fix: Only include project LICENSE and NOTICE in Spark Client Jar

Previously the build code would add LICENSE and NOTICE files
from other shaded dependencies, some of which could potentially
 shade the project's LICENSE or NOTICE or cause confusion as to
which file was correct.

To fix this a post-processing task is added which removes all
potentially confusing files and manually adds the project
LICENSE and NOTICE files back to the jar.

Author: RussellSpitzer

plugins/spark/v3.5/spark/build.gradle.kts

@@ -85,12 +85,6 @@ tasks.register<ShadowJar>("createPolarisSparkJar") {
   archiveClassifier = "bundle"
   isZip64 = true
 
-  // include the LICENSE and NOTICE files for the shadow Jar
-  from(projectDir) {
-    include("LICENSE")
-    include("NOTICE")
-  }
-
   // pack both the source code and dependencies
   from(sourceSets.main.get().output)
   configurations = listOf(project.configurations.runtimeClasspath.get())
@@ -99,9 +93,91 @@ tasks.register<ShadowJar>("createPolarisSparkJar") {
   // The iceberg-spark-runtime plugin is always packaged along with our polaris-spark plugin,
   // therefore excluded from the optimization.
   minimize { exclude(dependency("org.apache.iceberg:iceberg-spark-runtime-*.*")) }
+
+  // Always run the license file addition after this task completes
+  finalizedBy("addLicenseFilesToJar")
+}
+
+// Post-processing task to add our project's LICENSE and NOTICE files to the jar and remove any
+// other LICENSE or NOTICE files that were shaded in.
+tasks.register("addLicenseFilesToJar") {
+  dependsOn("createPolarisSparkJar")
+
+  doLast {
+    val shadowTask = tasks.named("createPolarisSparkJar", ShadowJar::class.java).get()
+    val jarFile = shadowTask.archiveFile.get().asFile
+    val tempDir =
+      File(
+        "${project.layout.buildDirectory.get().asFile}/tmp/jar-cleanup-${shadowTask.archiveBaseName.get()}-${shadowTask.archiveClassifier.get()}"
+      )
+    val projectLicenseFile = File(projectDir, "LICENSE")
+    val projectNoticeFile = File(projectDir, "NOTICE")
+
+    // Validate that required license files exist
+    if (!projectLicenseFile.exists()) {
+      throw GradleException("Project LICENSE file not found at: ${projectLicenseFile.absolutePath}")
+    }
+    if (!projectNoticeFile.exists()) {
+      throw GradleException("Project NOTICE file not found at: ${projectNoticeFile.absolutePath}")
+    }
+
+    println("Processing jar: ${jarFile.absolutePath}")
+    println("Using temp directory: ${tempDir.absolutePath}")
+
+    // Clean up temp directory
+    if (tempDir.exists()) {
+      tempDir.deleteRecursively()
+    }
+    tempDir.mkdirs()
+
+    // Extract the jar
+    copy {
+      from(zipTree(jarFile))
+      into(tempDir)
+    }
+
+    fileTree(tempDir)
+      .matching {
+        include("LICENSE*")
+        include("NOTICE*")
+        include("META-INF/LICENSE*")
+        include("META-INF/NOTICE*")
+      }
+      .forEach { file ->
+        println("Removing license file: ${file.relativeTo(tempDir)}")
+        file.delete()
+      }
+
+    // Copy our project's license files to root
+    copy {
+      from(projectLicenseFile)
+      into(tempDir)
+    }
+    println("Added project LICENSE file")
+
+    copy {
+      from(projectNoticeFile)
+      into(tempDir)
+    }
+    println("Added project NOTICE file")
+
+    // Delete the original jar
+    jarFile.delete()
+
+    // Create new jar with only project LICENSE and NOTICE files
+    ant.withGroovyBuilder {
+      "jar"("destfile" to jarFile.absolutePath) { "fileset"("dir" to tempDir.absolutePath) }
+    }
+
+    println("Recreated jar with only project LICENSE and NOTICE files")
+
+    // Clean up temp directory
+    tempDir.deleteRecursively()
+  }
 }
 
-// ensure the ShadowJar job is run for both `assemble` and `build` task
+// ensure the shadow jar job (which will automatically run license addition) is run for both
+// `assemble` and `build` task
 tasks.named("assemble") { dependsOn("createPolarisSparkJar") }
 
 tasks.named("build") { dependsOn("createPolarisSparkJar") }