allow augmentation for entities exported via 'export='

src/compiler/checker.ts

@@ -395,10 +395,17 @@ namespace ts {
                 if (!mainModule) {
                     return;
                 }
-                // if module symbol has already been merged - it is safe to use it.
-                // otherwise clone it
-                mainModule = mainModule.flags & SymbolFlags.Merged ? mainModule : cloneSymbol(mainModule);
-                mergeSymbol(mainModule, moduleAugmentation.symbol);
+                // obtain item referenced by 'export='
+                mainModule = resolveExternalModuleSymbol(mainModule);
+                if (mainModule.flags & SymbolFlags.Namespace) {
+                    // if module symbol has already been merged - it is safe to use it.
+                    // otherwise clone it
+                    mainModule = mainModule.flags & SymbolFlags.Merged ? mainModule : cloneSymbol(mainModule);
+                    mergeSymbol(mainModule, moduleAugmentation.symbol);
+                }
+                else {
+                    error(moduleName, Diagnostics.Cannot_augment_module_0_because_it_resolves_to_a_non_module_entity, moduleName.text);
+                }
             }
         }
 
@@ -891,7 +898,7 @@ namespace ts {
                     error(node.name, Diagnostics.Module_0_has_no_default_export, symbolToString(moduleSymbol));
                 }
                 else if (!exportDefaultSymbol && allowSyntheticDefaultImports) {
-                    return resolveSymbol(moduleSymbol.exports["export="]) || resolveSymbol(moduleSymbol);
+                    return resolveExternalModuleSymbol(moduleSymbol) || resolveSymbol(moduleSymbol);
                 }
                 return exportDefaultSymbol;
             }
@@ -1182,7 +1189,7 @@ namespace ts {
         // An external module with an 'export =' declaration resolves to the target of the 'export =' declaration,
         // and an external module with no 'export =' declaration resolves to the module itself.
         function resolveExternalModuleSymbol(moduleSymbol: Symbol): Symbol {
-            return moduleSymbol && resolveSymbol(moduleSymbol.exports["export="]) || moduleSymbol;
+            return moduleSymbol && getMergedSymbol(resolveSymbol(moduleSymbol.exports["export="])) || moduleSymbol;
         }
 
         // An external module with an 'export =' declaration may be referenced as an ES6 module provided the 'export ='
@@ -1197,8 +1204,8 @@ namespace ts {
             return symbol;
         }
 
-        function getExportAssignmentSymbol(moduleSymbol: Symbol): Symbol {
-            return moduleSymbol.exports["export="];
+        function hasExportAssignmentSymbol(moduleSymbol: Symbol): boolean {
+            return moduleSymbol.exports["export="] !== undefined;
         }
 
         function getExportsOfModuleAsArray(moduleSymbol: Symbol): Symbol[] {
@@ -14845,7 +14852,7 @@ namespace ts {
                 else {
                     // export * from "foo"
                     const moduleSymbol = resolveExternalModuleName(node, node.moduleSpecifier);
-                    if (moduleSymbol && moduleSymbol.exports["export="]) {
+                    if (moduleSymbol && hasExportAssignmentSymbol(moduleSymbol)) {
                         error(node.moduleSpecifier, Diagnostics.Module_0_uses_export_and_cannot_be_used_with_export_Asterisk, symbolToString(moduleSymbol));
                     }
                 }
@@ -15683,7 +15690,7 @@ namespace ts {
                 return true;
             }
 
-            const hasExportAssignment = getExportAssignmentSymbol(moduleSymbol) !== undefined;
+            const hasExportAssignment = hasExportAssignmentSymbol(moduleSymbol);
             // if module has export assignment then 'resolveExternalModuleSymbol' will return resolved symbol for export assignment
             // otherwise it will return moduleSymbol itself
             moduleSymbol = resolveExternalModuleSymbol(moduleSymbol);
@@ -16042,7 +16049,7 @@ namespace ts {
                 if (!isExternalOrCommonJsModule(file)) {
                     mergeSymbolTable(globals, file.locals);
                 }
-                if (file.moduleAugmentations) {
+                if (file.moduleAugmentations.length) {
                     (augmentations || (augmentations = [])).push(file.moduleAugmentations);
                 }
             });

src/compiler/diagnosticMessages.json

@@ -1819,6 +1819,10 @@
         "category": "Error",
         "code": 2670
     },
+    "Cannot augment module '{0}' because it resolves to a non-module entity.": {
+        "category": "Error",
+        "code": 2671
+    },
     "Import declaration '{0}' is using private name '{1}'.": {
         "category": "Error",
         "code": 4000

tests/baselines/reference/augmentExportEquals1.errors.txt

@@ -0,0 +1,26 @@
+tests/cases/compiler/file2.ts(6,16): error TS2671: Cannot augment module './file1' because it resolves to a non-module entity.
+tests/cases/compiler/file3.ts(3,8): error TS2503: Cannot find namespace 'x'.
+
+
+==== tests/cases/compiler/file3.ts (1 errors) ====
+    import x = require("./file1");
+    import "./file2";
+    let a: x.A; // should not work
+           ~
+!!! error TS2503: Cannot find namespace 'x'.
+==== tests/cases/compiler/file1.ts (0 errors) ====
+    var x = 1;
+    export = x;
+
+==== tests/cases/compiler/file2.ts (1 errors) ====
+
+    import x = require("./file1"); 
+
+    // augmentation for './file1'
+    // should error since './file1' does not have namespace meaning
+    declare module "./file1" {
+                   ~~~~~~~~~
+!!! error TS2671: Cannot augment module './file1' because it resolves to a non-module entity.
+        interface A { a }
+    }
+

tests/baselines/reference/augmentExportEquals1.js

@@ -0,0 +1,36 @@
+//// [tests/cases/compiler/augmentExportEquals1.ts] ////
+
+//// [file1.ts]
+var x = 1;
+export = x;
+
+//// [file2.ts]
+
+import x = require("./file1"); 
+
+// augmentation for './file1'
+// should error since './file1' does not have namespace meaning
+declare module "./file1" {
+    interface A { a }
+}
+
+//// [file3.ts]
+import x = require("./file1");
+import "./file2";
+let a: x.A; // should not work
+
+//// [file1.js]
+define(["require", "exports"], function (require, exports) {
+    "use strict";
+    var x = 1;
+    return x;
+});
+//// [file2.js]
+define(["require", "exports"], function (require, exports) {
+    "use strict";
+});
+//// [file3.js]
+define(["require", "exports", "./file2"], function (require, exports) {
+    "use strict";
+    var a; // should not work
+});

tests/baselines/reference/augmentExportEquals1_1.errors.txt

@@ -0,0 +1,29 @@
+tests/cases/compiler/file2.ts(6,16): error TS2671: Cannot augment module 'file1' because it resolves to a non-module entity.
+tests/cases/compiler/file3.ts(3,8): error TS2503: Cannot find namespace 'x'.
+
+
+==== tests/cases/compiler/file3.ts (1 errors) ====
+    import x = require("file1");
+    import "file2";
+    let a: x.A; // should not work
+           ~
+!!! error TS2503: Cannot find namespace 'x'.
+==== tests/cases/compiler/file1.d.ts (0 errors) ====
+
+    declare module "file1" {
+        var x: number;
+        export = x;
+    }
+
+==== tests/cases/compiler/file2.ts (1 errors) ====
+    /// <reference path="file1.d.ts"/>
+    import x = require("file1"); 
+
+    // augmentation for 'file1'
+    // should error since 'file1' does not have namespace meaning
+    declare module "file1" {
+                   ~~~~~~~
+!!! error TS2671: Cannot augment module 'file1' because it resolves to a non-module entity.
+        interface A { a }
+    }
+

tests/baselines/reference/augmentExportEquals1_1.js

@@ -0,0 +1,33 @@
+//// [tests/cases/compiler/augmentExportEquals1_1.ts] ////
+
+//// [file1.d.ts]
+
+declare module "file1" {
+    var x: number;
+    export = x;
+}
+
+//// [file2.ts]
+/// <reference path="file1.d.ts"/>
+import x = require("file1"); 
+
+// augmentation for 'file1'
+// should error since 'file1' does not have namespace meaning
+declare module "file1" {
+    interface A { a }
+}
+
+//// [file3.ts]
+import x = require("file1");
+import "file2";
+let a: x.A; // should not work
+
+//// [file2.js]
+define(["require", "exports"], function (require, exports) {
+    "use strict";
+});
+//// [file3.js]
+define(["require", "exports", "file2"], function (require, exports) {
+    "use strict";
+    var a; // should not work
+});

tests/baselines/reference/augmentExportEquals2.errors.txt

@@ -0,0 +1,25 @@
+tests/cases/compiler/file2.ts(4,16): error TS2671: Cannot augment module './file1' because it resolves to a non-module entity.
+tests/cases/compiler/file3.ts(3,8): error TS2503: Cannot find namespace 'x'.
+
+
+==== tests/cases/compiler/file3.ts (1 errors) ====
+    import x = require("./file1");
+    import "./file2";
+    let a: x.A; // should not work
+           ~
+!!! error TS2503: Cannot find namespace 'x'.
+==== tests/cases/compiler/file1.ts (0 errors) ====
+
+    function foo() {}
+    export = foo;
+
+==== tests/cases/compiler/file2.ts (1 errors) ====
+    import x = require("./file1"); 
+
+    // should error since './file1' does not have namespace meaning
+    declare module "./file1" {
+                   ~~~~~~~~~
+!!! error TS2671: Cannot augment module './file1' because it resolves to a non-module entity.
+        interface A { a }
+    }
+

tests/baselines/reference/augmentExportEquals2.js

@@ -0,0 +1,35 @@
+//// [tests/cases/compiler/augmentExportEquals2.ts] ////
+
+//// [file1.ts]
+
+function foo() {}
+export = foo;
+
+//// [file2.ts]
+import x = require("./file1"); 
+
+// should error since './file1' does not have namespace meaning
+declare module "./file1" {
+    interface A { a }
+}
+
+//// [file3.ts]
+import x = require("./file1");
+import "./file2";
+let a: x.A; // should not work
+
+//// [file1.js]
+define(["require", "exports"], function (require, exports) {
+    "use strict";
+    function foo() { }
+    return foo;
+});
+//// [file2.js]
+define(["require", "exports"], function (require, exports) {
+    "use strict";
+});
+//// [file3.js]
+define(["require", "exports", "./file2"], function (require, exports) {
+    "use strict";
+    var a; // should not work
+});

tests/baselines/reference/augmentExportEquals2_1.errors.txt

@@ -0,0 +1,29 @@
+tests/cases/compiler/file2.ts(6,16): error TS2671: Cannot augment module 'file1' because it resolves to a non-module entity.
+tests/cases/compiler/file3.ts(3,8): error TS2503: Cannot find namespace 'x'.
+
+
+==== tests/cases/compiler/file3.ts (1 errors) ====
+    import x = require("file1");
+    import "file2";
+    let a: x.A; // should not work
+           ~
+!!! error TS2503: Cannot find namespace 'x'.
+==== tests/cases/compiler/file1.d.ts (0 errors) ====
+
+    declare module "file1" {
+        function foo(): void;
+        export = foo;
+    }
+
+==== tests/cases/compiler/file2.ts (1 errors) ====
+
+    /// <reference path="file1.d.ts"/> 
+    import x = require("file1"); 
+
+    // should error since './file1' does not have namespace meaning
+    declare module "file1" {
+                   ~~~~~~~
+!!! error TS2671: Cannot augment module 'file1' because it resolves to a non-module entity.
+        interface A { a }
+    }
+

tests/baselines/reference/augmentExportEquals2_1.js

@@ -0,0 +1,33 @@
+//// [tests/cases/compiler/augmentExportEquals2_1.ts] ////
+
+//// [file1.d.ts]
+
+declare module "file1" {
+    function foo(): void;
+    export = foo;
+}
+
+//// [file2.ts]
+
+/// <reference path="file1.d.ts"/> 
+import x = require("file1"); 
+
+// should error since './file1' does not have namespace meaning
+declare module "file1" {
+    interface A { a }
+}
+
+//// [file3.ts]
+import x = require("file1");
+import "file2";
+let a: x.A; // should not work
+
+//// [file2.js]
+define(["require", "exports"], function (require, exports) {
+    "use strict";
+});
+//// [file3.js]
+define(["require", "exports", "file2"], function (require, exports) {
+    "use strict";
+    var a; // should not work
+});

tests/baselines/reference/augmentExportEquals3.errors.txt

@@ -0,0 +1,31 @@
+tests/cases/compiler/file2.ts(6,15): error TS2665: Module augmentation cannot introduce new names in the top level scope.
+tests/cases/compiler/file2.ts(7,9): error TS2665: Module augmentation cannot introduce new names in the top level scope.
+
+
+==== tests/cases/compiler/file1.ts (0 errors) ====
+
+    function foo() {}
+    namespace foo {
+        export var v = 1;
+    }
+    export = foo;
+
+==== tests/cases/compiler/file2.ts (2 errors) ====
+    import x = require("./file1"); 
+    x.b = 1;
+
+    // OK - './file1' is a namespace
+    declare module "./file1" {
+        interface A { a }
+                  ~
+!!! error TS2665: Module augmentation cannot introduce new names in the top level scope.
+        let b: number;
+            ~
+!!! error TS2665: Module augmentation cannot introduce new names in the top level scope.
+    }
+
+==== tests/cases/compiler/file3.ts (0 errors) ====
+    import * as x from "./file1";
+    import "./file2";
+    let a: x.A;
+    let b = x.b;