fix: add option to avoid addition of --locked to uv sync

Fixes: #225

Author: ssbarnea

README.md

@@ -18,6 +18,7 @@ will get both the benefits (performance) or downsides (bugs) of `uv`.
   - [no_default_groups](#no_default_groups)
   - [dependency_groups](#dependency_groups)
   - [uv_sync_flags](#uv_sync_flags)
+  - [uv_sync_locked](#uv_sync_locked)
   - [External package support](#external-package-support)
 - [Environment creation](#environment-creation)
   - [uv_seed](#uv_seed)
@@ -132,6 +133,12 @@ installed into the environment you can do:
 uv_sync_flags = --no-editable, --inexact
 ```
 
+### `uv_sync_locked`
+
+By default tox-uv will call `uv sync` with `--locked` argument, which is incompatible with other arguments like
+`--prerelease` or `--upgrade ` that you might want to add to `uv_sync_flags` for some test scenarios. You can set this
+to `false` to avoid such conflicts.
+
 ### External package support
 
 Should tox be invoked with the [`--installpkg`](https://tox.wiki/en/stable/cli_interface.html#tox-run---installpkg) flag

src/tox_uv/_run_lock.py

@@ -63,6 +63,12 @@ def register_config(self) -> None:
             default=[],
             desc="Additional flags to pass to uv sync (for flags not configurable via environment variables)",
         )
+        self.conf.add_config(
+            keys=["uv_sync_locked"],
+            of_type=bool,
+            default=True,
+            desc="When set to 'false', it will remove `--locked` argument from 'uv sync' implicit arguments.",
+        )
         self.conf.add_config(
             keys=["package"],
             of_type=Literal["editable", "wheel", "skip"],  # type: ignore[arg-type]
@@ -71,15 +77,16 @@ def register_config(self) -> None:
         )
         add_skip_missing_interpreters_to_core(self.core, self.options)
 
-    def _setup_env(self) -> None:  # noqa: C901
+    def _setup_env(self) -> None:  # noqa: C901,PLR0912
         super()._setup_env()
         install_pkg = getattr(self.options, "install_pkg", None)
         if not getattr(self.options, "skip_uv_sync", False):
             cmd = [
                 "uv",
                 "sync",
-                "--locked",
             ]
+            if self.conf["uv_sync_locked"]:
+                cmd.append("--locked")
             if self.conf["uv_python_preference"] != "none":
                 cmd.extend(("--python-preference", self.conf["uv_python_preference"]))
             if self.conf["uv_resolution"]:

tests/test_tox_uv_lock.py

@@ -231,13 +231,16 @@ def test_uv_lock_with_install_pkg(tox_project: ToxProjectCreator, name: str) ->
 
 
 @pytest.mark.usefixtures("clear_python_preference_env_var")
-def test_uv_sync_extra_flags(tox_project: ToxProjectCreator) -> None:
+@pytest.mark.parametrize("uv_sync_locked", [True, False])
+def test_uv_sync_extra_flags(tox_project: ToxProjectCreator, uv_sync_locked: bool) -> None:
+    uv_sync_locked_str = str(uv_sync_locked).lower()
     project = tox_project({
-        "tox.ini": """
+        "tox.ini": f"""
     [testenv]
     runner = uv-venv-lock-runner
     no_default_groups = false
     uv_sync_flags = --no-editable, --inexact
+    uv_sync_locked = {uv_sync_locked_str}
     commands = python hello
     """
     })
@@ -269,7 +272,7 @@ def test_uv_sync_extra_flags(tox_project: ToxProjectCreator) -> None:
             [
                 "uv",
                 "sync",
-                "--locked",
+                *(["--locked"] if uv_sync_locked else []),
                 "--python-preference",
                 "system",
                 "--no-editable",