Support open-ended ranges in getInputStream, fail loudly on unreadable zip (#103)

HttpStore.getInputStream formatted "bytes=%d-%d" unconditionally, so the
default Store.getInputStream(keys) — which delegates to (keys, 0, -1) —
sent "bytes=0--1" and returned null. Emit "bytes=<start>-" when end is
negative, mirroring get(keys, start). S3Store had the identical bug.

ReadOnlyZipStore.ensureCache treated a null stream from the underlying
store as an empty archive, turning a read failure into valid-but-empty
data. Throw StoreException.readFailed instead; a genuinely empty archive
still parses to an empty index through the normal path.

Fixes #100
Fixes #101

Co-authored-by: Claude Opus 5 <noreply@anthropic.com>

Author: normanrz

src/main/java/dev/zarr/zarrjava/store/HttpStore.java

@@ -128,8 +128,12 @@ public InputStream getInputStream(String[] keys, long start, long end) {
         if (start < 0) {
             throw new IllegalArgumentException("Argument 'start' needs to be non-negative.");
         }
-        Request request = new Request.Builder().url(resolveKeys(keys)).header(
-                "Range", String.format("bytes=%d-%d", start, end - 1)).build();
+        // A negative end means "until the end of the object", which HTTP expresses as an
+        // open-ended range.
+        String range = end < 0
+                ? String.format("bytes=%d-", start)
+                : String.format("bytes=%d-%d", start, end - 1);
+        Request request = new Request.Builder().url(resolveKeys(keys)).header("Range", range).build();
 
         try {
             // We do NOT use try-with-resources here because the stream must remain open

src/main/java/dev/zarr/zarrjava/store/ReadOnlyZipStore.java

@@ -50,8 +50,10 @@ private synchronized void ensureCache() {
 
         InputStream inputStream = underlyingStore.getInputStream();
         if (inputStream == null) {
-            isCached = true;
-            return;
+            throw StoreException.readFailed(
+                    underlyingStore.toString(),
+                    new String[]{},
+                    new IOException("Could not open the ZIP archive from the underlying store"));
         }
 
         try (ZipArchiveInputStream zis = new ZipArchiveInputStream(inputStream)) {

src/main/java/dev/zarr/zarrjava/store/S3Store.java

@@ -103,10 +103,17 @@ public ByteBuffer get(String[] keys, long start) {
     @Nullable
     @Override
     public ByteBuffer get(String[] keys, long start, long end) {
+        if (start < 0) {
+            throw new IllegalArgumentException("Argument 'start' needs to be non-negative.");
+        }
+        // S3 ranges are inclusive; a negative end means "until the end of the object".
+        String range = end < 0
+                ? String.format("bytes=%d-", start)
+                : String.format("bytes=%d-%d", start, end - 1);
         GetObjectRequest req = GetObjectRequest.builder()
                 .bucket(bucketName)
                 .key(resolveKeys(keys))
-                .range(String.format("bytes=%d-%d", start, end - 1)) // S3 range is inclusive
+                .range(range)
                 .build();
         return get(req);
     }
@@ -221,10 +228,17 @@ public StoreHandle resolve(String... keys) {
 
     @Override
     public InputStream getInputStream(String[] keys, long start, long end) {
+        if (start < 0) {
+            throw new IllegalArgumentException("Argument 'start' needs to be non-negative.");
+        }
+        // S3 ranges are inclusive; a negative end means "until the end of the object".
+        String range = end < 0
+                ? String.format("bytes=%d-", start)
+                : String.format("bytes=%d-%d", start, end - 1);
         GetObjectRequest req = GetObjectRequest.builder()
                 .bucket(bucketName)
                 .key(resolveKeys(keys))
-                .range(String.format("bytes=%d-%d", start, end - 1)) // S3 range is inclusive
+                .range(range)
                 .build();
         return s3client.getObject(req);
     }

src/test/java/dev/zarr/zarrjava/store/HttpStoreTest.java

@@ -87,6 +87,28 @@ public void testNoRetryOn404() throws IOException {
         }
     }
 
+    @Test
+    public void testOpenEndedRangeHeader() throws IOException, InterruptedException {
+        try (MockWebServer server = new MockWebServer()) {
+            server.enqueue(new MockResponse().setBody("data").setResponseCode(206));
+            server.start();
+            HttpStore httpStore = new HttpStore(server.url("/").toString(), 1, 3, 10);
+            Assertions.assertNotNull(httpStore.getInputStream(new String[]{"path"}, 0, -1));
+            Assertions.assertEquals("bytes=0-", server.takeRequest().getHeader("Range"));
+        }
+    }
+
+    @Test
+    public void testBoundedRangeHeader() throws IOException, InterruptedException {
+        try (MockWebServer server = new MockWebServer()) {
+            server.enqueue(new MockResponse().setBody("dat").setResponseCode(206));
+            server.start();
+            HttpStore httpStore = new HttpStore(server.url("/").toString(), 1, 3, 10);
+            Assertions.assertNotNull(httpStore.getInputStream(new String[]{"path"}, 1, 4));
+            Assertions.assertEquals("bytes=1-3", server.takeRequest().getHeader("Range"));
+        }
+    }
+
     @Override
     @Test
     @Disabled("List is not supported in HttpStore")

src/test/java/dev/zarr/zarrjava/store/ReadOnlyZipStoreTest.java

@@ -42,6 +42,13 @@ Store storeWithArrays() {
     }
 
 
+    @Test
+    public void testUnreadableArchiveThrows() {
+        ReadOnlyZipStore zipStore = new ReadOnlyZipStore(TESTOUTPUT.resolve("does_not_exist.zip"));
+        Assertions.assertThrows(StoreException.class, () -> zipStore.resolve().listChildren().count());
+        Assertions.assertThrows(StoreException.class, () -> zipStore.resolve("array", "0.0.0").exists());
+    }
+
     @Override
     @Test
     public void testListChildren() {

src/test/java/dev/zarr/zarrjava/store/StoreTest.java

@@ -46,6 +46,29 @@ public void testInputStream() throws IOException {
         Assertions.assertArrayEquals(expectedBuffer, buffer);
     }
 
+    @Test
+    public void testInputStreamOpenEnded() throws IOException {
+        StoreHandle storeHandle = storeHandleWithData();
+        ByteBuffer expected = storeHandle.read();
+        try (InputStream is = storeHandle.getInputStream()) {
+            Assertions.assertNotNull(is, "Open-ended getInputStream() returned null");
+            byte[] actual = readFully(is);
+            byte[] expectedBytes = new byte[expected.remaining()];
+            expected.get(expectedBytes);
+            Assertions.assertArrayEquals(expectedBytes, actual);
+        }
+    }
+
+    private static byte[] readFully(InputStream is) throws IOException {
+        java.io.ByteArrayOutputStream baos = new java.io.ByteArrayOutputStream();
+        byte[] buffer = new byte[8192];
+        int len;
+        while ((len = is.read(buffer)) != -1) {
+            baos.write(buffer, 0, len);
+        }
+        return baos.toByteArray();
+    }
+
     @Test
     public void testExists() throws ZarrException, IOException {
         Assertions.assertTrue(storeHandleWithData().exists());