Treat dict log_config without a version key as an overlay on uvicorn defaults.

A partial log_config (no "version" key) is deep-merged over uvicorn's
default config before our patching, so users pass only their
customizations, e.g. log_config={"loggers": {"myapp": {"level":
"DEBUG"}}}.  Previously such dicts crashed at startup: dictConfig
requires a version, and our root entry referenced a "default" handler
that might not exist; that reference is now only added when the handler
exists.  The stock default formatter is replaced only when untouched,
so an overlaid fmt survives.  Dicts with version and non-dict configs
behave as before.  Documented in the README logging section, with tests
under fastapi-vue/tests (each patched config validated through
dictConfig).

fastapi-vue/tests/__init__.py

@@ -0,0 +1 @@
+"""Tests for the fastapi_vue package."""

fastapi-vue/tests/test_logging.py

@@ -0,0 +1,60 @@
+"""Tests for fastapi_vue.logging.patch_log_config overlay behavior."""
+
+import logging.config
+
+from fastapi_vue.logging import patch_log_config
+
+
+def test_empty_dict_overlays_uvicorn_defaults() -> None:
+    """An empty dict is a partial config: merged over uvicorn's defaults."""
+    config = patch_log_config({})
+    assert config["version"] == 1
+    assert config["disable_existing_loggers"] is False
+    assert config["root"]["handlers"] == ["default"]
+    assert "uvicorn" in config["loggers"]
+    logging.config.dictConfig(config)  # must be a valid, complete config
+
+
+def test_partial_logger_customization() -> None:
+    """The documented use case: only the customization, no boilerplate."""
+    config = patch_log_config({"loggers": {"kanta": {"level": "DEBUG"}}})
+    assert config["loggers"]["kanta"] == {"level": "DEBUG"}
+    assert config["loggers"]["uvicorn"]["handlers"] == ["default"]
+    assert config["loggers"]["watchfiles.main"]["level"] == "WARNING"
+    logging.config.dictConfig(config)
+    assert logging.getLogger("kanta").level == logging.DEBUG
+
+
+def test_overlay_root_level_wins() -> None:
+    """User-supplied root level is kept; our handler wiring still applies."""
+    config = patch_log_config({"root": {"level": "ERROR"}})
+    assert config["root"]["level"] == "ERROR"
+    assert config["root"]["handlers"] == ["default"]
+    logging.config.dictConfig(config)
+    assert logging.getLogger().level == logging.ERROR
+
+
+def test_overlay_formatter_customization_keeps_stock_siblings() -> None:
+    """A user formatter replaces ours; the access formatter still works."""
+    config = patch_log_config({"formatters": {"default": {"fmt": "%(name)s %(message)s"}}})
+    assert config["formatters"]["default"] == {
+        "()": "uvicorn.logging.DefaultFormatter",  # stock class, user's fmt
+        "fmt": "%(name)s %(message)s",
+        "use_colors": None,
+    }
+    assert "access" in config["formatters"]
+    logging.config.dictConfig(config)
+
+
+def test_full_config_used_as_is() -> None:
+    """A dict with version is complete: no uvicorn loggers appear."""
+    config = patch_log_config({"version": 1})
+    assert "uvicorn" not in config.get("loggers", {})
+    # No "default" handler exists, so root must not reference one.
+    assert "handlers" not in config["root"]
+    logging.config.dictConfig(config)
+
+
+def test_non_dict_passes_through() -> None:
+    """Non-dict configs (e.g. an ini file path) are returned untouched."""
+    assert patch_log_config("logging.ini") == "logging.ini"