post_live_metrics: Pass params on start event.

dvc/repo/experiments/queue/workspace.py

@@ -22,7 +22,7 @@ from ..executor.base import (
 )
 from ..executor.local import WorkspaceExecutor
 from ..refs import EXEC_BRANCH, WORKSPACE_STASH
-from ..utils import get_exp_rwlock
+from ..utils import get_exp_rwlock, to_studio_params
 from .base import BaseStashQueue, QueueDoneResult, QueueEntry, QueueGetResult
 
 if TYPE_CHECKING:
@@ -104,10 +104,14 @@ class WorkspaceQueue(BaseStashQueue):
         exec_name = self._EXEC_NAME or entry.stash_rev
         infofile = self.get_infofile_path(exec_name)
         try:
-            post_live_metrics(
-                "start", executor.info.baseline_rev, executor.info.name, "dvc"
-            )
             rev = entry.stash_rev
+            post_live_metrics(
+                "start",
+                executor.info.baseline_rev,
+                executor.info.name,
+                "dvc",
+                params=to_studio_params(self.repo.params.show()),
+            )
             exec_result = executor.reproduce(
                 info=executor.info,
                 rev=rev,

dvc/repo/experiments/utils.py

@@ -310,3 +310,32 @@ def get_random_exp_name(scm, baseline_rev):
         exp_ref = ExpRefInfo(baseline_sha=baseline_rev, name=name)
         if not scm.get_ref(str(exp_ref)):
             return name
+
+
+def to_studio_params(dvc_params):
+    """Convert from internal DVC format to Studio format.
+
+    From:
+
+    {
+        "workspace": {
+            "data": {
+                "params.yaml": {
+                    "data": {"foo": 1}
+                }
+            }
+        }
+    }
+
+    To:
+
+    {
+        "params.yaml": {"foo": 1}
+    }
+    """
+    result = {}
+    for rev_data in dvc_params.values():
+        for file_name, file_data in rev_data["data"].items():
+            result[file_name] = file_data["data"]
+
+    return result

tests/func/experiments/test_utils.py

@@ -53,6 +53,7 @@ def test_post_to_studio(tmp_dir, dvc, scm, exp_stage, mocker, monkeypatch):
         "repo_url": "STUDIO_REPO_URL",
         "baseline_sha": baseline_sha,
         "name": name,
+        "params": {"params.yaml": {"foo": 1}},
         "client": "dvc",
     }