Address Copilot code review comments

- Use strict equality (===, !==) instead of loose equality (==, !=) for all comparisons
- Properly handle caught errors with instanceof type narrowing before accessing properties
- Only fall back to legacy AdoptOpenJDK for specific version-not-found errors
- Rethrow unexpected errors to avoid masking real issues (network failures, rate limits, etc.)
- Fix error message check to match actual error text ('No matching version found')
- Remove unnecessary undefined check since method return type is never undefined
- Add @internal JSDoc annotation to TemurinDistribution.findPackageForDownload()
- Update tests to properly mock Temurin lookup failures for fallback behavior testing
- Rebuild dist files

__tests__/distributors/adopt-installer.test.ts

@@ -278,6 +278,10 @@ describe('findPackageForDownload', () => {
       },
       AdoptImplementation.Hotspot
     );
+    // Mock Temurin to fail so fallback to AdoptOpenJDK is tested
+    distribution['temurinDistribution']!['findPackageForDownload'] = async () => {
+      throw new Error('No matching version found for SemVer');
+    };
     distribution['getAvailableVersions'] = async () => manifestData as any;
     const resolvedVersion = await distribution['findPackageForDownload'](input);
     expect(resolvedVersion.version).toBe(expected);
@@ -293,6 +297,10 @@ describe('findPackageForDownload', () => {
       },
       AdoptImplementation.Hotspot
     );
+    // Mock Temurin to fail so fallback to AdoptOpenJDK is tested
+    distribution['temurinDistribution']!['findPackageForDownload'] = async () => {
+      throw new Error('No matching version found for SemVer');
+    };
     distribution['getAvailableVersions'] = async () => manifestData as any;
     await expect(
       distribution['findPackageForDownload']('9.0.8')
@@ -309,6 +317,10 @@ describe('findPackageForDownload', () => {
       },
       AdoptImplementation.Hotspot
     );
+    // Mock Temurin to fail so fallback to AdoptOpenJDK is tested
+    distribution['temurinDistribution']!['findPackageForDownload'] = async () => {
+      throw new Error('No matching version found for SemVer');
+    };
     distribution['getAvailableVersions'] = async () => manifestData as any;
     await expect(distribution['findPackageForDownload']('7.x')).rejects.toThrow(
       /No matching version found for SemVer */
@@ -325,6 +337,10 @@ describe('findPackageForDownload', () => {
       },
       AdoptImplementation.Hotspot
     );
+    // Mock Temurin to fail so fallback to AdoptOpenJDK is tested
+    distribution['temurinDistribution']!['findPackageForDownload'] = async () => {
+      throw new Error('No matching version found for SemVer');
+    };
     distribution['getAvailableVersions'] = async () => [];
     await expect(distribution['findPackageForDownload']('11')).rejects.toThrow(
       /No matching version found for SemVer */

dist/setup/index.js

@@ -77815,17 +77815,56 @@ const path_1 = __importDefault(__nccwpck_require__(71017));
 const semver_1 = __importDefault(__nccwpck_require__(11383));
 const base_installer_1 = __nccwpck_require__(59741);
 const util_1 = __nccwpck_require__(92629);
+const installer_1 = __nccwpck_require__(18579);
 var AdoptImplementation;
 (function (AdoptImplementation) {
     AdoptImplementation["Hotspot"] = "Hotspot";
     AdoptImplementation["OpenJ9"] = "OpenJ9";
 })(AdoptImplementation || (exports.AdoptImplementation = AdoptImplementation = {}));
 class AdoptDistribution extends base_installer_1.JavaBase {
-    constructor(installerOptions, jvmImpl) {
+    constructor(installerOptions, jvmImpl, temurinDistribution = null) {
         super(`Adopt-${jvmImpl}`, installerOptions);
         this.jvmImpl = jvmImpl;
+        this.temurinDistribution = temurinDistribution;
+        if (temurinDistribution !== null &&
+            jvmImpl !== AdoptImplementation.Hotspot) {
+            throw new Error('Only Hotspot JVM is supported by Temurin.');
+        }
+        // Only use the temurin repo for Hotspot JVMs
+        if (temurinDistribution === null &&
+            jvmImpl === AdoptImplementation.Hotspot) {
+            this.temurinDistribution = new installer_1.TemurinDistribution(installerOptions, installer_1.TemurinImplementation.Hotspot);
+        }
     }
     findPackageForDownload(version) {
+        return __awaiter(this, void 0, void 0, function* () {
+            if (this.jvmImpl === AdoptImplementation.Hotspot) {
+                core.notice("AdoptOpenJDK has moved to Eclipse Temurin https://github.com/actions/setup-java#supported-distributions please consider changing to the 'temurin' distribution type in your setup-java configuration.");
+            }
+            if (this.jvmImpl === AdoptImplementation.Hotspot &&
+                this.temurinDistribution !== null) {
+                try {
+                    return yield this.temurinDistribution.findPackageForDownload(version);
+                }
+                catch (error) {
+                    // Only fall back to legacy AdoptOpenJDK for version-not-found errors
+                    if (error instanceof Error &&
+                        error.message.includes('No matching version found')) {
+                        core.notice('The JVM you are looking for could not be found in the Temurin repository, this likely indicates ' +
+                            'that you are using an out of date version of Java, consider updating and moving to using the Temurin distribution type in setup-java.');
+                    }
+                    else {
+                        // Rethrow unexpected errors to avoid masking real issues
+                        core.debug(`Unexpected error from Temurin lookup: ${error instanceof Error ? error.message : String(error)}`);
+                        throw error;
+                    }
+                }
+            }
+            // failed to find a Temurin version, so fall back to AdoptOpenJDK
+            return this.findPackageForDownloadOldAdoptOpenJdk(version);
+        });
+    }
+    findPackageForDownloadOldAdoptOpenJdk(version) {
         return __awaiter(this, void 0, void 0, function* () {
             const availableVersionsRaw = yield this.getAvailableVersions();
             const availableVersionsWithBinaries = availableVersionsRaw
@@ -80195,6 +80234,9 @@ class TemurinDistribution extends base_installer_1.JavaBase {
         super(`Temurin-${jvmImpl}`, installerOptions);
         this.jvmImpl = jvmImpl;
     }
+    /**
+     * @internal For cross-distribution reuse only. Not intended as a public API.
+     */
     findPackageForDownload(version) {
         return __awaiter(this, void 0, void 0, function* () {
             const availableVersionsRaw = yield this.getAvailableVersions();

src/distributions/adopt/installer.ts

@@ -36,12 +36,18 @@ export class AdoptDistribution extends JavaBase {
   ) {
     super(`Adopt-${jvmImpl}`, installerOptions);
 
-    if (temurinDistribution != null && jvmImpl != AdoptImplementation.Hotspot) {
+    if (
+      temurinDistribution !== null &&
+      jvmImpl !== AdoptImplementation.Hotspot
+    ) {
       throw new Error('Only Hotspot JVM is supported by Temurin.');
     }
 
     // Only use the temurin repo for Hotspot JVMs
-    if (temurinDistribution == null && jvmImpl == AdoptImplementation.Hotspot) {
+    if (
+      temurinDistribution === null &&
+      jvmImpl === AdoptImplementation.Hotspot
+    ) {
       this.temurinDistribution = new TemurinDistribution(
         installerOptions,
         TemurinImplementation.Hotspot
@@ -52,30 +58,34 @@ export class AdoptDistribution extends JavaBase {
   protected async findPackageForDownload(
     version: string
   ): Promise<JavaDownloadRelease> {
-    if (this.jvmImpl == AdoptImplementation.Hotspot) {
+    if (this.jvmImpl === AdoptImplementation.Hotspot) {
       core.notice(
         "AdoptOpenJDK has moved to Eclipse Temurin https://github.com/actions/setup-java#supported-distributions please consider changing to the 'temurin' distribution type in your setup-java configuration."
       );
     }
 
     if (
-      this.jvmImpl == AdoptImplementation.Hotspot &&
-      this.temurinDistribution != null
+      this.jvmImpl === AdoptImplementation.Hotspot &&
+      this.temurinDistribution !== null
     ) {
       try {
-        const result = await this.temurinDistribution.findPackageForDownload(
-          version
-        );
-
-        if (result != undefined) {
-          return result;
-        }
+        return await this.temurinDistribution.findPackageForDownload(version);
       } catch (error) {
-        if (error.message.includes('Could not find satisfied version')) {
+        // Only fall back to legacy AdoptOpenJDK for version-not-found errors
+        if (
+          error instanceof Error &&
+          error.message.includes('No matching version found')
+        ) {
           core.notice(
             'The JVM you are looking for could not be found in the Temurin repository, this likely indicates ' +
               'that you are using an out of date version of Java, consider updating and moving to using the Temurin distribution type in setup-java.'
           );
+        } else {
+          // Rethrow unexpected errors to avoid masking real issues
+          core.debug(
+            `Unexpected error from Temurin lookup: ${error instanceof Error ? error.message : String(error)}`
+          );
+          throw error;
         }
       }
     }

src/distributions/temurin/installer.ts

@@ -34,6 +34,9 @@ export class TemurinDistribution extends JavaBase {
     super(`Temurin-${jvmImpl}`, installerOptions);
   }
 
+  /**
+   * @internal For cross-distribution reuse only. Not intended as a public API.
+   */
   public async findPackageForDownload(
     version: string
   ): Promise<JavaDownloadRelease> {