Full support for CommonJS auto-imports in JS

src/compiler/checker.ts

@@ -607,6 +607,9 @@ namespace ts {
             getJsxNamespace: n => unescapeLeadingUnderscores(getJsxNamespace(n)),
             getAccessibleSymbolChain,
             getTypePredicateOfSignature,
+            resolveExternalModuleName: moduleSpecifier => {
+                return resolveExternalModuleName(moduleSpecifier, moduleSpecifier, /*ignoreErrors*/ true);
+            },
             resolveExternalModuleSymbol,
             tryGetThisTypeAt: (node, includeGlobalThis) => {
                 node = getParseTreeNode(node);
@@ -2560,7 +2563,7 @@ namespace ts {
         }
 
         function getTargetOfExportAssignment(node: ExportAssignment | BinaryExpression, dontResolveAlias: boolean): Symbol | undefined {
-            const expression = (isExportAssignment(node) ? node.expression : node.right) as EntityNameExpression | ClassExpression;
+            const expression = isExportAssignment(node) ? node.expression : node.right;
             const resolved = getTargetOfAliasLikeExpression(expression, dontResolveAlias);
             markSymbolOfAliasDeclarationIfTypeOnly(node, /*immediateTarget*/ undefined, resolved, /*overwriteEmpty*/ false);
             return resolved;

src/compiler/types.ts

@@ -3583,6 +3583,7 @@ namespace ts {
          */
         /* @internal */ getAccessibleSymbolChain(symbol: Symbol, enclosingDeclaration: Node | undefined, meaning: SymbolFlags, useOnlyExternalAliasing: boolean): Symbol[] | undefined;
         /* @internal */ getTypePredicateOfSignature(signature: Signature): TypePredicate | undefined;
+        /* @internal */ resolveExternalModuleName(moduleSpecifier: Expression): Symbol | undefined;
         /**
          * 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.
@@ -3817,6 +3818,10 @@ namespace ts {
     /* @internal */
     export type AnyImportSyntax = ImportDeclaration | ImportEqualsDeclaration;
 
+    /* @internal */
+    export type AnyImportOrRequire = AnyImportSyntax | RequireVariableDeclaration;
+
+
     /* @internal */
     export type AnyImportOrReExport = AnyImportSyntax | ExportDeclaration;
 
@@ -3833,7 +3838,13 @@ namespace ts {
         | ValidImportTypeNode;
 
     /* @internal */
-    export type RequireOrImportCall = CallExpression & { arguments: [StringLiteralLike] };
+    export type RequireOrImportCall = CallExpression & { expression: Identifier, arguments: [StringLiteralLike] };
+
+    /* @internal */
+    export interface RequireVariableDeclaration extends VariableDeclaration {
+
+        initializer: RequireOrImportCall;
+    }
 
     /* @internal */
     export type LateVisibilityPaintedStatement =

src/compiler/utilities.ts

@@ -1853,6 +1853,20 @@ namespace ts {
         return !requireStringLiteralLikeArgument || isStringLiteralLike(arg);
     }
 
+    /**
+     * Returns true if the node is a VariableDeclaration initialized to a require call (see `isRequireCall`).
+     * This function does not test if the node is in a JavaScript file or not.
+     */
+    export function isRequireVariableDeclaration(node: Node, requireStringLiteralLikeArgument: true): node is RequireVariableDeclaration;
+    export function isRequireVariableDeclaration(node: Node, requireStringLiteralLikeArgument: boolean): node is VariableDeclaration;
+    export function isRequireVariableDeclaration(node: Node, requireStringLiteralLikeArgument: boolean): node is VariableDeclaration {
+        return isVariableDeclaration(node) && !!node.initializer && isRequireCall(node.initializer, requireStringLiteralLikeArgument);
+    }
+
+    export function isRequireVariableDeclarationStatement(node: Node, requireStringLiteralLikeArgument = true): node is VariableStatement {
+        return isVariableStatement(node) && every(node.declarationList.declarations, decl => isRequireVariableDeclaration(decl, requireStringLiteralLikeArgument));
+    }
+
     export function isSingleOrDoubleQuote(charCode: number) {
         return charCode === CharacterCodes.singleQuote || charCode === CharacterCodes.doubleQuote;
     }

src/harness/fourslashImpl.ts

@@ -2700,7 +2700,7 @@ namespace FourSlash {
                     const oldText = this.tryGetFileContent(change.fileName);
                     ts.Debug.assert(!!change.isNewFile === (oldText === undefined));
                     const newContent = change.isNewFile ? ts.first(change.textChanges).newText : ts.textChanges.applyChanges(oldText!, change.textChanges);
-                    assert.equal(newContent, expectedNewContent, `String mis-matched in file ${change.fileName}`);
+                    this.verifyTextMatches(newContent, /*includeWhitespace*/ true, expectedNewContent);
                 }
                 for (const newFileName in newFileContent) {
                     ts.Debug.assert(changes.some(c => c.fileName === newFileName), "No change in file", () => newFileName);