IDEA-314175 PathClassLoader disallows relative jar paths on the Java classpath

GitOrigin-RevId: 0de0f55b91c8b7bfee04113c62a5441a14bda9bf

platform/util-class-loader/src/com/intellij/util/lang/ClassPath.java

@@ -339,7 +339,10 @@ public final class ClassPath {
         return null;
       }
 
-      Path path = files[searchOffset++];
+      // https://youtrack.jetbrains.com/issue/IDEA-314175
+      // some environments (e.g. Bazel tests) put relative jar paths on the Java classpath,
+      // because relative paths are useful for hermeticity.
+      Path path = files[searchOffset++].toAbsolutePath();
       try {
         Loader loader = createLoader(path);
         if (loader != null) {

platform/util/testSrc/com/intellij/util/lang/PathClassLoaderTest.kt

@@ -9,6 +9,8 @@ import org.junit.jupiter.api.Test
 import org.junit.jupiter.api.io.TempDir
 import java.net.URL
 import java.nio.file.Path
+import java.nio.file.Paths
+import kotlin.io.path.invariantSeparatorsPathString
 
 class PathClassLoaderTest {
   @Test
@@ -24,4 +26,17 @@ class PathClassLoaderTest {
     assertThat(resource).isNotNull()
     assertThat(URL(resource!!.url, "screenshot.png").content).isEqualTo(expectedData)
   }
+
+  @Test
+  fun `relative jar path`(@TempDir dir: Path) {
+    // Regression test for IDEA-314175.
+    val jarAbsolutePath = dir.resolve("lib.jar")
+    Compressor.Zip(jarAbsolutePath.toFile()).use { compressor ->
+      compressor.addFile("resource.txt", "contents".encodeToByteArray())
+    }
+    val jarRelativePath = Paths.get("").toAbsolutePath().relativize(jarAbsolutePath)
+    val classPath = ClassPath(listOf(jarRelativePath), UrlClassLoader.build(), PathClassLoader.RESOURCE_FILE_FACTORY, true)
+    val resource = checkNotNull(classPath.findResource("resource.txt"))
+    assertThat(resource.url.toString()).isEqualTo("jar:file:${jarAbsolutePath.invariantSeparatorsPathString}!/resource.txt")
+  }
 }