Add parseduration() function

[remilapeyre]

Closes #16474

[remilapeyre]

I found myself needing this to better express durations where an integer is expected. I made the choice to truncate the result when it cannot be exactly represented in the given unit because it seems to me that most of the time providers are expecting an integer rather than an Int more often than a Float to express durations.

[codecov]

Codecov Report

Merging #27048 (564e86a) into master (111825d) will decrease coverage by 0.04%.
The diff coverage is 3.03%.

Impacted Files	Coverage Δ
lang/funcs/datetime.go	28.88% <0.00%> (-71.12%)	⬇️
lang/functions.go	92.19% <100.00%> (+0.05%)	⬆️
terraform/eval_diff.go	66.51% <0.00%> (-0.92%)	⬇️
terraform/node_resource_apply_instance.go	75.00% <0.00%> (-0.79%)	⬇️
terraform/evaluate.go	52.89% <0.00%> (-0.42%)	⬇️
states/statefile/version4.go	58.19% <0.00%> (+0.23%)	⬆️

[reist01]

Is there anything needed here apart from resolving conflicts?

[hashicorp-cla]

All committers have signed the CLA.

[zx8]

Can we get some movement on this?

I have found myself needing this several times in the years since this PR was originally raised and it seems like a relatively simple thing to review & merge (once conflicts have been resolved).

[crw]

Thanks for this submission and the PR bump. As for getting a PR accepted, please see this comment: #28855 (comment), specifically:

We're being pretty cautious about adding new functions that overlap with existing use-cases because Terraform has grown quite an unwieldy collection of builtins over the years, and so we've been considering various ways to allow for externally-defined functions (e.g. #2771) to avoid continuing to grow that set. However, that's not something we'll be working on in the very near future, due to our current focus being elsewhere, so we'll revisit this at a later time and post any updates in those other issues.

Reviewing the comments on the original issue, my guess is that this would more likely be considered as a plugin function, rather than as a built-in function. However, I'll bring this up for review in triage to see where it stands. Thanks again!

[crw]

Reviewing the comments on the original issue, my guess is that this would more likely be considered as a plugin function, rather than as a built-in function.

Confirmed that this is currently considered more appropriate as a plugin function rather than as a built-in. I will update this PR when such functionality is available. Thanks!