Add error for unsafe CJS-style resolution

Author: andrewbranch

src/compiler/checker.ts

@@ -352,6 +352,7 @@ import {
     getPropertyAssignmentAliasLikeExpression,
     getPropertyNameForPropertyNameNode,
     getPropertyNameFromType,
+    getRelativePathFromFile,
     getResolutionDiagnostic,
     getResolutionModeOverride,
     getResolveJsonModule,
@@ -414,6 +415,7 @@ import {
     hasSyntacticModifiers,
     hasType,
     HeritageClause,
+    hostGetCanonicalFileName,
     Identifier,
     identifierToKeywordKind,
     IdentifierTypePredicate,
@@ -692,6 +694,7 @@ import {
     isParenthesizedTypeNode,
     isPartOfParameterDeclaration,
     isPartOfTypeNode,
+    isPartOfTypeOnlyImportOrExportDeclaration,
     isPartOfTypeQuery,
     isPlainJsFile,
     isPrefixUnaryExpression,
@@ -992,6 +995,7 @@ import {
     ShorthandPropertyAssignment,
     shouldAllowImportingTsExtension,
     shouldPreserveConstEnums,
+    shouldRewriteModuleSpecifier,
     Signature,
     SignatureDeclaration,
     SignatureFlags,
@@ -4656,6 +4660,19 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
                     error(errorNode, Diagnostics.An_import_path_can_only_end_with_a_0_extension_when_allowImportingTsExtensions_is_enabled, tsExtension);
                 }
             }
+            else if (
+                !(location.flags & NodeFlags.Ambient)
+                && !resolvedModule.resolvedUsingTsExtension
+                && shouldRewriteModuleSpecifier(moduleReference, compilerOptions)
+                && !isLiteralImportTypeNode(location)
+                && !isPartOfTypeOnlyImportOrExportDeclaration(location)
+            ) {
+                error(
+                    errorNode,
+                    Diagnostics.This_relative_import_path_is_unsafe_to_rewrite_because_it_looks_like_a_file_name_but_actually_resolves_to_0,
+                    getRelativePathFromFile(getNormalizedAbsolutePath(currentSourceFile.fileName, host.getCurrentDirectory()), resolvedModule.resolvedFileName, hostGetCanonicalFileName(host)),
+                );
+            }
 
             if (sourceFile.symbol) {
                 if (errorNode && resolvedModule.isExternalLibraryImport && !resolutionExtensionIsTSOrJson(resolvedModule.extension)) {

src/compiler/diagnosticMessages.json

@@ -3948,6 +3948,11 @@
         "category": "Error",
         "code": 2873
     },
+    "This relative import path is unsafe to rewrite because it looks like a file name, but actually resolves to \"$0\".": {
+        "category": "Error",
+        "code": 2874
+    },
+
     "Import declaration '{0}' is using private name '{1}'.": {
         "category": "Error",
         "code": 4000

src/compiler/transformers/ts.ts

@@ -182,6 +182,7 @@ import {
     setTypeNode,
     ShorthandPropertyAssignment,
     shouldPreserveConstEnums,
+    shouldRewriteModuleSpecifier,
     skipOuterExpressions,
     skipPartiallyEmittedExpressions,
     skipTrivia,
@@ -2283,7 +2284,7 @@ export function transformTypeScript(context: TransformationContext) {
     function rewriteModuleSpecifier(node: Expression): Expression;
     function rewriteModuleSpecifier(node: Expression | undefined): Expression | undefined;
     function rewriteModuleSpecifier(node: Expression | undefined): Expression | undefined {
-        if (!node || !compilerOptions.rewriteRelativeImportExtensions || !isStringLiteral(node) || !pathIsRelative(node.text) || isDeclarationFileName(node.text)) {
+        if (!node || !isStringLiteral(node) || !shouldRewriteModuleSpecifier(node.text, compilerOptions)) {
             return node;
         }
         const updatedText = changeExtension(node.text, getOutputExtension(node.text, compilerOptions));

src/compiler/utilities.ts

@@ -4233,6 +4233,11 @@ export function tryGetImportFromModuleSpecifier(node: StringLiteralLike): AnyVal
     }
 }
 
+/** @internal */
+export function shouldRewriteModuleSpecifier(specifier: string, compilerOptions: CompilerOptions): boolean {
+    return !!compilerOptions.rewriteRelativeImportExtensions && pathIsRelative(specifier) && !isDeclarationFileName(specifier);
+}
+
 /** @internal */
 export function getExternalModuleName(node: AnyImportOrReExport | ImportTypeNode | ImportCall | ModuleDeclaration | JSDocImportTag): Expression | undefined {
     switch (node.kind) {

src/compiler/utilitiesPublic.ts

@@ -1553,6 +1553,10 @@ export function isTypeOnlyImportOrExportDeclaration(node: Node): node is TypeOnl
     return isTypeOnlyImportDeclaration(node) || isTypeOnlyExportDeclaration(node);
 }
 
+export function isPartOfTypeOnlyImportOrExportDeclaration(node: Node): boolean {
+    return findAncestor(node, isTypeOnlyImportOrExportDeclaration) !== undefined;
+}
+
 export function isStringTextContainingNode(node: Node): node is StringLiteral | TemplateLiteralToken {
     return node.kind === SyntaxKind.StringLiteral || isTemplateLiteralKind(node.kind);
 }

tests/baselines/reference/cjsErrors.errors.txt

@@ -0,0 +1,11 @@
+index.ts(1,16): error TS2874: This relative import path is unsafe to rewrite because it looks like a file name, but actually resolves to "$0".
+
+
+==== foo.ts/index.ts (0 errors) ====
+    export {};
+    
+==== index.ts (1 errors) ====
+    import {} from "./foo.ts";
+                   ~~~~~~~~~~
+!!! error TS2874: This relative import path is unsafe to rewrite because it looks like a file name, but actually resolves to "$0".
+    

tests/baselines/reference/cjsErrors.js

@@ -0,0 +1,15 @@
+//// [tests/cases/conformance/externalModules/rewriteRelativeImportExtensions/cjsErrors.ts] ////
+
+//// [index.ts]
+export {};
+
+//// [index.ts]
+import {} from "./foo.ts";
+
+
+//// [index.js]
+"use strict";
+Object.defineProperty(exports, "__esModule", { value: true });
+//// [index.js]
+"use strict";
+Object.defineProperty(exports, "__esModule", { value: true });

tests/baselines/reference/cjsErrors.symbols

@@ -0,0 +1,10 @@
+//// [tests/cases/conformance/externalModules/rewriteRelativeImportExtensions/cjsErrors.ts] ////
+
+=== foo.ts/index.ts ===
+
+export {};
+
+=== index.ts ===
+
+import {} from "./foo.ts";
+

tests/baselines/reference/cjsErrors.types

@@ -0,0 +1,10 @@
+//// [tests/cases/conformance/externalModules/rewriteRelativeImportExtensions/cjsErrors.ts] ////
+
+=== foo.ts/index.ts ===
+
+export {};
+
+=== index.ts ===
+
+import {} from "./foo.ts";
+

tests/cases/conformance/externalModules/rewriteRelativeImportExtensions/cjsErrors.ts

@@ -0,0 +1,8 @@
+// @module: nodenext
+// @rewriteRelativeImportExtensions: true
+
+// @Filename: foo.ts/index.ts
+export {};
+
+// @Filename: index.ts
+import {} from "./foo.ts";