Support pinning java-version as "latest" (#1093)

* Support pinning java-version as "latest"

Add a `latest` alias for the `java-version` input that floats to the newest
available stable (GA) release. It is normalized to the SemVer wildcard at the
base-installer layer and always resolves from remote (like `check-latest: true`).

List-based distributions resolve it automatically via the existing newest-first
matching. Corretto selects its newest available major; Oracle and GraalVM look up
the newest GA major via the Adoptium API and request it, failing with an actionable
error if that major isn't published yet. The jdkfile distribution rejects `latest`.

Closes #832

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

* Clarify latest note for oracle/graalvm version resolution vs download

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

* graalvm-community: float latest to its own newest GA release

GraalVM Community publishes its releases on GitHub, so the `latest`
alias now matches against that real release list using the SemVer
wildcard instead of asking the Adoptium API for the newest GA major.
This prevents `latest` from hard-failing when GraalVM lags behind a
freshly released Java major (e.g. Adoptium reports 26 before GraalVM
ships it). Oracle GraalVM has no listing endpoint, so it keeps deriving
the newest major from Adoptium and errors clearly if that major is not
yet published.

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

* Potential fix for pull request finding

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

* Give latest+qualifier inputs (e.g. latest-ea) a targeted error

Inputs like 'latest-ea' had their '-ea' suffix stripped and fell through
to the generic SemVer validation, failing with a confusing "'latest' is
not valid SemVer" message even though 'latest' is supported. Add an
explicit guard so any 'latest*' value other than exactly 'latest' throws
a targeted error explaining that 'latest' resolves GA releases only and
cannot be combined with '-ea' or other qualifiers.

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

---------

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

src/distributions/base-installer.ts

@@ -23,6 +23,7 @@ export abstract class JavaBase {
   protected architecture: string;
   protected packageType: string;
   protected stable: boolean;
+  protected latest: boolean;
   protected checkLatest: boolean;
   protected setDefault: boolean;
   protected verifySignature: boolean;
@@ -37,9 +38,11 @@ export abstract class JavaBase {
       maxRetries: 3
     });
 
-    ({version: this.version, stable: this.stable} = this.normalizeVersion(
-      installerOptions.version
-    ));
+    ({
+      version: this.version,
+      stable: this.stable,
+      latest: this.latest
+    } = this.normalizeVersion(installerOptions.version));
     this.architecture = installerOptions.architecture || os.arch();
     this.packageType = installerOptions.packageType;
     this.checkLatest = installerOptions.checkLatest;
@@ -66,7 +69,7 @@ export abstract class JavaBase {
     }
 
     let foundJava = this.findInToolcache();
-    if (foundJava && !this.checkLatest) {
+    if (foundJava && !this.checkLatest && !this.latest) {
       core.info(`Resolved Java ${foundJava.version} from tool-cache`);
     } else {
       core.info('Trying to resolve the latest version from remote');
@@ -267,6 +270,30 @@ export abstract class JavaBase {
 
   protected normalizeVersion(version: string) {
     let stable = true;
+    const latest = false;
+
+    // Support the `latest` alias (case-insensitive), which floats to the newest
+    // available stable/GA release. It is translated to the SemVer wildcard `x`
+    // so the existing "newest satisfying version wins" resolution applies.
+    const normalized = version.trim().toLowerCase();
+    if (normalized === 'latest') {
+      return {
+        version: 'x',
+        stable: true,
+        latest: true
+      };
+    }
+
+    // Reject `latest` combined with any qualifier (e.g. `latest-ea`). Such inputs
+    // would otherwise have their `-ea` suffix stripped and fall through to the
+    // generic SemVer check, which fails with a confusing "'latest' is not valid
+    // SemVer" message even though `latest` is a supported value. Fail early with a
+    // targeted explanation instead.
+    if (normalized.startsWith('latest')) {
+      throw new Error(
+        `The 'latest' alias resolves stable (GA) releases only and cannot be combined with '-ea' or other qualifiers (received '${version}'). Use 'latest' on its own, or specify a concrete version.`
+      );
+    }
 
     if (version.endsWith('-ea')) {
       version = version.replace(/-ea$/, '');
@@ -294,7 +321,8 @@ export abstract class JavaBase {
 
     return {
       version,
-      stable
+      stable,
+      latest
     };
   }