RewriteTest: framework-agnostic ExecutionContext customizer registry

Adds `RewriteTest.defaultExecutionContextCustomizers`, a `Map<Class<?>, Consumer<ExecutionContext>>`
applied to the context built by `defaultExecutionContext`. Test framework integrations
(JUnit, TestNG, Spock, …) can register a customizer keyed by their own class without
`rewrite-test` taking a dependency on any framework; `putIfAbsent` makes registration
naturally idempotent.

First consumer: a JUnit Jupiter `BeforeAllCallback` in rewrite-gradle's test sources,
auto-detected via service loader, that loads `~/.m2/settings.xml` into the ExecutionContext.
Recipes resolving Maven artifacts during rewrite-gradle tests then honor any configured
mirror, sidestepping Maven Central rate limits (HTTP 404 + Retry-After) under parallel load.
Gradle does not normally read the user's Maven settings, so this opt-in lives entirely in
test sources of openrewrite/rewrite — not in any published API surface.

Author: jkschneider

rewrite-gradle/src/test/java/org/openrewrite/gradle/MavenSettingsAutoLoadingExtension.java

@@ -0,0 +1,55 @@
+/*
+ * Copyright 2026 the original author or authors.
+ * <p>
+ * 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
+ * <p>
+ * https://www.apache.org/licenses/LICENSE-2.0
+ * <p>
+ * 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 org.openrewrite.gradle;
+
+import org.junit.jupiter.api.extension.BeforeAllCallback;
+import org.junit.jupiter.api.extension.ExtensionContext;
+import org.openrewrite.ExecutionContext;
+import org.openrewrite.maven.MavenExecutionContextView;
+import org.openrewrite.maven.MavenSettings;
+import org.openrewrite.test.RewriteTest;
+
+import static org.openrewrite.maven.tree.MavenRepository.MAVEN_LOCAL_DEFAULT;
+
+/**
+ * Loads {@code ~/.m2/settings.xml} (and {@code $M2_HOME/conf/settings.xml}) into the
+ * default {@link ExecutionContext} for every {@link RewriteTest} in this module, so a
+ * configured Maven mirror or repository is honored by recipes that resolve artifacts.
+ * Auto-registered via {@code META-INF/services/org.junit.jupiter.api.extension.Extension};
+ * Gradle does not normally read the user's Maven settings, so this is opt-in at the
+ * module test classpath level.
+ */
+public class MavenSettingsAutoLoadingExtension implements BeforeAllCallback {
+
+    @Override
+    public void beforeAll(ExtensionContext context) {
+        RewriteTest.defaultExecutionContextCustomizers.putIfAbsent(
+                MavenSettingsAutoLoadingExtension.class,
+                MavenSettingsAutoLoadingExtension::loadMavenSettings);
+    }
+
+    private static void loadMavenSettings(ExecutionContext ctx) {
+        MavenExecutionContextView mctx = MavenExecutionContextView.view(ctx);
+        boolean nothingConfigured = mctx.getSettings() == null &&
+                                    mctx.getLocalRepository().equals(MAVEN_LOCAL_DEFAULT) &&
+                                    mctx.getRepositories().isEmpty() &&
+                                    mctx.getActiveProfiles().isEmpty() &&
+                                    mctx.getMirrors().isEmpty();
+        if (nothingConfigured) {
+            mctx.setMavenSettings(MavenSettings.readMavenSettingsFromDisk(mctx));
+        }
+    }
+}

rewrite-gradle/src/test/resources/META-INF/services/org.junit.jupiter.api.extension.Extension

@@ -0,0 +1 @@
+org.openrewrite.gradle.MavenSettingsAutoLoadingExtension

rewrite-gradle/src/test/resources/junit-platform.properties

@@ -0,0 +1 @@
+junit.jupiter.extensions.autodetection.enabled=true

rewrite-test/src/main/java/org/openrewrite/test/RewriteTest.java

@@ -35,6 +35,7 @@
 import java.nio.charset.StandardCharsets;
 import java.nio.file.Path;
 import java.util.*;
+import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.CopyOnWriteArrayList;
 import java.util.function.Consumer;
 import java.util.function.Function;
@@ -51,6 +52,18 @@
 
 @SuppressWarnings("unused")
 public interface RewriteTest extends SourceSpecs {
+    /**
+     * Registry of customizers applied to the {@link ExecutionContext} produced by
+     * {@link #defaultExecutionContext(SourceSpec[])}. Test framework integrations
+     * (e.g. a JUnit Jupiter {@code BeforeAllCallback}) can register a customizer
+     * once at startup without {@code rewrite-test} taking a dependency on the
+     * framework.
+     * <p>
+     * The map is keyed by the integration's class so {@code putIfAbsent(MyExt.class, MyExt::load)}
+     * is naturally idempotent — callers do not need their own one-shot guard.
+     */
+    Map<Class<?>, Consumer<ExecutionContext>> defaultExecutionContextCustomizers = new ConcurrentHashMap<>();
+
     static AdHocRecipe toRecipe(Supplier<TreeVisitor<?, ExecutionContext>> visitor) {
         return new AdHocRecipe(null, null, null, visitor, null, null);
     }
@@ -696,6 +709,9 @@ default ExecutionContext defaultExecutionContext(SourceSpec<?>[] sourceSpecs) {
             }
             fail("Failed to parse sources or run recipe", t);
         });
+        for (Consumer<ExecutionContext> customizer : defaultExecutionContextCustomizers.values()) {
+            customizer.accept(ctx);
+        }
         return ParsingExecutionContextView.view(ctx).setCharset(StandardCharsets.UTF_8);
     }