Move PreferPreconditions to JavaCodeClarity to run on changed lines

and only emit findings if `Preconditions` is already on the classpath.

This check is producing a lot of findings on unchanged lines and for third_party/ code that doesn't depend on Guava (like SafeRE).

PiperOrigin-RevId: 942497251

Author: cushon

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

@@ -35,6 +35,7 @@
 import com.google.errorprone.fixes.SuggestedFix;
 import com.google.errorprone.matchers.Description;
 import com.google.errorprone.matchers.Matcher;
+import com.google.errorprone.suppliers.Supplier;
 import com.sun.source.tree.BinaryTree;
 import com.sun.source.tree.BlockTree;
 import com.sun.source.tree.ExpressionTree;
@@ -55,6 +56,7 @@
 import java.util.List;
 import javax.inject.Inject;
 import javax.lang.model.element.ElementKind;
+import javax.lang.model.element.TypeElement;
 import org.jspecify.annotations.Nullable;
 
 /**
@@ -66,6 +68,10 @@
     severity = WARNING)
 public final class PreferPreconditions extends BugChecker implements IfTreeMatcher {
 
+  private static final Supplier<@Nullable TypeElement> PRECONDITIONS =
+      VisitorState.memoize(
+          state -> state.getElements().getTypeElement("com.google.common.base.Preconditions"));
+
   private final ConstantExpressions constantExpressions;
 
   @Inject
@@ -75,6 +81,10 @@ public final class PreferPreconditions extends BugChecker implements IfTreeMatch
 
   @Override
   public Description matchIf(IfTree tree, VisitorState state) {
+    if (PRECONDITIONS.get(state) == null) {
+      // Only emit findings if Preconditions is already on the classpath
+      return NO_MATCH;
+    }
     if (tree.getElseStatement() != null) {
       return NO_MATCH;
     }

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

@@ -1137,7 +1137,6 @@ public static ScannerSupplier warningChecks() {
           PreconditionsCheckNotNullRepeated.class,
           PreferCharsetOverload.class,
           PreferInstanceofOverGetKind.class,
-          PreferPreconditions.class,
           PreferTestParameter.class,
           PreferThrowsTag.class,
           PrimitiveAtomicReference.class,
@@ -1314,6 +1313,7 @@ public static ScannerSupplier warningChecks() {
           ParameterComment.class,
           ParameterMissingNullable.class,
           PreferJavaTimeOverload.class,
+          PreferPreconditions.class,
           PreferredInterfaceType.class,
           PrimitiveArrayPassedToVarargsMethod.class,
           PrivateConstructorForNoninstantiableModule.class,