steph suggestions

src/pynwb/__init__.py

@@ -561,9 +561,9 @@ def read_nwb(**kwargs):
     This function uses the following defaults:
     * Always opens in read-only mode
     * Automatically loads namespaces
-    * Detects file format based on extension
+    * Reads any backend (e.g. HDF5 or Zarr) if there is an IO class available.
 
-    Advanced features requiring direct use of IO classes include:
+    Advanced features requiring direct use of IO classes (e.g. NWBHDF5IO NWBZarrIO) include:
     * Streaming data from s3
     * Custom namespace extensions
     * Parallel I/O with MPI
@@ -583,16 +583,27 @@ def read_nwb(**kwargs):
     """
 
     path = popargs('path', kwargs)
+    # HDF5 is always available so we try that first
     backend_is_hdf5 = NWBHDF5IO.can_read(path=path)
     if backend_is_hdf5:
         return NWBHDF5IO.read_nwb(path=path)
     else:
-        from hdmf_zarr import NWBZarrIO
-        backend_is_zarr = NWBZarrIO.can_read(path=path)
-        if backend_is_zarr:
-            return NWBZarrIO.read_nwb(path=path) 
-        else:
-            raise ValueError(f"Unsupported backend for file: {path}")    
+        # If hdmf5 zarr is available we try that next
+        try:
+            from hdmf_zarr import NWBZarrIO
+            backend_is_zarr = NWBZarrIO.can_read(path=path)
+            if backend_is_zarr:
+                return NWBZarrIO.read_nwb(path=path) 
+            else:
+                raise ValueError(
+                    f"Unable to read file: '{path}'. The file exists but is not recognized as "
+                    "either a valid HDF5 or Zarr NWB file. Please ensure the file contains valid NWB data."
+                )     
+        except ImportError:
+            raise ValueError(
+                f"Unable to read file: '{path}'. The file is not recognized as an HDF5 NWB file. "
+                "If you are trying to read a Zarr file, please install hdmf-zarr using: pip install hdmf-zarr"
+            )
 
 
 

tests/integration/io/test_read.py

@@ -14,14 +14,13 @@
 
 
 class TestReadNWBMethod(TestCase):
-    """
-    Test that H5DataIO functions correctly on round trip with the HDF5IO backend
-    """
+    """Test suite for the read_nwb function."""
+
     def setUp(self):
         self.nwbfile = mock_NWBFile()
 
-
     def test_read_nwb_hdf5(self):
+        """Test reading a valid HDF5 NWB file."""
         from pynwb import NWBHDF5IO
 
         with tempfile.TemporaryDirectory() as temp_dir:
@@ -35,14 +34,41 @@ def test_read_nwb_hdf5(self):
 
     @unittest.skipIf(not HAVE_NWBZarrIO, "NWBZarrIO library not available")
     def test_read_zarr(self):
-        # from pynwb import NWBZarrIO
-        from hdmf_zarr import NWBZarrIO
-
+        """Test reading a valid Zarr NWB file."""
         with tempfile.TemporaryDirectory() as temp_dir:
-            path = Path(temp_dir) / "test.nwb"
+            path = Path(temp_dir) / "test.zarr"
             with NWBZarrIO(path, 'w') as io:
                 io.write(self.nwbfile)
 
             read_nwbfile = read_nwb(path=path)
             self.assertContainerEqual(read_nwbfile, self.nwbfile)
-            read_nwbfile.get_read_io().close()
+            read_nwbfile.get_read_io().close()
+
+    def test_read_zarr_without_hdmf_zarr(self):
+        """Test attempting to read a Zarr file without hdmf_zarr installed."""
+        if HAVE_NWBZarrIO:
+            self.skipTest("hdmf_zarr is installed")
+
+        with tempfile.TemporaryDirectory() as temp_dir:
+            path = Path(temp_dir) / "test.zarr"
+            path.mkdir()  # Create empty directory to simulate Zarr store
+
+            expected_message = (
+                f"Unable to read file: '{path}'. The file is not recognized as an HDF5 NWB file. "
+                "If you are trying to read a Zarr file, please install hdmf-zarr using: pip install hdmf-zarr"
+            )
+
+            with self.assertRaisesWith(ValueError, expected_message):
+                read_nwb(path=path)
+
+    @unittest.skipIf(not HAVE_NWBZarrIO, "NWBZarrIO library not available. Neeed for correct error message.")
+    def test_read_invalid_file(self):
+        """Test attempting to read a file that exists but is neither HDF5 nor Zarr."""
+        with tempfile.TemporaryDirectory() as temp_dir:
+            path = Path(temp_dir) / "test.txt"
+            path.write_text("Not an NWB file")
+
+            with self.assertRaisesWith(ValueError,
+                f"Unable to read file: '{path}'. The file exists but is not recognized as "
+                "either a valid HDF5 or Zarr NWB file. Please ensure the file contains valid NWB data."):
+                read_nwb(path=path)