Macro mox::mox

macro_rules! mox {
    #[proc_macro_hack::proc_macro_hack(support_nested)] => { ... };
}

Accepts an XML-like expression and expands it to builder method calls.

Outputs

The mox! macro's contents are expanded to a nested builder pattern.

Tags

Each tag expands to a function call with the same name as the tag. The function call, all attributes, and children are wrapped in topo::call to create a nested scope in the callgraph.

Each attribute expands to a method called on the value returned from the tag opening or the previous attribute. The attribute name is used as the method name, with the attribute value passed as the argument.

A tag with children has each child passed as the argument to a call to .child(...), one per child in order of declaration. The calls to child come after attributes.

After all attributes and children, .build() is called on the final value.

Fragments

Fragments are not currently supported.

Content/Text

Text nodes are wrapped in calls to text(...).

If an expression is a formatter, the arguments are wrapped in the format!(...) macro before being treated as a text node.

Inputs

Each macro invocation must resolve to a single item. Items can be tags, fragments, or content.

snax is used to tokenize the input as JSX(ish).

Tags

Tags always have a name and can have zero or more arguments, attributes, and children.

They take the form <NAME ATTR=VAL ...> CHILDREN </NAME>. Each optional portion can be omitted.

Attributes

Each attribute takes the form NAME=VAL where NAME is an identifier and VALUE is an expression.

If the attribute's name is async, for, loop, or type an underscore is appended to avoid colliding with the Rust keyword.

Children

Tags have zero or more nested items (tags, fragments, content) as children.

If there are no children the tag can be "self-closing": <NAME ... />.

Fragments

Fragments are opened with <> and closed with </>. Their only purpose is to provide a parent for children. They do not accept arguments or attributes.

Expressions

Raw Rust expressions can be inserted as a child node. They are delimited with { and }.

Format expressions

Expressions can optionally be opened with {% to denote a "formatter" item. The enclosed tokens are passed

Example

use mox::mox;

#[derive(Debug, PartialEq)]
struct Tag {
    name: String,
    children: Vec<Tag>,
}

fn built() -> TagBuilder {
    TagBuilder::default()
}

#[derive(Default)]
struct TagBuilder {
    name: Option<String>,
    children: Vec<Tag>,
}

impl TagBuilder {
    fn name(mut self, name: impl Into<String>) -> Self {
        self.name = Some(name.into());
        self
    }

    fn child(mut self, child: Tag) -> Self {
        self.children.push(child);
        self
    }

    fn build(self) -> Tag {
        Tag { name: self.name.unwrap(), children: self.children }
    }
}

assert_eq!(
    mox! {
        <built name="alice">
            <built name="bob"/>
        </built>
    },
    Tag {
        name: String::from("alice"),
        children: vec![Tag { name: String::from("bob"), children: vec![] }],
    },
);