removeWildcardImports: throw new AssertionError instead of removing

Author: Vincent Potucek

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.
@@ -35,6 +35,15 @@ public static FormatterStep create(String name, String regex, String replacement
 				State::toFormatter);
 	}
 
+	public static FormatterStep find(String name, String regex, String error) {
+		Objects.requireNonNull(name, "name");
+		Objects.requireNonNull(regex, "regex");
+		Objects.requireNonNull(error, "error");
+		return FormatterStep.createLazy(name,
+				() -> new State(Pattern.compile(regex, Pattern.UNIX_LINES | Pattern.MULTILINE), error),
+				State::toFormatFinder);
+	}
+
 	private static final class State implements Serializable {
 		private static final long serialVersionUID = 1L;
 
@@ -49,5 +58,14 @@ private static final class State implements Serializable {
 		FormatterFunc toFormatter() {
 			return raw -> regex.matcher(raw).replaceAll(replacement);
 		}
+
+		FormatterFunc toFormatFinder() {
+			return raw -> {
+				if (regex.matcher(raw).find()) {
+					throw new IllegalArgumentException(replacement);
+				}
+				return raw;
+			};
+		}
 	}
 }

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

@@ -24,9 +24,9 @@ private RemoveWildcardImportsStep() {}
 
 	public static FormatterStep create() {
 		// Matches lines like 'import foo.*;' or 'import static foo.*;'.
-		return ReplaceRegexStep.create(
+		return ReplaceRegexStep.find(
 				"removeWildcardImports",
 				"(?m)^import\\s+(?:static\\s+)?[^;\\n]*\\*;\\R?",
-				"");
+				"Do not use wildcard imports. 'spotlessApply' cannot resolve this issue.");
 	}
 }

plugin-maven/src/test/java/com/diffplug/spotless/maven/java/RemoveWildcardImportsStepTest.java

@@ -15,6 +15,8 @@
  */
 package com.diffplug.spotless.maven.java;
 
+import static org.assertj.core.api.Assertions.assertThat;
+
 import org.junit.jupiter.api.Test;
 
 import com.diffplug.spotless.maven.MavenIntegrationHarness;
@@ -27,7 +29,17 @@ void testRemoveWildcardImports() throws Exception {
 
 		String path = "src/main/java/test.java";
 		setFile(path).toResource("java/removewildcardimports/JavaCodeWildcardsUnformatted.test");
-		mavenRunner().withArguments("spotless:apply").runNoError();
 		assertFile(path).sameAsResource("java/removewildcardimports/JavaCodeWildcardsFormatted.test");
+		assertThat(mavenRunner().withArguments("spotless:apply").runHasError().stdOutUtf8()).contains("Do not use wildcard imports. 'spotlessApply' cannot resolve this issue.");
+	}
+
+	@Test
+	void testRemoveWildcardImportsNoError() throws Exception {
+		writePomWithJavaSteps("<removeWildcardImports/>");
+
+		String path = "src/main/java/test.java";
+		setFile(path).toResource("java/removewildcardimports/JavaCodeEmptyWildcardsUnformatted.test");
+		assertFile(path).sameAsResource("java/removewildcardimports/JavaCodeEmptyWildcardsFormatted.test");
+		mavenRunner().withArguments("spotless:apply").runNoError();
 	}
 }

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

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

testlib/src/main/resources/java/removewildcardimports/JavaCodeEmptyWildcardsUnformatted.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 {}