Use MavenSelfie to assert linting error messages.

Author: nedtwigg

plugin-maven/src/main/java/com/diffplug/spotless/maven/SpotlessApplyMojo.java

@@ -97,7 +97,7 @@ protected void process(String name, Iterable<File> files, Formatter formatter, U
 							lint.addWarningMessageTo(message, stepName, true);
 						}
 					}
-					message.append("\n  Resolve these lints or suppress with `suppressLintsFor`");
+					message.append("\n  Resolve these lints or suppress with `<lintSuppressions>`");
 					throw new MojoExecutionException(message.toString());
 				}
 			} catch (IOException | RuntimeException e) {

plugin-maven/src/test/java/com/diffplug/spotless/maven/biome/BiomeMavenTest.java

@@ -19,6 +19,7 @@
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 import static org.owasp.encoder.Encode.forXml;
+import static selfie.MavenSelfie.expectSelfieErrorMsg;
 
 import java.io.File;
 
@@ -247,9 +248,11 @@ void failureWhenNotParseable() throws Exception {
 		setFile("biome_test.js").toResource("biome/js/fileBefore.js");
 		var result = mavenRunner().withArguments("spotless:apply").runHasError();
 		assertFile("biome_test.js").sameAsResource("biome/js/fileBefore.js");
-		assertThat(result.stdOutUtf8()).contains("Format with errors is disabled.");
-		assertThat(result.stdOutUtf8()).contains("Unable to format file");
-		assertThat(result.stdOutUtf8()).contains("Step 'biome' found problem in 'biome_test.js'");
+		expectSelfieErrorMsg(result).toBe("""
+				Failed to execute goal com.diffplug.spotless:spotless-maven-plugin:VERSION:apply (default-cli) on project spotless-maven-plugin-tests: There were 1 lint error(s), they must be fixed or suppressed.
+				biome_test.js:LINE_UNDEFINED biome(java.lang.RuntimeException) > arguments: [/Users/ntwigg/.m2/repository/com/diffplug/spotless/spotless-data/biome/biome-mac_os-arm64-1.2.0, format, --stdin-file-path, file.json] (...)
+				Resolve these lints or suppress with `<lintSuppressions>`
+				""");
 	}
 
 	/**

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

@@ -15,6 +15,8 @@
  */
 package com.diffplug.spotless.maven.java;
 
+import static selfie.MavenSelfie.expectSelfieErrorMsg;
+
 import org.junit.jupiter.api.Test;
 
 import com.diffplug.spotless.maven.MavenIntegrationHarness;
@@ -27,7 +29,20 @@ void testRemoveWildcardImports() throws Exception {
 
 		String path = "src/main/java/test.java";
 		setFile(path).toResource("java/removewildcardimports/JavaCodeWildcardsUnformatted.test");
-		mavenRunner().withArguments("spotless:apply").runNoError();
+		expectSelfieErrorMsg(mavenRunner().withArguments("spotless:apply").runHasError()).toBe("""
+				Failed to execute goal com.diffplug.spotless:spotless-maven-plugin:VERSION:apply (default-cli) on project spotless-maven-plugin-tests: There were 5 lint error(s), they must be fixed or suppressed.
+				src/main/java/test.java:L1 removeWildcardImports(import java.util.*;
+				) 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
+				src/main/java/test.java:L2 removeWildcardImports(import static java.util.Collections.*;
+				) 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
+				src/main/java/test.java:L5 removeWildcardImports(import io.quarkus.maven.dependency.*;
+				) 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
+				src/main/java/test.java:L6 removeWildcardImports(import static io.quarkus.vertx.web.Route.HttpMethod.*;
+				) 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
+				src/main/java/test.java:L7 removeWildcardImports(import static org.springframework.web.reactive.function.BodyInserters.*;
+				) 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
+				Resolve these lints or suppress with `<lintSuppressions>`
+				""");
 		assertFile(path).sameAsResource("java/removewildcardimports/JavaCodeWildcardsFormatted.test");
 	}
 }

plugin-maven/src/test/java/selfie/MavenSelfie.java

@@ -0,0 +1,40 @@
+/*
+ * 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 selfie;
+
+import java.util.stream.Collectors;
+
+import com.diffplug.selfie.Selfie;
+import com.diffplug.selfie.StringSelfie;
+import com.diffplug.spotless.ProcessRunner;
+
+public class MavenSelfie {
+	private static final String ERROR_PREFIX = "[ERROR] ";
+
+	public static StringSelfie expectSelfieErrorMsg(ProcessRunner.Result result) {
+		String concatenatedError = result.stdOutUtf8().lines()
+				.map(line -> line.startsWith(ERROR_PREFIX) ? line.substring(ERROR_PREFIX.length()) : null)
+				.filter(line -> line != null)
+				.collect(Collectors.joining("\n"));
+
+		String sanitizedVersion = concatenatedError.replaceFirst("com\\.diffplug\\.spotless:spotless-maven-plugin:([^:]+):", "com.diffplug.spotless:spotless-maven-plugin:VERSION:");
+
+		int help1 = sanitizedVersion.indexOf("-> [Help 1]");
+		String trimTrailingString = sanitizedVersion.substring(0, help1);
+
+		return Selfie.expectSelfie(trimTrailingString);
+	}
+}