Re: [PATCH pve-common v4 01/17] json schema: add multiline string format

[Wolfgang Bumiller <w.bumiller@proxmox.com>]

Given that right now, newlines are almost never wanted/allowed in our
API (apart from comments), there's a case to be made here that we might
just want a multiline schema flag. (Where by default we'd reject
newlines. This could potentially remove a whole class of possible future
section-config related bugs…)

Also, consider that on the rust side, 'format', 'enum', 'pattern', and
the verify-functions are part of the `ApiStringFormat` *enum*, so you
can only have one, and we do not have *named* formats at all.

Thomas also played around with the thought of adding a multiline boolean
to string schemas, so this may be a good time to come to a decision
here.

IMO, while not strictly being part of any JSONSchema/openapi spec, it
would be fine to have that. Also, I'm quite sure that whenever we use
patterns or other formats, a pattern which does not want to opt into
multiline support should be written in a way which does not allow
newlines *anyway*, so for the most part it would act as a hint, but
additionally provide a safe-guard just in case.

On Fri, Nov 06, 2026 at 04:45:37PM +0100, Max R. Carrara wrote:
> Add a new format named "multiline".
> 
> This format explicitly signals to other components (e.g. a client)
> that a string is a multiline string and should remain one, without
> folding newlines or replacing them with spaces, for example.
> 
> Signed-off-by: Max R. Carrara <m.carrara@proxmox.com>
> ---
>  src/PVE/JSONSchema.pm | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/src/PVE/JSONSchema.pm b/src/PVE/JSONSchema.pm
> index 34f2949..5790a32 100644
> --- a/src/PVE/JSONSchema.pm
> +++ b/src/PVE/JSONSchema.pm
> @@ -236,10 +236,15 @@ sub get_renderer {
>  
>  # register some common type for pve
>  
>  register_format('string', sub { }); # allow format => 'string-list'
>  
> +# A multiline string.
> +# Used to explicitly tell other components that a string should not
> +# have its newlines folded or replaced with spaces.
> +register_format('multiline', sub { });
> +
>  register_format('urlencoded', \&pve_verify_urlencoded);
>  
>  sub pve_verify_urlencoded {
>      my ($text, $noerr) = @_;
>      if ($text !~ /^[-%a-zA-Z0-9_.!~*'()]*\z/) {
> -- 
> 2.47.3