Handle locals in InlineFormatString

PiperOrigin-RevId: 749587178

Author: cushon

core/src/main/java/com/google/errorprone/bugpatterns/formatstring/InlineFormatString.java

@@ -21,8 +21,10 @@
 import static com.google.errorprone.matchers.Matchers.allOf;
 import static com.google.errorprone.matchers.Matchers.anyOf;
 import static com.google.errorprone.matchers.Matchers.staticMethod;
+import static com.google.errorprone.util.ASTHelpers.constValue;
 import static com.google.errorprone.util.ASTHelpers.getSymbol;
 import static com.google.errorprone.util.ASTHelpers.hasAnnotation;
+import static com.google.errorprone.util.ASTHelpers.isConsideredFinal;
 import static com.google.errorprone.util.ASTHelpers.isSubtype;
 import static com.google.errorprone.util.AnnotationNames.FORMAT_METHOD_ANNOTATION;
 import static com.google.errorprone.util.AnnotationNames.FORMAT_STRING_ANNOTATION;
@@ -37,7 +39,6 @@
 import com.google.errorprone.fixes.SuggestedFix;
 import com.google.errorprone.matchers.Description;
 import com.google.errorprone.matchers.Matcher;
-import com.google.errorprone.util.ASTHelpers;
 import com.sun.source.tree.CompilationUnitTree;
 import com.sun.source.tree.ExpressionTree;
 import com.sun.source.tree.IdentifierTree;
@@ -54,7 +55,6 @@
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
-import javax.lang.model.element.ElementKind;
 import org.jspecify.annotations.Nullable;
 
 /** A {@link BugChecker}; see the associated {@link BugPattern} annotation for details. */
@@ -134,14 +134,21 @@ private void handle(MethodInvocationTree tree) {
               return;
             }
             Symbol variable = getSymbol(arg);
-            if (variable == null
-                || variable.getKind() != ElementKind.FIELD
-                || !variable.isPrivate()
-                || ASTHelpers.constValue(arg, String.class) == null) {
+            if (variable == null || !isConstant(variable, arg)) {
               return;
             }
             uses.put(variable, arg);
           }
+
+          private boolean isConstant(Symbol variable, ExpressionTree arg) {
+            return switch (variable.getKind()) {
+              case FIELD -> variable.isPrivate() && constValue(arg, String.class) != null;
+              // locals don't have a computed constant value, this will be handled below when we
+              // scan for constant initializers
+              case LOCAL_VARIABLE -> isConsideredFinal(variable);
+              default -> false;
+            };
+          }
         },
         null);
     // find all uses of the candidate fields, and reject them if they are used outside for calls to

core/src/test/java/com/google/errorprone/bugpatterns/formatstring/InlineFormatStringTest.java

@@ -206,4 +206,64 @@ void f() {
             """)
         .doTest();
   }
+
+  @Test
+  public void negativeLocal() {
+    compilationHelper
+        .addSourceLines(
+            "Test.java",
+            """
+            class Test {
+              void f(String a) {
+                String format = a;
+                System.err.printf(format, 42);
+              }
+            }
+            """)
+        .doTest();
+  }
+
+  @Test
+  public void refactoringLocal() {
+    refactoringHelper
+        .addInputLines(
+            "Test.java",
+            """
+            class Test {
+              void f() {
+                String format = "hello %s";
+                System.err.printf(format, 42);
+              }
+            }
+            """)
+        .addOutputLines(
+            "Test.java",
+            """
+            class Test {
+              void f() {
+                System.err.printf("hello %s", 42);
+              }
+            }
+            """)
+        .doTest();
+  }
+
+  @Test
+  public void multipleUses() {
+    compilationHelper
+        .addSourceLines(
+            "Test.java",
+            """
+            class Test {
+              void f() {
+                String format = "hello %s";
+                // BUG: Diagnostic contains
+                System.err.printf(format, 42);
+                // BUG: Diagnostic contains
+                System.err.printf(format, 42);
+              }
+            }
+            """)
+        .doTest();
+  }
 }