Add refactoring to convert CommonJS module to ES6 module

Author: Andy Hanson

src/compiler/binder.ts

@@ -2267,30 +2267,13 @@ namespace ts {
             declareSymbol(file.symbol.exports, file.symbol, <PropertyAccessExpression>node.left, SymbolFlags.Property | SymbolFlags.ExportValue, SymbolFlags.None);
         }
 
-        function isExportsOrModuleExportsOrAlias(node: Node): boolean {
-            return isExportsIdentifier(node) ||
-                isModuleExportsPropertyAccessExpression(node) ||
-                isIdentifier(node) && isNameOfExportsOrModuleExportsAliasDeclaration(node);
-        }
-
-        function isNameOfExportsOrModuleExportsAliasDeclaration(node: Identifier): boolean {
-            const symbol = lookupSymbolForName(node.escapedText);
-            return symbol && symbol.valueDeclaration && isVariableDeclaration(symbol.valueDeclaration) &&
-                symbol.valueDeclaration.initializer && isExportsOrModuleExportsOrAliasOrAssignment(symbol.valueDeclaration.initializer);
-        }
-
-        function isExportsOrModuleExportsOrAliasOrAssignment(node: Node): boolean {
-            return isExportsOrModuleExportsOrAlias(node) ||
-                (isAssignmentExpression(node, /*excludeCompoundAssignements*/ true) && (isExportsOrModuleExportsOrAliasOrAssignment(node.left) || isExportsOrModuleExportsOrAliasOrAssignment(node.right)));
-        }
-
         function bindModuleExportsAssignment(node: BinaryExpression) {
             // A common practice in node modules is to set 'export = module.exports = {}', this ensures that 'exports'
             // is still pointing to 'module.exports'.
             // We do not want to consider this as 'export=' since a module can have only one of these.
             // Similarly we do not want to treat 'module.exports = exports' as an 'export='.
             const assignedExpression = getRightMostAssignedExpression(node.right);
-            if (isEmptyObjectLiteral(assignedExpression) || isExportsOrModuleExportsOrAlias(assignedExpression)) {
+            if (isEmptyObjectLiteral(assignedExpression) || container === file && isExportsOrModuleExportsOrAlias(file, assignedExpression)) {
                 // Mark it as a module in case there are no other exports in the file
                 setCommonJsModuleIndicator(node);
                 return;
@@ -2357,7 +2340,7 @@ namespace ts {
                 leftSideOfAssignment.parent = node;
                 target.parent = leftSideOfAssignment;
 
-                if (isNameOfExportsOrModuleExportsAliasDeclaration(target)) {
+                if (container === file && isNameOfExportsOrModuleExportsAliasDeclaration(file, target)) {
                     // This can be an alias for the 'exports' or 'module.exports' names, e.g.
                     //    var util = module.exports;
                     //    util.property = function ...
@@ -2370,7 +2353,7 @@ namespace ts {
         }
 
         function lookupSymbolForName(name: __String) {
-            return (container.symbol && container.symbol.exports && container.symbol.exports.get(name)) || (container.locals && container.locals.get(name));
+            return lookupSymbolForNameWorker(container, name);
         }
 
         function bindPropertyAssignment(functionName: __String, propertyAccessExpression: PropertyAccessExpression, isPrototypeProperty: boolean) {
@@ -2589,6 +2572,29 @@ namespace ts {
         }
     }
 
+    /* @internal */
+    export function isExportsOrModuleExportsOrAlias(sourceFile: SourceFile, node: Expression): boolean {
+        return isExportsIdentifier(node) ||
+            isModuleExportsPropertyAccessExpression(node) ||
+            isIdentifier(node) && isNameOfExportsOrModuleExportsAliasDeclaration(sourceFile, node);
+    }
+
+    function isNameOfExportsOrModuleExportsAliasDeclaration(sourceFile: SourceFile, node: Identifier): boolean {
+        const symbol = lookupSymbolForNameWorker(sourceFile, node.escapedText);
+        return symbol && symbol.valueDeclaration && isVariableDeclaration(symbol.valueDeclaration) &&
+            symbol.valueDeclaration.initializer && isExportsOrModuleExportsOrAliasOrAssignment(sourceFile, symbol.valueDeclaration.initializer);
+    }
+
+    function isExportsOrModuleExportsOrAliasOrAssignment(sourceFile: SourceFile, node: Expression): boolean {
+        return isExportsOrModuleExportsOrAlias(sourceFile, node) ||
+            (isAssignmentExpression(node, /*excludeCompoundAssignements*/ true) && (
+                isExportsOrModuleExportsOrAliasOrAssignment(sourceFile, node.left) || isExportsOrModuleExportsOrAliasOrAssignment(sourceFile, node.right)));
+    }
+
+    function lookupSymbolForNameWorker(container: Node, name: __String): Symbol | undefined {
+        return (container.symbol && container.symbol.exports && container.symbol.exports.get(name)) || (container.locals && container.locals.get(name));
+    }
+
     /**
      * Computes the transform flags for a node, given the transform flags of its subtree
      *

src/compiler/checker.ts

@@ -250,8 +250,8 @@ namespace ts {
             getSuggestionForNonexistentProperty: (node, type) => getSuggestionForNonexistentProperty(node, type),
             getSuggestionForNonexistentSymbol: (location, name, meaning) => getSuggestionForNonexistentSymbol(location, escapeLeadingUnderscores(name), meaning),
             getBaseConstraintOfType,
-            resolveName(name, location, meaning) {
-                return resolveName(location, escapeLeadingUnderscores(name), meaning, /*nameNotFoundMessage*/ undefined, /*nameArg*/ undefined, /*isUse*/ false);
+            resolveName(name, location, meaning, includeGlobals) {
+                return resolveName(location, escapeLeadingUnderscores(name), meaning, /*nameNotFoundMessage*/ undefined, /*nameArg*/ undefined, /*isUse*/ false, includeGlobals);
             },
             getJsxNamespace: () => unescapeLeadingUnderscores(getJsxNamespace()),
         };
@@ -909,8 +909,9 @@ namespace ts {
             nameNotFoundMessage: DiagnosticMessage | undefined,
             nameArg: __String | Identifier,
             isUse: boolean,
+            includeGlobals = true,
             suggestedNameNotFoundMessage?: DiagnosticMessage): Symbol {
-            return resolveNameHelper(location, name, meaning, nameNotFoundMessage, nameArg, isUse, getSymbol, suggestedNameNotFoundMessage);
+            return resolveNameHelper(location, name, meaning, nameNotFoundMessage, nameArg, isUse,  includeGlobals, getSymbol, suggestedNameNotFoundMessage);
         }
 
         function resolveNameHelper(
@@ -920,6 +921,7 @@ namespace ts {
             nameNotFoundMessage: DiagnosticMessage,
             nameArg: __String | Identifier,
             isUse: boolean,
+            includeGlobals: boolean,
             lookup: typeof getSymbol,
             suggestedNameNotFoundMessage?: DiagnosticMessage): Symbol {
             const originalLocation = location; // needed for did-you-mean error reporting, which gathers candidates starting from the original location
@@ -1166,7 +1168,9 @@ namespace ts {
                     }
                 }
 
-                result = lookup(globals, name, meaning);
+                if (includeGlobals) {
+                    result = lookup(globals, name, meaning);
+                }
             }
 
             if (!result) {
@@ -11250,6 +11254,7 @@ namespace ts {
                         Diagnostics.Cannot_find_name_0,
                         node,
                         !isWriteOnlyAccess(node),
+                        /*includeGlobals*/ true,
                         Diagnostics.Cannot_find_name_0_Did_you_mean_1) || unknownSymbol;
             }
             return links.resolvedSymbol;
@@ -15352,7 +15357,7 @@ namespace ts {
 
         function getSuggestionForNonexistentSymbol(location: Node, outerName: __String, meaning: SymbolFlags): string {
             Debug.assert(outerName !== undefined, "outername should always be defined");
-            const result = resolveNameHelper(location, outerName, meaning, /*nameNotFoundMessage*/ undefined, outerName, /*isUse*/ false, (symbols, name, meaning) => {
+            const result = resolveNameHelper(location, outerName, meaning, /*nameNotFoundMessage*/ undefined, outerName, /*isUse*/ false, /*includeGlobals*/ true, (symbols, name, meaning) => {
                 Debug.assertEqual(outerName, name, "name should equal outerName");
                 const symbol = getSymbol(symbols, name, meaning);
                 // Sometimes the symbol is found when location is a return type of a function: `typeof x` and `x` is declared in the body of the function

src/compiler/core.ts

@@ -394,6 +394,16 @@ namespace ts {
         return result;
     }
 
+    export function mapIter<T, U>(iter: Iterator<T>, mapFn: (x: T) => U): U[] {
+        const result: U[] = [];
+        while (true) {
+            const { value, done } = iter.next();
+            if (done) break;
+            result.push(mapFn(value));
+        }
+        return result;
+    }
+
     // Maps from T to T and avoids allocation if all elements map to themselves
     export function sameMap<T>(array: T[], f: (x: T, i: number) => T): T[];
     export function sameMap<T>(array: ReadonlyArray<T>, f: (x: T, i: number) => T): ReadonlyArray<T>;
@@ -515,12 +525,23 @@ namespace ts {
         return result || array;
     }
 
+    export function mapAllOrFail<T, U>(array: ReadonlyArray<T>, mapFn: (x: T, i: number) => U | undefined): U[] | undefined {
+        const result: U[] = [];
+        for (let i = 0; i < array.length; i++) {
+            const mapped = mapFn(array[i], i);
+            if (!mapped) {
+                return undefined;
+            }
+            result.push(mapped);
+        }
+        return result;
+    }
+
     export function mapDefined<T, U>(array: ReadonlyArray<T> | undefined, mapFn: (x: T, i: number) => U | undefined): U[] {
         const result: U[] = [];
         if (array) {
             for (let i = 0; i < array.length; i++) {
-                const item = array[i];
-                const mapped = mapFn(item, i);
+                const mapped = mapFn(array[i], i);
                 if (mapped !== undefined) {
                     result.push(mapped);
                 }

src/compiler/diagnosticMessages.json

@@ -3809,5 +3809,9 @@
     "Import * as '{0}' from \"{1}\".": {
         "category": "Message",
         "code": 95016
+    },
+    "Convert to ES6 module": {
+        "category": "Message",
+        "code": 95017
     }
 }

src/compiler/emitter.ts

@@ -1194,27 +1194,15 @@ namespace ts {
         //
 
         function emitObjectBindingPattern(node: ObjectBindingPattern) {
-            const elements = node.elements;
-            if (elements.length === 0) {
-                write("{}");
-            }
-            else {
-                write("{");
-                emitList(node, elements, ListFormat.ObjectBindingPatternElements);
-                write("}");
-            }
+            write("{");
+            emitList(node, node.elements, ListFormat.ObjectBindingPatternElements);
+            write("}");
         }
 
         function emitArrayBindingPattern(node: ArrayBindingPattern) {
-            const elements = node.elements;
-            if (elements.length === 0) {
-                write("[]");
-            }
-            else {
-                write("[");
-                emitList(node, node.elements, ListFormat.ArrayBindingPatternElements);
-                write("]");
-            }
+            write("[");
+            emitList(node, node.elements, ListFormat.ArrayBindingPatternElements);
+            write("]");
         }
 
         function emitBindingElement(node: BindingElement) {
@@ -3167,8 +3155,8 @@ namespace ts {
         TupleTypeElements = CommaDelimited | SpaceBetweenSiblings | SingleLine | Indented,
         UnionTypeConstituents = BarDelimited | SpaceBetweenSiblings | SingleLine,
         IntersectionTypeConstituents = AmpersandDelimited | SpaceBetweenSiblings | SingleLine,
-        ObjectBindingPatternElements = SingleLine | AllowTrailingComma | SpaceBetweenBraces | CommaDelimited | SpaceBetweenSiblings,
-        ArrayBindingPatternElements = SingleLine | AllowTrailingComma | CommaDelimited | SpaceBetweenSiblings,
+        ObjectBindingPatternElements = SingleLine | AllowTrailingComma | SpaceBetweenBraces | CommaDelimited | SpaceBetweenSiblings | NoSpaceIfEmpty,
+        ArrayBindingPatternElements = SingleLine | AllowTrailingComma | CommaDelimited | SpaceBetweenSiblings | NoSpaceIfEmpty,
         ObjectLiteralExpressionProperties = PreserveLines | CommaDelimited | SpaceBetweenSiblings | SpaceBetweenBraces | Indented | Braces | NoSpaceIfEmpty,
         ArrayLiteralExpressionElements = PreserveLines | CommaDelimited | SpaceBetweenSiblings | AllowTrailingComma | Indented | SquareBrackets,
         CommaListElements = CommaDelimited | SpaceBetweenSiblings | SingleLine,

src/compiler/factory.ts

@@ -101,7 +101,7 @@ namespace ts {
         return node;
     }
 
-    function createLiteralFromNode(sourceNode: StringLiteral | NumericLiteral | Identifier): StringLiteral {
+    function createLiteralFromNode(sourceNode: StringLiteralLike | NumericLiteral | Identifier): StringLiteral {
         const node = createStringLiteral(getTextOfIdentifierOrLiteral(sourceNode));
         node.textSourceNode = sourceNode;
         return node;
@@ -3624,7 +3624,7 @@ namespace ts {
         return qualifiedName;
     }
 
-    export function convertToFunctionBody(node: ConciseBody, multiLine?: boolean) {
+    export function convertToFunctionBody(node: ConciseBody, multiLine?: boolean): Block {
         return isBlock(node) ? node : setTextRange(createBlock([setTextRange(createReturn(node), node)], multiLine), node);
     }
 

src/compiler/types.ts

@@ -1074,11 +1074,13 @@ namespace ts {
 
     export interface StringLiteral extends LiteralExpression {
         kind: SyntaxKind.StringLiteral;
-        /* @internal */ textSourceNode?: Identifier | StringLiteral | NumericLiteral; // Allows a StringLiteral to get its text from another node (used by transforms).
+        /* @internal */ textSourceNode?: Identifier | StringLiteralLike | NumericLiteral; // Allows a StringLiteral to get its text from another node (used by transforms).
         /** Note: this is only set when synthesizing a node, not during parsing. */
         /* @internal */ singleQuote?: boolean;
     }
 
+    /* @internal */ export type StringLiteralLike = StringLiteral | NoSubstitutionTemplateLiteral;
+
     // Note: 'brands' in our syntax nodes serve to give us a small amount of nominal typing.
     // Consider 'Expression'.  Without the brand, 'Expression' is actually no different
     // (structurally) than 'Node'.  Because of this you can pass any Node to a function that
@@ -1424,6 +1426,7 @@ namespace ts {
         kind: SyntaxKind.ArrowFunction;
         equalsGreaterThanToken: EqualsGreaterThanToken;
         body: ConciseBody;
+        name: never;
     }
 
     // The text property of a LiteralExpression stores the interpreted value of the literal in text form. For a StringLiteral,
@@ -2075,6 +2078,7 @@ namespace ts {
     export interface ExportDeclaration extends DeclarationStatement {
         kind: SyntaxKind.ExportDeclaration;
         parent?: SourceFile | ModuleBlock;
+        /** Will not be assigned in the case of `export * from "foo";` */
         exportClause?: NamedExports;
         /** If this is not a StringLiteral it will be a grammar error. */
         moduleSpecifier?: Expression;
@@ -2779,7 +2783,7 @@ namespace ts {
          */
         /* @internal */ isArrayLikeType(type: Type): boolean;
         /* @internal */ getAllPossiblePropertiesOfTypes(type: ReadonlyArray<Type>): Symbol[];
-        /* @internal */ resolveName(name: string, location: Node, meaning: SymbolFlags): Symbol | undefined;
+        /* @internal */ resolveName(name: string, location: Node, meaning: SymbolFlags, includeGlobals: boolean): Symbol | undefined;
         /* @internal */ getJsxNamespace(): string;
     }
 

src/compiler/utilities.ts

@@ -1385,6 +1385,8 @@ namespace ts {
      * exactly one argument (of the form 'require("name")').
      * This function does not test if the node is in a JavaScript file or not.
      */
+    export function isRequireCall(callExpression: Node, checkArgumentIsStringLiteral: true): callExpression is CallExpression & { expression: Identifier, arguments: [StringLiteralLike] };
+    export function isRequireCall(callExpression: Node, checkArgumentIsStringLiteral: boolean): callExpression is CallExpression;
     export function isRequireCall(callExpression: Node, checkArgumentIsStringLiteral: boolean): callExpression is CallExpression {
         if (callExpression.kind !== SyntaxKind.CallExpression) {
             return false;
@@ -1422,7 +1424,7 @@ namespace ts {
         return false;
     }
 
-    export function getRightMostAssignedExpression(node: Node) {
+    export function getRightMostAssignedExpression(node: Expression): Expression {
         while (isAssignmentExpression(node, /*excludeCompoundAssignements*/ true)) {
             node = node.right;
         }

src/harness/fourslash.ts

@@ -448,7 +448,7 @@ namespace FourSlash {
             const ranges = this.getRanges();
             assert(ranges.length);
             for (const range of ranges) {
-                this.goToRangeStart(range);
+                this.selectRange(range);
                 action();
             }
         }
@@ -476,6 +476,11 @@ namespace FourSlash {
             this.selectionEnd = end.position;
         }
 
+        public selectRange(range: Range): void {
+            this.goToRangeStart(range);
+            this.selectionEnd = range.end;
+        }
+
         public moveCaretRight(count = 1) {
             this.currentCaretPosition += count;
             this.currentCaretPosition = Math.min(this.currentCaretPosition, this.getFileContent(this.activeFile.fileName).length);
@@ -3776,6 +3781,10 @@ namespace FourSlashInterface {
         public select(startMarker: string, endMarker: string) {
             this.state.select(startMarker, endMarker);
         }
+
+        public selectRange(range: FourSlash.Range): void {
+            this.state.selectRange(range);
+        }
     }
 
     export class VerifyNegatable {

src/services/codefixes/importFixes.ts

@@ -658,7 +658,7 @@ namespace ts.codefix {
         }
         else if (isJsxOpeningLikeElement(symbolToken.parent) && symbolToken.parent.tagName === symbolToken) {
             // The error wasn't for the symbolAtLocation, it was for the JSX tag itself, which needs access to e.g. `React`.
-            symbol = checker.getAliasedSymbol(checker.resolveName(checker.getJsxNamespace(), symbolToken.parent.tagName, SymbolFlags.Value));
+            symbol = checker.getAliasedSymbol(checker.resolveName(checker.getJsxNamespace(), symbolToken.parent.tagName, SymbolFlags.Value, /*includeGlobals*/ true));
             symbolName = symbol.name;
         }
         else {
@@ -737,7 +737,7 @@ namespace ts.codefix {
         return moduleSpecifierToValidIdentifier(removeFileExtension(getBaseFileName(moduleSymbol.name)), target);
     }
 
-    function moduleSpecifierToValidIdentifier(moduleSpecifier: string, target: ScriptTarget): string {
+    export function moduleSpecifierToValidIdentifier(moduleSpecifier: string, target: ScriptTarget): string {
         let res = "";
         let lastCharWasValid = true;
         const firstCharCode = moduleSpecifier.charCodeAt(0);