Introduce C library for Pkl (#1238)

This uses native-image to generate a C library for Pkl.
This generated library from native-image is wrapped with our own library,
in `pkl.h`.

This produces a static and a dynamic library for each os/arch variant
that Pkl currently supports.

Co-authored-by: Kushal Pisavadia <kushal.p@apple.com>
Co-authored-by: Jen Basch <jbasch94@gmail.com>
Co-authored-by: Islon Scherer <i_desouzascherer@apple.com>

pkl-commons-test/pkl-commons-test.gradle.kts

@@ -26,7 +26,10 @@ dependencies {
   api(libs.junitApi)
   api(libs.junitEngine)
   api(libs.junitParams)
+  api(libs.wiremock)
   api(projects.pklCommons) // for convenience
+  implementation(projects.pklCore)
+  implementation(projects.pklServer)
   implementation(libs.assertj)
   implementation(libs.msgpack)
 }

pkl-commons-test/src/main/kotlin/org/pkl/commons/test/MessagePackDebugRenderer.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright © 2025 Apple Inc. and the Pkl project authors. All rights reserved.
+ * Copyright © 2025-2026 Apple Inc. and the Pkl project authors. All rights reserved.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -179,3 +179,6 @@ class MessagePackDebugRenderer(bytes: ByteArray) {
     currIndent.setLength(currIndent.length - indent.length)
   }
 }
+
+val ByteArray.debugRendering: String
+  get() = MessagePackDebugRenderer(this).output

pkl-commons-test/src/main/kotlin/org/pkl/commons/test/server/AbstractHttpServerTest.kt

@@ -0,0 +1,74 @@
+/*
+ * Copyright © 2026 Apple Inc. and the Pkl project authors. All rights reserved.
+ *
+ * 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
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * 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.pkl.commons.test.server
+
+import com.github.tomakehurst.wiremock.client.WireMock.equalTo
+import com.github.tomakehurst.wiremock.client.WireMock.get
+import com.github.tomakehurst.wiremock.client.WireMock.getRequestedFor
+import com.github.tomakehurst.wiremock.client.WireMock.ok
+import com.github.tomakehurst.wiremock.client.WireMock.stubFor
+import com.github.tomakehurst.wiremock.client.WireMock.urlEqualTo
+import com.github.tomakehurst.wiremock.client.WireMock.verify
+import com.github.tomakehurst.wiremock.junit5.WireMockRuntimeInfo
+import com.github.tomakehurst.wiremock.junit5.WireMockTest
+import java.net.URI
+import org.assertj.core.api.Assertions.assertThat
+import org.junit.jupiter.api.Nested
+import org.junit.jupiter.api.Test
+import org.pkl.server.EvaluateRequest
+import org.pkl.server.EvaluateResponse
+import org.pkl.server.Http
+
+/**
+ * Extends [AbstractServerTest] with HTTP tests backed by a WireMock server.
+ *
+ * Some transports can't run these at all (e.g. `LibPklServerTest` - a real outbound HTTP request
+ * causes `doClose` to hang for about a minute, suspected to be an unclosed `HttpClient`'s default
+ * thread pool blocking native isolate teardown) - those extend [AbstractServerTest] directly
+ * instead of this class.
+ */
+abstract class AbstractHttpServerTest : AbstractServerTest() {
+  @Nested
+  @WireMockTest
+  inner class HttpTests {
+    @Test
+    fun `http headers`(wwRuntimeInfo: WireMockRuntimeInfo) {
+      stubFor(get(urlEqualTo("/foo.pkl")).willReturn(ok("foo = 1")))
+      val evaluatorId =
+        client.sendCreateEvaluatorRequest(
+          http =
+            Http(
+              caCertificates = null,
+              proxy = null,
+              rewrites = null,
+              headers = mapOf("**" to mapOf("X-Foo" to listOf("Foo"))),
+            )
+        )
+      client.send(
+        EvaluateRequest(
+          1,
+          evaluatorId,
+          URI("repl:text"),
+          "res = import(\"${wwRuntimeInfo.httpBaseUrl}/foo.pkl\")",
+          "output.text",
+        )
+      )
+      val response = client.receive<EvaluateResponse>()
+      assertThat(response.error).isNull()
+      verify(getRequestedFor(urlEqualTo("/foo.pkl")).withHeader("X-Foo", equalTo("Foo")))
+    }
+  }
+}

pkl-commons-test/src/main/kotlin/org/pkl/commons/test/server/TestTransport.kt

@@ -0,0 +1,52 @@
+/*
+ * Copyright © 2024-2026 Apple Inc. and the Pkl project authors. All rights reserved.
+ *
+ * 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
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * 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.pkl.commons.test.server
+
+import java.util.concurrent.ArrayBlockingQueue
+import java.util.concurrent.BlockingQueue
+import org.assertj.core.api.Assertions.*
+import org.pkl.core.messaging.Message
+import org.pkl.core.messaging.MessageTransport
+
+class TestTransport(private val delegate: MessageTransport) : AutoCloseable {
+  val incomingMessages: BlockingQueue<Message> = ArrayBlockingQueue(10)
+
+  fun start() {
+    delegate.start({ incomingMessages.put(it) }, { incomingMessages.put(it) })
+  }
+
+  override fun close() {
+    delegate.close()
+  }
+
+  fun send(message: Message.Client.OneWay) {
+    delegate.send(message)
+  }
+
+  fun send(message: Message.Client.Request) {
+    delegate.send(message) { incomingMessages.put(it) }
+  }
+
+  fun send(message: Message.Client.Response) {
+    delegate.send(message)
+  }
+
+  inline fun <reified T : Message> receive(): T {
+    val message = incomingMessages.take()
+    assertThat(message).isInstanceOf(T::class.java)
+    return message as T
+  }
+}