allow ReplaceRegexStep to function as a Linter, use that to improve RemoveWildcardImports

CHANGES.md

@@ -24,6 +24,8 @@ We adhere to the [keepachangelog](https://keepachangelog.com/en/1.0.0/) format (
 ### Fixed
 * Fix `spaceBeforeSeparator` in Jackson formatter. ([#2103](https://github.com/diffplug/spotless/pull/2103))
 * `GitPrePushHookInstaller` uses a lock to run gracefully if it is called many times in parallel. ([#2570](https://github.com/diffplug/spotless/pull/2570))
+### Added
+* Add a `lint` mode to `ReplaceRegexStep` ([#2571](https://github.com/diffplug/spotless/pull/2571))
 
 ## [3.3.1] - 2025-07-21
 ### Fixed

lib/src/main/java/com/diffplug/spotless/Lint.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2022-2024 DiffPlug
+ * Copyright 2022-2025 DiffPlug
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -91,7 +91,7 @@ public ShortcutException(Lint... lints) {
 private final List<Lint> lints;
 
 ShortcutException(Collection<Lint> lints) {
-super(lints.iterator().next().detail);
+super(lints.iterator().next().toString());
 this.lints = List.copyOf(lints);
 }
 

lib/src/main/java/com/diffplug/spotless/generic/ReplaceRegexStep.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2016 DiffPlug
+ * Copyright 2016-2025 DiffPlug
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -15,12 +15,16 @@
  */
 package com.diffplug.spotless.generic;
 
+import java.io.File;
 import java.io.Serializable;
+import java.util.ArrayList;
+import java.util.List;
 import java.util.Objects;
 import java.util.regex.Pattern;
 
 import com.diffplug.spotless.FormatterFunc;
 import com.diffplug.spotless.FormatterStep;
+import com.diffplug.spotless.Lint;
 
 public final class ReplaceRegexStep {
 // prevent direct instantiation
@@ -35,6 +39,15 @@ public static FormatterStep create(String name, String regex, String replacement
 State::toFormatter);
 }
 
+public static FormatterStep lint(String name, String regex, String lintDetail) {
+Objects.requireNonNull(name, "name");
+Objects.requireNonNull(regex, "regex");
+Objects.requireNonNull(lintDetail, "lintDetail");
+return FormatterStep.createLazy(name,
+() -> new LintState(Pattern.compile(regex, Pattern.UNIX_LINES | Pattern.MULTILINE), name, lintDetail),
+LintState::toLinter);
+}
+
 private static final class State implements Serializable {
 private static final long serialVersionUID = 1L;
 
@@ -50,4 +63,38 @@ FormatterFunc toFormatter() {
 return raw -> regex.matcher(raw).replaceAll(replacement);
 }
 }
+
+private static final class LintState implements Serializable {
+private static final long serialVersionUID = 1L;
+
+private final Pattern regex;
+private final String ruleId;
+private final String lintDetail;
+
+LintState(Pattern regex, String ruleId, String lintDetail) {
+this.regex = regex;
+this.ruleId = ruleId;
+this.lintDetail = lintDetail;
+}
+
+FormatterFunc toLinter() {
+return new FormatterFunc() {
+@Override
+public String apply(String raw) {
+return raw;
+}
+
+@Override
+public List<Lint> lint(String raw, File file) {
+List<Lint> lints = new ArrayList<>();
+var matcher = regex.matcher(raw);
+while (matcher.find()) {
+int line = 1 + (int) raw.codePoints().limit(matcher.start()).filter(c -> c == '\n').count();
+lints.add(Lint.atLine(line, matcher.group(0), lintDetail));
+}
+return lints;
+}
+};
+}
+}
 }

lib/src/main/java/com/diffplug/spotless/java/RemoveWildcardImportsStep.java

@@ -20,13 +20,17 @@
 
 /** Removes any wildcard import statements. */
 public final class RemoveWildcardImportsStep {
+
+/**
+ * Matches lines like 'import foo.*;' or 'import static foo.*;'.
+ */
+private static final String REGEX = "(?m)^import\\s+(?:static\\s+)?[^;\\n]*\\*;\\R?";
+private static final String NAME = "removeWildcardImports";
+private static final String ERROR = "Do not use wildcard imports (e.g. java.util.*) - replace with specific class imports (e.g. java.util.List) as 'spotlessApply' cannot auto-fix this";
+
 private RemoveWildcardImportsStep() {}
 
 public static FormatterStep create() {
-// Matches lines like 'import foo.*;' or 'import static foo.*;'.
-return ReplaceRegexStep.create(
-"removeWildcardImports",
-"(?m)^import\\s+(?:static\\s+)?[^;\\n]*\\*;\\R?",
-"");
+return ReplaceRegexStep.lint(NAME, REGEX, ERROR);
 }
 }

plugin-gradle/src/test/java/com/diffplug/gradle/spotless/JavaDefaultTargetTest.java

@@ -97,7 +97,7 @@ void removeWildCardImports() throws IOException {
 "}");
 
 setFile("test.java").toResource("java/removewildcardimports/JavaCodeWildcardsUnformatted.test");
-gradleRunner().withArguments("spotlessApply").build();
+gradleRunner().withArguments("spotlessApply").buildAndFail();
 assertFile("test.java").sameAsResource("java/removewildcardimports/JavaCodeWildcardsFormatted.test");
 }
 

testlib/src/main/resources/java/removewildcardimports/JavaCodeNoWildcardsFormatted.test

@@ -0,0 +1,4 @@
+import java.util.List;
+import mylib.Helper;
+
+public class Test {}

testlib/src/main/resources/java/removewildcardimports/JavaCodeNoWildcardsUnformatted.test

@@ -0,0 +1,4 @@
+import java.util.List;
+import mylib.Helper;
+
+public class Test {}

testlib/src/main/resources/java/removewildcardimports/JavaCodeWildcardsFormatted.test

@@ -1,4 +1,9 @@
+import java.util.*;
+import static java.util.Collections.*;
 import java.util.List;
 import mylib.Helper;
+import io.quarkus.maven.dependency.*;
+import static io.quarkus.vertx.web.Route.HttpMethod.*;
+import static org.springframework.web.reactive.function.BodyInserters.*;
 
 public class Test {}

testlib/src/test/java/com/diffplug/spotless/generic/ReplaceRegexStepTest.java

@@ -0,0 +1,44 @@
+/*
+ * Copyright 2025 DiffPlug
+ *
+ * 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.diffplug.spotless.generic;
+
+import org.junit.jupiter.api.Test;
+
+import com.diffplug.common.base.StringPrinter;
+import com.diffplug.spotless.FormatterStep;
+import com.diffplug.spotless.StepHarness;
+
+class ReplaceRegexStepTest {
+@Test
+void formatter() throws Exception {
+FormatterStep step = ReplaceRegexStep.create("replace", "bad", "good");
+StepHarness.forStep(step)
+.test("bad bad", "good good");
+}
+
+@Test
+void lint() throws Exception {
+FormatterStep step = ReplaceRegexStep.lint("stayPositive", "(bad|awful)", "no negative words");
+StepHarness.forStep(step)
+.expectLintsOf(StringPrinter.buildStringFromLines(
+"bad",
+"oh boy",
+"x awful y",
+"yippeee"))
+.toBe("L1 stayPositive(bad) no negative words",
+"L3 stayPositive(awful) no negative words");
+}
+}