Re: [pbs-devel] [PATCH proxmox 1/1] schema: add print_property_string function

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

On Tue, Jul 05, 2022 at 01:08:08PM +0000, Hannes Laimer wrote:
> helpful when property string field are not updated through the API
> 
> Signed-off-by: Hannes Laimer <h.laimer@proxmox.com>
> ---
>  proxmox-schema/src/schema.rs | 28 ++++++++++++++++++++++++++++
>  1 file changed, 28 insertions(+)
> 
> diff --git a/proxmox-schema/src/schema.rs b/proxmox-schema/src/schema.rs
> index a2b165c..8c93452 100644
> --- a/proxmox-schema/src/schema.rs
> +++ b/proxmox-schema/src/schema.rs
> @@ -7,6 +7,7 @@
>  use std::fmt;
>  
>  use anyhow::{bail, format_err, Error};
> +use serde::Serialize;
>  use serde_json::{json, Value};
>  
>  use crate::ConstRegexPattern;
> @@ -932,6 +933,33 @@ impl Schema {
>          Ok(value)
>      }
>  
> +    /// Generate property string of structs with only simple fields
> +    pub fn print_property_string<T: Serialize>(&'static self, data: &T) -> Result<String, Error> {

I think this should start right away with `to_value` and then pass it to a
non-generic private helper taking the `Value`, to avoid multiple
instances, since we need the `Value` anyway, at least for now.

> +        fn print_simple_value(value: Value) -> Result<String, Error> {

essentially this, but this should also be handling `Object`, and also
`Array` which you're currently not handling at all, since we now support
quoted values which *technically* allow more nesting (even though we
currently don't make use of that).

I'd also *prefer* to avoid the temporary strings by eg. adding 2 more
parameters: `output: &mut String` to avoid all the temporary string
allocations, and `quoting: u32` to know how many times we need to quote
the contents - which you're also not doing at all currently.

(but if that seems too tedious for you now, you can keep going with the
string values for now)

> +            let string = match value {
> +                Value::Bool(b) if b => "1".to_string(),
> +                Value::Bool(_) => "0".to_string(),
> +                Value::Number(n) => n.to_string(),
> +                Value::String(s) => s,
> +                _ => {
> +                    bail!("Only structs with only simple fields can be formatted as a property string.")
> +                }
> +            };
> +            Ok(string)
> +        }
> +
> +        match serde_json::to_value(data)? {
> +            Value::Object(obj) => {
> +                let mut props: Vec<String> = Vec::new();
> +                for (key, value) in obj.into_iter() {
> +                    props.push(format!("{}=\"{}\"", key, print_simple_value(value)?));

We don't typically put quotes around values unless required by their
contents (if they contain commas, or - if inside an array - semicolons,
so you might need to pass along a list of in-use separators while
recursing through the data).

Note that objects can define a `default_key` which would come first and
not actually write out `key=` before.
This means you also need to walk through the *schema* here, not only the
values.

Also: This definitely needs `#[test]` cases for at least arrays and
objects with simple contents and objects containing simple arrays.

> +                }
> +                Ok(props.join(","))
> +            }
> +            value => print_simple_value(value),
> +        }
> +    }
> +
>      /// Parse a complex property string (`ApiStringFormat::PropertyString`)
>      pub fn parse_property_string(&'static self, value_str: &str) -> Result<Value, Error> {
>          // helper for object/allof schemas:
> -- 
> 2.30.2