Use platform classloader for lint invokers

src/cli/AndroidLintCliInvoker.kt

@@ -85,7 +85,12 @@ class AndroidLintCliInvoker(
     const val ERRNO_INTERNAL_CONTINUE = 100
 
     fun createUsingJars(
-      parentClassloader: ClassLoader = this::class.java.classLoader,
+      // Parent on the platform classloader (JDK classes only) so lint loads its entire runtime —
+      // crucially kotlin-stdlib AND kotlin-reflect — from its own deploy jar. Parenting on the
+      // worker's classloader instead lets the worker's kotlin-stdlib shadow lint's, and since the
+      // worker has no kotlin-reflect, Kotlin reflection inside lint detectors (e.g. the partial
+      // analysis "fx" checks) silently fails. This mirrors AGP's AndroidLintWorkAction.
+      parentClassloader: ClassLoader = ClassLoader.getPlatformClassLoader(),
       vararg jars: Path,
     ): AndroidLintCliInvoker {
       require(jars.isNotEmpty()) {

src/cli/AndroidLintCliInvokerCache.kt

@@ -15,7 +15,12 @@ import java.nio.file.Path
  * while a request against the old jar is still running, so the old classloader is only disposed
  * once its last lease is released.
  */
-internal class AndroidLintCliInvokerCache {
+internal class AndroidLintCliInvokerCache(
+  // The classloader lint's deploy jar is parented on. Defaults to the platform classloader so lint
+  // is fully isolated from the worker's classpath. Tests override this to resolve stub lint classes
+  // from the test classpath.
+  private val parentClassloader: ClassLoader = ClassLoader.getPlatformClassLoader(),
+) {
   private class Entry(
     val key: String,
     val invoker: AndroidLintCliInvoker,
@@ -44,7 +49,11 @@ internal class AndroidLintCliInvokerCache {
       }
       current = null
     }
-    val invoker = AndroidLintCliInvoker.createUsingJars(jars = jars.toTypedArray())
+    val invoker =
+      AndroidLintCliInvoker.createUsingJars(
+        parentClassloader = parentClassloader,
+        jars = jars.toTypedArray(),
+      )
     createdCount += 1
     current = Entry(key = key, invoker = invoker, activeLeases = 1)
     return invoker

tests/src/cli/AndroidLintActionTest.kt

@@ -26,7 +26,7 @@ class AndroidLintActionTest {
 
   @Test
   fun `sequential work requests reuse a single cached lint classloader`() {
-    val cache = AndroidLintCliInvokerCache()
+    val cache = AndroidLintCliInvokerCache(parentClassloader = javaClass.classLoader)
     val executor = AndroidLintAction.AndroidLintExecutor(cache)
     val jar = writeStubLintJar()
 
@@ -43,7 +43,7 @@ class AndroidLintActionTest {
   fun `lint issue exit codes do not fail the work request or evict the cache`() {
     // By design the action always succeeds and produces a report; enforcement happens in the
     // android_lint_test validator. A lint exit code must not kill or degrade the worker.
-    val cache = AndroidLintCliInvokerCache()
+    val cache = AndroidLintCliInvokerCache(parentClassloader = javaClass.classLoader)
     val executor = AndroidLintAction.AndroidLintExecutor(cache)
     val jar = writeStubLintJar()
 
@@ -61,7 +61,7 @@ class AndroidLintActionTest {
 
   @Test
   fun `lint runs with an invocation-scoped user home`() {
-    val cache = AndroidLintCliInvokerCache()
+    val cache = AndroidLintCliInvokerCache(parentClassloader = javaClass.classLoader)
     val executor = AndroidLintAction.AndroidLintExecutor(cache)
     val jar = writeStubLintJar()
 
@@ -75,7 +75,7 @@ class AndroidLintActionTest {
 
   @Test
   fun `lint receives sdk home from android home`() {
-    val cache = AndroidLintCliInvokerCache()
+    val cache = AndroidLintCliInvokerCache(parentClassloader = javaClass.classLoader)
     val executor = AndroidLintAction.AndroidLintExecutor(cache)
     val jar = writeStubLintJar()
 

tests/src/cli/AndroidLintCliInvokerCacheTest.kt

@@ -30,7 +30,7 @@ class AndroidLintCliInvokerCacheTest {
 
   @Test
   fun `acquiring twice with an unchanged jar reuses the invoker`() {
-    val cache = AndroidLintCliInvokerCache()
+    val cache = AndroidLintCliInvokerCache(parentClassloader = javaClass.classLoader)
     val jar = writeJar("lint.jar", entryCount = 1)
 
     val first = cache.acquire(listOf(jar))
@@ -44,7 +44,7 @@ class AndroidLintCliInvokerCacheTest {
 
   @Test
   fun `a changed jar evicts the cached invoker and disposes it`() {
-    val cache = AndroidLintCliInvokerCache()
+    val cache = AndroidLintCliInvokerCache(parentClassloader = javaClass.classLoader)
     val jar = writeJar("lint.jar", entryCount = 1)
 
     val first = cache.acquire(listOf(jar))
@@ -62,7 +62,7 @@ class AndroidLintCliInvokerCacheTest {
 
   @Test
   fun `eviction defers disposal until the last lease is released`() {
-    val cache = AndroidLintCliInvokerCache()
+    val cache = AndroidLintCliInvokerCache(parentClassloader = javaClass.classLoader)
     val jar = writeJar("lint.jar", entryCount = 1)
 
     val first = cache.acquire(listOf(jar))
@@ -83,7 +83,7 @@ class AndroidLintCliInvokerCacheTest {
 
   @Test
   fun `invoke creates a fresh Main per call and applies checkDependencies per call`() {
-    val cache = AndroidLintCliInvokerCache()
+    val cache = AndroidLintCliInvokerCache(parentClassloader = javaClass.classLoader)
     val jar = writeJar("lint.jar", entryCount = 1)
     val invoker = cache.acquire(listOf(jar))
 
@@ -103,7 +103,7 @@ class AndroidLintCliInvokerCacheTest {
 
   @Test
   fun `concurrent invocations share one classloader with independent Main instances`() {
-    val cache = AndroidLintCliInvokerCache()
+    val cache = AndroidLintCliInvokerCache(parentClassloader = javaClass.classLoader)
     val jar = writeJar("lint.jar", entryCount = 1)
     // Both runs must be in flight at the same time before either completes.
     Main.runBarrier = CyclicBarrier(2)