A PUT that must not erase your note

Habit days are set with an absolute PUT /habits/{id}/days/{date}: send the amount, the server stores it. Absolute rather than incremental on purpose, so an offline retry can never double-count.

When notes came along, the same endpoint took an optional note. The first version did the obvious thing:

row.amount = body.amount
row.note = (body.note or "").strip() or None

Which means ticking a day you’d already written about erased what you wrote. The app’s tick button sends {"amount": 1} with no note, and None overwrote the text.

Not sent is not the same as empty

Pydantic records which fields the client actually sent in model_fields_set. That gives three honest cases:

• note not sent: keep whatever is there.
• note: "" sent empty: clear it.
• note: "...": set it.

if "note" in body.model_fields_set:
    row.note = (body.note or "").strip() or None

A day that’s only a note

The same change raised a second question: what if you untick a day that has a note? Before, amount zero deleted the row. Now a day can hold just a note (ill, rested): amount zero, so not done, but kept. Clearing both the amount and the note removes it.

Tested as a sequence

The test walks through what a person would do: write a note, tick again, untick, and finally clear everything, checking the stored day after each step. The bug was in the sequence, so the test is one.