Allow setting the local P2 cache dir in the Spotless Gradle plugin (#2944)

Author: nedtwigg

CHANGES.md

@@ -11,6 +11,7 @@ We adhere to the [keepachangelog](https://keepachangelog.com/en/1.0.0/) format (
 
 ## [Unreleased]
 ### Fixed
+- `P2Provisioner` now passes cache directory overrides directly to Solstice. ([#2944](https://github.com/diffplug/spotless/pull/2944))
 - `forbidWildcardImports` and `forbidModuleImports` now detect imports that have leading whitespace (indentation/tabs). ([#2939](https://github.com/diffplug/spotless/pull/2939))
 - `versionCatalog` step no longer splits long inline tables across multiple lines — Gradle's TOML 1.0 parser cannot read multi-line inline tables. The `maxLineLength` option has been removed. ([#2948](https://github.com/diffplug/spotless/issues/2948))
 ### Changes

lib-extra/src/main/java/com/diffplug/spotless/extra/P2Provisioner.java

@@ -42,7 +42,7 @@ public interface P2Provisioner {
 	 *
 	 * @param modelWrapper wrapper around P2Model describing repositories and plugins to install
 	 * @param mavenProvisioner provisioner for Maven dependencies (some P2 bundles are on Maven Central)
-	 * @param cacheDirectory optional cache directory override
+	 * @param cacheDirectory optional cache directory override passed directly to Solstice
 	 * @return ordered list of JAR files forming the classpath
 	 */
 	List<File> provisionP2Dependencies(
@@ -55,7 +55,7 @@ static P2Provisioner createDefault() {
 		return (modelWrapper, mavenProvisioner, cacheDirectory) -> {
 			try {
 				if (cacheDirectory != null) {
-					CacheLocations.override_p2data = cacheDirectory.toPath().resolve("dev/equo/p2-data").toFile();
+					CacheLocations.override_p2data = cacheDirectory;
 				}
 				P2Model model = modelWrapper.unwrap();
 				P2QueryResult query = model.query(P2ClientCache.PREFER_OFFLINE, P2QueryCache.ALLOW);

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2025 DiffPlug
+ * Copyright 2016-2026 DiffPlug
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.

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]
+### Added
+- Add `cacheDirectory(...)` to `eclipse()`, `eclipseCdt()`, and `greclipse()`; the default P2 cache is `$GRADLE_USER_HOME/caches/p2-data`. ([#2944](https://github.com/diffplug/spotless/pull/2944))
 ### Fixed
 - `forbidWildcardImports` and `forbidModuleImports` now detect imports that have leading whitespace (indentation/tabs). ([#2939](https://github.com/diffplug/spotless/pull/2939))
 - `versionCatalog()` no longer splits long inline tables across multiple lines — Gradle's TOML 1.0 parser cannot read multi-line inline tables. The `maxLineLength` option has been removed. ([#2948](https://github.com/diffplug/spotless/issues/2948))

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

@@ -92,5 +92,19 @@ public GrEclipseConfig withP2Mirrors(Map<String, String> mirrors) {
 			extension.replaceStep(builder.build());
 			return this;
 		}
+
+		/**
+		 * Overrides the directory used to cache the P2 dependencies fetched by
+		 * Equo/Solstice. Defaults to {@code $GRADLE_USER_HOME/caches/p2-data}.
+		 *
+		 * <p>Useful when the default location is not writable, or when you want to
+		 * place the cache elsewhere.
+		 */
+		public GrEclipseConfig cacheDirectory(Object cacheDirectory) {
+			Objects.requireNonNull(cacheDirectory);
+			builder.setCacheDirectory(extension.getProject().file(cacheDirectory));
+			extension.replaceStep(builder.build());
+			return this;
+		}
 	}
 }

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

@@ -19,6 +19,7 @@
 
 import java.util.List;
 import java.util.Map;
+import java.util.Objects;
 
 import javax.inject.Inject;
 
@@ -81,6 +82,20 @@ public EclipseConfig withP2Mirrors(Map<String, String> mirrors) {
 			replaceStep(builder.build());
 			return this;
 		}
+
+		/**
+		 * Overrides the directory used to cache the P2 dependencies fetched by
+		 * Equo/Solstice. Defaults to {@code $GRADLE_USER_HOME/caches/p2-data}.
+		 *
+		 * <p>Useful when the default location is not writable, or when you want to
+		 * place the cache elsewhere.
+		 */
+		public EclipseConfig cacheDirectory(Object cacheDirectory) {
+			Objects.requireNonNull(cacheDirectory);
+			builder.setCacheDirectory(getProject().file(cacheDirectory));
+			replaceStep(builder.build());
+			return this;
+		}
 	}
 
 	@Override

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

@@ -61,7 +61,7 @@ public DedupingProvisioner dedupingProvisioner(Project project) {
 
 		public DedupingP2Provisioner dedupingP2Provisioner(Project project) {
 			return switch (this) {
-				case ROOT_PROJECT, ROOT_BUILDSCRIPT -> new DedupingP2Provisioner(P2Provisioner.createDefault());
+				case ROOT_PROJECT, ROOT_BUILDSCRIPT -> new DedupingP2Provisioner(P2Provisioner.createDefault(), defaultP2CacheDirectory(project));
 				default -> throw Unhandled.enumException(this);
 			};
 		}
@@ -156,6 +156,10 @@ private static Provisioner forConfigurationContainer(Project project, Configurat
 
 	private static final Logger LOGGER = LoggerFactory.getLogger(GradleProvisioner.class);
 
+	static File defaultP2CacheDirectory(Project project) {
+		return new File(project.getGradle().getGradleUserHomeDir(), "caches/p2-data");
+	}
+
 	/** Models a request to the provisioner. */
 	private static class Request {
 		final boolean withTransitives;
@@ -199,9 +203,15 @@ public String toString() {
 	static class DedupingP2Provisioner implements P2Provisioner {
 		private final Map<P2Request, List<File>> cache = new HashMap<>();
 		private final P2Provisioner p2Provisioner;
+		@Nullable private final File defaultCacheDirectory;
 
 		public DedupingP2Provisioner(P2Provisioner p2Provisioner) {
+			this(p2Provisioner, null);
+		}
+
+		public DedupingP2Provisioner(P2Provisioner p2Provisioner, @Nullable File defaultCacheDirectory) {
 			this.p2Provisioner = p2Provisioner;
+			this.defaultCacheDirectory = defaultCacheDirectory;
 		}
 
 		@Override
@@ -210,33 +220,35 @@ public synchronized List<File> provisionP2Dependencies(
 				Provisioner mavenProvisioner,
 				@Nullable File cacheDirectory) throws IOException {
 
+			File effectiveCacheDirectory = effectiveCacheDirectory(cacheDirectory);
 			P2Request req = new P2Request(
 					List.copyOf(modelWrapper.getP2Repos()),
 					List.copyOf(modelWrapper.getInstallList()),
 					Set.copyOf(modelWrapper.getFilterNames()),
 					List.copyOf(modelWrapper.getPureMaven()),
 					modelWrapper.isUseMavenCentral(),
-					cacheDirectory);
+					effectiveCacheDirectory);
 
 			List<File> result = cache.get(req);
 			if (result != null) {
 				return result;
 			}
 
-			result = p2Provisioner.provisionP2Dependencies(modelWrapper, mavenProvisioner, cacheDirectory);
+			result = p2Provisioner.provisionP2Dependencies(modelWrapper, mavenProvisioner, effectiveCacheDirectory);
 			cache.put(req, List.copyOf(result));
 			return result;
 		}
 
 		/** A child P2Provisioner which retrieves cached elements only. */
 		final P2Provisioner cachedOnly = (modelWrapper, mavenProvisioner, cacheDirectory) -> {
+			File effectiveCacheDirectory = effectiveCacheDirectory(cacheDirectory);
 			P2Request req = new P2Request(
 					List.copyOf(modelWrapper.getP2Repos()),
 					List.copyOf(modelWrapper.getInstallList()),
 					Set.copyOf(modelWrapper.getFilterNames()),
 					List.copyOf(modelWrapper.getPureMaven()),
 					modelWrapper.isUseMavenCentral(),
-					cacheDirectory);
+					effectiveCacheDirectory);
 			List<File> result;
 			synchronized (cache) {
 				result = cache.get(req);
@@ -247,6 +259,10 @@ public synchronized List<File> provisionP2Dependencies(
 			throw new GradleException("P2 dependencies not predeclared. Add Eclipse formatter configuration to the `spotlessPredeclare` block in the root project.");
 		};
 
+		@Nullable private File effectiveCacheDirectory(@Nullable File cacheDirectory) {
+			return cacheDirectory != null ? cacheDirectory : defaultCacheDirectory;
+		}
+
 		/**
 		 * Cache key capturing all P2Model state that affects query results.
 		 * Based on P2Model fields from equo-ide:

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

@@ -385,6 +385,20 @@ public EclipseConfig withP2Mirrors(Map<String, String> mirrors) {
 			return this;
 		}
 
+		/**
+		 * Overrides the directory used to cache the P2 dependencies fetched by
+		 * Equo/Solstice. Defaults to {@code $GRADLE_USER_HOME/caches/p2-data}.
+		 *
+		 * <p>Useful when the default location is not writable, or when you want to
+		 * place the cache elsewhere.
+		 */
+		public EclipseConfig cacheDirectory(Object cacheDirectory) {
+			Objects.requireNonNull(cacheDirectory);
+			builder.setCacheDirectory(getProject().file(cacheDirectory));
+			replaceStep(builder.build());
+			return this;
+		}
+
 	}
 
 	/** Removes newlines between type annotations and types. */

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

@@ -85,7 +85,7 @@ P2Provisioner p2ProvisionerFor(SpotlessExtension spotless) {
 				return predeclaredP2Provisioner.cachedOnly;
 			} else {
 				return p2Provisioner.computeIfAbsent(spotless.project.getPath(),
-						unused -> new GradleProvisioner.DedupingP2Provisioner(P2Provisioner.createDefault()));
+						unused -> new GradleProvisioner.DedupingP2Provisioner(P2Provisioner.createDefault(), GradleProvisioner.defaultP2CacheDirectory(spotless.project)));
 			}
 		}
 	}

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

@@ -23,6 +23,7 @@
 import java.util.List;
 import java.util.Set;
 import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.atomic.AtomicReference;
 import java.util.function.Function;
 import java.util.stream.Stream;
 
@@ -262,6 +263,72 @@ void cachedOnlyCacheHitReturnsResult() throws IOException {
 			assertThat(result).isNotEmpty();
 		}
 
+		@Test
+		void defaultCacheDirectoryUsedWhenNoOverride() throws IOException {
+			AtomicReference<File> capturedCacheDirectory = new AtomicReference<>();
+			File defaultCacheDirectory = new File("gradle-home/caches/p2-data");
+			P2Provisioner underlying = (modelWrapper, mavenProvisioner, cacheDirectory) -> {
+				capturedCacheDirectory.set(cacheDirectory);
+				return List.of(new File("/mock/p2.jar"));
+			};
+			GradleProvisioner.DedupingP2Provisioner deduping = new GradleProvisioner.DedupingP2Provisioner(underlying, defaultCacheDirectory);
+
+			P2ModelWrapper model = createMockModel(
+					List.of("https://download.eclipse.org/eclipse/updates/4.26/"),
+					List.of("org.eclipse.jdt.core"),
+					Set.of(),
+					List.of(),
+					true,
+					null);
+
+			deduping.provisionP2Dependencies(model, mockProvisioner(), null);
+
+			assertThat(capturedCacheDirectory.get()).isEqualTo(defaultCacheDirectory);
+		}
+
+		@Test
+		void explicitCacheDirectoryOverridesDefault() throws IOException {
+			AtomicReference<File> capturedCacheDirectory = new AtomicReference<>();
+			File defaultCacheDirectory = new File("gradle-home/caches/p2-data");
+			File explicitCacheDirectory = new File("project/.spotless-p2");
+			P2Provisioner underlying = (modelWrapper, mavenProvisioner, cacheDirectory) -> {
+				capturedCacheDirectory.set(cacheDirectory);
+				return List.of(new File("/mock/p2.jar"));
+			};
+			GradleProvisioner.DedupingP2Provisioner deduping = new GradleProvisioner.DedupingP2Provisioner(underlying, defaultCacheDirectory);
+
+			P2ModelWrapper model = createMockModel(
+					List.of("https://download.eclipse.org/eclipse/updates/4.26/"),
+					List.of("org.eclipse.jdt.core"),
+					Set.of(),
+					List.of(),
+					true,
+					null);
+
+			deduping.provisionP2Dependencies(model, mockProvisioner(), explicitCacheDirectory);
+
+			assertThat(capturedCacheDirectory.get()).isEqualTo(explicitCacheDirectory);
+		}
+
+		@Test
+		void cachedOnlyUsesDefaultCacheDirectoryForLookup() throws IOException {
+			File defaultCacheDirectory = new File("gradle-home/caches/p2-data");
+			P2Provisioner underlying = mockP2Provisioner(new AtomicInteger(0));
+			GradleProvisioner.DedupingP2Provisioner deduping = new GradleProvisioner.DedupingP2Provisioner(underlying, defaultCacheDirectory);
+
+			P2ModelWrapper model = createMockModel(
+					List.of("https://download.eclipse.org/eclipse/updates/4.26/"),
+					List.of("org.eclipse.jdt.core"),
+					Set.of(),
+					List.of(),
+					true,
+					null);
+
+			deduping.provisionP2Dependencies(model, mockProvisioner(), null);
+
+			assertThat(deduping.cachedOnly.provisionP2Dependencies(model, mockProvisioner(), null)).isNotEmpty();
+		}
+
 		@Test
 		void cachedOnlyCacheMissThrowsException() {
 			P2Provisioner underlying = mockP2Provisioner(new AtomicInteger(0));