Hi Maxime!

>> I am confused. It is used only during check phase (which is build-time),
>> so when cross-compiling, the arch for build machine is used for
>> native-inputs right?
> 
> The Go build system doesn't support cross-compilation currently.
> So, for explanation, let's assume gnu-build-system instead.
> 
> The issue is that, when cross-compiling, 'inputs' consists solely
> of the packages listed in the 'inputs' field of the package definition
> (When compiling natively, 'native-inputs' is merged into 'inputs'.)
> 
> As "coreutils" is not in "inputs", it follows that that (assoc-ref inputs "coreutils")
> returns #f. Thus, when (string-append (assoc-ref inputs "coreutils") "/bin/sleep")
> is executed, it raises an exception, as string-append expects strings only.
> Now, about:
> 
>> I am confused. It is used only during check phase (which is build-time),
>> so when cross-compiling, [...]
> 
> The [...]/bin/sleep binary is only used during the check phase (and therefore
> ignored when cross-compiling), yes, but the (string-append [...]) is _always_
> executed!
> 
>> so when cross-compiling, the arch for build machine is used for native-inputs,
>> right?
> 
> Yes.
> 
>> I wonder how other native-inputs like gettext etc doesn't give this error.
> 
> There's very little code doing (assoc-ref inputs "gettext"),
> (assoc-ref native-inputs "gettext") or (assoc-ref native-inputs "gettext")
> in Guix. The only case I found:
> 
>     # cargo-build-system
>    (when (assoc-ref inputs "gettext")
>      (setenv "GETTEXT_SYSTEM" (assoc-ref inputs "gettext")))
> 
> So, I'm not sure what you're referring to.
> 
> Simply including gettext in native-inputs doesn't cause an error.
> 
> It it trying to (string-append (assoc-ref inputs "gettext") "stuff") that
> raises an error when 'gettext' is not in 'inputs' or 'native-inputs' when compiling natively,
> or when 'gettext' is not in 'inputs' when cross-compiling,
> as in these cases, (assoc-ref inputs "gettext") returns #f.

Thanks so much for the explanation. I understood it now. :)

I have added your suggestion in v5.

Regards,
RG.