Do not set scheme if unset

changelog/@unreleased/pr-667.v2.yml

@@ -0,0 +1,6 @@
+type: fix
+fix:
+  description: StandaloneEncryptedFileSystem returns to its old behavior, of only
+    overriding the scheme when the uri uses a scheme
+  links:
+  - https://github.com/palantir/hadoop-crypto/pull/667

hadoop-crypto/src/main/java/com/palantir/crypto2/hadoop/PathConvertingFileSystem.java

@@ -16,6 +16,7 @@
 
 package com.palantir.crypto2.hadoop;
 
+import com.google.common.annotations.VisibleForTesting;
 import java.io.IOException;
 import java.net.URI;
 import java.util.EnumSet;
@@ -146,7 +147,8 @@ public FileChecksum getFileChecksum(Path path) throws IOException {
         return fs.getFileChecksum(to(path));
     }
 
-    private Path to(Path path) {
+    @VisibleForTesting
+    Path to(Path path) {
         return toFunc.apply(path);
     }
 

hadoop-crypto/src/main/java/com/palantir/crypto2/hadoop/StandaloneEncryptedFileSystem.java

@@ -164,6 +164,9 @@ private static Function<Path, Path> setSchemeFunc(final String scheme) {
 
     private static Function<URI, URI> setUriSchemeFunc(final String scheme) {
         return uri -> {
+            if (uri.getScheme() == null) {
+                return uri;
+            }
             try {
                 return new URI(
                         scheme,

hadoop-crypto/src/test/java/com/palantir/crypto2/hadoop/StandaloneEncryptedFileSystemTest.java

@@ -296,6 +296,25 @@ public void testCopyFromLocalFile() throws IOException {
         assertThat(readBytes).containsExactly(DATA_BYTES);
     }
 
+    /**
+     * Preserving paths with no scheme present is helpful to bypass validation in
+     * {@link org.apache.hadoop.fs.s3native.S3xLoginHelper#checkPath} when using S3A.
+     */
+    @Test
+    public void testNoScheme() {
+        // Convert the file path, because that normally happens by the time FileSystem calls checkPath internally
+        StandaloneEncryptedFileSystem standaloneEncryptedFileSystem = (StandaloneEncryptedFileSystem) efs;
+        EncryptedFileSystem encryptedFileSystem =
+                (EncryptedFileSystem) standaloneEncryptedFileSystem.getRawFileSystem();
+        PathConvertingFileSystem pathConvertingFileSystem =
+                (PathConvertingFileSystem) encryptedFileSystem.getRawFileSystem();
+        Path convertedPath = pathConvertingFileSystem.to(path);
+
+        // Just like the original path, the converted path should not have a scheme
+        assertThat(path.toUri().getScheme()).isNull();
+        assertThat(convertedPath.toUri().getScheme()).isNull();
+    }
+
     private static Configuration getBaseConf() {
         Configuration conf = new Configuration();
         conf.set("fs.efile.impl", StandaloneEncryptedFileSystem.class.getCanonicalName());