[SPARK-57081][TESTS] Fix percent-encoding issue in SparkTestUtils classpath handling

common/utils/src/main/scala/org/apache/spark/util/SparkTestUtils.scala

@@ -53,8 +53,8 @@ private[spark] trait SparkTestUtils {
       Seq(
         "-classpath",
         classpathUrls
-          .map {
-            _.getFile
+          .map { u =>
+            new File(u.toURI).getPath
           }
           .mkString(File.pathSeparator))
     } else {
@@ -123,7 +123,8 @@ private[spark] trait SparkTestUtils {
 
     val options = Seq("-d", classDir.getAbsolutePath) ++ (
       if (classpathUrls.nonEmpty) {
-        Seq("-classpath", classpathUrls.map(_.getFile).mkString(File.pathSeparator))
+        Seq("-classpath",
+          classpathUrls.map(u => new File(u.toURI).getPath).mkString(File.pathSeparator))
       } else Seq.empty
     )
 
@@ -177,7 +178,7 @@ private[spark] trait SparkTestUtils {
     // on Windows to work around CMD's command-line length limit and by some build/CI
     // tools. Expand any such JARs before invoking scalac so the classpath is complete.
     val expandedClasspath = classpathUrls.flatMap(expandManifestClasspath)
-    val cpStr = expandedClasspath.map(_.getFile).mkString(File.pathSeparator)
+    val cpStr = expandedClasspath.map(u => new File(u.toURI).getPath).mkString(File.pathSeparator)
     val args = Array("-classpath", cpStr, "-d", classDir.getAbsolutePath) ++
       sourceFiles.map(_.getAbsolutePath)
 
@@ -216,7 +217,7 @@ private[spark] trait SparkTestUtils {
    * original URL unchanged.
    */
   private[spark] def expandManifestClasspath(url: URL): Seq[URL] = {
-    val file = new File(url.getFile)
+    val file = new File(url.toURI)
     if (!file.exists() || !file.getName.endsWith(".jar")) return Seq(url)
     try {
       val jarFile = new JarFile(file)

common/utils/src/test/scala/org/apache/spark/util/SparkTestUtilsSuite.scala

@@ -0,0 +1,30 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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
+ *
+ *    http://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.apache.spark.util
+
+import org.scalatest.funsuite.AnyFunSuite // scalastyle:ignore funsuite
+
+class SparkTestUtilsSuite extends AnyFunSuite with SparkTestUtils { // scalastyle:ignore funsuite
+
+  test("SPARK-57081: createCompiledClass with spaces in classpath") {
+    val dir = SparkFileUtils.createTempDir(namePrefix = "path with spaces")
+    val sourceFile = new JavaSourceFromString("Hello", "public class Hello {}")
+    val result = createCompiledClass("Hello", dir, sourceFile, Seq(dir.toURI.toURL))
+    assert(result.exists(), s"Compiled class file should exist at ${result.getPath}")
+  }
+}