add hexadecimal support for tonumber()

[joe-bowman]

fixes #22584

add ability for tonumber() to support 0x prefixed hexadecimal strings

e.g.

variable "v1" {
    default = "0x99"
}
output "input-v1" {
    value = tonumber(var.v1)
}

will return:

Apply complete! Resources: 0 added, 0 changed, 0 destroyed.

Outputs:

input-v1 = 153

[hashicorp-cla]

All committers have signed the CLA.

[apparentlymart]

Hi @joe-bowman! Thanks for working on this.

As you've seen in the implementation, tonumber (and the other similar to... functions) are intended as ways to hint to Terraform to perform one of its normal type conversion behaviors. I think it'd be confusing to add this exception only in the case of converting numbers, since numbers are intentionally required to be decimal in normal conversions to reduce the risk inadvertent implicit misbehavior.

What do you think about adding a new function called parseint instead, which would be explicitly about integer parsing, rather than type conversion, and could thus have a more explicit interface for handling numbers of different bases.

For example, it could have the signature parseint(string, base) so that to parse hexadecimal you'd call parseint("ff", 16) and get back 255.

We tend to prefer to avoid "implicit" behaviors like saying that a 0x prefix implies base 16, so my preference would be to instead just make the base argument be required and thus be explicit about which base a particular situation is expecting. However, if you have a specific use-case for accepting strings containing numbers in arbitrary bases defined by prefixes, rather than a configuration being explicit about which base it's expecting, I'd be happy to talk about it further and see if the use-case is common enough to override our default design principle.

[jeet-parekh]

@joe-bowman, I would like to give it a shot if you aren't working on this.

[joe-bowman]

Please feel free - don't have the capacity to do it this week. Thanks, Joe

…

On Wed, 4 Sep 2019, 18:44 Jeet Parekh, ***@***.***> wrote: @joe-bowman <https://github.com/joe-bowman>, I would like to give it a shot if you aren't working on this. — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#22585?email_source=notifications&email_token=ABA7QYC3PRBY5Q22NNZBI2TQH7XXNA5CNFSM4IPFN7VKYY3PNVWWK3TUL52HS4DFVREXG43VMVBW63LNMVXHJKTDN5WW2ZLOORPWSZGOD54MKNI#issuecomment-528008501>, or mute the thread <https://github.com/notifications/unsubscribe-auth/ABA7QYG6DPOYVPKZXKRMSKDQH7XXNANCNFSM4IPFN7VA> .

[jeet-parekh]

Cool, thanks. Will let you know if there's an update.

[danieldreier]

I'm going to close this because the parseint function PR was merged and so obviates this. Thanks @joe-bowman for suggesting this!

[ghost]

I'm going to lock this issue because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active issues.

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