Correct #platform subpath mappings in generated package metadata and emitted helper imports (#3997)

* Initial plan

* fix platform subpath imports in generated package metadata and helper imports

Agent-Logs-Url: https://github.com/Azure/autorest.typescript/sessions/2d603179-9c3b-465f-a2a0-60f5faa2f36d

Co-authored-by: jeremymeng <7583839+jeremymeng@users.noreply.github.com>

* fix: gate react-native platform import on generateReactNativeTarget in updatePackageFile

The fresh-generation path in getEsmEntrypointInformation (packageCommon.ts) correctly gates the react-native condition on the generateReactNativeTarget option (PR #3943), but updatePackageFile in buildPackageFile.ts was always re-injecting react-native into the #platform/* imports map on regeneration.

Mirror the fresh-generation behavior: only include the react-native condition when generateReactNativeTarget is true, and preserve key ordering (browser, react-native, default) for Node's conditional resolution.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: jeremymeng <7583839+jeremymeng@users.noreply.github.com>
Co-authored-by: JialinHuang803 <jialinhuang@microsoft.com>
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Co-authored-by: JialinHuang803 <139532647+JialinHuang803@users.noreply.github.com>

Author: 4 people

packages/rlc-common/src/metadata/buildPackageFile.ts

@@ -144,15 +144,30 @@ export function updatePackageFile(
     return;
   }
 
-  // Ensure warp packages have #platform/* imports for polyfill resolution
+  // Ensure warp packages have #platform/* imports for polyfill resolution.
+  // The `react-native` condition is only added when explicitly opted in via
+  // `generateReactNativeTarget`, matching the fresh-generation path in
+  // `getEsmEntrypointInformation` (packageCommon.ts).
   if (needsPlatformImportsUpdate) {
-    packageInfo.imports = {
-      "#platform/*.js": {
-        browser: "./src/*-browser.mjs",
-        "react-native": "./src/*-react-native.mjs",
-        default: "./src/*.js"
-      }
+    const platformImports: Record<string, string> = {
+      browser: "./src/*-browser.mts",
+      default: "./src/*.ts"
     };
+    if (model.options?.generateReactNativeTarget) {
+      // Insert `react-native` before `default` so Node's conditional
+      // resolution order matches the fresh-generation output.
+      packageInfo.imports = {
+        "#platform/*": {
+          browser: platformImports.browser,
+          "react-native": "./src/*-react-native.mts",
+          default: platformImports.default
+        }
+      };
+    } else {
+      packageInfo.imports = {
+        "#platform/*": platformImports
+      };
+    }
   }
 
   // Update exports based on build system (warp for monorepo, tshy for others)

packages/rlc-common/src/metadata/packageJson/packageCommon.ts

@@ -118,9 +118,9 @@ function getEsmEntrypointInformation(config: PackageCommonInfoConfig) {
       types: "./dist/commonjs/index.d.ts",
       browser: "./dist/browser/index.js",
       imports: {
-        "#platform/*.js": {
-          browser: "./src/*-browser.mjs",
-          default: "./src/*.js"
+        "#platform/*": {
+          browser: "./src/*-browser.mts",
+          default: "./src/*.ts"
         } as Record<string, string>
       },
       exports: resolveWarpExports(
@@ -131,15 +131,15 @@ function getEsmEntrypointInformation(config: PackageCommonInfoConfig) {
 
     if (config.generateReactNativeTarget) {
       result["react-native"] = "./dist/react-native/index.js";
-      (result.imports["#platform/*.js"] as Record<string, string>)[
+      (result.imports["#platform/*"] as Record<string, string>)[
         "react-native"
-      ] = "./src/*-react-native.mjs";
+      ] = "./src/*-react-native.mts";
       // Reorder so react-native comes before default
-      const importsEntry = result.imports["#platform/*.js"] as Record<
+      const importsEntry = result.imports["#platform/*"] as Record<
         string,
         string
       >;
-      result.imports["#platform/*.js"] = {
+      result.imports["#platform/*"] = {
         browser: importsEntry.browser,
         "react-native": importsEntry["react-native"],
         default: importsEntry.default

packages/rlc-common/test/integration/packageJson.spec.ts

@@ -278,6 +278,13 @@ describe("Package file generation", () => {
       // Default: no react-native entrypoint
       expect(packageFile).to.not.have.property("react-native");
       expect(packageFile).to.have.property("exports");
+      expect(packageFile).to.have.property("imports");
+      expect(packageFile.imports).to.deep.equal({
+        "#platform/*": {
+          browser: "./src/*-browser.mts",
+          default: "./src/*.ts"
+        }
+      });
       expect(packageFile.exports["./package.json"]).to.equal("./package.json");
       expect(packageFile.exports["."]).to.have.property("browser");
       // Default: no react-native in exports
@@ -304,6 +311,14 @@ describe("Package file generation", () => {
         "react-native",
         "./dist/react-native/index.js"
       );
+      expect(packageFile).to.have.property("imports");
+      expect(packageFile.imports).to.deep.equal({
+        "#platform/*": {
+          browser: "./src/*-browser.mts",
+          "react-native": "./src/*-react-native.mts",
+          default: "./src/*.ts"
+        }
+      });
       expect(packageFile.exports["."]).to.have.property("react-native");
       expect(packageFile.exports["."]["react-native"]).to.deep.equal({
         types: "./dist/react-native/index.d.ts",
@@ -1087,9 +1102,83 @@ describe("Package file generation", () => {
         "^2.3.1"
       );
 
-      // Platform imports should be added for Azure monorepo ESM packages
+      // Platform imports should be added for Azure monorepo ESM packages.
+      // By default (generateReactNativeTarget=false) the `react-native`
+      // condition must NOT be emitted, matching the fresh-generation path.
+      expect(packageFile).to.have.property("imports");
+      expect(packageFile.imports).to.deep.equal({
+        "#platform/*": {
+          browser: "./src/*-browser.mts",
+          default: "./src/*.ts"
+        }
+      });
+    });
+
+    it("should include react-native in platform imports when generateReactNativeTarget is true", () => {
+      const model = createMockModel({
+        moduleKind: "esm",
+        flavor: "azure",
+        isMonorepo: true,
+        hasLro: false,
+        generateReactNativeTarget: true
+      });
+
+      const initialPackageInfo = {
+        name: "@azure/test-package",
+        version: "1.0.0",
+        dependencies: {
+          "@azure-rest/core-client": "^2.3.1",
+          "@azure/core-rest-pipeline": "^1.20.0",
+          "tslib": "^2.8.1"
+        }
+      };
+
+      const packageFileContent = updatePackageFile(model, initialPackageInfo);
+      expect(packageFileContent).to.not.be.undefined;
+      const packageFile = JSON.parse(packageFileContent?.content ?? "{}");
+
+      // When opted-in, the `react-native` condition is added and must be
+      // positioned before `default` so Node's conditional resolution order
+      // matches the fresh-generation output in packageCommon.ts.
       expect(packageFile).to.have.property("imports");
-      expect(packageFile.imports).to.have.property("#platform/*.js");
+      expect(packageFile.imports).to.deep.equal({
+        "#platform/*": {
+          browser: "./src/*-browser.mts",
+          "react-native": "./src/*-react-native.mts",
+          default: "./src/*.ts"
+        }
+      });
+      expect(
+        Object.keys(packageFile.imports["#platform/*"])
+      ).to.deep.equal(["browser", "react-native", "default"]);
+    });
+
+    it("should NOT add react-native to platform imports for non-monorepo packages even if generateReactNativeTarget is true", () => {
+      // needsPlatformImportsUpdate requires azureSdkForJs (isMonorepo) to be true.
+      // For non-monorepo packages, the platform imports block must be skipped
+      // entirely regardless of generateReactNativeTarget.
+      const model = createMockModel({
+        moduleKind: "esm",
+        flavor: "azure",
+        isMonorepo: false,
+        hasLro: false,
+        generateReactNativeTarget: true
+      });
+
+      const initialPackageInfo = {
+        name: "@azure/test-package",
+        version: "1.0.0",
+        dependencies: {
+          "@azure/core-client": "^1.9.3",
+          "tslib": "^2.6.2"
+        }
+      };
+
+      const packageFileContent = updatePackageFile(model, initialPackageInfo);
+      expect(packageFileContent).to.not.be.undefined;
+      const packageFile = JSON.parse(packageFileContent?.content ?? "{}");
+
+      expect(packageFile).to.not.have.property("imports");
     });
 
     it("should migrate @azure/core-client for non-monorepo Azure packages", () => {

packages/typespec-ts/src/framework/hooks/binder.ts

@@ -223,7 +223,7 @@ class BinderImp implements Binder {
    * that has a polyfill variant (-browser.mts or -react-native.mts sibling),
    * or undefined if subpath imports are disabled or no variant exists.
    * e.g. "src/static-helpers/serialization/get-binary-response.ts"
-   *   -> "#platform/static-helpers/serialization/get-binary-response.js"
+   *   -> "#platform/static-helpers/serialization/get-binary-response"
    */
   private getPlatformImportSpecifier(
     declarationSourceFile: SourceFile
@@ -242,7 +242,7 @@ class BinderImp implements Binder {
     );
     if (!hasBrowserVariant && !hasReactNativeVariant) return undefined;
     const relativePath = filePath.substring(srcIndex + "/src/".length);
-    return "#platform/" + relativePath.replace(/\.ts$/, ".js");
+    return "#platform/" + relativePath.replace(/\.ts$/, "");
   }
 
   /**

packages/typespec-ts/src/framework/load-static-helpers.ts

@@ -129,7 +129,7 @@ export async function loadStaticHelpers(
             !specifier.includes("-browser") &&
             !specifier.includes("-react-native")
           ) {
-            i.setModuleSpecifier("#platform/static-helpers/platform-types.js");
+            i.setModuleSpecifier("#platform/static-helpers/platform-types");
           }
         }
       });

packages/typespec-ts/test-next/integration/assets/static-helpers/platform-import.ts

@@ -0,0 +1,5 @@
+import { platformTag } from "./platform-types";
+
+export function usesPlatformImport() {
+  return platformTag;
+}

packages/typespec-ts/test-next/integration/assets/static-helpers/platform-types.ts

@@ -0,0 +1 @@
+export const platformTag = "platform";

packages/typespec-ts/test-next/integration/hooks/binder.test.ts

@@ -393,6 +393,45 @@ describe("Binder", () => {
       //
       // buildCsvCollection();
     });
+
+    it("should use #platform subpath imports without extension for helpers with platform variants", () => {
+      binder = provideBinder(project, { useSubpathImports: true });
+      const helperFile = project.createSourceFile(
+        "src/static-helpers/serialization/get-binary-response.ts",
+        "",
+        {
+          overwrite: true
+        }
+      );
+      project.createSourceFile(
+        "src/static-helpers/serialization/get-binary-response-browser.mts",
+        "export {};",
+        {
+          overwrite: true
+        }
+      );
+      addDeclaration(
+        helperFile,
+        {
+          kind: StructureKind.Function,
+          name: "getBinaryResponse"
+        },
+        "getBinaryResponse"
+      );
+
+      const sourceFile = project.createSourceFile("src/test-platform.ts", "", {
+        overwrite: true
+      });
+      sourceFile.addStatements(`${resolveReference("getBinaryResponse")}();`);
+
+      binder.resolveAllReferences("/modularPackageFolder/src");
+
+      assertGetImportStatements(
+        sourceFile,
+        "#platform/static-helpers/serialization/get-binary-response"
+      );
+      assertGetStatement(sourceFile, "getBinaryResponse();");
+    });
   });
 
   describe("External Dependencies Override", () => {

packages/typespec-ts/test-next/integration/load-static-files.test.ts

@@ -26,7 +26,11 @@ describe("loadStaticHelpers", () => {
     const helperDeclarations = await loadStaticHelpers(project, helpers, {
       helpersAssetDirectory
     });
-    expect(project.getSourceFiles()).to.toHaveLength(1);
+    expect(
+      project
+        .getSourceFiles()
+        .some((file) => file.getFilePath().endsWith("/static-helpers/utils.ts"))
+    ).toBe(true);
     const buildCsvCollectionDeclaration = helperDeclarations.get(
       refkey(helpers.buildCsvCollection)
     );
@@ -64,4 +68,33 @@ describe("loadStaticHelpers", () => {
       })
     ).rejects.toThrowError(/invalid helper kind/);
   });
+
+  it("should rewrite platform-types imports to #platform subpath without extension for azure monorepo", async () => {
+    const helpers = {
+      usesPlatformImport: {
+        kind: "function",
+        name: "usesPlatformImport",
+        location: "platform-import.ts"
+      }
+    } as const;
+
+    await loadStaticHelpers(project, helpers, {
+      helpersAssetDirectory,
+      options: {
+        flavor: "azure",
+        azureSdkForJs: true
+      } as any
+    });
+
+    const sourceFile = project
+      .getSourceFiles()
+      .find((file) =>
+        file.getFilePath().endsWith("/static-helpers/platform-import.ts")
+      );
+    assert(sourceFile);
+    const importDecl = sourceFile.getImportDeclaration(
+      "#platform/static-helpers/platform-types"
+    );
+    expect(importDecl).toBeDefined();
+  });
 });