exp: fail fast in empty git repo (#8840)

dvc/repo/experiments/__init__.py

@@ -65,6 +65,11 @@ class Experiments:
 
     @property
     def scm(self):
+        from dvc.scm import SCMError
+
+        if self.repo.scm.no_commits:
+            raise SCMError("Empty Git repo. Add a commit to use experiments.")
+
         return self.repo.scm
 
     @cached_property

pyproject.toml

@@ -205,6 +205,7 @@ module = [
     "celery.*",
     "configobj.*",
     "dpath.*",
+    "distro",
     "dvc_http",
     "dvc_render.*",
     "dvc_ssh",
@@ -219,9 +220,12 @@ module = [
     "networkx.*",  # https://github.com/networkx/networkx/issues/3988
     "pygtrie.*",
     "pyinstrument",
+    "pyparsing",
     "pytest_docker.plugin",
     "ruamel.*",
     "ruamel.yaml.*",
+    "shortuuid",
+    "shtab",
     "tpi.*",
     "viztracer",
     "voluptuous",

tests/func/experiments/test_diff.py

@@ -1,16 +1,6 @@
 from funcy import first
 
 
-def test_diff_no_commits(tmp_dir):
-    from dvc.repo import Repo
-    from dvc.scm import Git
-
-    git = Git.init(tmp_dir.fs_path)
-    assert git.no_commits
-
-    assert Repo.init().experiments.diff() == {}
-
-
 def test_diff_empty(tmp_dir, scm, dvc, exp_stage):
     assert dvc.experiments.diff() == {"params": {}, "metrics": {}}
 

tests/func/experiments/test_experiments.py

@@ -13,7 +13,7 @@ from dvc.repo.experiments.exceptions import ExperimentExistsError
 from dvc.repo.experiments.queue.base import BaseStashQueue
 from dvc.repo.experiments.refs import CELERY_STASH
 from dvc.repo.experiments.utils import exp_refs_by_rev
-from dvc.scm import resolve_rev
+from dvc.scm import SCMError, resolve_rev
 from dvc.stage.exceptions import StageFileDoesNotExistError
 from dvc.utils.serialize import PythonFileCorruptedError
 from tests.scripts import COPY_SCRIPT
@@ -646,3 +646,20 @@ def test_clean(tmp_dir, scm, dvc, mocker):
     clean = mocker.spy(dvc.experiments.celery_queue.celery, "clean")
     dvc.experiments.clean()
     clean.assert_called_once_with()
+
+
+def test_experiment_no_commit(tmp_dir):
+    from scmrepo.git import Git
+
+    from dvc.repo import Repo
+
+    Git.init(tmp_dir.fs_path).close()
+
+    repo = Repo.init()
+    assert repo.scm.no_commits
+
+    try:
+        with pytest.raises(SCMError):  # noqa: PT011
+            repo.experiments.ls()
+    finally:
+        repo.close()

tests/func/experiments/test_show.py

@@ -41,17 +41,6 @@ def make_executor_info(**kwargs):
     return ExecutorInfo(**kwargs)
 
 
-@pytest.mark.vscode
-def test_show_no_commits(tmp_dir):
-    from dvc.repo import Repo
-    from dvc.scm import Git
-
-    git = Git.init(tmp_dir.fs_path)
-    assert git.no_commits
-
-    assert Repo.init().experiments.show() == {}
-
-
 @pytest.mark.vscode
 def test_show_branch_and_tag_name(tmp_dir, scm, dvc, exp_stage):
     with tmp_dir.branch("new/branch", new=True):