Macro query_setters 

macro_rules! query_setters {
    (@setters $field:ident;) => { ... };
    (@setters $field:ident;
        $(#[$meta:meta])* $name:ident: impl Into<String> => $key:literal
        $(, $($rest:tt)*)?
    ) => { ... };
    (@setters $field:ident;
        $(#[$meta:meta])* $name:ident: many $ty:ty => $key:literal
        $(, $($rest:tt)*)?
    ) => { ... };
    (@setters $field:ident;
        $(#[$meta:meta])* $name:ident: csv<I, S> => $key:literal
        $(, $($rest:tt)*)?
    ) => { ... };
    (@setters $field:ident;
        $(#[$meta:meta])* $name:ident: csv $ty:ty => $key:literal
        $(, $($rest:tt)*)?
    ) => { ... };
    (@setters $field:ident;
        $(#[$meta:meta])* $name:ident($arg:ident: $ty:ty) => csv $key:literal = $value:expr
        $(, $($rest:tt)*)?
    ) => { ... };
    (@setters $field:ident;
        $(#[$meta:meta])* $name:ident($arg:ident: $ty:ty) => $key:literal = $value:expr
        $(, $($rest:tt)*)?
    ) => { ... };
    (@setters $field:ident;
        $(#[$meta:meta])* $name:ident($arg:ident: $ty:ty) => $key:literal if $cond:expr
        $(, $($rest:tt)*)?
    ) => { ... };
    (@setters $field:ident;
        $(#[$meta:meta])* $name:ident: $ty:ty => $key:literal
        $(, $($rest:tt)*)?
    ) => { ... };
    (self.$field:ident; $($setters:tt)*) => { ... };
    ($($setters:tt)*) => { ... };
}

Generates a request builder’s query-parameter setters.

Each setter writes its parameter to self.request, or to self.<field> when the invocation starts with self.<field>;. The field may be core’s Request, or any type with a query(key, impl ToString) method of its own, which is then preferred (and query_many, for the many arm). Each setter keeps the attributes written above it, its doc comment included.

The arms, one per setter, separated by commas:

• name: T => "key" takes a T and sends it as key.
• name: impl Into<String> => "key" takes anything that converts into a String.
• name: many T => "key" takes T, an iterator, and repeats key once per value.
• name: csv T => "key" takes T, an iterator, and sends its values comma-joined, or nothing when the joined value is empty.
• name: csv<I, S> => "key" is the same, with explicit generics (I: IntoIterator<Item = S>, S: ToString).
• name(arg: T) => "key" = expr sends expr, computed from arg.
• name(arg: T) => "key" if cond sends arg only when cond holds.
• name(arg: T) => csv "key" = expr comma-joins the iterator expr.

use polyoxide_core::{ApiError, HttpClientBuilder, Request};

pub struct ListThings {
    request: Request<Vec<String>, ApiError>,
}

impl ListThings {
    polyoxide_core::query_setters! {
        /// Page size.
        limit: u32 => "limit",
        /// Only things with these ids.
        ids: many impl IntoIterator<Item = i64> => "id",
        /// Only open things.
        open(open: bool) => "closed" = !open,
    }
}

let http = HttpClientBuilder::new("https://example.com").build().unwrap();
let _things = ListThings { request: Request::new(http, "/things") }
    .limit(10)
    .ids([1, 2])
    .open(true);