Don't override proto target when protoLibrary is true

wire-gradle-plugin/src/main/kotlin/com/squareup/wire/gradle/WirePlugin.kt

@@ -82,8 +82,16 @@ class WirePlugin : Plugin<Project> {
 
     project.afterEvaluate {
       if (extension.protoLibrary) {
-        extension.proto { protoOutput ->
-          protoOutput.out = File(project.libraryProtoOutputPath()).path
+        val existingProtoOutput = extension.outputs.filterIsInstance<ProtoOutput>().singleOrNull()
+        if (existingProtoOutput != null) {
+          // There exists a `proto {}` target already, we only set the output path if need be.
+          if (existingProtoOutput.out == null) {
+            existingProtoOutput.out = File(project.libraryProtoOutputPath()).path
+          }
+        } else {
+          extension.proto { protoOutput ->
+            protoOutput.out = File(project.libraryProtoOutputPath()).path
+          }
         }
       }
 

wire-gradle-plugin/src/test/kotlin/com/squareup/wire/gradle/WirePluginTest.kt

@@ -692,6 +692,18 @@ class WirePluginTest {
     }
   }
 
+  @Test
+  fun protoLibraryWithProtoBlock() {
+    val fixtureRoot = File("src/test/projects/proto-library-with-proto-block")
+
+    fixtureGradleRunner(fixtureRoot, "clean", "jar").build()
+
+    ZipFile(File(fixtureRoot, "build/libs/proto-library-with-proto-block.jar")).use {
+      assertThat(it.getEntry("squareup/geology/period.proto")).isNotNull()
+      assertThat(it.getEntry("squareup/dinosaurs/dinosaur.proto")).isNotNull()
+    }
+  }
+
   @Test
   fun sourceDirExclude() {
     val fixtureRoot = File("src/test/projects/sourcedir-exclude")

wire-gradle-plugin/src/test/projects/proto-library-with-proto-block/build.gradle

@@ -0,0 +1,23 @@
+buildscript {
+  dependencies {
+    classpath "com.squareup.wire:wire-gradle-plugin:$wireVersion"
+    classpath libs.pluginz.kotlin
+  }
+
+  repositories {
+    maven {
+      url new File(rootDir, "../../../../../build/localMaven").toURI().toString()
+    }
+    mavenCentral()
+    google()
+  }
+}
+
+apply plugin: 'kotlin'
+apply plugin: 'com.squareup.wire'
+
+wire {
+  protoLibrary = true
+
+  proto {}
+}

wire-gradle-plugin/src/test/projects/proto-library-with-proto-block/settings.gradle

@@ -0,0 +1,9 @@
+include ':'
+
+dependencyResolutionManagement {
+  versionCatalogs {
+    libs {
+      from(files('../../../../../gradle/libs.versions.toml'))
+    }
+  }
+}

wire-gradle-plugin/src/test/projects/proto-library-with-proto-block/src/main/proto/squareup/dinosaurs/dinosaur.proto

@@ -0,0 +1,19 @@
+syntax = "proto2";
+
+package squareup.dinosaurs;
+
+option java_package = "com.squareup.dinosaurs";
+
+import "squareup/geology/period.proto";
+
+message Dinosaur {
+  /** Common name of this dinosaur, like "Stegosaurus". */
+  optional string name = 1;
+
+  /** URLs with images of this dinosaur. */
+  repeated string picture_urls = 2;
+
+  optional double length_meters = 3;
+  optional double mass_kilograms = 4;
+  optional squareup.geology.Period period = 5;
+}

wire-gradle-plugin/src/test/projects/proto-library-with-proto-block/src/main/proto/squareup/geology/period.proto

@@ -0,0 +1,16 @@
+syntax = "proto2";
+
+package squareup.geology;
+
+option java_package = "com.squareup.geology";
+
+enum Period {
+  /** 145.5 million years ago — 66.0 million years ago. */
+  CRETACEOUS = 1;
+
+  /** 201.3 million years ago — 145.0 million years ago. */
+  JURASSIC = 2;
+
+  /** 252.17 million years ago — 201.3 million years ago. */
+  TRIASSIC = 3;
+}