kdl

kdl is a "document-oriented" parser and API for the KDL Document Language, a node-based, human-friendly configuration and serialization format. Unlike serde-based implementations, this crate preserves formatting when editing, as well as when inserting or changing values with custom formatting. This is most useful when working with human-maintained KDL files.

You can think of this crate as toml_edit, but for KDL.

If you don't care about formatting or programmatic manipulation, you might check out knuffel or kaydle instead for serde (or serde-like) parsing.

Example

use kdl::KdlDocument;

let doc_str = r#"
hello 1 2 3

world prop="value" {
    child 1
    child 2
}
"#;

let doc: KdlDocument = doc_str.parse().expect("failed to parse KDL");

assert_eq!(
    doc.get_args("hello"),
    vec![&1.into(), &2.into(), &3.into()]
);

assert_eq!(
    doc.get("world").map(|node| &node["prop"]),
    Some(&"value".into())
);

// Documents fully roundtrip:
assert_eq!(doc.to_string(), doc_str);

Controlling Formatting

By default, everything is created with default formatting. You can parse items manually to provide custom representations, comments, etc:

let node_str = r#"
  // indented comment
  "formatted" 1 /* comment */ \
    2;
"#;

let mut doc = kdl::KdlDocument::new();
doc.nodes_mut().push(node_str.parse().unwrap());

assert_eq!(&doc.to_string(), node_str);

KdlDocument, KdlNode, KdlEntry, and KdlIdentifier can all be parsed and managed this way.

Error Reporting

KdlError implements miette::Diagnostic and can be used to display detailed, pretty-printed diagnostic messages when using miette::Result and the "fancy" feature flag for miette:

# Cargo.toml
[dependencies]
miette = { version = "x.y.z", features = ["fancy"] }

fn main() -> miette::Result<()> {
    "foo 1.".parse::<kdl::KdlDocument>()?;
    Ok(())
}

This will display a message like:

Error:
  × Expected valid value.
   ╭────
 1 │ foo 1.
   ·     ─┬
   ·      ╰── invalid float
   ╰────
  help: Floating point numbers must be base 10, and have numbers after the decimal point.

License

The code in this repository is covered by the Apache-2.0 License.