installTypesForPackage refactor: Trigger even if resolved to a ".js" file (#20353)

* installTypesForPackage refactor: Trigger even if resolved to a ".js" file

* Use `extensionIsTypeScript`

src/services/refactors/installTypesForPackage.ts

@@ -46,9 +46,19 @@ namespace ts.refactor.installTypesForPackage {
     function getAction(context: RefactorContext): CodeAction | undefined {
         const { file, startPosition } = context;
         const node = getTokenAtPosition(file, startPosition, /*includeJsDocComment*/ false);
-        if (isStringLiteral(node) && isModuleIdentifier(node) && getResolvedModule(file, node.text) === undefined) {
-            return codefix.tryGetCodeActionForInstallPackageTypes(context.host, file.fileName, node.text);
+        if (!isStringLiteral(node) || !isModuleIdentifier(node)) {
+            return undefined;
         }
+
+        const resolvedTo = getResolvedModule(file, node.text);
+        // Still offer to install types if it resolved to e.g. a ".js" file.
+        // `tryGetCodeActionForInstallPackageTypes` will verify that we're looking for a valid package name,
+        // so the fix won't trigger for imports of ".js" files that couldn't be better replaced by typings.
+        if (resolvedTo && extensionIsTypeScript(resolvedTo.extension)) {
+            return undefined;
+        }
+
+        return codefix.tryGetCodeActionForInstallPackageTypes(context.host, file.fileName, node.text);
     }
 
     function isModuleIdentifier(node: StringLiteral): boolean {

tests/cases/fourslash/refactorInstallTypesForPackage_js.ts

@@ -0,0 +1,29 @@
+/// <reference path='fourslash.ts' />
+
+// @allowJs: true
+
+// @Filename: /node_modules/abs/index.js
+////not read
+
+// @Filename: /a.js
+////import abs = require("/*a*/abs/*b*/");
+
+test.setTypesRegistry({ "abs": undefined });
+
+goTo.select("a", "b");
+verify.refactor({
+    name: "Install missing types package",
+    actionName: "install",
+    refactors: [
+        {
+            name: "Install missing types package",
+            description: "Install missing types package",
+            actions: [
+                {
+                    description: "Install '@types/abs'",
+                    name: "install",
+                }
+            ]
+        }
+    ],
+});