-      const variableDeclaration = t.variableDeclaration("var", [
-        t.variableDeclarator(
-          t.identifier(helperIndentifier),
-          helper.expression.right,
+    const isExportedHelper =
+      t.isAssignmentExpression(possibleAssignment) &&
+      t.isMemberExpression(possibleAssignment.left) &&
+      possibleAssignment.left.object.name === namespace.name;
+
+    if (!isExportedHelper) {
+      return helperNode;
+    }
+
+    const exportedHelper = possibleAssignment;
+
+    const identifier = exportedHelper.left.property.name;
+    const isKeywordHelper = keywordHelpers.indexOf(identifier) !== -1;
+
+    if (isKeywordHelper) {
+      return t.exportNamedDeclaration(null, [
+        t.exportSpecifier(
+          t.identifier(`_${identifier}`),
+          t.identifier(identifier),
         ),
       ]);
+    }
 
-      return isKeywordHelper
-        ? variableDeclaration
-        : t.exportNamedDeclaration(variableDeclaration, []);
-    })
-    .concat(
-      t.exportNamedDeclaration(
-        null,
-        keywordHelpers.map(keywordHelper =>
-          t.exportSpecifier(
-            t.identifier(`_${keywordHelper}`),
-            t.identifier(keywordHelper),
-          ),
-        ),
-      ),
+    return t.exportNamedDeclaration(
+      t.variableDeclaration("var", [
+        t.variableDeclarator(t.identifier(identifier), exportedHelper.right),
+      ]),
+      [],
     );
+  });
 
   return t.program(module);
 }
@@ -133,9 +138,10 @@ function buildVar(namespace, builder) {
       t.variableDeclarator(namespace, t.objectExpression([])),
     ]),
   );
+  const tree = t.program(body);
   builder(body);
   body.push(t.expressionStatement(namespace));
-  return t.program(body);
+  return tree;
 }
 
 function buildHelpers(body, namespace, whitelist) {

packages/babel-core/test/api.js

@@ -1,5 +1,4 @@
 import * as babel from "../lib/index";
-import buildExternalHelpers from "../lib/tools/build-external-helpers";
 import sourceMap from "source-map";
 import assert from "assert";
 import path from "path";
@@ -817,26 +816,44 @@ describe("api", function() {
   });
 
   describe("buildExternalHelpers", function() {
+    describe("smoke tests", function() {
+      it("builds external helpers in global output type", function() {
+        babel.buildExternalHelpers(null, "global");
+      });
+
+      it("builds external helpers in module output type", function() {
+        babel.buildExternalHelpers(null, "module");
+      });
+
+      it("builds external helpers in umd output type", function() {
+        babel.buildExternalHelpers(null, "umd");
+      });
+
+      it("builds external helpers in var output type", function() {
+        babel.buildExternalHelpers(null, "var");
+      });
+    });
+
     it("all", function() {
-      const script = buildExternalHelpers();
+      const script = babel.buildExternalHelpers();
       assert.ok(script.indexOf("classCallCheck") >= -1);
       assert.ok(script.indexOf("inherits") >= 0);
     });
 
     it("whitelist", function() {
-      const script = buildExternalHelpers(["inherits"]);
+      const script = babel.buildExternalHelpers(["inherits"]);
       assert.ok(script.indexOf("classCallCheck") === -1);
       assert.ok(script.indexOf("inherits") >= 0);
     });
 
     it("empty whitelist", function() {
-      const script = buildExternalHelpers([]);
+      const script = babel.buildExternalHelpers([]);
       assert.ok(script.indexOf("classCallCheck") === -1);
       assert.ok(script.indexOf("inherits") === -1);
     });
 
     it("underscored", function() {
-      const script = buildExternalHelpers(["typeof"]);
+      const script = babel.buildExternalHelpers(["typeof"]);
       assert.ok(script.indexOf("typeof") >= 0);
     });
   });

packages/babel-helpers/src/index.js

@@ -27,7 +27,7 @@ function getHelperMetadata(file) {
 
   traverse(file, {
     ImportDeclaration(child) {
-      throw child.buildCodeFrameError("Helpers may import anything.");
+      throw child.buildCodeFrameError("Helpers may not import anything.");
     },
     ExportDefaultDeclaration(child) {
       const decl = child.get("declaration");