Implement loading MemoryItems from file in JSONFileMemory (#4703)

Further changes:
* remove `init` param from `get_memory()`, replace usages by `memory.clear()`
* make token length calculation optional in `MemoryItem.dump()`

tests/conftest.py

@@ -94,7 +94,8 @@ def agent(config: Config, workspace: Workspace) -> Agent:
     ai_config.command_registry = command_registry
 
     config.set_memory_backend("json_file")
-    memory_json_file = get_memory(config, init=True)
+    memory_json_file = get_memory(config)
+    memory_json_file.clear()
 
     system_prompt = ai_config.construct_full_prompt()
 

tests/integration/agent_factory.py

@@ -28,7 +28,9 @@ def memory_json_file(agent_test_config: Config):
     was_memory_backend = agent_test_config.memory_backend
 
     agent_test_config.set_memory_backend("json_file")
-    yield get_memory(agent_test_config, init=True)
+    memory = get_memory(agent_test_config)
+    memory.clear()
+    yield memory
 
     agent_test_config.set_memory_backend(was_memory_backend)
 

tests/integration/memory/test_json_file_memory.py

@@ -34,7 +34,9 @@ def test_json_memory_init_with_backing_empty_file(config: Config, workspace: Wor
     assert index_file.read_text() == "[]"
 
 
-def test_json_memory_init_with_backing_file(config: Config, workspace: Workspace):
+def test_json_memory_init_with_backing_invalid_file(
+    config: Config, workspace: Workspace
+):
     index_file = workspace.root / f"{config.memory_index}.json"
     index_file.touch()
 
@@ -78,6 +80,24 @@ def test_json_memory_get(config: Config, memory_item: MemoryItem, mock_get_embed
     assert retrieved.memory_item == memory_item
 
 
+def test_json_memory_load_index(config: Config, memory_item: MemoryItem):
+    index = JSONFileMemory(config)
+    index.add(memory_item)
+
+    try:
+        assert index.file_path.exists(), "index was not saved to file"
+        assert len(index) == 1, f"index constains {len(index)} items instead of 1"
+        assert index.memories[0] == memory_item, "item in index != added mock item"
+    except AssertionError as e:
+        raise ValueError(f"Setting up for load_index test failed: {e}")
+
+    index.memories = []
+    index.load_index()
+
+    assert len(index) == 1
+    assert index.memories[0] == memory_item
+
+
 @pytest.mark.vcr
 @requires_api_key("OPENAI_API_KEY")
 def test_json_memory_get_relevant(config: Config, patched_api_requestor: None) -> None: