bug#37523: Print hint if build fails due to invalid character in package source base name

[zimoun]

Hi,

On Thu, 26 Sep 2019 at 18:01, Hartmut Goebel <h.goebel@crazy-compilers.com> 
wrote:

> guix shall print a hint if building fails due to the package source base
> name containing a character invalid in a store filename (e.g. "@" or "%").
>
> Currently, when building such a package, one gets an error message like:
>
> guix build: error: invalid character `@' in name 
> `kde-l10n-ca@valencia-14.11.80.tar.xz.drv'
>
>
> guix build should catch this error and print a hint like:
>
> You may add a ‘file-name’ field to the package source to work around
> this.
>
>
> Ludovic Courtès wrote on Sun Sep 08 22:07:10+0200 2019
>
>> Unfortunately it cannot really be caught. I mean, you could catch
>> ‘&store-protocol-error’ error conditions, but then the error message is
>> just a string, there’s no error code you can compare against.

If I read correctly, the error is raised by nix/libstore/store-api.cc:

--8<---------------cut here---------------start------------->8---
void checkStoreName(const string & name)
{
    string validChars = "+-._?=";
    /* Disallow names starting with a dot for possible security
       reasons (e.g., "." and ".."). */
    if (string(name, 0, 1) == ".")
        throw Error(format("invalid name: `%1%'") % name);
    foreach (string::const_iterator, i, name)
        if (!((*i >= 'A' && *i <= 'Z') ||
              (*i >= 'a' && *i <= 'z') ||
              (*i >= '0' && *i <= '9') ||
              validChars.find(*i) != string::npos))
        {
            throw Error(format("invalid character `%1%' in name `%2%'")
                % *i % name);
        }
}
--8<---------------cut here---------------end--------------->8---

Therefore, I am missing if this message “invalid character” should be
improved or if the check of the name should be done before on the Scheme
side.  Well, I am missing what could be the path to improve the
situation, if it needs.


All the best,
simon