exp show: show exp when checkpoint is running(#7329)

fix: #7329
In a previous PR, we introduce a bug which use `HEAD` as the workspace
commit, while if there is a checkpoint is running, the `HEAD` is
actually changing all the time, we should use
`refs/exps/exec/EXEC_BASELINE` instead.

1. add `fix_exp_head` transfer in `dvc/scm.py::resolve_rev`
2. remove fix_exp_head from `diff`, `metrics diff`, `params diff` and
   `plots diff`
3. modify a functional test to simulate the running conditions

dvc/repo/diff.py

@@ -5,7 +5,6 @@ from typing import Dict, List
 
 from dvc.exceptions import PathMissingError
 from dvc.repo import locked
-from dvc.repo.experiments.utils import fix_exp_head
 
 logger = logging.getLogger(__name__)
 
@@ -27,8 +26,7 @@ def diff(self, a_rev="HEAD", b_rev=None, targets=None):
 
     repo_fs = RepoFileSystem(self)
 
-    a_rev = fix_exp_head(self.scm, a_rev)
-    b_rev = fix_exp_head(self.scm, b_rev) if b_rev else "workspace"
+    b_rev = b_rev if b_rev else "workspace"
     results = {}
     missing_targets = {}
     for rev in self.brancher(revs=[a_rev, b_rev]):

dvc/repo/experiments/diff.py

@@ -1,6 +1,5 @@
 import logging
 
-from dvc.repo.experiments.utils import fix_exp_head
 from dvc.utils.diff import diff as _diff
 from dvc.utils.diff import format_dict
 
@@ -15,16 +14,12 @@ def diff(repo, *args, a_rev=None, b_rev=None, param_deps=False, **kwargs):
         return {}
 
     if a_rev:
-        a_rev = fix_exp_head(repo.scm, a_rev)
         rev = resolve_rev(repo.scm, a_rev)
         old = _collect_experiment_commit(repo, rev, param_deps=param_deps)
     else:
-        old = _collect_experiment_commit(
-            repo, fix_exp_head(repo.scm, "HEAD"), param_deps=param_deps
-        )
+        old = _collect_experiment_commit(repo, "HEAD", param_deps=param_deps)
 
     if b_rev:
-        b_rev = fix_exp_head(repo.scm, b_rev)
         rev = resolve_rev(repo.scm, b_rev)
         new = _collect_experiment_commit(repo, rev, param_deps=param_deps)
     else:

dvc/repo/metrics/diff.py

@@ -1,4 +1,3 @@
-from dvc.repo.experiments.utils import fix_exp_head
 from dvc.utils.diff import diff as _diff
 from dvc.utils.diff import format_dict
 
@@ -10,8 +9,7 @@ def diff(repo, *args, a_rev=None, b_rev=None, **kwargs):
     with_unchanged = kwargs.pop("all", False)
 
     a_rev = a_rev or "HEAD"
-    a_rev = fix_exp_head(repo.scm, a_rev)
-    b_rev = fix_exp_head(repo.scm, b_rev) or "workspace"
+    b_rev = b_rev or "workspace"
 
     metrics = repo.metrics.show(*args, **kwargs, revs=[a_rev, b_rev])
     old = metrics.get(a_rev, {}).get("data", {})

dvc/repo/params/diff.py

@@ -1,4 +1,3 @@
-from dvc.repo.experiments.utils import fix_exp_head
 from dvc.utils.diff import diff as _diff
 from dvc.utils.diff import format_dict
 
@@ -10,8 +9,7 @@ def diff(repo, *args, a_rev=None, b_rev=None, **kwargs):
     with_unchanged = kwargs.pop("all", False)
 
     a_rev = a_rev or "HEAD"
-    a_rev = fix_exp_head(repo.scm, a_rev)
-    b_rev = fix_exp_head(repo.scm, b_rev) or "workspace"
+    b_rev = b_rev or "workspace"
 
     params = repo.params.show(*args, **kwargs, revs=[a_rev, b_rev])
 

dvc/repo/plots/diff.py

@@ -1,6 +1,3 @@
-from dvc.repo.experiments.utils import fix_exp_head
-
-
 def _revisions(repo, revs, experiment):
     revisions = revs or []
     if experiment and len(revisions) == 1:
@@ -9,7 +6,7 @@ def _revisions(repo, revs, experiment):
             revisions.append(baseline[:7])
     if len(revisions) <= 1:
         if len(revisions) == 0 and repo.scm.is_dirty():
-            revisions.append(fix_exp_head(repo.scm, "HEAD"))
+            revisions.append("HEAD")
         revisions.append("workspace")
     return revisions
 

dvc/scm.py

@@ -111,8 +111,10 @@ def clone(url: str, to_path: str, **kwargs):
 def resolve_rev(scm: "Git", rev: str) -> str:
     from scmrepo.exceptions import RevError as InternalRevError
 
+    from dvc.repo.experiments.utils import fix_exp_head
+
     try:
-        return scm.resolve_rev(rev)
+        return scm.resolve_rev(fix_exp_head(scm, rev))
     except InternalRevError as exc:
         # `scm` will only resolve git branch and tag names,
         # if rev is not a sha it may be an abbreviated experiment name
@@ -141,7 +143,6 @@ def iter_revs(
     all_commits: bool = False,
     all_experiments: bool = False,
 ) -> Mapping[str, List[str]]:
-    from dvc.repo.experiments.utils import fix_exp_head
 
     if num < 1 and num != -1:
         raise InvalidArgumentError(f"Invalid number of commits '{num}'")
@@ -160,8 +161,7 @@ def iter_revs(
             if num == n:
                 break
             try:
-                head = fix_exp_head(scm, f"{rev}~{n}")
-                assert head
+                head = f"{rev}~{n}"
                 revs.append(resolve_rev(scm, head))
             except RevError:
                 break

tests/func/experiments/test_show.py

@@ -388,7 +388,7 @@ def test_show_running_executor(tmp_dir, scm, dvc, exp_stage):
 def test_show_running_checkpoint(
     tmp_dir, scm, dvc, checkpoint_stage, workspace, mocker
 ):
-    from dvc.repo.experiments.base import EXEC_BRANCH
+    from dvc.repo.experiments.base import EXEC_BASELINE, EXEC_BRANCH
     from dvc.repo.experiments.executor.local import TempDirExecutor
 
     baseline_rev = scm.get_rev()
@@ -422,6 +422,8 @@ def test_show_running_checkpoint(
     )
     if workspace:
         scm.set_ref(EXEC_BRANCH, str(exp_ref), symbolic=True)
+        scm.set_ref(EXEC_BASELINE, str(baseline_rev))
+        scm.checkout(str(exp_ref))
 
     results = dvc.experiments.show()