Macro horrorshow::labels_sep_by

macro_rules! labels_sep_by {
    (@ inner_expand $has_before : expr ; $sep : expr ; $tmpl : ident $item : expr) => { ... };
    (@ inner_expand $has_before : expr ; $sep : expr ; $tmpl : ident $item : expr
 => $should_include : expr) => { ... };
    (@ inner_expand $has_before : expr ; $sep : expr ; $tmpl : ident $item : expr,
 $($tail : tt) +) => { ... };
    (@ inner_expand $has_before : expr ; $sep : expr ; $tmpl : ident $item : expr
 => $should_include : expr, $($tail : tt) +) => { ... };
    ($sep : expr ; $item : expr) => { ... };
    ($sep : expr ; $item : expr => $should_include : expr) => { ... };
    ($sep : expr ; $item : expr, $($tail : tt) +) => { ... };
    ($sep : expr ; $item : expr => $should_include : expr, $($tail : tt) +) => { ... };
}

Utility macro for generating a delimited string from a set of labels; some of which may be conditionally included into the final string. The delimiter/seperator and labels are anything that implements the RenderOnce trait (e.g. String or &str).

Usage: labels_sep_by!(seperator; maybe_label,...)

• seperator – Delimiter/seperator that implements the RenderOnce trait (e.g. String or &str).

• maybe_label – Either label_expression, or label_expression => cond_test.

• label_expression – An expression that returns a label that implements the RenderOnce trait (e.g. String or &str).

• label_expression => cond_test – Conditionally include label_expression whenever cond_test is true. cond_test is an expression that returns either true or false.

This useful in generating style attribute as follows:

html! {
    div(style = labels_sep_by!(";"; "color: #000" => true, "font-weight: bold")) {
        : "This is a button"
    }
}