A DESCRIPTION OF THE PROBLEM :
JavaCompiler was mostly modified to work with general Path and Files API, not just File objects. But there remains a case where paths are converted to files and shouldn't be. This makes the code crash if the paths can't be converted to files.

That is because JavacFileManager#getClassLoader(Location location) calls getLocation, which tries to return File instances, instead of getLocationAsPaths(Location location): https://github.com/openjdk/jdk/blob/master/src/jdk.compiler/share/classes/com/sun/tools/javac/file/JavacFileManager.java#L744.

More completely, this is because the initialization of annotation processing (involving #getClassLoader) uses the class path, which fails if the paths do not refer to File instances for the above reason.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Run the code below

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
Expected: task.call() returns a result.
ACTUAL -
Actual: task.call() throws:
java.lang.IllegalStateException: java.lang.UnsupportedOperationException
at jdk.compiler/com.sun.tools.javac.file.JavacFileManager$3.next(JavacFileManager.java:1159)
at jdk.compiler/com.sun.tools.javac.file.JavacFileManager$3.next(JavacFileManager.java:1146)
at jdk.compiler/com.sun.tools.javac.file.JavacFileManager.getClassLoader(JavacFileManager.java:682)
at jdk.compiler/com.sun.tools.javac.processing.JavacProcessingEnvironment.initProcessorLoader(JavacProcessingEnvironment.java:269)
at jdk.compiler/com.sun.tools.javac.processing.JavacProcessingEnvironment.<init>(JavacProcessingEnvironment.java:237)
at jdk.compiler/com.sun.tools.javac.processing.JavacProcessingEnvironment.instance(JavacProcessingEnvironment.java:193)
at jdk.compiler/com.sun.tools.javac.main.JavaCompiler.initProcessAnnotations(JavaCompiler.java:1136)
at jdk.compiler/com.sun.tools.javac.main.JavaCompiler.compile(JavaCompiler.java:922)
at jdk.compiler/com.sun.tools.javac.api.JavacTaskImpl.lambda$doCall$0(JavacTaskImpl.java:104)
at jdk.compiler/com.sun.tools.javac.api.JavacTaskImpl.handleExceptions(JavacTaskImpl.java:147)
at jdk.compiler/com.sun.tools.javac.api.JavacTaskImpl.doCall(JavacTaskImpl.java:100)
at jdk.compiler/com.sun.tools.javac.api.JavacTaskImpl.call(JavacTaskImpl.java:94)
at io.github.oliviercailloux.bytecode.CompilerTests.testBugJdk(CompilerTests.java:121)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:566)
at org.junit.platform.commons.util.ReflectionUtils.invokeMethod(ReflectionUtils.java:675)
at org.junit.jupiter.engine.execution.MethodInvocation.proceed(MethodInvocation.java:60)
at org.junit.jupiter.engine.execution.InvocationInterceptorChain$ValidatingInvocation.proceed(InvocationInterceptorChain.java:125)
at org.junit.jupiter.engine.extension.TimeoutExtension.intercept(TimeoutExtension.java:132)
at org.junit.jupiter.engine.extension.TimeoutExtension.interceptTestableMethod(TimeoutExtension.java:124)
at org.junit.jupiter.engine.extension.TimeoutExtension.interceptTestMethod(TimeoutExtension.java:74)
at org.junit.jupiter.engine.execution.ExecutableInvoker$ReflectiveInterceptorCall.lambda$ofVoidMethod$0(ExecutableInvoker.java:115)
at org.junit.jupiter.engine.execution.ExecutableInvoker.lambda$invoke$0(ExecutableInvoker.java:105)
at org.junit.jupiter.engine.execution.InvocationInterceptorChain$InterceptedInvocation.proceed(InvocationInterceptorChain.java:104)
at org.junit.jupiter.engine.execution.InvocationInterceptorChain.proceed(InvocationInterceptorChain.java:62)
at org.junit.jupiter.engine.execution.InvocationInterceptorChain.chainAndInvoke(InvocationInterceptorChain.java:43)
at org.junit.jupiter.engine.execution.InvocationInterceptorChain.invoke(InvocationInterceptorChain.java:35)
at org.junit.jupiter.engine.execution.ExecutableInvoker.invoke(ExecutableInvoker.java:104)
at org.junit.jupiter.engine.execution.ExecutableInvoker.invoke(ExecutableInvoker.java:98)
at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.lambda$invokeTestMethod$6(TestMethodTestDescriptor.java:202)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.invokeTestMethod(TestMethodTestDescriptor.java:198)
at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.execute(TestMethodTestDescriptor.java:135)
at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.execute(TestMethodTestDescriptor.java:69)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:135)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:125)
at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:135)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:123)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:122)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:80)
at java.base/java.util.ArrayList.forEach(ArrayList.java:1540)
at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:38)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:139)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:125)
at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:135)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:123)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:122)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:80)
at java.base/java.util.ArrayList.forEach(ArrayList.java:1540)
at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:38)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:139)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:125)
at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:135)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:123)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:122)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:80)
at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.submit(SameThreadHierarchicalTestExecutorService.java:32)
at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor.execute(HierarchicalTestExecutor.java:57)
at org.junit.platform.engine.support.hierarchical.HierarchicalTestEngine.execute(HierarchicalTestEngine.java:51)
at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:229)
at org.junit.platform.launcher.core.DefaultLauncher.lambda$execute$6(DefaultLauncher.java:197)
at org.junit.platform.launcher.core.DefaultLauncher.withInterceptedStreams(DefaultLauncher.java:211)
at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:191)
at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:137)
at org.eclipse.jdt.internal.junit5.runner.JUnit5TestReference.run(JUnit5TestReference.java:89)
at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:41)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:542)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:770)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:464)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:210)
Caused by: java.lang.UnsupportedOperationException
at com.google.common.jimfs.JimfsPath.toFile(JimfsPath.java:411)
at jdk.compiler/com.sun.tools.javac.file.JavacFileManager$3.next(JavacFileManager.java:1157)
... 77 more



---------- BEGIN SOURCE ----------
Path sourcePath = Path.of(getClass().getResource("SourceWithNoWarnings.java").toURI());
try (FileSystem jimFs = Jimfs.newFileSystem(Configuration.unix())) {
Path work = jimFs.getPath("");

JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
DiagnosticCollector<JavaFileObject> diagnosticCollector = new DiagnosticCollector<>();
try (StandardJavaFileManager fileManager = compiler.getStandardFileManager(diagnosticCollector, null,
null)) {
fileManager.setLocationFromPaths(StandardLocation.CLASS_PATH, ImmutableList.of(work));
final Iterable<? extends JavaFileObject> srcToCompileObjs = fileManager
.getJavaFileObjectsFromPaths(ImmutableList.of(sourcePath));
CompilationTask task = compiler.getTask(new StringWriter(), fileManager, diagnosticCollector,
ImmutableList.of(), null, srcToCompileObjs);
task.call();
}
}

---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
Add fileManager.setLocationFromPaths(StandardLocation.ANNOTATION_PROCESSOR_PATH, ImmutableList.of()).

FREQUENCY : always