Spotless now checks to make sure that Gradle is modern enough.

plugin-gradle/CHANGES.md

@@ -3,6 +3,8 @@
 We adhere to the [keepachangelog](https://keepachangelog.com/en/1.0.0/) format (starting after version `3.27.0`).
 
 ## [Unreleased]
+### Fixed
+* We did not proactively check to ensure that the Gradle version was modern enough, now we do (fixes [#684](https://github.com/diffplug/spotless/pull/684)).
 
 ## [5.3.0] - 2020-08-29
 ### Added

plugin-gradle/src/main/java/com/diffplug/gradle/spotless/SpotlessPlugin.java

@@ -15,6 +15,7 @@
  */
 package com.diffplug.gradle.spotless;
 
+import org.gradle.api.GradleException;
 import org.gradle.api.Plugin;
 import org.gradle.api.Project;
 import org.gradle.api.plugins.BasePlugin;
@@ -27,6 +28,9 @@ public class SpotlessPlugin implements Plugin<Project> {
 
 	@Override
 	public void apply(Project project) {
+		if (SpotlessPluginRedirect.gradleIsTooOld(project)) {
+			throw new GradleException("Spotless requires Gradle " + MINIMUM_GRADLE + " or newer, this was " + project.getGradle().getGradleVersion());
+		}
 		// if -PspotlessModern=true, then use the modern stuff instead of the legacy stuff
 		if (project.hasProperty(SPOTLESS_MODERN)) {
 			project.getLogger().warn("'spotlessModern' has no effect as of Spotless 5.0, recommend removing it.");

plugin-gradle/src/main/java/com/diffplug/gradle/spotless/SpotlessPluginRedirect.java

@@ -15,16 +15,45 @@
  */
 package com.diffplug.gradle.spotless;
 
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
 import org.gradle.api.GradleException;
 import org.gradle.api.Plugin;
 import org.gradle.api.Project;
 
 import com.diffplug.common.base.StringPrinter;
 
 public class SpotlessPluginRedirect implements Plugin<Project> {
+	private static final Pattern BAD_SEMVER = Pattern.compile("(\\d+)\\.(\\d+)");
+
+	private static int badSemver(String input) {
+		Matcher matcher = BAD_SEMVER.matcher(input);
+		if (!matcher.find() || matcher.start() != 0) {
+			throw new IllegalArgumentException("Version must start with " + BAD_SEMVER.pattern());
+		}
+		String major = matcher.group(1);
+		String minor = matcher.group(2);
+		return badSemver(Integer.parseInt(major), Integer.parseInt(minor));
+	}
+
+	/** Ambiguous after 2147.483647.blah-blah */
+	private static int badSemver(int major, int minor) {
+		return major * 1_000_000 + minor;
+	}
+
+	static Boolean gradleIsTooOld;
+
+	static boolean gradleIsTooOld(Project project) {
+		if (gradleIsTooOld == null) {
+			gradleIsTooOld = badSemver(project.getGradle().getGradleVersion()) < badSemver(SpotlessPlugin.MINIMUM_GRADLE);
+		}
+		return gradleIsTooOld.booleanValue();
+	}
+
 	@Override
 	public void apply(Project project) {
-		throw new GradleException(StringPrinter.buildStringFromLines(
+		String errorMsg = StringPrinter.buildStringFromLines(
 				"We have moved from 'com.diffplug.gradle.spotless'",
 				"                to 'com.diffplug.spotless'",
 				"To migrate:",
@@ -42,6 +71,10 @@ public void apply(Project project) {
 				"to be useful, hope you do too.",
 				"",
 				"If you like the idea behind 'ratchetFrom', you should checkout spotless-changelog",
-				"https://github.com/diffplug/spotless-changelog"));
+				"https://github.com/diffplug/spotless-changelog");
+		if (gradleIsTooOld(project)) {
+			errorMsg = errorMsg.replace("To migrate:\n", "To migrate:\n- Upgrade gradle to " + SpotlessPlugin.MINIMUM_GRADLE + " or newer (you're on " + project.getGradle().getGradleVersion() + ")\n");
+		}
+		throw new GradleException(errorMsg);
 	}
 }

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

@@ -38,7 +38,7 @@
 
 public class GradleIntegrationHarness extends ResourceHarness {
 	public enum GradleVersionSupport {
-		MINIMUM(SpotlessPlugin.MINIMUM_GRADLE), SETTINGS_PLUGINS("6.0");
+		JRE_11("5.0"), MINIMUM(SpotlessPlugin.MINIMUM_GRADLE), SETTINGS_PLUGINS("6.0");
 
 		final String version;
 

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

@@ -24,7 +24,7 @@
 
 public class SpotlessPluginRedirectTest extends GradleIntegrationHarness {
 	@Test
-	public void test() throws IOException {
+	public void redirectPluginModernGradle() throws IOException {
 		setFile("build.gradle").toLines(
 				"plugins {",
 				"    id 'com.diffplug.gradle.spotless'",
@@ -34,6 +34,36 @@ public void test() throws IOException {
 						"> Failed to apply plugin [id 'com.diffplug.gradle.spotless']",
 						"   > We have moved from 'com.diffplug.gradle.spotless'",
 						"                     to 'com.diffplug.spotless'",
-						"     To migrate:"));
+						"     To migrate:",
+						"     - Test your build with: id 'com.diffplug.gradle.spotless' version '4.5.1'"));
+	}
+
+	@Test
+	public void redirectPluginOldGradle() throws IOException {
+		setFile("build.gradle").toLines(
+				"plugins {",
+				"    id 'com.diffplug.gradle.spotless'",
+				"}");
+		Assertions.assertThat(gradleRunner().withGradleVersion(GradleVersionSupport.JRE_11.version)
+				.buildAndFail().getOutput().replace("\r", ""))
+				.contains(StringPrinter.buildStringFromLines(
+						"> Failed to apply plugin [id 'com.diffplug.gradle.spotless']",
+						"   > We have moved from 'com.diffplug.gradle.spotless'",
+						"                     to 'com.diffplug.spotless'",
+						"     To migrate:",
+						"     - Upgrade gradle to 5.4 or newer (you're on 5.0)",
+						"     - Test your build with: id 'com.diffplug.gradle.spotless' version '4.5.1'"));
+	}
+
+	@Test
+	public void realPluginOldGradle() throws IOException {
+		setFile("build.gradle").toLines(
+				"plugins {",
+				"    id 'com.diffplug.spotless'",
+				"}");
+		Assertions.assertThat(gradleRunner().withGradleVersion(GradleVersionSupport.JRE_11.version)
+				.buildAndFail().getOutput().replace("\r", ""))
+				.contains(StringPrinter.buildStringFromLines(
+						"Spotless requires Gradle 5.4 or newer, this was 5.0"));
 	}
 }