system hoisting and export refinements (#8104)

packages/babel-helper-hoist-variables/src/index.js

@@ -29,7 +29,7 @@ const visitor = {
       }
 
       for (const name in declar.getBindingIdentifiers()) {
-        state.emit(t.identifier(name), name);
+        state.emit(t.identifier(name), name, declar.node.init !== null);
       }
     }
 

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

@@ -21,6 +21,81 @@ const buildExportAll = template(`
   }
 `);
 
+function constructExportCall(
+  path,
+  exportIdent,
+  exportNames,
+  exportValues,
+  exportStarTarget,
+) {
+  const statements = [];
+  if (exportNames.length === 1) {
+    statements.push(
+      t.expressionStatement(
+        t.callExpression(exportIdent, [
+          t.stringLiteral(exportNames[0]),
+          exportValues[0],
+        ]),
+      ),
+    );
+  } else if (!exportStarTarget) {
+    const objectProperties = [];
+    for (let i = 0; i < exportNames.length; i++) {
+      const exportName = exportNames[i];
+      const exportValue = exportValues[i];
+      objectProperties.push(
+        t.objectProperty(t.identifier(exportName), exportValue),
+      );
+    }
+    statements.push(
+      t.expressionStatement(
+        t.callExpression(exportIdent, [t.objectExpression(objectProperties)]),
+      ),
+    );
+  } else {
+    const exportObj = path.scope.generateUid("exportObj");
+
+    statements.push(
+      t.variableDeclaration("var", [
+        t.variableDeclarator(t.identifier(exportObj), t.objectExpression([])),
+      ]),
+    );
+
+    statements.push(
+      buildExportAll({
+        KEY: path.scope.generateUidIdentifier("key"),
+        EXPORT_OBJ: t.identifier(exportObj),
+        TARGET: exportStarTarget,
+      }),
+    );
+
+    for (let i = 0; i < exportNames.length; i++) {
+      const exportName = exportNames[i];
+      const exportValue = exportValues[i];
+
+      statements.push(
+        t.expressionStatement(
+          t.assignmentExpression(
+            "=",
+            t.memberExpression(
+              t.identifier(exportObj),
+              t.identifier(exportName),
+            ),
+            exportValue,
+          ),
+        ),
+      );
+    }
+
+    statements.push(
+      t.expressionStatement(
+        t.callExpression(exportIdent, [t.identifier(exportObj)]),
+      ),
+    );
+  }
+  return statements;
+}
+
 const TYPE_IMPORT = "Import";
 
 export default declare((api, options) => {
@@ -35,6 +110,25 @@ export default declare((api, options) => {
       path.node[IGNORE_REASSIGNMENT_SYMBOL] = true;
 
       const arg = path.get(path.isAssignmentExpression() ? "left" : "argument");
+
+      if (arg.isObjectPattern() || arg.isArrayPattern()) {
+        const exprs = [path.node];
+        for (const name in arg.getBindingIdentifiers()) {
+          if (this.scope.getBinding(name) !== path.scope.getBinding(name)) {
+            return;
+          }
+          const exportedNames = this.exports[name];
+          if (!exportedNames) return;
+          for (const exportedName of exportedNames) {
+            exprs.push(
+              this.buildCall(exportedName, t.identifier(name)).expression,
+            );
+          }
+        }
+        path.replaceWith(t.sequenceExpression(exprs));
+        return;
+      }
+
       if (!arg.isIdentifier()) return;
 
       const name = arg.node.name;
@@ -163,17 +257,8 @@ export default declare((api, options) => {
 
           const body: Array<Object> = path.get("body");
 
-          let canHoist = true;
-          for (let path of body) {
-            if (path.isExportDeclaration()) path = path.get("declaration");
-            if (path.isVariableDeclaration() && path.node.kind !== "var") {
-              canHoist = false;
-              break;
-            }
-          }
-
           for (const path of body) {
-            if (canHoist && path.isFunctionDeclaration()) {
+            if (path.isFunctionDeclaration()) {
               beforeBody.push(path.node);
               removedPaths.push(path);
             } else if (path.isImportDeclaration()) {
@@ -206,7 +291,7 @@ export default declare((api, options) => {
                   );
                 }
 
-                if (!canHoist || declar.isClassDeclaration()) {
+                if (declar.isClassDeclaration()) {
                   path.replaceWithMultiple(nodes);
                 } else {
                   beforeBody = beforeBody.concat(nodes);
@@ -221,29 +306,22 @@ export default declare((api, options) => {
               if (declar.node) {
                 path.replaceWith(declar);
 
-                const nodes = [];
-                let bindingIdentifiers;
                 if (path.isFunction()) {
                   const node = declar.node;
                   const name = node.id.name;
-                  if (canHoist) {
-                    addExportName(name, name);
-                    beforeBody.push(node);
-                    beforeBody.push(
-                      buildExportCall(name, t.cloneNode(node.id)),
-                    );
-                    removedPaths.push(path);
-                  } else {
-                    bindingIdentifiers = { [name]: node.id };
-                  }
-                } else {
-                  bindingIdentifiers = declar.getBindingIdentifiers();
-                }
-                for (const name in bindingIdentifiers) {
                   addExportName(name, name);
-                  nodes.push(buildExportCall(name, t.identifier(name)));
+                  beforeBody.push(node);
+                  beforeBody.push(buildExportCall(name, t.cloneNode(node.id)));
+                  removedPaths.push(path);
+                } else if (path.isClass()) {
+                  const name = declar.node.id.name;
+                  addExportName(name, name);
+                  path.insertAfter([buildExportCall(name, t.identifier(name))]);
+                } else {
+                  for (const name in declar.getBindingIdentifiers()) {
+                    addExportName(name, name);
+                  }
                 }
-                path.insertAfter(nodes);
               } else {
                 const specifiers = path.node.specifiers;
                 if (specifiers && specifiers.length) {
@@ -254,12 +332,15 @@ export default declare((api, options) => {
                     const nodes = [];
 
                     for (const specifier of specifiers) {
-                      nodes.push(
+                      // only globals exported this way
-                        buildExportCall(
+                      if (!path.scope.getBinding(specifier.local.name)) {
-                          specifier.exported.name,
+                        nodes.push(
-                          specifier.local,
+                          buildExportCall(
-                        ),
+                            specifier.exported.name,
-                      );
+                            specifier.local,
+                          ),
+                        );
+                      }
                       addExportName(
                         specifier.local.name,
                         specifier.exported.name,
@@ -274,7 +355,7 @@ export default declare((api, options) => {
           }
 
           modules.forEach(function(specifiers) {
-            const setterBody = [];
+            let setterBody = [];
             const target = path.scope.generateUid(specifiers.key);
 
             for (let specifier of specifiers.imports) {
@@ -312,49 +393,30 @@ export default declare((api, options) => {
             }
 
             if (specifiers.exports.length) {
-              const exportObj = path.scope.generateUid("exportObj");
+              const exportNames = [];
-
+              const exportValues = [];
-              setterBody.push(
+              let hasExportStar = false;
-                t.variableDeclaration("var", [
-                  t.variableDeclarator(
-                    t.identifier(exportObj),
-                    t.objectExpression([]),
-                  ),
-                ]),
-              );
 
               for (const node of specifiers.exports) {
                 if (t.isExportAllDeclaration(node)) {
-                  setterBody.push(
+                  hasExportStar = true;
-                    buildExportAll({
-                      KEY: path.scope.generateUidIdentifier("key"),
-                      EXPORT_OBJ: t.identifier(exportObj),
-                      TARGET: t.identifier(target),
-                    }),
-                  );
                 } else if (t.isExportSpecifier(node)) {
-                  setterBody.push(
+                  exportNames.push(node.exported.name);
-                    t.expressionStatement(
+                  exportValues.push(
-                      t.assignmentExpression(
+                    t.memberExpression(t.identifier(target), node.local),
-                        "=",
-                        t.memberExpression(
-                          t.identifier(exportObj),
-                          node.exported,
-                        ),
-                        t.memberExpression(t.identifier(target), node.local),
-                      ),
-                    ),
                   );
                 } else {
                   // todo
                 }
               }
 
-              setterBody.push(
+              setterBody = setterBody.concat(
-                t.expressionStatement(
+                constructExportCall(
-                  t.callExpression(t.identifier(exportIdent), [
+                  path,
-                    t.identifier(exportObj),
+                  t.identifier(exportIdent),
-                  ]),
+                  exportNames,
+                  exportValues,
+                  hasExportStar ? t.identifier(target) : null,
                 ),
               );
             }
@@ -372,9 +434,17 @@ export default declare((api, options) => {
           let moduleName = this.getModuleName();
           if (moduleName) moduleName = t.stringLiteral(moduleName);
 
-          if (canHoist) {
+          const uninitializedVars = [];
-            hoistVariables(path, id => variableIds.push(id));
+          hoistVariables(
-          }
+            path,
+            (id, name, hasInit) => {
+              variableIds.push(id);
+              if (!hasInit) {
+                uninitializedVars.push(name);
+              }
+            },
+            null,
+          );
 
           if (variableIds.length) {
             beforeBody.unshift(
@@ -385,6 +455,23 @@ export default declare((api, options) => {
             );
           }
 
+          if (uninitializedVars.length) {
+            const undefinedValues = [];
+            const undefinedIdent = path.scope.buildUndefinedNode();
+            for (let i = 0; i < uninitializedVars.length; i++) {
+              undefinedValues[i] = undefinedIdent;
+            }
+            beforeBody = beforeBody.concat(
+              constructExportCall(
+                path,
+                t.identifier(exportIdent),
+                uninitializedVars,
+                undefinedValues,
+                null,
+              ),
+            );
+          }
+
           path.traverse(reassignmentVisitor, {
             exports: exportNames,
             buildCall: buildExportCall,

packages/babel-plugin-transform-modules-systemjs/test/fixtures/systemjs/export-const-destructuring-array-default-params/output.mjs

@@ -1,14 +1,11 @@
 System.register([], function (_export, _context) {
   "use strict";
 
+  var foo, bar;
   return {
     setters: [],
     execute: function () {
-      const [foo, bar = 2] = [];
+      [foo, bar = 2] = [], _export("foo", foo), _export("bar", bar);
-
-      _export("foo", foo);
-
-      _export("bar", bar);
     }
   };
 });

packages/babel-plugin-transform-modules-systemjs/test/fixtures/systemjs/export-const-destructuring-array-rest/output.mjs

@@ -1,16 +1,11 @@
 System.register([], function (_export, _context) {
   "use strict";
 
+  var foo, bar, baz;
   return {
     setters: [],
     execute: function () {
-      const [foo, bar, ...baz] = [];
+      [foo, bar, ...baz] = [], _export("foo", foo), _export("bar", bar), _export("baz", baz);
-
-      _export("foo", foo);
-
-      _export("bar", bar);
-
-      _export("baz", baz);
     }
   };
 });

packages/babel-plugin-transform-modules-systemjs/test/fixtures/systemjs/export-const-destructuring-array/output.mjs

@@ -1,14 +1,11 @@
 System.register([], function (_export, _context) {
   "use strict";
 
+  var foo, bar;
   return {
     setters: [],
     execute: function () {
-      const [foo, bar] = [];
+      [foo, bar] = [], _export("foo", foo), _export("bar", bar);
-
-      _export("foo", foo);
-
-      _export("bar", bar);
     }
   };
 });

packages/babel-plugin-transform-modules-systemjs/test/fixtures/systemjs/export-const-destructuring-deep/output.mjs

@@ -1,18 +1,15 @@
 System.register([], function (_export, _context) {
   "use strict";
 
+  var baz, qux;
   return {
     setters: [],
     execute: function () {
-      const {
+      ({
         foo: {
           bar: [baz, qux]
         }
-      } = {};
+      } = {}), _export("baz", baz), _export("qux", qux);
-
-      _export("baz", baz);
-
-      _export("qux", qux);
     }
   };
 });

packages/babel-plugin-transform-modules-systemjs/test/fixtures/systemjs/export-const-destructuring-object-default-params/output.mjs

@@ -1,17 +1,14 @@
 System.register([], function (_export, _context) {
   "use strict";
 
+  var foo, bar;
   return {
     setters: [],
     execute: function () {
-      const {
+      ({
         foo,
         bar = 1
-      } = {};
+      } = {}), _export("foo", foo), _export("bar", bar);
-
-      _export("foo", foo);
-
-      _export("bar", bar);
     }
   };
 });

packages/babel-plugin-transform-modules-systemjs/test/fixtures/systemjs/export-const-destructuring-object-rest/output.mjs

@@ -1,17 +1,14 @@
 System.register([], function (_export, _context) {
   "use strict";
 
+  var foo, bar;
   return {
     setters: [],
     execute: function () {
-      const {
+      ({
         foo,
         ...bar
-      } = {};
+      } = {}), _export("foo", foo), _export("bar", bar);
-
-      _export("foo", foo);
-
-      _export("bar", bar);
     }
   };
 });

packages/babel-plugin-transform-modules-systemjs/test/fixtures/systemjs/export-const-destructuring-object/output.mjs

@@ -1,17 +1,14 @@
 System.register([], function (_export, _context) {
   "use strict";
 
+  var bar, baz;
   return {
     setters: [],
     execute: function () {
-      const {
+      ({
         foo: bar,
         baz
-      } = {};
+      } = {}), _export("bar", bar), _export("baz", baz);
-
-      _export("bar", bar);
-
-      _export("baz", baz);
     }
   };
 });

packages/babel-plugin-transform-modules-systemjs/test/fixtures/systemjs/export-from-2/output.mjs

@@ -3,10 +3,7 @@ System.register(["foo"], function (_export, _context) {
 
   return {
     setters: [function (_foo) {
-      var _exportObj = {};
+      _export("foo", _foo.foo);
-      _exportObj.foo = _foo.foo;
-
-      _export(_exportObj);
     }],
     execute: function () {}
   };

packages/babel-plugin-transform-modules-systemjs/test/fixtures/systemjs/export-from-3/output.mjs

@@ -3,11 +3,10 @@ System.register(["foo"], function (_export, _context) {
 
   return {
     setters: [function (_foo) {
-      var _exportObj = {};
+      _export({
-      _exportObj.foo = _foo.foo;
+        foo: _foo.foo,
-      _exportObj.bar = _foo.bar;
+        bar: _foo.bar
-
+      });
-      _export(_exportObj);
     }],
     execute: function () {}
   };

packages/babel-plugin-transform-modules-systemjs/test/fixtures/systemjs/export-from-4/output.mjs

@@ -3,10 +3,7 @@ System.register(["foo"], function (_export, _context) {
 
   return {
     setters: [function (_foo) {
-      var _exportObj = {};
+      _export("bar", _foo.foo);
-      _exportObj.bar = _foo.foo;
-
-      _export(_exportObj);
     }],
     execute: function () {}
   };

packages/babel-plugin-transform-modules-systemjs/test/fixtures/systemjs/export-from-5/output.mjs

@@ -3,10 +3,7 @@ System.register(["foo"], function (_export, _context) {
 
   return {
     setters: [function (_foo) {
-      var _exportObj = {};
+      _export("default", _foo.foo);
-      _exportObj.default = _foo.foo;
-
-      _export(_exportObj);
     }],
     execute: function () {}
   };

packages/babel-plugin-transform-modules-systemjs/test/fixtures/systemjs/export-from-6/output.mjs

@@ -3,11 +3,10 @@ System.register(["foo"], function (_export, _context) {
 
   return {
     setters: [function (_foo) {
-      var _exportObj = {};
+      _export({
-      _exportObj.default = _foo.foo;
+        default: _foo.foo,
-      _exportObj.bar = _foo.bar;
+        bar: _foo.bar
-
+      });
-      _export(_exportObj);
     }],
     execute: function () {}
   };

packages/babel-plugin-transform-modules-systemjs/test/fixtures/systemjs/export-uninitialized/input.mjs

@@ -0,0 +1 @@
+export var m;

packages/babel-plugin-transform-modules-systemjs/test/fixtures/systemjs/export-uninitialized/output.mjs

@@ -0,0 +1,12 @@
+System.register([], function (_export, _context) {
+  "use strict";
+
+  var m;
+
+  _export("m", void 0);
+
+  return {
+    setters: [],
+    execute: function () {}
+  };
+});

packages/babel-plugin-transform-modules-systemjs/test/fixtures/systemjs/exports-variable/output.mjs

@@ -1,36 +1,27 @@
 System.register([], function (_export, _context) {
   "use strict";
 
+  var foo, foo2, foo3, foo4, foo5, foo6;
+
+  function foo7() {}
+
+  _export("foo7", foo7);
+
+  _export({
+    foo3: void 0,
+    foo5: void 0
+  });
+
   return {
     setters: [],
     execute: function () {
-      var foo = 1;
+      _export("foo", foo = 1);
 
-      _export("foo", foo);
+      _export("foo2", foo2 = function () {});
 
-      var foo2 = function () {};
+      _export("foo4", foo4 = 2);
 
-      _export("foo2", foo2);
+      _export("foo6", foo6 = 3);
-
-      var foo3;
-
-      _export("foo3", foo3);
-
-      let foo4 = 2;
-
-      _export("foo4", foo4);
-
-      let foo5;
-
-      _export("foo5", foo5);
-
-      const foo6 = 3;
-
-      _export("foo6", foo6);
-
-      function foo7() {}
-
-      _export("foo7", foo7);
 
       class foo8 {}
 

packages/babel-plugin-transform-modules-systemjs/test/fixtures/systemjs/hoist-function-exports/output.mjs

@@ -9,6 +9,8 @@ System.register(["./evens"], function (_export, _context) {
 
   _export("nextOdd", nextOdd);
 
+  _export("a", void 0);
+
   return {
     setters: [function (_evens) {
       isEven = _evens.isEven;
@@ -16,8 +18,6 @@ System.register(["./evens"], function (_export, _context) {
     execute: function () {
       _export("p", p = 5);
 
-      _export("p", p);
-
       for (a in b);
 
       for (i = 0, j = 0;;);
@@ -27,8 +27,6 @@ System.register(["./evens"], function (_export, _context) {
           return !isEven(n);
         };
       }(isEven));
-
-      _export("isOdd", isOdd);
     }
   };
 });

packages/babel-plugin-transform-modules-systemjs/test/fixtures/systemjs/hoisting-bindings/output.mjs

@@ -19,8 +19,6 @@ System.register([], function (_export, _context) {
     execute: function () {
       _export("c", c = 5);
 
-      _export("c", c);
-
       b();
     }
   };

packages/babel-plugin-transform-modules-systemjs/test/fixtures/systemjs/module-name/output.mjs

@@ -6,8 +6,6 @@ System.register([], function (_export, _context) {
     setters: [],
     execute: function () {
       _export("name", name = _context.id);
-
-      _export("name", name);
     }
   };
 });

packages/babel-plugin-transform-modules-systemjs/test/fixtures/systemjs/overview/output.mjs

@@ -14,8 +14,6 @@ System.register(["foo", "foo-bar", "./directory/foo-bar"], function (_export, _c
 
       _export("test2", test2 = 5);
 
-      _export("test2", test2);
-
       _export("default", test);
     }
   };

packages/babel-plugin-transform-modules-systemjs/test/fixtures/systemjs/remap/output.mjs

@@ -7,8 +7,6 @@ System.register([], function (_export, _context) {
     execute: function () {
       _export("test", test = 2);
 
-      _export("test", test);
-
       _export("test", test = 5);
 
       _export("test", +test + 1), test++;
@@ -21,22 +19,14 @@ System.register([], function (_export, _context) {
 
       _export("a", a = 2);
 
-      _export("a", a);
-
       _export("a", a = 3);
 
       _export("c", b = 2);
 
-      _export("c", b);
-
       _export("c", b = 3);
 
       _export("f", _export("e", d = 3));
 
-      _export("e", d);
-
-      _export("f", d);
-
       _export("f", _export("e", d = 4));
     }
   };