Fix models not getting downloaded in Python bindings (nomic-ai#1262)

- custom callbacks & session improvements PR (v1.0.6) had one too many checks
- remove the problematic config['url'] check
- add a crude test
- fixes nomic-ai#1261

gpt4all-bindings/python/gpt4all/gpt4all.py

@@ -168,10 +168,6 @@ def retrieve_model(
 
         # If model file does not exist, download
         elif allow_download:
-            # Make sure valid model filename before attempting download
-
-            if "url" not in config:
-                raise ValueError(f"Model filename not in model list: {model_filename}")
             url = config.pop("url", None)
 
             config["path"] = GPT4All.download_model(

gpt4all-bindings/python/gpt4all/tests/test_gpt4all.py

@@ -1,5 +1,6 @@
 import sys
 from io import StringIO
+from pathlib import Path
 
 from gpt4all import GPT4All, Embed4All
 import time
@@ -114,3 +115,15 @@ def test_empty_embedding():
     embedder = Embed4All()
     with pytest.raises(ValueError):
         output = embedder.embed(text)
+
+def test_download_model(tmp_path: Path):
+    import gpt4all.gpt4all
+    old_default_dir = gpt4all.gpt4all.DEFAULT_MODEL_DIRECTORY
+    gpt4all.gpt4all.DEFAULT_MODEL_DIRECTORY = tmp_path  # temporary pytest directory to ensure a download happens
+    try:
+        model = GPT4All(model_name='ggml-all-MiniLM-L6-v2-f16.bin')
+        model_path = tmp_path / model.config['filename']
+        assert model_path.absolute() == Path(model.config['path']).absolute()
+        assert model_path.stat().st_size == int(model.config['filesize'])
+    finally:
+        gpt4all.gpt4all.DEFAULT_MODEL_DIRECTORY = old_default_dir