Module template 

Template rendering for Texl.

A template is plain text containing Swan expressions delimited by <% and %>. render replaces each <% expr %> tag with the text form of the value that expr evaluates to, and copies all other text through unchanged.

Syntax

• A tag starts at <% and ends at the first following %>. Tags cannot be nested, and the sequence %> cannot appear inside an expression.
• If a <% has no matching %>, rendering stops at that point and the rest of the template, including the stray <%, is copied through literally.

Evaluation model

• Tags are evaluated strictly in order, all against the same Scope. Assignments made in one tag are therefore visible in later tags (e.g. <% count = 1 %>Count is <% count %>).
• If an expression yields a Value::Promise, rendering suspends until the promise resolves (repeating if the result is itself a promise) and then renders the resolved value. This is why render is async.
• The future is single-threaded: it holds Rc values and is not Send.

Output format

Value	Output
Text	the text itself
Numb	Rust f64 display (30, not 30.0; 1.5)
Bool	TRUE / FALSE
Nothing	empty text
Tuple	the items, rendered and joined with ", "
List	[[List of N]]
Namespace	[[Namespace of N]] (N = number of local bindings)
Func	[[Func]]
Undefined	[[Undefined]]
Promise (resolved)	the rendered resolved value
Promise (pending)	[[Pending Promise]]

Promises returned by a tag are awaited, so [[Pending Promise]] only appears for promises nested inside other values, such as tuple items.

Example

use swan_core::builtins::root_scope;
use swan_core::value::Value;
use texl_core::template::render;

let scope = root_scope();
scope.set("name", Value::Text("World".into()));
let out = block_on(render("Hello <% name %>!", &scope));
assert_eq!(out, "Hello World!");

Functions

render

Renders template, evaluating every <% ... %> expression against scope.