Favour the ErrorProneFlags constructor over the zero-args one.

I was a bit lazy and figured this edge case wouldn't matter too much, but it turns out to annoy people. Fixes external #3931 PiperOrigin-RevId: 535569770
google · May 26, 2023 · bafa50f · bafa50f
1 parent 1b1494a
commit bafa50f
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Showing 2 changed files with 27 additions and 2 deletions.
diff --git a/check_api/src/main/java/com/google/errorprone/scanner/ErrorProneInjector.java b/check_api/src/main/java/com/google/errorprone/scanner/ErrorProneInjector.java
@@ -106,8 +106,10 @@ public static <T> Optional<Constructor<T>> findConstructor(Class<T> clazz) {
                 findConstructorMatching(
                     clazz,
                     c ->
-                        stream(c.getParameters())
-                            .allMatch(p -> p.getType().equals(ErrorProneFlags.class))));
+                        c.getParameters().length != 0
+                            && stream(c.getParameters())
+                                .allMatch(p -> p.getType().equals(ErrorProneFlags.class))))
+        .or(() -> findConstructorMatching(clazz, c -> c.getParameters().length == 0));
   }
 
   @SuppressWarnings("unchecked")

diff --git a/check_api/src/test/java/com/google/errorprone/scanner/ErrorProneInjectorTest.java b/check_api/src/test/java/com/google/errorprone/scanner/ErrorProneInjectorTest.java
@@ -19,6 +19,7 @@
 import static com.google.common.truth.Truth.assertThat;
 import static org.junit.Assert.assertThrows;
 
+import com.google.errorprone.ErrorProneFlags;
 import com.google.errorprone.scanner.ErrorProneInjector.ProvisionException;
 import javax.inject.Inject;
 import org.junit.Test;
@@ -58,6 +59,16 @@ public void bothConstructors_injectable() {
     assertThat(obj.x).isEqualTo(2);
   }
 
+  @Test
+  public void errorProneFlags_favouredOverZeroArg() {
+    var injector =
+        ErrorProneInjector.create().addBinding(ErrorProneFlags.class, ErrorProneFlags.empty());
+
+    var obj = injector.getInstance(ErrorProneFlagsAndZeroArgsConstructor.class);
+
+    assertThat(obj.x).isEqualTo(1);
+  }
+
   @Test
   public void pathInError() {
     var injector = ErrorProneInjector.create();
@@ -89,4 +100,16 @@ public static final class InjectConstructorAndZeroArgConstructor {
       this.x = 0;
     }
   }
+
+  public static final class ErrorProneFlagsAndZeroArgsConstructor {
+    final int x;
+
+    ErrorProneFlagsAndZeroArgsConstructor() {
+      this.x = 0;
+    }
+
+    ErrorProneFlagsAndZeroArgsConstructor(ErrorProneFlags flags) {
+      this.x = 1;
+    }
+  }
 }