Diagnose incompatible annotation processors

When an annotation processor is built targeting a language level that isn't supported by the Java runtime used for compilation, JavaBuilder now throws an exception with actionable information.

Example:
```
java.lang.IllegalStateException: The Java 17 runtime used to run javac is not recent enough to run the processor com.google.devtools.build.runfiles.AutoBazelRepositoryProcessor, which has been compiled targeting Java 20. Either register a Java toolchain with a newer java_runtime or, if this processor has been built with Bazel, specify a lower --tool_java_language_version.
	at com.google.devtools.build.buildjar.javac.BlazeJavaCompiler.initProcessAnnotations(BlazeJavaCompiler.java:119)
        ...
```

Work towards #17281

Closes #19548.

PiperOrigin-RevId: 570766544
Change-Id: I71a53201a63f153b2318fff0a938a6626149e02f

src/java_tools/buildjar/java/com/google/devtools/build/buildjar/javac/BlazeJavacMain.java

@@ -54,6 +54,8 @@
 import java.util.Map;
 import java.util.Optional;
 import java.util.Set;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
 import javax.annotation.Nullable;
 import javax.tools.Diagnostic;
 import javax.tools.DiagnosticListener;
@@ -70,6 +72,11 @@
  */
 public class BlazeJavacMain {
 
+  private static final Pattern UNSUPPORTED_CLASS_VERSION_ERROR =
+      Pattern.compile(
+          "^(?<class>[^ ]*) has been compiled by a more recent version of the Java Runtime "
+              + "\\(class file version (?<version>[4-9][0-9])\\.");
+
   /**
    * Sets up a BlazeJavaCompiler with the given plugins within the given context.
    *
@@ -139,8 +146,23 @@ public static BlazeJavacResult compile(BlazeJavacArguments arguments) {
         throw e.getCause();
       }
     } catch (Exception t) {
-      if (t.getCause() instanceof CancelRequestException) {
-        return BlazeJavacResult.cancelled(t.getCause().getMessage());
+      Throwable cause = t.getCause();
+      if (cause instanceof CancelRequestException) {
+        return BlazeJavacResult.cancelled(cause.getMessage());
+      }
+      Matcher matcher;
+      if (cause instanceof UnsupportedClassVersionError
+          && (matcher = UNSUPPORTED_CLASS_VERSION_ERROR.matcher(cause.getMessage())).find()) {
+        // Java 8 corresponds to class file major version 52.
+        int processorVersion = Integer.parseUnsignedInt(matcher.group("version")) - 44;
+        errWriter.printf(
+            "The Java %d runtime used to run javac is not recent enough to run the processor %s, "
+                + "which has been compiled targeting Java %d. Either register a Java toolchain "
+                + "with a newer java_runtime or, if this processor has been built with Bazel, "
+                + "specify a lower --tool_java_language_version.%n",
+            Runtime.version().feature(),
+            matcher.group("class").replace('/', '.'),
+            processorVersion);
       }
       t.printStackTrace(errWriter);
       status = Status.CRASH;

src/test/shell/bazel/bazel_java17_test.sh

@@ -140,5 +140,50 @@ EOF
   expect_log "^World\$"
 }
 
+function test_incompatible_processor() {
+  mkdir -p pkg
+  # This test defines a custom Java toolchain as it relies on the availability of a runtime that is
+  # strictly newer than the one specified as the toolchain's java_runtime.
+  cat >pkg/BUILD <<EOF
+load("@bazel_tools//tools/jdk:default_java_toolchain.bzl", "default_java_toolchain")
+java_binary(
+    name = "Main",
+    srcs = ["Main.java"],
+    main_class = "com.example.Main",
+    # Exports an annotation processor.
+    deps = ["@bazel_tools//tools/java/runfiles"],
+)
+default_java_toolchain(
+    name = "java_toolchain",
+    source_version = "17",
+    target_version = "17",
+    java_runtime = "@bazel_tools//tools/jdk:remotejdk_17",
+)
+EOF
+
+  cat >pkg/Main.java <<'EOF'
+package com.example;
+public class Main {
+  public static void main(String[] args) {
+    System.out.println("Hello, world!");
+  }
+}
+EOF
+
+  # Specify a --tool_java_language_version higher than any tested runtime.
+  bazel build //pkg:Main \
+    --extra_toolchains=//pkg:java_toolchain_definition \
+    --java_language_version=17 \
+    --java_runtime_version=remotejdk_17 \
+    --tool_java_language_version=20 \
+    --tool_java_runtime_version=remotejdk_20 \
+    &>"${TEST_log}" && fail "Expected build to fail"
+
+  expect_log "The Java 17 runtime used to run javac is not recent enough to run the processor " \
+    "com\.google\.devtools\.build\.runfiles\.AutoBazelRepositoryProcessor, which has been " \
+    "compiled targeting Java 20\. Either register a Java toolchain with a newer java_runtime " \
+    "or, if this processor has been built with Bazel, specify a lower " \
+    "--tool_java_language_version\."
+}
 
 run_suite "Tests Java 17 language features"