Don't make UnnecessarilyFullyQualified suggestions in package-infos

Fixes #1652

PiperOrigin-RevId: 350823261

Author: cushon

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

@@ -71,6 +71,9 @@ public Description matchCompilationUnit(CompilationUnitTree tree, VisitorState s
             t -> getSymbol(tree) != null && !getGeneratedBy(getSymbol(tree), state).isEmpty())) {
       return NO_MATCH;
     }
+    if (isPackageInfo(tree)) {
+      return NO_MATCH;
+    }
     Table<Name, TypeSymbol, List<TreePath>> table = HashBasedTable.create();
     Set<Name> identifiersSeen = new HashSet<>();
     new SuppressibleTreePathScanner<Void, Void>() {
@@ -183,4 +186,13 @@ public Void visitIdentifier(IdentifierTree identifierTree, Void aVoid) {
     }
     return NO_MATCH;
   }
+
+  private boolean isPackageInfo(CompilationUnitTree tree) {
+    String name = tree.getSourceFile().getName();
+    int idx = name.lastIndexOf('/');
+    if (idx != -1) {
+      name = name.substring(idx + 1);
+    }
+    return name.equals("package-info.java");
+  }
 }

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

@@ -16,6 +16,7 @@
 package com.google.errorprone.bugpatterns;
 
 import com.google.errorprone.BugCheckerRefactoringTestHelper;
+import com.google.errorprone.CompilationTestHelper;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.junit.runners.JUnit4;
@@ -130,4 +131,18 @@ public void builder() {
             "}")
         .doTest();
   }
+
+  @Test
+  public void packageInfo() {
+    CompilationTestHelper.newInstance(UnnecessarilyFullyQualified.class, getClass())
+        .addSourceLines(
+            "a/A.java", //
+            "package a;",
+            "public @interface A {}")
+        .addSourceLines(
+            "b/package-info.java", //
+            "@a.A",
+            "package b;")
+        .doTest();
+  }
 }