exp: add support for --no-hydra flag

dvc/commands/experiments/run.py

@@ -20,6 +20,7 @@ def run(self):
             tmp_dir=self.args.tmp_dir,
             copy_paths=self.args.copy_paths,
             message=self.args.message,
+            no_hydra=self.args.no_hydra,
             **self._common_kwargs,
         )
 
@@ -107,4 +108,14 @@ def _add_run_common(parser):
         default=None,
         help="Custom commit message to use when committing the experiment.",
     )
+    parser.add_argument(
+        "--no-hydra",
+        action="store_true",
+        default=False,
+        help=(
+            "Disables automatically updating `params.yaml` with Hydra configuration. "
+            " You can still use `--set-param` to update individual params if needed."
+            " Default is False."
+        ),
+    )
     parser.add_argument("-M", dest="message", help=argparse.SUPPRESS)  # obsolete

dvc/repo/experiments/queue/base.py

@@ -287,6 +287,7 @@ def _stash_exp(
         baseline_rev: Optional[str] = None,
         branch: Optional[str] = None,
         name: Optional[str] = None,
+        no_hydra: bool = False,
         **kwargs,
     ) -> QueueEntry:
         """Stash changes from the workspace as an experiment.
@@ -302,6 +303,7 @@ def _stash_exp(
             name: Optional experiment name. If specified this will be used as
                 the human-readable name in the experiment branch ref. Has no
                 effect of branch is specified.
+            no_hydra: Disable Hydra from automatically overwriting all params.
 
         .. _Hydra Override:
             https://hydra.cc/docs/next/advanced/override_grammar/basic/
@@ -318,7 +320,7 @@ def _stash_exp(
 
                     # update experiment params from command line
                     if params:
-                        self._update_params(params)
+                        self._update_params(params, no_hydra=no_hydra)
 
                     # DVC commit data deps to preserve state across workspace
                     # & tempdir runs
@@ -441,12 +443,13 @@ def _format_new_params_msg(new_params, config_path):
             f"from '{config_path}': {param_list}"
         )
 
-    def _update_params(self, params: dict[str, list[str]]):
+    def _update_params(self, params: dict[str, list[str]], no_hydra: bool = False):
         """Update param files with the provided `Hydra Override`_ patterns.
 
         Args:
             params: Dict mapping paths to `Hydra Override`_ patterns,
                 provided via `exp run --set-param`.
+            no_hydra: Disable Hydra from automatically overwriting all params.
 
         .. _Hydra Override:
             https://hydra.cc/docs/advanced/override_grammar/basic/
@@ -456,7 +459,7 @@ def _update_params(self, params: dict[str, list[str]]):
         logger.debug("Using experiment params '%s'", params)
 
         hydra_config = self.repo.config.get("hydra", {})
-        hydra_enabled = hydra_config.get("enabled", False)
+        hydra_enabled = hydra_config.get("enabled", False) and not no_hydra
         hydra_output_file = ParamsDependency.DEFAULT_PARAMS_FILE
         for path, overrides in params.items():
             if hydra_enabled and path == hydra_output_file:

dvc/repo/experiments/run.py

@@ -22,6 +22,7 @@ def run(  # noqa: C901, PLR0912
     queue: bool = False,
     copy_paths: Optional[Iterable[str]] = None,
     message: Optional[str] = None,
+    no_hydra: bool = False,
     **kwargs,
 ) -> dict[str, str]:
     """Reproduce the specified targets as an experiment.
@@ -67,7 +68,7 @@ def run(  # noqa: C901, PLR0912
     else:
         path_overrides = {}
 
-    hydra_enabled = repo.config.get("hydra", {}).get("enabled", False)
+    hydra_enabled = repo.config.get("hydra", {}).get("enabled", False) and not no_hydra
     hydra_output_file = ParamsDependency.DEFAULT_PARAMS_FILE
     if hydra_enabled and hydra_output_file not in path_overrides:
         # Force `_update_params` even if `--set-param` was not used
@@ -80,6 +81,7 @@ def run(  # noqa: C901, PLR0912
             tmp_dir=tmp_dir,
             copy_paths=copy_paths,
             message=message,
+            no_hydra=no_hydra,
             **kwargs,
         )
 
@@ -100,6 +102,7 @@ def run(  # noqa: C901, PLR0912
             params=sweep_overrides,
             copy_paths=copy_paths,
             message=message,
+            no_hydra=no_hydra,
             **kwargs,
         )
         if sweep_overrides:

tests/func/experiments/test_set_params.py

@@ -26,8 +26,9 @@ def test_modify_params(params_repo, dvc, changes, expected):
         ("conf", "bar"),
     ],
 )
+@pytest.mark.parametrize("no_hydra", [True, False])
 def test_hydra_compose_and_dump(
-    tmp_dir, params_repo, dvc, hydra_enabled, config_dir, config_name
+    tmp_dir, params_repo, dvc, hydra_enabled, config_dir, config_name, no_hydra
 ):
     hydra_setup(
         tmp_dir,
@@ -50,14 +51,14 @@ def test_hydra_compose_and_dump(
         if config_name is not None:
             conf["hydra"]["config_name"] = config_name
 
-    dvc.experiments.run()
+    dvc.experiments.run(no_hydra=no_hydra)
 
-    if hydra_enabled:
+    if hydra_enabled and not no_hydra:
         assert (tmp_dir / "params.yaml").parse() == {
             "db": {"driver": "mysql", "user": "omry", "pass": "secret"},
         }
 
-        dvc.experiments.run(params=["db=postgresql"])
+        dvc.experiments.run(params=["db=postgresql"], no_hydra=no_hydra)
         assert (tmp_dir / "params.yaml").parse() == {
             "db": {
                 "driver": "postgresql",
@@ -117,6 +118,7 @@ def test_hydra_sweep(
             targets=None,
             copy_paths=None,
             message=None,
+            no_hydra=False,
         )
 
 
@@ -137,3 +139,76 @@ def test_hydra_sweep_prefix_name(tmp_dir, params_repo, dvc):
     exp_names = [entry.name for entry in dvc.experiments.celery_queue.iter_queued()]
     for name, expected in zip(exp_names, expected_names):
         assert name == expected
+
+
+def test_mixing_no_hydra_and_params_flags(tmp_dir, params_repo, dvc):
+    # Passing no_hydra should not prevent user from
+    # using --set-param on unmodified params.yaml
+    hydra_setup(
+        tmp_dir,
+        config_dir="conf",
+        config_name="config",
+    )
+
+    with dvc.config.edit() as conf:
+        conf["hydra"]["enabled"] = True
+        conf["hydra"]["config_dir"] = "conf"
+        conf["hydra"]["config_name"] = "config"
+
+    dvc.experiments.run(no_hydra=True, params=["goo.bag=10.0"])
+
+    assert (tmp_dir / "params.yaml").parse() == {
+        "foo": [{"bar": 1}, {"baz": 2}],
+        "goo": {"bag": 10.0},
+        "lorem": False,
+    }
+
+
+@pytest.mark.parametrize(
+    "hydra_enabled,overrides,expected",
+    [
+        (
+            True,
+            ["db=mysql,postgresql"],
+            [
+                {"params.yaml": ["db=mysql"]},
+                {"params.yaml": ["db=postgresql"]},
+            ],
+        ),
+        (
+            False,
+            ["foo=bar,baz"],
+            [{"params.yaml": ["foo=bar"]}, {"params.yaml": ["foo=baz"]}],
+        ),
+        (
+            False,
+            [],
+            [{}],
+        ),
+    ],
+)
+@pytest.mark.parametrize("no_hydra", [True, False])
+def test_mixing_no_hydra_and_sweeps(
+    tmp_dir, params_repo, dvc, mocker, hydra_enabled, overrides, expected, no_hydra
+):
+    # Passing no_hydra should not prevent user from
+    # queuing sweeps with --set-param and --queue
+    patched = mocker.patch.object(dvc.experiments, "queue_one")
+
+    if hydra_enabled:
+        hydra_setup(tmp_dir, config_dir="conf", config_name="config")
+        with dvc.config.edit() as conf:
+            conf["hydra"]["enabled"] = True
+
+    dvc.experiments.run(params=overrides, queue=True, no_hydra=no_hydra)
+
+    assert patched.call_count == len(expected)
+    for e in expected:
+        patched.assert_any_call(
+            mocker.ANY,
+            params=e,
+            targets=None,
+            copy_paths=None,
+            message=None,
+            no_hydra=no_hydra,
+        )

tests/unit/command/test_experiments.py

@@ -130,6 +130,7 @@ def test_experiments_run(dvc, scm, mocker):
         "tmp_dir": False,
         "copy_paths": [],
         "message": None,
+        "no_hydra": False,
     }
     default_arguments.update(repro_arguments)
 
@@ -151,6 +152,7 @@ def test_experiments_run_message(dvc, scm, mocker, flag):
         "tmp_dir": False,
         "copy_paths": [],
         "message": "mymessage",
+        "no_hydra": False,
     }
     default_arguments.update(repro_arguments)