Support message. (#33)

Optional string in the `start` event.
Internally cutting to 72 characters to match commit tile limit.

src/dvc_studio_client/post_live_metrics.py

@@ -68,13 +68,14 @@ def get_studio_token_and_repo_url(studio_token=None, studio_repo_url=None):
     return studio_token, studio_repo_url
 
 
-def post_live_metrics(
+def post_live_metrics(  # noqa: C901
     event_type: Literal["start", "data", "done"],
     baseline_sha: str,
     name: str,
     client: Literal["dvc", "dvclive"],
     experiment_rev: Optional[str] = None,
     machine: Optional[Dict[str, Any]] = None,
+    message: Optional[str] = None,
     metrics: Optional[Dict[str, Any]] = None,
     params: Optional[Dict[str, Any]] = None,
     plots: Optional[Dict[str, Any]] = None,
@@ -110,6 +111,8 @@ def post_live_metrics(
                 "instance": "t2.micro"
             }
             ```
+        message: (Optional[str]): Custom message to be displayed as the commit
+            message in Studio UI.
         metrics (Optional[Dict[str, Any]]): Updates to DVC metric files.
             Defaults to `None`.
             Only used when `event_type="data"`.
@@ -178,7 +181,11 @@ def post_live_metrics(
     if machine:
         body["machine"] = machine
 
-    if event_type == "data":
+    if event_type == "start":
+        if message:
+            # Cutting the message to match the commit title length limit.
+            body["message"] = message[:72]
+    elif event_type == "data":
         if step is None:
             logger.warning("Missing `step` in `data` event.")
             return None

src/dvc_studio_client/schema.py

@@ -29,7 +29,11 @@ def Choices(*choices):
     }
 )
 SCHEMAS_BY_TYPE = {
-    "start": BASE_SCHEMA,
+    "start": BASE_SCHEMA.extend(
+        {
+            "message": str,
+        }
+    ),
     "data": BASE_SCHEMA.extend(
         {
             Required("step"): int,

tests/test_post_live_metrics.py

@@ -378,3 +378,64 @@ def test_post_live_metrics_token_and_repo_url_args(mocker, monkeypatch):
         },
         timeout=5,
     )
+
+
+def test_post_live_metrics_message(mocker, monkeypatch):
+    monkeypatch.setenv(DVC_STUDIO_URL, "https://0.0.0.0")
+    monkeypatch.setenv(DVC_STUDIO_TOKEN, "FOO_TOKEN")
+    monkeypatch.setenv(STUDIO_REPO_URL, "FOO_REPO_URL")
+
+    mocked_response = mocker.MagicMock()
+    mocked_response.status_code = 200
+    mocked_post = mocker.patch("requests.post", return_value=mocked_response)
+
+    assert post_live_metrics(
+        "start",
+        "f" * 40,
+        "fooname",
+        "fooclient",
+        message="FOO_MESSAGE",
+    )
+
+    mocked_post.assert_called_with(
+        "https://0.0.0.0/api/live",
+        json={
+            "type": "start",
+            "repo_url": "FOO_REPO_URL",
+            "baseline_sha": "f" * 40,
+            "name": "fooname",
+            "client": "fooclient",
+            "message": "FOO_MESSAGE",
+        },
+        headers={
+            "Authorization": "token FOO_TOKEN",
+            "Content-type": "application/json",
+        },
+        timeout=5,
+    )
+
+    # Test message length limit
+    assert post_live_metrics(
+        "start",
+        "f" * 40,
+        "fooname",
+        "fooclient",
+        message="X" * 100,
+    )
+
+    mocked_post.assert_called_with(
+        "https://0.0.0.0/api/live",
+        json={
+            "type": "start",
+            "repo_url": "FOO_REPO_URL",
+            "baseline_sha": "f" * 40,
+            "name": "fooname",
+            "client": "fooclient",
+            "message": "X" * 72,
+        },
+        headers={
+            "Authorization": "token FOO_TOKEN",
+            "Content-type": "application/json",
+        },
+        timeout=5,
+    )