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Author SHA1 Message Date
Fraser Waters ab7ed92b87
Use promise rather than `atomic.Value` to record step errors. ()
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# Description

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Please also include relevant motivation and context. -->

Fixes https://github.com/pulumi/pulumi/issues/14611.

`atomic.Value` panics if a second value is written to it which isn't
_exactly_ the same type. We were using this to atomically record any
errors that happened, although where only interested in saving the first
error.

This was fine if no or one error happened, or if multiple errors
happened that all were the same error type. But if two errors if
different error types happened `sync.Value` would panic.

Switched to use a promise completion source instead. If any error
happens we use it to reject the completion source, we also log if this
isn't the first error we've seen (a capabilitiy that `sync.Value` didn't
give us). At the end of the step executor being used when `Errored()` is
called we try to get the result of the completion source.

## Checklist

- [x] I have run `make tidy` to update any new dependencies
- [x] I have run `make lint` to verify my code passes the lint check
  - [ ] I have formatted my code using `gofumpt`

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- [x] I have added tests that prove my fix is effective or that my
feature works - Added tests for the new promise function `TryResult`,
not sure it's that needed to try and write a test for the error case we
hit in  now that it's type safe.
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- [x] I have run `make changelog` and committed the
`changelog/pending/<file>` documenting my change
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2023-11-18 19:03:35 +00:00
Fraser Waters 478c29908f
Add a strict opinionated promise library ()
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# Description

<!--- Please include a summary of the change and which issue is fixed.
Please also include relevant motivation and context. -->

Prompted by having another case in
https://github.com/pulumi/pulumi/pull/14548 that looked like "this is
just a promise".

We already had a mini-promise library for provider config in
sdk/go/common/resource/plugin/provider_plugin.go. Plus a couple of
places where we did a poor mans Go promise by having a WaitGroup plus a
variable to set (see the two changes in /pkg).

This adds a little promise library to safely cover all three of these
cases plus the case I'll be adding in . It is _minimal_ adding
just the features of promises needed for these initial cases. We can add
to it as needed.

I suspect we've got a number of places in test code that could probably
use this as well, but I haven't gone through that. I also suspect that
having this type available will result in more places in the future
being simpler because "its just a promise" is a fairly common scenario
in async systems. In fact Output's internally _are just a promise_ so we
could probably rewrite their internals using this, add a `Then()` like
method for apply and all the async complexity gets handled in the
promise layer while the output layer just cares about
unknowns/secrets/etc.

## Checklist

- [x] I have run `make tidy` to update any new dependencies
- [x] I have run `make lint` to verify my code passes the lint check
  - [ ] I have formatted my code using `gofumpt`

<!--- Please provide details if the checkbox below is to be left
unchecked. -->
- [x] I have added tests that prove my fix is effective or that my
feature works
<!--- 
User-facing changes require a CHANGELOG entry.
-->
- [ ] I have run `make changelog` and committed the
`changelog/pending/<file>` documenting my change - This is in
sdk/go/common and I'm considering it an non-public api for now.
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You must then bump the API version in
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it to the service.
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- [ ] Yes, there are changes in this PR that warrants bumping the Pulumi
Cloud API version
<!-- @Pulumi employees: If yes, you must submit corresponding changes in
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2023-11-15 14:53:12 +00:00