fix(wellness): harden Form/TSB and date rendering from code review

Address findings from the pre-merge review:
- Form (TSB) now computes only when ctl/atl are numeric (isinstance guard),
  so a non-numeric value can no longer raise out of format_wellness_entry and
  take down the entire wellness render.
- The Date line uses `or` chaining so a present-but-null `date` falls back to
  `id` instead of rendering "Date: None".
- update_wellness injects the written date into the API echo when it lacks
  id/date, so the confirmation body can't read "Date: N/A" under a dated header.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NGzHtDvJur9U7ysgRKRUTN

src/intervals_mcp_server/tools/wellness.py

@@ -180,6 +180,10 @@ async def update_wellness(  # pylint: disable=too-many-arguments,too-many-positi
         return f"Error updating wellness data: {result.get('message')}"
 
     # Intervals.icu echoes back the full updated record; render it for confirmation.
+    # If the echo omits the date, inject the one we wrote to so the confirmation
+    # body doesn't read "Date: N/A" under a dated header.
     if isinstance(result, dict):
+        if not result.get("id") and not result.get("date"):
+            result["date"] = date
         return f"Updated wellness for {date}:\n\n" + format_wellness_entry(result)
     return f"Updated wellness for {date}."

src/intervals_mcp_server/utils/formatting.py

@@ -167,9 +167,11 @@ def _format_training_metrics(entries: dict[str, Any]) -> list[str]:
 
     # Form (a.k.a. TSB, Training Stress Balance) = CTL - ATL. Intervals.icu does
     # not return this on the wellness record, so compute it when both components
-    # are present. Positive = fresher/tapered, negative = carrying fatigue.
+    # are present AND numeric. The isinstance guard keeps a non-numeric value from
+    # raising out of the formatter and taking down the whole wellness render.
+    # Positive = fresher/tapered, negative = carrying fatigue.
     ctl, atl = entries.get("ctl"), entries.get("atl")
-    if ctl is not None and atl is not None:
+    if isinstance(ctl, (int, float)) and isinstance(atl, (int, float)):
         training_metrics.append(f"- Form (TSB): {ctl - atl:.1f}")
 
     for k, label in [
@@ -350,8 +352,10 @@ def format_wellness_entry(entries: dict[str, Any], include_all_fields: bool = Fa
 
     lines = ["Wellness Data:"]
     # The wellness record's own date lives in `id` (e.g. "2025-05-24"); some call
-    # sites also inject an explicit `date`. Prefer `date`, fall back to `id`.
-    lines.append(f"Date: {entries.get('date', entries.get('id', 'N/A'))}")
+    # sites also inject an explicit `date`. Prefer `date`, fall back to `id`. Use
+    # `or` chaining (not get-with-default) so a present-but-null `date` still falls
+    # back rather than rendering "Date: None".
+    lines.append(f"Date: {entries.get('date') or entries.get('id') or 'N/A'}")
     lines.append("")
 
     training_metrics = _format_training_metrics(entries)

tests/test_formatting.py

@@ -82,6 +82,20 @@ def test_format_wellness_entry_prefers_explicit_date_over_id():
     assert "Date: 2024-06-02" in result
 
 
+def test_format_wellness_entry_null_date_falls_back_to_id():
+    """A present-but-null `date` falls back to `id`, not 'None'."""
+    result = format_wellness_entry({"id": "2024-06-01", "date": None, "ctl": 50})
+    assert "Date: 2024-06-01" in result
+    assert "Date: None" not in result
+
+
+def test_format_wellness_entry_non_numeric_ctl_atl_does_not_crash():
+    """Non-numeric ctl/atl must not raise; Form is simply omitted."""
+    result = format_wellness_entry({"id": "2024-06-01", "ctl": "n/a", "atl": "n/a"})
+    assert "Form (TSB)" not in result
+    assert "Date: 2024-06-01" in result
+
+
 def test_format_wellness_entry_include_all_fields():
     """
     Test that format_wellness_entry with include_all_fields=True includes additional unknown fields.

tests/test_wellness.py

@@ -126,3 +126,11 @@ def test_update_wellness_non_dict_result(monkeypatch):
     _patch_request(monkeypatch, [])
     out = asyncio.run(wellness.update_wellness(date="2025-05-24", weight=80))
     assert out == "Updated wellness for 2025-05-24."
+
+
+def test_update_wellness_echo_without_date_shows_written_date(monkeypatch):
+    # If the API echo omits id/date, the confirmation body must not read "Date: N/A".
+    _patch_request(monkeypatch, {"weight": 80})
+    out = asyncio.run(wellness.update_wellness(date="2025-05-24", weight=80))
+    assert "Date: 2025-05-24" in out
+    assert "Date: N/A" not in out