Strip "/index" from import fix module specifiers

src/compiler/core.ts

@@ -2169,6 +2169,10 @@ namespace ts {
         return expectedPos >= 0 && str.indexOf(suffix, expectedPos) === expectedPos;
     }
 
+    export function removeSuffix(str: string, suffix: string): string {
+        return endsWith(str, suffix) ? str.slice(0, str.length - suffix.length) : str;
+    }
+
     export function stringContains(str: string, substring: string): boolean {
         return str.indexOf(substring) !== -1;
     }

src/harness/fourslash.ts

@@ -2549,6 +2549,9 @@ Actual: ${stringify(fullActual)}`);
             }
             const sortedExpectedArray = expectedTextArray.sort();
             const sortedActualArray = actualTextArray.sort();
+            if (sortedExpectedArray.length !== sortedActualArray.length) {
+                this.raiseError(`Expected ${sortedExpectedArray.length} import fixes, got ${sortedActualArray.length}`);
+            }
             ts.zipWith(sortedExpectedArray, sortedActualArray, (expected, actual, index) => {
                 if (expected !== actual) {
                     this.raiseError(`Import fix at index ${index} doesn't match.\n${showTextDiff(expected, actual)}`);
@@ -2867,7 +2870,7 @@ Actual: ${stringify(fullActual)}`);
 
             if (negative) {
                 if (codeFixes.length) {
-                    this.raiseError(`verifyCodeFixAvailable failed - expected no fixes but found one.`);
+                    this.raiseError(`verifyCodeFixAvailable failed - expected no fixes but found ${codeFixes.map(c => c.description)}.`);
                 }
                 return;
             }

src/services/codefixes/importFixes.ts

@@ -322,7 +322,7 @@ namespace ts.codefix {
             tryGetModuleNameAsNodeModule(options, moduleFileName, host, getCanonicalFileName, sourceDirectory) ||
             tryGetModuleNameFromBaseUrl(options, moduleFileName, getCanonicalFileName) ||
             options.rootDirs && tryGetModuleNameFromRootDirs(options.rootDirs, moduleFileName, sourceDirectory, getCanonicalFileName) ||
-            removeFileExtension(getRelativePath(moduleFileName, sourceDirectory, getCanonicalFileName));
+            removeExtensionAndIndexPostFix(getRelativePath(moduleFileName, sourceDirectory, getCanonicalFileName), options);
     }
 
     function tryGetModuleNameFromAmbientModule(moduleSymbol: Symbol): string | undefined {
@@ -343,7 +343,7 @@ namespace ts.codefix {
         }
 
         const relativeNameWithIndex = removeFileExtension(relativeName);
-        relativeName = removeExtensionAndIndexPostFix(relativeName);
+        relativeName = removeExtensionAndIndexPostFix(relativeName, options);
 
         if (options.paths) {
             for (const key in options.paths) {
@@ -393,7 +393,7 @@ namespace ts.codefix {
         return roots && firstDefined(roots, unNormalizedTypeRoot => {
             const typeRoot = toPath(unNormalizedTypeRoot, /*basePath*/ undefined, getCanonicalFileName);
             if (startsWith(moduleFileName, typeRoot)) {
-                return removeExtensionAndIndexPostFix(moduleFileName.substring(typeRoot.length + 1));
+                return removeExtensionAndIndexPostFix(moduleFileName.substring(typeRoot.length + 1), options);
             }
         });
     }
@@ -527,12 +527,9 @@ namespace ts.codefix {
         return firstDefined(rootDirs, rootDir => getRelativePathIfInDirectory(path, rootDir, getCanonicalFileName));
     }
 
-    function removeExtensionAndIndexPostFix(fileName: string) {
-        fileName = removeFileExtension(fileName);
-        if (endsWith(fileName, "/index")) {
-            fileName = fileName.substr(0, fileName.length - 6/* "/index".length */);
-        }
-        return fileName;
+    function removeExtensionAndIndexPostFix(fileName: string, options: CompilerOptions): string {
+        const noExtension = removeFileExtension(fileName);
+        return getEmitModuleResolutionKind(options) === ModuleResolutionKind.NodeJs ? removeSuffix(noExtension, "/index") : noExtension;
     }
 
     function getRelativePathIfInDirectory(path: string, directoryPath: string, getCanonicalFileName: (fileName: string) => string): string | undefined {

tests/cases/fourslash/importNameCodeFixNewImportIndex.ts

@@ -0,0 +1,16 @@
+/// <reference path="fourslash.ts" />
+
+// @Filename: /a/index.ts
+////export const foo = 0;
+
+// @Filename: /b.ts
+////[|/**/foo;|]
+
+goTo.file("/a/index.ts");
+goTo.file("/b.ts");
+
+verify.importFixAtPosition([
+`import { foo } from "./a";
+
+foo;`
+]);

tests/cases/fourslash/importNameCodeFixNewImportIndex_notForClassicResolution.ts

@@ -0,0 +1,27 @@
+/// <reference path="fourslash.ts" />
+
+// @moduleResolution: classic
+
+// @Filename: /a/index.ts
+////export const foo = 0;
+
+// @Filename: /node_modules/x/index.d.ts
+////export const bar = 0;
+
+// @Filename: /b.ts
+////[|foo;|]
+
+// @Filename: /c.ts
+////bar;
+
+goTo.file("/a/index.ts");
+
+goTo.file("/b.ts");
+verify.importFixAtPosition([
+`import { foo } from "./a/index";
+
+foo;`
+]);
+
+goTo.file("/c.ts");
+// TODO: GH#20050 verify.not.codeFixAvailable();

tests/cases/fourslash/importNameCodeFixUMDGlobalReact0.ts

@@ -3,6 +3,7 @@
 // @jsx: react
 // @allowSyntheticDefaultImports: false
 // @module: es2015
+// @moduleResolution: node
 
 // @Filename: /node_modules/@types/react/index.d.ts
 ////export = React;

tests/cases/fourslash/importNameCodeFixUMDGlobalReact1.ts

@@ -3,6 +3,7 @@
 // @jsx: react
 // @allowSyntheticDefaultImports: false
 // @module: es2015
+// @moduleResolution: node
 
 // @Filename: /node_modules/@types/react/index.d.ts
 ////export = React;