Allow to access exports from inside a commonjs module (#17745)

* Allow to access `exports` from inside a commonjs module

* Don't contextually type `this` in `exports.f = function() { ... }`

* Update test

Author: Andy

src/compiler/checker.ts

@@ -1125,6 +1125,13 @@ namespace ts {
             }
 
             if (!result) {
+                if (lastLocation) {
+                    Debug.assert(lastLocation.kind === SyntaxKind.SourceFile);
+                    if ((lastLocation as SourceFile).commonJsModuleIndicator && name === "exports") {
+                        return lastLocation.symbol;
+                    }
+                }
+
                 result = lookup(globals, name, meaning);
             }
 
@@ -12885,7 +12892,8 @@ namespace ts {
                     }
                 }
             }
-            if (noImplicitThis || isInJavaScriptFile(func)) {
+            const inJs = isInJavaScriptFile(func);
+            if (noImplicitThis || inJs) {
                 const containingLiteral = getContainingObjectLiteral(func);
                 if (containingLiteral) {
                     // We have an object literal method. Check if the containing object literal has a contextual type
@@ -12912,10 +12920,20 @@ namespace ts {
                 }
                 // In an assignment of the form 'obj.xxx = function(...)' or 'obj[xxx] = function(...)', the
                 // contextual type for 'this' is 'obj'.
-                if (func.parent.kind === SyntaxKind.BinaryExpression && (<BinaryExpression>func.parent).operatorToken.kind === SyntaxKind.EqualsToken) {
-                    const target = (<BinaryExpression>func.parent).left;
+                const { parent } = func;
+                if (parent.kind === SyntaxKind.BinaryExpression && (<BinaryExpression>parent).operatorToken.kind === SyntaxKind.EqualsToken) {
+                    const target = (<BinaryExpression>parent).left;
                     if (target.kind === SyntaxKind.PropertyAccessExpression || target.kind === SyntaxKind.ElementAccessExpression) {
-                        return checkExpressionCached((<PropertyAccessExpression | ElementAccessExpression>target).expression);
+                        const { expression } = target as PropertyAccessExpression | ElementAccessExpression;
+                        // Don't contextually type `this` as `exports` in `exports.Point = function(x, y) { this.x = x; this.y = y; }`
+                        if (inJs && isIdentifier(expression)) {
+                            const sourceFile = getSourceFileOfNode(parent);
+                            if (sourceFile.commonJsModuleIndicator && getResolvedSymbol(expression) === sourceFile.symbol) {
+                                return undefined;
+                            }
+                        }
+
+                        return checkExpressionCached(expression);
                     }
                 }
             }

tests/baselines/reference/commonjsAccessExports.symbols

@@ -0,0 +1,30 @@
+=== /a.js ===
+exports.x = 0;
+>exports.x : Symbol(x, Decl(a.js, 0, 0))
+>exports : Symbol(x, Decl(a.js, 0, 0))
+>x : Symbol(x, Decl(a.js, 0, 0))
+
+exports.x;
+>exports.x : Symbol(x, Decl(a.js, 0, 0))
+>exports : Symbol("/a", Decl(a.js, 0, 0))
+>x : Symbol(x, Decl(a.js, 0, 0))
+
+// Works nested
+{
+    // 'exports' does not provide a contextual type to a function-class
+    exports.Cls = function() {
+>exports.Cls : Symbol(Cls, Decl(a.js, 4, 1))
+>exports : Symbol(Cls, Decl(a.js, 4, 1))
+>Cls : Symbol(Cls, Decl(a.js, 4, 1))
+
+        this.x = 0;
+>x : Symbol((Anonymous function).x, Decl(a.js, 6, 30))
+    }
+}
+
+const instance = new exports.Cls();
+>instance : Symbol(instance, Decl(a.js, 11, 5))
+>exports.Cls : Symbol(Cls, Decl(a.js, 4, 1))
+>exports : Symbol("/a", Decl(a.js, 0, 0))
+>Cls : Symbol(Cls, Decl(a.js, 4, 1))
+

tests/baselines/reference/commonjsAccessExports.types

@@ -0,0 +1,39 @@
+=== /a.js ===
+exports.x = 0;
+>exports.x = 0 : 0
+>exports.x : number
+>exports : typeof "/a"
+>x : number
+>0 : 0
+
+exports.x;
+>exports.x : number
+>exports : typeof "/a"
+>x : number
+
+// Works nested
+{
+    // 'exports' does not provide a contextual type to a function-class
+    exports.Cls = function() {
+>exports.Cls = function() {        this.x = 0;    } : () => void
+>exports.Cls : () => void
+>exports : typeof "/a"
+>Cls : () => void
+>function() {        this.x = 0;    } : () => void
+
+        this.x = 0;
+>this.x = 0 : 0
+>this.x : any
+>this : any
+>x : any
+>0 : 0
+    }
+}
+
+const instance = new exports.Cls();
+>instance : { x: number; }
+>new exports.Cls() : { x: number; }
+>exports.Cls : () => void
+>exports : typeof "/a"
+>Cls : () => void
+

tests/baselines/reference/jsFileCompilationExternalPackageError.symbols

@@ -17,6 +17,7 @@ var a = 10;
 
 === tests/cases/compiler/node_modules/c.js ===
 exports.a = 10;
+>exports.a : Symbol(a, Decl(c.js, 0, 0))
 >exports : Symbol(a, Decl(c.js, 0, 0))
 >a : Symbol(a, Decl(c.js, 0, 0))
 

tests/baselines/reference/jsFileCompilationExternalPackageError.types

@@ -21,9 +21,9 @@ var a = 10;
 === tests/cases/compiler/node_modules/c.js ===
 exports.a = 10;
 >exports.a = 10 : 10
->exports.a : any
->exports : any
->a : any
+>exports.a : number
+>exports : typeof "tests/cases/compiler/node_modules/c"
+>a : number
 >10 : 10
 
 c = 10;

tests/baselines/reference/moduleExportAlias.symbols

@@ -106,11 +106,15 @@ b.func20;
 === tests/cases/conformance/salsa/b.js ===
 var exportsAlias = exports;
 >exportsAlias : Symbol(exportsAlias, Decl(b.js, 0, 3))
+>exports : Symbol("tests/cases/conformance/salsa/b", Decl(b.js, 0, 0))
 
 exportsAlias.func1 = function () { };
+>exportsAlias.func1 : Symbol(func1, Decl(b.js, 0, 27))
 >exportsAlias : Symbol(exportsAlias, Decl(b.js, 0, 3))
+>func1 : Symbol(func1, Decl(b.js, 0, 27))
 
 exports.func2 = function () { };
+>exports.func2 : Symbol(func2, Decl(b.js, 1, 37))
 >exports : Symbol(func2, Decl(b.js, 1, 37))
 >func2 : Symbol(func2, Decl(b.js, 1, 37))
 
@@ -126,25 +130,32 @@ module.exports.func4 = function () { };
 
 var multipleDeclarationAlias1 = exports = module.exports;
 >multipleDeclarationAlias1 : Symbol(multipleDeclarationAlias1, Decl(b.js, 8, 3))
+>exports : Symbol("tests/cases/conformance/salsa/b", Decl(b.js, 0, 0))
 
 multipleDeclarationAlias1.func5 = function () { };
 >multipleDeclarationAlias1 : Symbol(multipleDeclarationAlias1, Decl(b.js, 8, 3))
 
 var multipleDeclarationAlias2 = module.exports = exports;
 >multipleDeclarationAlias2 : Symbol(multipleDeclarationAlias2, Decl(b.js, 11, 3))
+>exports : Symbol("tests/cases/conformance/salsa/b", Decl(b.js, 0, 0))
 
 multipleDeclarationAlias2.func6 = function () { };
+>multipleDeclarationAlias2.func6 : Symbol(func6, Decl(b.js, 11, 57))
 >multipleDeclarationAlias2 : Symbol(multipleDeclarationAlias2, Decl(b.js, 11, 3))
+>func6 : Symbol(func6, Decl(b.js, 11, 57))
 
 var someOtherVariable;
 >someOtherVariable : Symbol(someOtherVariable, Decl(b.js, 14, 3))
 
 var multipleDeclarationAlias3 = someOtherVariable = exports;
 >multipleDeclarationAlias3 : Symbol(multipleDeclarationAlias3, Decl(b.js, 15, 3))
 >someOtherVariable : Symbol(someOtherVariable, Decl(b.js, 14, 3))
+>exports : Symbol("tests/cases/conformance/salsa/b", Decl(b.js, 0, 0))
 
 multipleDeclarationAlias3.func7 = function () { };
+>multipleDeclarationAlias3.func7 : Symbol(func7, Decl(b.js, 15, 60))
 >multipleDeclarationAlias3 : Symbol(multipleDeclarationAlias3, Decl(b.js, 15, 3))
+>func7 : Symbol(func7, Decl(b.js, 15, 60))
 
 var multipleDeclarationAlias4 = someOtherVariable = module.exports;
 >multipleDeclarationAlias4 : Symbol(multipleDeclarationAlias4, Decl(b.js, 18, 3))
@@ -155,20 +166,24 @@ multipleDeclarationAlias4.func8 = function () { };
 
 var multipleDeclarationAlias5 = module.exports = exports = {};
 >multipleDeclarationAlias5 : Symbol(multipleDeclarationAlias5, Decl(b.js, 21, 3))
+>exports : Symbol("tests/cases/conformance/salsa/b", Decl(b.js, 0, 0))
 
 multipleDeclarationAlias5.func9 = function () { };
 >multipleDeclarationAlias5 : Symbol(multipleDeclarationAlias5, Decl(b.js, 21, 3))
 
 var multipleDeclarationAlias6 = exports = module.exports = {};
 >multipleDeclarationAlias6 : Symbol(multipleDeclarationAlias6, Decl(b.js, 24, 3))
+>exports : Symbol("tests/cases/conformance/salsa/b", Decl(b.js, 0, 0))
 
 multipleDeclarationAlias6.func10 = function () { };
 >multipleDeclarationAlias6 : Symbol(multipleDeclarationAlias6, Decl(b.js, 24, 3))
 
 exports = module.exports = someOtherVariable = {};
+>exports : Symbol("tests/cases/conformance/salsa/b", Decl(b.js, 0, 0))
 >someOtherVariable : Symbol(someOtherVariable, Decl(b.js, 14, 3))
 
 exports.func11 = function () { };
+>exports.func11 : Symbol(func11, Decl(b.js, 27, 50), Decl(b.js, 31, 50))
 >exports : Symbol(func11, Decl(b.js, 27, 50), Decl(b.js, 31, 50))
 >func11 : Symbol(func11, Decl(b.js, 27, 50), Decl(b.js, 31, 50))
 
@@ -177,9 +192,11 @@ module.exports.func12 = function () { };
 >func12 : Symbol(func12, Decl(b.js, 28, 33), Decl(b.js, 32, 33))
 
 exports = module.exports = someOtherVariable = {};
+>exports : Symbol("tests/cases/conformance/salsa/b", Decl(b.js, 0, 0))
 >someOtherVariable : Symbol(someOtherVariable, Decl(b.js, 14, 3))
 
 exports.func11 = function () { };
+>exports.func11 : Symbol(func11, Decl(b.js, 27, 50), Decl(b.js, 31, 50))
 >exports : Symbol(func11, Decl(b.js, 27, 50), Decl(b.js, 31, 50))
 >func11 : Symbol(func11, Decl(b.js, 27, 50), Decl(b.js, 31, 50))
 
@@ -188,7 +205,10 @@ module.exports.func12 = function () { };
 >func12 : Symbol(func12, Decl(b.js, 28, 33), Decl(b.js, 32, 33))
 
 exports = module.exports = {};
+>exports : Symbol("tests/cases/conformance/salsa/b", Decl(b.js, 0, 0))
+
 exports.func13 = function () { };
+>exports.func13 : Symbol(func13, Decl(b.js, 35, 30))
 >exports : Symbol(func13, Decl(b.js, 35, 30))
 >func13 : Symbol(func13, Decl(b.js, 35, 30))
 
@@ -197,7 +217,10 @@ module.exports.func14 = function () { };
 >func14 : Symbol(func14, Decl(b.js, 36, 33))
 
 exports = module.exports = {};
+>exports : Symbol("tests/cases/conformance/salsa/b", Decl(b.js, 0, 0))
+
 exports.func15 = function () { };
+>exports.func15 : Symbol(func15, Decl(b.js, 39, 30))
 >exports : Symbol(func15, Decl(b.js, 39, 30))
 >func15 : Symbol(func15, Decl(b.js, 39, 30))
 
@@ -206,7 +229,10 @@ module.exports.func16 = function () { };
 >func16 : Symbol(func16, Decl(b.js, 40, 33))
 
 module.exports = exports = {};
+>exports : Symbol("tests/cases/conformance/salsa/b", Decl(b.js, 0, 0))
+
 exports.func17 = function () { };
+>exports.func17 : Symbol(func17, Decl(b.js, 43, 30))
 >exports : Symbol(func17, Decl(b.js, 43, 30))
 >func17 : Symbol(func17, Decl(b.js, 43, 30))
 
@@ -216,6 +242,7 @@ module.exports.func18 = function () { };
 
 module.exports = {};
 exports.func19 = function () { };
+>exports.func19 : Symbol(func19, Decl(b.js, 47, 20))
 >exports : Symbol(func19, Decl(b.js, 47, 20))
 >func19 : Symbol(func19, Decl(b.js, 47, 20))