lockfile: key params by def_path to match how they are loaded

[KR-Ravindra]

Problem

When a params file is written in dvc.yaml with a ./ prefix (e.g. params: [./my_params.yaml]), dvc status reports the whole file as new forever, and dvc repro re-runs the stage on every invocation, even though nothing changed:

$ dvc status
test:
	changed deps:
		new:                my_params.yaml

Reproduced on current main (3.67.2.dev) with the script from the issue.

Root cause

dvc.lock entries for deps and outs are keyed verbatim by def_path (dvc/stage/serialize.py:159, _dumpd), but the params section is keyed through Output.dumpd() (dvc/stage/serialize.py:104-105, _serialize_params_values), which rewrites in-repo paths as relpath(fs_path, stage.wdir) (dvc/output.py:843-846). The lock therefore ends up with params: {my_params.yaml: ...} while the ParamsDependency keeps def_path == "./my_params.yaml".

On load, StageLoader.fill_from_lock looks every item up by def_path (dvc/stage/loader.py:63-65): get_in(lock_data, ["params", "./my_params.yaml"]) returns None, fill_values is a no-op, hash_info.value stays None, and workspace_status reports the whole file as new.

Fix

Key the lockfile params section by param_dep.def_path, the same way deps/outs are already keyed in the same lockfile, so the serializer and the loader agree. One line in _serialize_params_values; the now-unused module constant PARAM_PATH is removed.

Lock files previously written with the normalized key are rewritten on the next dvc repro/dvc commit (which affected repos already trigger on every run today); after that the stage is reported clean.

How tested

Added three tests that fail on main and pass with the fix:

• tests/unit/stage/test_serialize_pipeline_lock.py::test_lock_params_keeps_def_path
• tests/unit/stage/test_loader_pipeline_file.py::test_load_stage_with_params_def_path_roundtrip (serialize to lock, load back, values filled)
• tests/func/test_status.py::test_params_file_with_dot_slash_path (stage add + reproduce, then status == {})

Before:

FAILED tests/unit/stage/test_serialize_pipeline_lock.py::test_lock_params_keeps_def_path
E     {'params': OrderedDict({'my_params.yaml': OrderedDict({'foo': 'foo'})})} != {'params': {'./my_params.yaml': OrderedDict({'foo': 'foo'})}}
FAILED tests/unit/stage/test_loader_pipeline_file.py::test_load_stage_with_params_def_path_roundtrip
E       name: None != 'params'
E       value: None != {'foo': 1}
FAILED tests/func/test_status.py::test_params_file_with_dot_slash_path
E   AssertionError: assert {'my_params.yaml': {'foo': 1}} == {'./my_params...': {'foo': 1}}
3 failed

After:

3 passed in 0.36s

pytest tests/unit/stage tests/unit/dependency tests/func/test_status.py tests/func/params tests/func/test_lockfile.py tests/func/test_stage_load.py tests/func/test_run.py tests/func/test_stage.py passes. ruff check, ruff format --check and mypy are clean on the changed files.

End-to-end with the script from the issue: dvc.lock now contains params: {./my_params.yaml: {foo: 1}}, dvc status prints "Data and pipelines are up to date.", a second dvc repro skips the stage, and editing foo is still reported as modified.

Links

• Closes dvc status: shows that params have changed when they haven't #9518

---

• I have followed the Contributing to DVC checklist.

• Documentation: no changes to the docs are needed for this fix.

This change was prepared with an AI agent operated by KR-Ravindra, who reviewed and tested it.

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[KR-Ravindra]

Closing: opened against the wrong repository; this change is for iterative/dvc.

[KR-Ravindra]

Reopening: iterative/dvc now redirects to this repository, so this is the correct target. Issue #9518 lives here as well.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.98%. Comparing base (2431ec6) to head (5f73986).
⚠️ Report is 213 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #11097      +/-   ##
==========================================
+ Coverage   90.68%   90.98%   +0.30%     
==========================================
  Files         504      505       +1     
  Lines       39795    41158    +1363     
  Branches     3141     3263     +122     
==========================================
+ Hits        36087    37448    +1361     
- Misses       3042     3071      +29     
+ Partials      666      639      -27     

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[KR-Ravindra]

Round 1 self-review.

Checked against main (56e5982): _dumpd keys deps/outs by def_path (dvc/stage/serialize.py:159), while _serialize_params_values keyed params through Output.dumpd(), which rewrites in-repo paths as relpath(fs_path, wdir) (dvc/output.py:843-846); fill_from_lock then looks params up by def_path (dvc/stage/loader.py:63-65), so ./my_params.yaml never matched its lock entry. Keying by def_path makes the writer agree with the reader and with how the rest of the lockfile is already keyed. The three new tests fail on main and pass here.

CI: the red jobs are the same ones failing on main's latest scheduled run (34299452210): mypy in the lint job and tests/func/test_repo_index.py::test_ignored_dir_unignored_pattern on Windows. Nothing in this diff touches either.

Marking ready.