Fix release ProGuard: Adoptium JDK 25 ships no jmods

Compose Desktop's AbstractProguardTask builds ProGuard's -libraryjars by
walking <javaHome>/jmods and nothing else. Adoptium stopped shipping the
jmods/ directory in JDK 25 archives (verified: 0 jmods entries in both the
linux/x64 and macOS/aarch64 Temurin 25.0.4.1 tarballs, vs 71 for Temurin
17), so on the runners the desktop packaging JDK resolves to
/usr/lib/jvm/temurin-25-jdk-amd64 and ProGuard gets no JDK whatsoever.
Every class then fails to resolve java.lang.Object — 1.3M
"can't find superclass or interface java.lang.Object" warnings, followed by
"Please correct the above warnings first".

This is why the Java 25 toolchain bump broke every release while the
v1.2.0-beta release on the toolchain 17 build kept working, and why a local
build with the JetBrains Runtime (which does ship jmods) succeeded while CI
did not. ProGuard's version was never the cause; 7.10.0 was still kept
because it is what understands this project's Kotlin 2.4 metadata.

Install Zulu 25 (still ships jmods) in the desktop-proguard job and export
it as FROMCHAT_PACKAGING_JDK; setup-java runs before Temurin 17 so JAVA_HOME
stays on 17 for Gradle and the Android build. resolvePackagingJdkHome() now
warns loudly when the JDK it picks has no jmods/, instead of leaving it to
ProGuard's wall of warnings.

.github/actions/setup-java-gradle/action.yml

@@ -6,6 +6,16 @@ inputs:
     description: Optional JDK architecture (x64). Omit for host default.
     required: false
     default: ""
+  desktop-jdk:
+    description: >
+      Optional desktop JDK version. When set, a Zulu build of it is installed and exported as
+      FROMCHAT_PACKAGING_JDK. Needed by anything that runs Compose Desktop's release/ProGuard
+      tasks: Adoptium stopped shipping the jmods/ directory in JDK 25 archives, and the Compose
+      plugin derives ProGuard's -libraryjars by walking <javaHome>/jmods. A JDK without jmods
+      leaves ProGuard with no java.* classes at all, so the build dies on ~1.3M
+      "can't find superclass or interface java.lang.Object" warnings. Zulu still ships jmods.
+    required: false
+    default: ""
   cache-read-only:
     description: Restore Gradle User Home only; do not save (avoids parallel cache write races).
     required: false
@@ -14,12 +24,26 @@ inputs:
 runs:
   using: composite
   steps:
+    # Installed first so setup-java leaves JAVA_HOME on Temurin 17 below: Gradle itself and the
+    # Android build must keep running on 17.
+    - uses: actions/setup-java@v5
+      if: inputs.desktop-jdk != ''
+      id: desktop-jdk
+      with:
+        distribution: zulu
+        java-version: ${{ inputs.desktop-jdk }}
+
     - uses: actions/setup-java@v5
       with:
         distribution: temurin
         java-version: "17"
         architecture: ${{ inputs.java-architecture }}
 
+    - name: Export the jmods-capable desktop JDK
+      if: inputs.desktop-jdk != ''
+      shell: bash
+      run: echo "FROMCHAT_PACKAGING_JDK=${{ steps.desktop-jdk.outputs.java-path }}" >> "$GITHUB_ENV"
+
     - uses: gradle/actions/setup-gradle@v5
       with:
         gradle-version: wrapper

.github/workflows/release.yml

@@ -181,6 +181,8 @@ jobs:
         with:
           version: ${{ needs.resolve-version.outputs.version }}
       - uses: ./.github/actions/setup-java-gradle
+        with:
+          desktop-jdk: "25"
       - uses: ./.github/actions/cache-gradle-build
         id: gradle-build-cache
         with:

app/desktop/build.gradle.kts

@@ -263,6 +263,24 @@ fun resolvePackagingJdkHome(): String {
         )
     }
 
+    // Compose Desktop's release tasks run ProGuard on this JDK, and the Compose plugin builds
+    // ProGuard's -libraryjars by walking <javaHome>/jmods. Adoptium stopped shipping the jmods/
+    // directory with JDK 25 archives, so a jmods-less JDK leaves ProGuard with no java.* classes
+    // at all — the build then dies on a million "can't find superclass or interface
+    // java.lang.Object" warnings. Fail noisily here rather than in ProGuard's wall of text.
+    fun withJmods(home: String): String {
+        if (!File(home, "jmods").isDirectory) {
+            project.logger.warn(
+                "Packaging JDK $home ships no jmods/ directory. The release/ProGuard build needs " +
+                    "one: Compose Desktop reads the JDK from <javaHome>/jmods, so ProGuard will " +
+                    "report \"can't find superclass or interface java.lang.Object\" for every " +
+                    "class and abort. Point FROMCHAT_PACKAGING_JDK at a JDK that ships jmods " +
+                    "(e.g. Azul Zulu $desktopJvmTarget).",
+            )
+        }
+        return home
+    }
+
     System.getenv("FROMCHAT_PACKAGING_JDK")?.takeIf { it.isNotBlank() }?.let { candidate ->
         val major = jdkMajorVersion(File(candidate))
         if (major != null && major < desktopJvmTarget) {
@@ -274,7 +292,7 @@ fun resolvePackagingJdkHome(): String {
                     "FROMCHAT_PACKAGING_JDK must be ARM64 on Windows ARM64 (os.arch=$arch): $candidate"
                 }
             }
-            return candidate
+            return withJmods(candidate)
         }
     }
     System.getenv("JAVA_HOME")?.takeIf { it.isNotBlank() }?.let { home ->
@@ -289,7 +307,7 @@ fun resolvePackagingJdkHome(): String {
                         "JAVA_HOME must be ARM64 on Windows ARM64 (os.arch=$arch): $home"
                     }
                 }
-                return home
+                return withJmods(home)
             }
         }
     }
@@ -351,7 +369,7 @@ fun resolvePackagingJdkHome(): String {
         if (major != null && major < desktopJvmTarget) return@firstOrNull false
         if (!isWindowsArm64Host()) return@firstOrNull true
         jdkReportsArch(File(home, "bin/java.exe")) == "aarch64"
-    }?.let { return it }
+    }?.let { return withJmods(it) }
 
     // Toolchain fallback: foojay provisions the jvmToolchain JDK on every machine that builds
     // this project, and the full JDK ships jpackage — so the bundled runtime always matches the
@@ -372,7 +390,7 @@ fun resolvePackagingJdkHome(): String {
         if (isWindowsArm64Host() && jdkReportsArch(File(jdk, "bin/java.exe")) != "aarch64") {
             return@forEach
         }
-        return jdk.absolutePath.replace('\\', '/')
+        return withJmods(jdk.absolutePath.replace('\\', '/'))
     }
 
     error(