substr("x", 0, 0) returns "x" instead of ""

[alexyakunin]

It seems substr assumes the whole string tail must be returned when the last argument is zero:

terraform console
> substr("abc", 0, 0)
abc
> substr("abc", 1, 0)
bc

This behavior isn't described in the documentation; moreover, it seems this can lead to a number of issues when the length of a substring is computed rather than pre-defined.

[nick96]

I'm interested in contributing to terraform and thought this issue looked good (hope that's okay!). Looks like this is an issue in zclconf/go-cty. I've submitted a patch there (again, hope that's okay!)

[nick96]

My upstream patch got merged. They're not ready to release a new version of go-cty and there's also the issue of this potentially being a breaking change (?)

[alisdair]

Hi @nick96! The go-cty release has been pulled into master now, so this fix will go out as part of 0.13. Thanks for your contribution!

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