Add an Error Prone check that reimplements javac sunapi warnings

The javac diagnostic can't be configured using `-Xlint:` (https://bugs.openjdk.org/browse/JDK-8148808), and doesn't work when `--system` is configured (https://bugs.openjdk.org/browse/JDK-8332744)

PiperOrigin-RevId: 636969056

Author: cushon

core/src/main/java/com/google/errorprone/bugpatterns/SunApi.java

@@ -0,0 +1,82 @@
+/*
+ * Copyright 2024 The Error Prone Authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.errorprone.bugpatterns;
+
+import static com.google.errorprone.BugPattern.SeverityLevel.WARNING;
+import static com.google.errorprone.matchers.Description.NO_MATCH;
+
+import com.google.errorprone.BugPattern;
+import com.google.errorprone.VisitorState;
+import com.google.errorprone.bugpatterns.BugChecker.IdentifierTreeMatcher;
+import com.google.errorprone.bugpatterns.BugChecker.MemberSelectTreeMatcher;
+import com.google.errorprone.matchers.Description;
+import com.google.errorprone.util.ASTHelpers;
+import com.sun.source.tree.IdentifierTree;
+import com.sun.source.tree.ImportTree;
+import com.sun.source.tree.MemberSelectTree;
+import com.sun.source.tree.Tree;
+import com.sun.tools.javac.code.Flags;
+import com.sun.tools.javac.code.Symbol;
+import com.sun.tools.javac.code.Symbol.ModuleSymbol;
+import com.sun.tools.javac.code.Symbol.PackageSymbol;
+
+/** A {@link BugChecker}; see the associated {@link BugPattern} annotation for details. */
+@BugPattern(
+    summary = "Usage of internal proprietary API which may be removed in a future release",
+    severity = WARNING)
+public class SunApi extends BugChecker implements MemberSelectTreeMatcher, IdentifierTreeMatcher {
+  @Override
+  public Description matchIdentifier(IdentifierTree tree, VisitorState state) {
+    return match(tree, state);
+  }
+
+  @Override
+  public Description matchMemberSelect(MemberSelectTree tree, VisitorState state) {
+    return match(tree, state);
+  }
+
+  private Description match(Tree tree, VisitorState state) {
+    Symbol sym = ASTHelpers.getSymbol(tree);
+    if (sym == null) {
+      return NO_MATCH;
+    }
+    if (!inJdkUnsupportedModule(sym) && ((sym.flags() & Flags.PROPRIETARY) == 0)) {
+      return NO_MATCH;
+    }
+    if (state.findEnclosing(ImportTree.class) != null) {
+      return NO_MATCH;
+    }
+    return buildDescription(tree)
+        .setMessage(
+            String.format(
+                "%s is an internal JDK API which may be removed in a future release",
+                sym.getQualifiedName()))
+        .build();
+  }
+
+  private static boolean inJdkUnsupportedModule(Symbol sym) {
+    PackageSymbol packageSymbol = ASTHelpers.enclosingPackage(sym);
+    if (packageSymbol == null) {
+      return false;
+    }
+    ModuleSymbol moduleSymbol = (ModuleSymbol) packageSymbol.getEnclosingElement();
+    if (moduleSymbol == null) {
+      return false;
+    }
+    return moduleSymbol.name.contentEquals("jdk.unsupported");
+  }
+}

core/src/main/java/com/google/errorprone/scanner/BuiltInCheckerSuppliers.java

@@ -356,6 +356,7 @@
 import com.google.errorprone.bugpatterns.StringSplitter;
 import com.google.errorprone.bugpatterns.StronglyTypeByteString;
 import com.google.errorprone.bugpatterns.SubstringOfZero;
+import com.google.errorprone.bugpatterns.SunApi;
 import com.google.errorprone.bugpatterns.SuperCallToObjectMethod;
 import com.google.errorprone.bugpatterns.SuppressWarningsDeprecated;
 import com.google.errorprone.bugpatterns.SuppressWarningsWithoutExplanation;
@@ -1210,6 +1211,7 @@ public static ScannerSupplier warningChecks() {
           StringFormatWithLiteral.class,
           StronglyTypeByteString.class,
           StronglyTypeTime.class,
+          SunApi.class,
           SuppressWarningsWithoutExplanation.class,
           SwitchDefault.class,
           SymbolToString.class,

core/src/test/java/com/google/errorprone/bugpatterns/SunApiTest.java

@@ -0,0 +1,67 @@
+/*
+ * Copyright 2024 The Error Prone Authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.errorprone.bugpatterns;
+
+import com.google.errorprone.CompilationTestHelper;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+@RunWith(JUnit4.class)
+public class SunApiTest {
+
+  private final CompilationTestHelper compilationHelper =
+      CompilationTestHelper.newInstance(SunApi.class, getClass());
+
+  @Test
+  public void positive() {
+    compilationHelper
+        .addSourceLines(
+            "Test.java", //
+            "class Test {",
+            "  // BUG: Diagnostic contains: sun.misc.Unsafe",
+            "  sun.misc.Unsafe u;",
+            "}")
+        .doTest();
+  }
+
+  @Test
+  public void positiveSource8() {
+    compilationHelper
+        .addSourceLines(
+            "Test.java", //
+            "class Test {",
+            "  // BUG: Diagnostic contains: sun.misc.Unsafe",
+            "  sun.misc.Unsafe u;",
+            "}")
+        .setArgs("-source", "8", "-target", "8")
+        .doTest();
+  }
+
+  @Test
+  public void negative() {
+    compilationHelper
+        .addSourceLines(
+            "Test.java", //
+            "import jdk.internal.misc.Unsafe;",
+            "class Test {",
+            "  Unsafe u;",
+            "}")
+        .addModules("java.base/jdk.internal.misc")
+        .doTest();
+  }
+}

docs/bugpattern/SunApi.md

@@ -0,0 +1,7 @@
+Warn on internal, proprietary APIs that may be removed in future JDK versions.
+
+For `sun.misc.Unsafe`, note that the API will be removed from a future version
+of the JDK:
+[JEP 471: Deprecate the Memory-Access Methods in sun.misc.Unsafe for Removal](https://openjdk.org/jeps/471).
+
+This check is a re-implementation of javac's 'sunapi' diagnostic.