[2pt] fiber.cond():wait() throws an error if fiber is cancelled

[TarantoolBot]

fiber.cond():wait() throws an arror if fiber is cancelled

Product: Tarantool
Since: 2.7.1, 2.6.2, 2.5.3, 1.10.9
Audience/target:
Root document: https://www.tarantool.io/en/doc/latest/reference/reference_lua/fiber/#lua-function.cond_object.wait
SME: @sergos
Peer reviewer: @

Details

Currently fiber.cond():wait() throws an error if waiting fiber is
cancelled.
Requested by @sergos in tarantool/tarantool@bd03dfc.

See more details in the issue comments.

[Totktonada]

I would ask to explicitly document the behaviour difference explicitly: prior the x.y.z.r version is it so (exclusive), after the version x.y.z.r it is so. The new behaviour is in action in the following tarantool versions:

• All 1.10 since 1.10.8-27-g8fa32f9d4.
• All 2.5 since 2.5.2-37-gbe7120796.
• All 2.6 since 2.6.1-65-g64422754b.
• All 2.7 since 2.7.0-76-gbd03dfc76.
• All 2.8+.

The old behaviour is kept for the following versions:

• All versions below 1.10.8-27-g8fa32f9d4 (exclusive).
• All 2.1*, 2.2*. 2.3*, 2.4*.

Otherwise, if someone will be hit by the difference in the behaviour, it may be nightmare to spot a reason.

In the relevant email I gave an example of this kind (not ideal, though).