Generalise GuiceCreateInjectorWithCombineRefactor to match any use of…

… `combine` within a varargs position.

PiperOrigin-RevId: 630029267

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

@@ -0,0 +1,91 @@
+/*
+ * 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.common.collect.Iterables.getLast;
+import static com.google.errorprone.BugPattern.SeverityLevel.WARNING;
+import static com.google.errorprone.matchers.Description.NO_MATCH;
+import static com.google.errorprone.matchers.method.MethodMatchers.staticMethod;
+import static com.google.errorprone.suppliers.Suppliers.typeFromString;
+import static com.google.errorprone.util.ASTHelpers.getStartPosition;
+import static com.google.errorprone.util.ASTHelpers.getSymbol;
+import static com.google.errorprone.util.ASTHelpers.getType;
+import static com.google.errorprone.util.ASTHelpers.isSubtype;
+
+import com.google.errorprone.BugPattern;
+import com.google.errorprone.VisitorState;
+import com.google.errorprone.bugpatterns.BugChecker.MethodInvocationTreeMatcher;
+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.ExpressionTree;
+import com.sun.source.tree.MethodInvocationTree;
+import com.sun.tools.javac.code.Type;
+import java.util.List;
+
+/** A {@link BugChecker}; see the associated {@link BugPattern} annotation for details. */
+@BugPattern(summary = "Nesting Modules.combine() here is unnecessary.", severity = WARNING)
+public final class GuiceNestedCombine extends BugChecker implements MethodInvocationTreeMatcher {
+  private static final Matcher<ExpressionTree> MODULES_COMBINE_METHOD =
+      staticMethod().onClass("com.google.inject.util.Modules").named("combine");
+
+  private static final Supplier<Type> MODULE = typeFromString("com.google.inject.Module");
+
+  @Override
+  public Description matchMethodInvocation(MethodInvocationTree tree, VisitorState state) {
+    if (!MODULES_COMBINE_METHOD.matches(tree, state)) {
+      return NO_MATCH;
+    }
+    var module = MODULE.get(state);
+    if (module == null
+        || tree.getArguments().isEmpty()
+        || !tree.getArguments().stream().allMatch(a -> isSubtype(getType(a), module, state))) {
+      return NO_MATCH;
+    }
+
+    var parent = state.getPath().getParentPath().getLeaf();
+    if (!(parent instanceof MethodInvocationTree)) {
+      return NO_MATCH;
+    }
+    if (!isInVarargsPosition(tree, (MethodInvocationTree) parent, state)) {
+      return NO_MATCH;
+    }
+
+    var fix =
+        SuggestedFix.builder()
+            .replace(getStartPosition(tree), getStartPosition(tree.getArguments().get(0)), "")
+            .replace(
+                state.getEndPosition(getLast(tree.getArguments())), state.getEndPosition(tree), "")
+            .build();
+    return describeMatch(tree, fix);
+  }
+
+  private static boolean isInVarargsPosition(
+      ExpressionTree argTree, MethodInvocationTree methodInvocationTree, VisitorState state) {
+    var methodSymbol = getSymbol(methodInvocationTree);
+    if (!methodSymbol.isVarArgs()) {
+      return false;
+    }
+    int parameterCount = methodSymbol.getParameters().size();
+    List<? extends ExpressionTree> arguments = methodInvocationTree.getArguments();
+    // Don't match if we're passing an array into a varargs parameter, but do match if there are
+    // other parameters along with it.
+    return (arguments.size() > parameterCount || !state.getTypes().isArray(getType(argTree)))
+        && arguments.indexOf(argTree) >= parameterCount - 1;
+  }
+}

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

@@ -157,7 +157,7 @@
 import com.google.errorprone.bugpatterns.GetClassOnAnnotation;
 import com.google.errorprone.bugpatterns.GetClassOnClass;
 import com.google.errorprone.bugpatterns.GetClassOnEnum;
-import com.google.errorprone.bugpatterns.GuiceCreateInjectorWithCombineRefactor;
+import com.google.errorprone.bugpatterns.GuiceNestedCombine;
 import com.google.errorprone.bugpatterns.HashtableContains;
 import com.google.errorprone.bugpatterns.HidingField;
 import com.google.errorprone.bugpatterns.ICCProfileGetInstance;
@@ -918,7 +918,7 @@ public static ScannerSupplier warningChecks() {
           FragmentNotInstantiable.class,
           FutureReturnValueIgnored.class,
           GetClassOnEnum.class,
-          GuiceCreateInjectorWithCombineRefactor.class,
+          GuiceNestedCombine.class,
           HidingField.class,
           ICCProfileGetInstance.class,
           IdentityHashMapUsage.class,