Support depending on type safe projects.

src/main/java/net/fabricmc/loom/api/ModSettings.java

@@ -34,6 +34,7 @@
 import org.gradle.api.Project;
 import org.gradle.api.artifacts.Configuration;
 import org.gradle.api.artifacts.Dependency;
+import org.gradle.api.artifacts.ProjectDependency;
 import org.gradle.api.file.ConfigurableFileCollection;
 import org.gradle.api.provider.ListProperty;
 import org.gradle.api.tasks.SourceSet;
@@ -130,6 +131,18 @@ public void sourceSet(String sourceSetName, String projectPath) {
 		getExternalGroups().add(new ExternalClasspathGroup(projectPath, sourceSetName));
 	}
 
+	/**
+	 * Add {@link SourceSet}'s output directories from the supplied project to be grouped with the named mod.
+	 *
+	 * <p>If the other project is not a Loom project you must apply the `net.fabricmc.fabric-loom-companion` plugin.
+	 *
+	 * @param sourceSetName the name of the source set
+	 * @param projectDependency the {@link ProjectDependency} the source set belongs to
+	 */
+	public void sourceSet(String sourceSetName, ProjectDependency projectDependency) {
+		sourceSet(sourceSetName, projectDependency.getPath());
+	}
+
 	/**
 	 * Add a number of {@link Dependency} to the mod's classpath group. Should be used to include all dependencies that are shaded into your mod.
 	 *

src/test/resources/projects/multiproject/build.gradle

@@ -44,14 +44,14 @@ allprojects {
 loom {
 	mods {
 		core {
-			sourceSet("main", ":core")
+			sourceSet("main", projects.core)
 		}
 		example {
-			sourceSet("main", ":example")
+			sourceSet("main", projects.example)
 		}
 		root {
 			sourceSet sourceSets.main
-			sourceSet("main", ":javalib")
+			sourceSet("main", projects.javalib)
 		}
 	}
 }

src/test/resources/projects/multiproject/settings.gradle

@@ -1,5 +1,7 @@
 rootProject.name = "fabric-example-mod"
 
+enableFeaturePreview 'TYPESAFE_PROJECT_ACCESSORS'
+
 include 'core'
 include 'example'
 include 'javalib'