[−][src]Crate format_xml

Inline XML Templating

Minimal compile time templating for XML in Rust!

The format_xml! macro by example accepts an XML-like syntax and transforms it into a format_args! invocation. We say XML-like because due to limitations of the macro system some concessions had to be made, see the examples below.

Examples

Basic usage

let point = (20, 30);
let name = "World";

format_xml! {
	<svg width="200" height="200">
		<line x1="0" y1="0" x2={point.0} y2={point.1} stroke="black" stroke-width="2" />
		<text x={point.1} y={point.0}>"Hello '" {name} "'!"</text>
	</svg>
}.to_string()

The resulting string is <svg width="200" height="200"><line x1="0" y1="0" x2="20" y2="30" stroke="black" stroke-width="2" /><text x="30" y="20">Hello 'World!'</text></svg>.

Note how the expression values to be formatted are inlined in the formatting braces.

Formatting specifiers

let value = 42;

format_xml! {
	<span data-value={value}>{value;#x?}</span>
}.to_string()

The resulting string is <span data-value="42">0x2a</span>.

Due to limitations of macros by example, a semicolon is used to separate the value from the formatting specifiers. The rules for the specifiers are exactly the same as the standard library of Rust.

Supported tags

format_xml! {
	<!doctype html>
	<?xml version="1.0" encoding="UTF-8"?>
	<open-tag></open-tag>
	<ns:self-closing-tag />
}.to_string()

The resulting string is <!doctype html><?xml version="1.0" encoding="UTF-8"?><open-tag></open-tag><ns:self-closing-tag />.

Control flow

let switch = true;
let opt = Some("World");

format_xml! {
	if let Some(name) = (opt) {
		<h1>"Hello " {name}</h1>
	}
	if (switch) {
		<ul>
		for i in (1..=5) {
			let times_five = i * 5;
			<li>{i}"*5="{times_five}</li>
		}
		</ul>
	}
}.to_string()

The resulting string is <h1>Hello World</h1><ul><li>1*5=5</li><li>2*5=10</li><li>3*5=15</li><li>4*5=20</li><li>5*5=25</li></ul>.

Control flow are currently only supported outside tags. They are not supported in attributes. The expressions for if and for must be surrounded with parentheses due to macro by example limitations.

Limitations

This crate is implemented with standard macros by example (macro_rules!). Because of this there are various limitations:

It is not possible to check whether tags are closed by the appropriate closing tag. This crate will happily accept <open></close>. It does enforce more simple lexical rules such as rejecting </tag/>.
Escaping of <, &, > and " is not automatic. You can trivially break the structure by including these characters in either the formatting string or formatted values. Avoid untrusted input!
The formatting specifiers are separated from its value by a semicolon instead of a colon.
The compiler may complain about macro expansion recursion limit being reached, simply apply the suggested fix and increase the limit. This crate implements a 'tt muncher' which are known to hit these limits.
Text nodes must be valid Rust literals. Bare words are not supported.

Macros

format_xml

Format XML tokens with format_args!

Structs

FnFmt

Implements std::fmt::Display for the Fn closure matching fmt's signature.