Handle edge cases when generating embeddings (#1215)

* Handle edge cases when generating embeddings
* Improve Python handling & add llmodel_c.h note
- In the Python bindings fail fast with a ValueError when text is empty
- Advice other bindings authors to do likewise in llmodel_c.h

gpt4all-backend/llmodel_c.cpp

@@ -168,10 +168,14 @@ void llmodel_prompt(llmodel_model model, const char *prompt,
 
 float *llmodel_embedding(llmodel_model model, const char *text, size_t *embedding_size)
 {
+    if (model == nullptr || text == nullptr || !strlen(text)) {
+        *embedding_size = 0;
+        return nullptr;
+    }
     LLModelWrapper *wrapper = reinterpret_cast<LLModelWrapper*>(model);
     std::vector<float> embeddingVector = wrapper->llModel->embedding(text);
     float *embedding = (float *)malloc(embeddingVector.size() * sizeof(float));
-    if(embedding == nullptr) {
+    if (embedding == nullptr) {
         *embedding_size = 0;
         return nullptr;
     }

gpt4all-backend/llmodel_c.h

@@ -173,6 +173,8 @@ void llmodel_prompt(llmodel_model model, const char *prompt,
 
 /**
  * Generate an embedding using the model.
+ * NOTE: If given NULL pointers for the model or text, or an empty text, a NULL pointer will be
+ * returned. Bindings should signal an error when NULL is the return value.
  * @param model A pointer to the llmodel_model instance.
  * @param text A string representing the text to generate an embedding for.
  * @param embedding_size A pointer to a size_t type that will be set by the call indicating the length

gpt4all-bindings/python/gpt4all/pyllmodel.py

@@ -251,6 +251,8 @@ class LLModel:
         self,
         text: str
     ) -> list[float]:
+        if not text:
+            raise ValueError("Text must not be None or empty")
         embedding_size = ctypes.c_size_t()
         c_text = ctypes.c_char_p(text.encode('utf-8'))
         embedding_ptr = llmodel.llmodel_embedding(self.model, c_text, ctypes.byref(embedding_size))

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

@@ -3,6 +3,7 @@ from io import StringIO
 
 from gpt4all import GPT4All, Embed4All
 import time
+import pytest
 
 def test_inference():
     model = GPT4All(model_name='orca-mini-3b.ggmlv3.q4_0.bin')
@@ -107,3 +108,9 @@ def test_embedding():
     #for i, value in enumerate(output):
         #print(f'Value at index {i}: {value}')
     assert len(output) == 384
+
+def test_empty_embedding():
+    text = ''
+    embedder = Embed4All()
+    with pytest.raises(ValueError):
+        output = embedder.embed(text)