fix: set_status never ran in a transaction (db.IsInTransaction not called)

[sveneberth]

Problem

set_status in toolkit/db.py contains:

# In case of already in transaction, just call the function.
if db.IsInTransaction:
    return transaction()

db.IsInTransaction is a function (viur.core.db.utils.IsInTransaction), so the condition tests the function object itself — which is always truthy. Consequences:

• set_status always takes the "already in transaction" shortcut and executes transaction() directly, without ever opening a transaction
• the db.RunInTransaction retry loop below is unreachable dead code (the retry parameter has no effect)
• every read-check-write cycle built on set_status (precondition checks, +/- counter mutations, status changes) is not atomic — concurrent modifications of the same entity can interleave and lose updates

This is particularly relevant for consumers like viur-shop, where all order status transitions (set_ordered / set_paid / set_rts, payment appends) rely on set_status and can race with concurrent payment-provider callbacks (return handler vs. webhook).

Introduced with #25, which added the in-transaction shortcut but missed the call parentheses.

Solution

Call the function: if db.IsInTransaction():. Also documented the transactional behaviour in the set_status docstring.

🤖 Generated with Claude Code

[Copilot]

Pull request overview

Fixes a logic bug in set_status where db.IsInTransaction (a function) was previously checked without being called, causing the “already in transaction” branch to always be taken and preventing db.RunInTransaction (and its retry loop) from ever running. The PR also clarifies the transactional behavior in the function’s docstring.

Changes:

• Call db.IsInTransaction() instead of checking the function object.
• Document that the read-check-write cycle executes within a datastore transaction (joining an existing one or opening a new one with retries).

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[sveneberth]

@claude LGTM

[phorward]

Fortunately, this bug was not in Skeleton.patch() https://github.com/viur-framework/viur-core/blob/main/src/viur/core/skeleton/skeleton.py#L837 anyway, I advise to use skel.patch() now and remove this function entirely.