experiments: support dvc repro --exp command line params

dvc/command/repro.py

@@ -44,6 +44,7 @@ def run(self):
                     queue=self.args.queue,
                     run_all=self.args.run_all,
                     jobs=self.args.jobs,
+                    params=self.args.params,
                 )
 
                 if len(stages) == 0:
@@ -177,6 +178,13 @@ def add_parser(subparsers, parent_parser):
         default=False,
         help=argparse.SUPPRESS,
     )
+    repro_parser.add_argument(
+        "--params",
+        action="append",
+        default=[],
+        help="Declare parameter values for an experiment.",
+        metavar="[<filename>:]<params_list>",
+    )
     repro_parser.add_argument(
         "--queue", action="store_true", default=False, help=argparse.SUPPRESS
     )

dvc/exceptions.py

@@ -194,6 +194,14 @@ def __init__(self, path):
         )
 
 
+class TOMLFileCorruptedError(DvcException):
+    def __init__(self, path):
+        path = relpath(path)
+        super().__init__(
+            f"unable to read: '{path}', TOML file structure is corrupted"
+        )
+
+
 class RecursiveAddingWhileUsingFilename(DvcException):
     def __init__(self):
         super().__init__(

dvc/repo/experiments/__init__.py

@@ -2,13 +2,16 @@
 import os
 import re
 import tempfile
+from collections import defaultdict
+from collections.abc import Mapping
 from concurrent.futures import ProcessPoolExecutor, as_completed
 from contextlib import contextmanager
 from typing import Iterable, Optional
 
 from funcy import cached_property
 
 from dvc.exceptions import DvcException
+from dvc.path_info import PathInfo
 from dvc.repo.experiments.executor import ExperimentExecutor, LocalExecutor
 from dvc.scm.git import Git
 from dvc.stage.serialize import to_lockfile
@@ -139,21 +142,39 @@ def _scm_checkout(self, rev):
         logger.debug("Checking out experiment commit '%s'", rev)
         self.scm.checkout(rev)
 
-    def _stash_exp(self, *args, **kwargs):
+    def _stash_exp(self, *args, params: Optional[dict] = None, **kwargs):
         """Stash changes from the current (parent) workspace as an experiment.
+
+        Args:
+            params: Optional dictionary of parameter values to be used.
+                Values take priority over any parameters specified in the
+                user's workspace.
         """
         rev = self.scm.get_rev()
+
+        # patch user's workspace into experiments clone
         tmp = tempfile.NamedTemporaryFile(delete=False).name
         try:
             self.repo.scm.repo.git.diff(patch=True, output=tmp)
             if os.path.getsize(tmp):
                 logger.debug("Patching experiment workspace")
                 self.scm.repo.git.apply(tmp)
-            else:
+            elif not params:
+                # experiment matches original baseline
                 raise UnchangedExperimentError(rev)
         finally:
             remove(tmp)
+
+        # update experiment params from command line
+        if params:
+            self._update_params(params)
+
+        # save additional repro command line arguments
         self._pack_args(*args, **kwargs)
+
+        # save experiment as a stash commit w/message containing baseline rev
+        # (stash commits are merge commits and do not contain a parent commit
+        # SHA)
         msg = f"{self.STASH_MSG_PREFIX}{rev}"
         self.scm.repo.git.stash("push", "-m", msg)
         return self.scm.resolve_rev("stash@{0}")
@@ -166,6 +187,36 @@ def _unpack_args(self, tree=None):
         args_file = os.path.join(self.exp_dvc.tmp_dir, self.PACKED_ARGS_FILE)
         return ExperimentExecutor.unpack_repro_args(args_file, tree=tree)
 
+    def _update_params(self, params: dict):
+        """Update experiment params files with the specified values."""
+        from dvc.utils.toml import dump_toml, parse_toml_for_update
+        from dvc.utils.yaml import dump_yaml, parse_yaml_for_update
+
+        logger.debug("Using experiment params '%s'", params)
+
+        # recursive dict update
+        def _update(dict_, other):
+            for key, value in other.items():
+                if isinstance(value, Mapping):
+                    dict_[key] = _update(dict_.get(key, {}), value)
+                else:
+                    dict_[key] = value
+            return dict_
+
+        loaders = defaultdict(lambda: parse_yaml_for_update)
+        loaders.update({".toml": parse_toml_for_update})
+        dumpers = defaultdict(lambda: dump_yaml)
+        dumpers.update({".toml": dump_toml})
+
+        for params_fname in params:
+            path = PathInfo(self.exp_dvc.root_dir) / params_fname
+            with self.exp_dvc.tree.open(path, "r") as fobj:
+                text = fobj.read()
+            suffix = path.suffix.lower()
+            data = loaders[suffix](text, path)
+            _update(data, params[params_fname])
+            dumpers[suffix](path, data)
+
     def _commit(self, exp_hash, check_exists=True, branch=True):
         """Commit stages as an experiment and return the commit SHA."""
         if not self.scm.is_dirty():
@@ -207,23 +258,19 @@ def reproduce_queued(self, **kwargs):
             )
         return results
 
-    def new(self, *args, workspace=True, **kwargs):
+    def new(self, *args, **kwargs):
         """Create a new experiment.
 
         Experiment will be reproduced and checked out into the user's
         workspace.
         """
         rev = self.repo.scm.get_rev()
         self._scm_checkout(rev)
-        if workspace:
-            try:
-                stash_rev = self._stash_exp(*args, **kwargs)
-            except UnchangedExperimentError as exc:
-                logger.info("Reproducing existing experiment '%s'.", rev[:7])
-                raise exc
-        else:
-            # configure params via command line here
-            pass
+        try:
+            stash_rev = self._stash_exp(*args, **kwargs)
+        except UnchangedExperimentError as exc:
+            logger.info("Reproducing existing experiment '%s'.", rev[:7])
+            raise exc
         logger.debug(
             "Stashed experiment '%s' for future execution.", stash_rev[:7]
         )
@@ -365,8 +412,10 @@ def checkout_exp(self, rev):
         tmp = tempfile.NamedTemporaryFile(delete=False).name
         self.scm.repo.head.commit.diff("HEAD~1", patch=True, output=tmp)
 
-        logger.debug("Stashing workspace changes.")
-        self.repo.scm.repo.git.stash("push")
+        dirty = self.repo.scm.is_dirty()
+        if dirty:
+            logger.debug("Stashing workspace changes.")
+            self.repo.scm.repo.git.stash("push")
 
         try:
             if os.path.getsize(tmp):
@@ -379,7 +428,8 @@ def checkout_exp(self, rev):
             raise DvcException("failed to apply experiment changes.")
         finally:
             remove(tmp)
-            self._unstash_workspace()
+            if dirty:
+                self._unstash_workspace()
 
         if need_checkout:
             dvc_checkout(self.repo)

dvc/repo/reproduce.py

@@ -60,7 +60,7 @@ def reproduce(
     recursive=False,
     pipeline=False,
     all_pipelines=False,
-    **kwargs
+    **kwargs,
 ):
     from dvc.utils import parse_target
 
@@ -71,6 +71,7 @@ def reproduce(
         )
 
     experiment = kwargs.pop("experiment", False)
+    params = _parse_params(kwargs.pop("params", []))
     queue = kwargs.pop("queue", False)
     run_all = kwargs.pop("run_all", False)
     jobs = kwargs.pop("jobs", 1)
@@ -81,6 +82,7 @@ def reproduce(
                 target=target,
                 recursive=recursive,
                 all_pipelines=all_pipelines,
+                params=params,
                 queue=queue,
                 run_all=run_all,
                 jobs=jobs,
@@ -116,6 +118,31 @@ def reproduce(
     return _reproduce_stages(active_graph, targets, **kwargs)
 
 
+def _parse_params(path_params):
+    from flatten_json import unflatten
+    from yaml import safe_load, YAMLError
+    from dvc.dependency.param import ParamsDependency
+
+    ret = {}
+    for path_param in path_params:
+        path, _, params_str = path_param.rpartition(":")
+        # remove empty strings from params, on condition such as `-p "file1:"`
+        params = {}
+        for param_str in filter(bool, params_str.split(",")):
+            try:
+                # interpret value strings using YAML rules
+                key, value = param_str.split("=")
+                params[key] = safe_load(value)
+            except (ValueError, YAMLError):
+                raise InvalidArgumentError(
+                    f"Invalid param/value pair '{param_str}'"
+                )
+        if not path:
+            path = ParamsDependency.DEFAULT_PARAMS_FILE
+        ret[path] = unflatten(params, ".")
+    return ret
+
+
 def _reproduce_experiments(repo, run_all=False, jobs=1, **kwargs):
     if run_all:
         return repo.experiments.reproduce_queued(jobs=jobs)

dvc/utils/toml.py

@@ -0,0 +1,21 @@
+import toml
+
+from dvc.exceptions import TOMLFileCorruptedError
+
+
+def parse_toml_for_update(text, path):
+    """Parses text into Python structure.
+
+    NOTE: Python toml package does not currently use ordered dicts, so
+    keys may be re-ordered between load/dump, but this function will at
+    least preserve comments.
+    """
+    try:
+        return toml.loads(text, decoder=toml.TomlPreserveCommentDecoder())
+    except toml.TomlDecodeError as exc:
+        raise TOMLFileCorruptedError(path) from exc
+
+
+def dump_toml(path, data):
+    with open(path, "w", encoding="utf-8") as fobj:
+        toml.dump(data, fobj, encoder=toml.TomlPreserveCommentEncoder())

tests/unit/command/test_repro.py

@@ -15,6 +15,7 @@
     "recursive": False,
     "force_downstream": False,
     "experiment": False,
+    "params": [],
     "queue": False,
     "run_all": False,
     "jobs": None,