fix a couple of partial read/write bugs #11981
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If one end of a stream does a partial read or write, we leave the other end in a `GuestReady` state, allowing further reads or writes to proceed until the buffer has been drained or filled, respectively. However, once we've delivered the event regarding the partial operation, we need to set the state back to `Open`, since we'll have released the buffer back to the guest at that point. Signed-off-by: Joel Dice <joel.dice@fermyon.com>
If the `StreamProducer` calls `Destination::set_buffer`, we need to make sure all the items in that buffer have been delivered to the receiver (or the receiver closes its end) before telling it the write end has been dropped. Signed-off-by: Joel Dice <joel.dice@fermyon.com>
These cover a couple of scenarios where the guest and/or host read owned resource items one-at-a-time from writes of more than one item, forcing the writer to re-take ownership of the unwritten items between writes. This also covers the case where the host's `StreamProducer` returns `StreamResult::Dropped` after calling `Destination::set_buffer`, in which case Wasmtime must delay telling the other end about the dropped stream until that buffer has been drained. Signed-off-by: Joel Dice <joel.dice@fermyon.com>
alexcrichton
approved these changes
Nov 4, 2025
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This fixes and adds test coverage for a couple of bugs involving component model streams:
delay returning
Droppeduntil producer buffer drainedIf the
StreamProducercallsDestination::set_buffer, we need to make sure all the items in that buffer have been delivered to the receiver (or the receiver closes its end) before telling it the write end has been dropped.reset read/write state back to
Openon event deliveryIf one end of a stream does a partial read or write, we leave the other end in a
GuestReadystate, allowing further reads or writes to proceed until the buffer has been drained or filled, respectively. However, once we've delivered the event regarding the partial operation, we need to set the state back toOpen, since we'll have released the buffer back to the guest at that point.