Import fix add import require support (#19802)

* import fix: suggest import..require where supported if synthetic defaults are unavailable

* Add tests for import..require fix when targeting CommonJS, AMD, and UMD modules

* fix failing tests

src/services/codefixes/importFixes.ts

@@ -180,7 +180,8 @@ namespace ts.codefix {
     export const enum ImportKind {
         Named,
         Default,
-        Namespace
+        Namespace,
+        Equals
     }
 
     export function getCodeActionForImport(moduleSymbol: Symbol, context: ImportCodeFixOptions): ImportCodeAction[] {
@@ -252,11 +253,17 @@ namespace ts.codefix {
 
         const moduleSpecifierWithoutQuotes = stripQuotes(moduleSpecifier);
         const quotedModuleSpecifier = createStringLiteralWithQuoteStyle(sourceFile, moduleSpecifierWithoutQuotes);
-        const importDecl = createImportDeclaration(
+        const importDecl = kind !== ImportKind.Equals
+            ? createImportDeclaration(
                 /*decorators*/ undefined,
                 /*modifiers*/ undefined,
-            createImportClauseOfKind(kind, symbolName),
-            quotedModuleSpecifier);
+                createImportClauseOfKind(kind, symbolName),
+                quotedModuleSpecifier)
+            : createImportEqualsDeclaration(
+                /*decorators*/ undefined,
+                /*modifiers*/ undefined,
+                createIdentifier(symbolName),
+                createExternalModuleReference(quotedModuleSpecifier));
 
         const changes = ChangeTracker.with(context, changeTracker => {
             if (lastImportDeclaration) {
@@ -267,8 +274,10 @@ namespace ts.codefix {
             }
         });
 
-        const actionFormat = kind === ImportKind.Namespace
-            ? Diagnostics.Import_Asterisk_as_0_from_1
+        const actionFormat = kind === ImportKind.Equals
+            ? Diagnostics.Import_0_require_1
+            : kind === ImportKind.Namespace
+                ? Diagnostics.Import_Asterisk_as_0_from_1
                 : Diagnostics.Import_0_from_1;
 
         // if this file doesn't have any import statements, insert an import statement and then insert a new line
@@ -601,6 +610,9 @@ namespace ts.codefix {
                 return namedBindings ? undefined : ChangeTracker.with(context, t =>
                     t.replaceNode(sourceFile, importClause, createImportClause(name, createNamespaceImport(createIdentifier(symbolName)))));
 
+            case ImportKind.Equals:
+                return undefined;
+
             default:
                 Debug.assertNever(kind);
         }
@@ -659,6 +671,12 @@ namespace ts.codefix {
         if (allowSyntheticDefaultImports) {
             return getCodeActionForImport(symbol, { ...context, symbolName, kind: ImportKind.Default });
         }
+        const moduleKind = getEmitModuleKind(compilerOptions);
+
+        // When a synthetic `default` is unavailable, use `import..require` if the module kind supports it.
+        if (moduleKind === ModuleKind.AMD || moduleKind === ModuleKind.CommonJS || moduleKind === ModuleKind.UMD) {
+            return getCodeActionForImport(symbol, { ...context, symbolName, kind: ImportKind.Equals });
+        }
 
         // Fall back to the `import * as ns` style import.
         return getCodeActionForImport(symbol, { ...context, symbolName, kind: ImportKind.Namespace });

tests/cases/fourslash/importNameCodeFixNewImportAllowSyntheticDefaultImports2.ts

@@ -1,5 +1,6 @@
 /// <reference path="fourslash.ts" />
 // @AllowSyntheticDefaultImports: false
+// @Module: system
 
 // @Filename: a/f1.ts
 //// [|export var x = 0;

tests/cases/fourslash/importNameCodeFixNewImportAllowSyntheticDefaultImports3.ts

@@ -0,0 +1,19 @@
+/// <reference path="fourslash.ts" />
+// @AllowSyntheticDefaultImports: false
+// @Module: commonjs
+
+// @Filename: a/f1.ts
+//// [|export var x = 0;
+//// bar/*0*/();|]
+
+// @Filename: a/foo.d.ts
+//// declare function bar(): number;
+//// export = bar;
+//// export as namespace bar;
+
+verify.importFixAtPosition([
+`import bar = require("./foo");
+
+export var x = 0;
+bar();`
+]);

tests/cases/fourslash/importNameCodeFixNewImportAllowSyntheticDefaultImports4.ts

@@ -0,0 +1,19 @@
+/// <reference path="fourslash.ts" />
+// @AllowSyntheticDefaultImports: false
+// @Module: amd
+
+// @Filename: a/f1.ts
+//// [|export var x = 0;
+//// bar/*0*/();|]
+
+// @Filename: a/foo.d.ts
+//// declare function bar(): number;
+//// export = bar;
+//// export as namespace bar;
+
+verify.importFixAtPosition([
+`import bar = require("./foo");
+
+export var x = 0;
+bar();`
+]);

tests/cases/fourslash/importNameCodeFixNewImportAllowSyntheticDefaultImports5.ts

@@ -0,0 +1,19 @@
+/// <reference path="fourslash.ts" />
+// @AllowSyntheticDefaultImports: false
+// @Module: umd
+
+// @Filename: a/f1.ts
+//// [|export var x = 0;
+//// bar/*0*/();|]
+
+// @Filename: a/foo.d.ts
+//// declare function bar(): number;
+//// export = bar;
+//// export as namespace bar;
+
+verify.importFixAtPosition([
+`import bar = require("./foo");
+
+export var x = 0;
+bar();`
+]);

tests/cases/fourslash/importNameCodeFixUMDGlobal0.ts

@@ -1,5 +1,8 @@
 /// <reference path="fourslash.ts" />
 
+// @AllowSyntheticDefaultImports: false
+// @Module: es2015
+
 // @Filename: a/f1.ts
 //// [|export function test() { };
 //// bar1/*0*/.bar;|]

tests/cases/fourslash/importNameCodeFixUMDGlobal1.ts

@@ -1,5 +1,8 @@
 /// <reference path="fourslash.ts" />
 
+// @AllowSyntheticDefaultImports: false
+// @Module: esnext
+
 // @Filename: a/f1.ts
 //// [|import { bar } from "./foo";
 ////

tests/cases/fourslash/importNameCodeFixUMDGlobalReact0.ts

@@ -1,6 +1,8 @@
 /// <reference path="fourslash.ts" />
 
 // @jsx: react
+// @allowSyntheticDefaultImports: false
+// @module: es2015
 
 // @Filename: /node_modules/@types/react/index.d.ts
 ////export = React;

tests/cases/fourslash/importNameCodeFixUMDGlobalReact1.ts

@@ -1,6 +1,8 @@
 /// <reference path="fourslash.ts" />
 
 // @jsx: react
+// @allowSyntheticDefaultImports: false
+// @module: es2015
 
 // @Filename: /node_modules/@types/react/index.d.ts
 ////export = React;