# `kdl`
`kdl` is a "document-oriented" parser and API for the [KDL Document
Language](https://kdl.dev), 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`](https://crates.io/crates/toml_edit), but for KDL.
This crate supports both KDL v2.0.0 and v1.0.0 (when using the non-default
`v1` feature). It also supports converting documents between either format.
There is also a `v1-fallback` feature that may be enabled in order to have
the various `Kdl*::parse` methods try to parse their input as v2, and, if
that fails, try again as v1. In either case, a dedicated `Kdl*::parse_v1`
method is available for v1-exclusive parsing, as long as either `v1` or
`v1-fallback` are enabled.
### Example
```rust
use kdl::{KdlDocument, KdlValue};
let doc_str = r#"
hello 1 2 3
// Comment
world prop=string-value {
child 1
child 2
child #inf
}
"#;
let doc: KdlDocument = doc_str.parse().expect("failed to parse KDL");
assert_eq!(
doc.iter_args("hello").collect::<Vec<&KdlValue>>(),
vec![&1.into(), &2.into(), &3.into()]
);
assert_eq!(
doc.get("world").map(|node| &node["prop"]),
Some(&"string-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:
```rust
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`:
```toml
# Cargo.toml
[dependencies]
miette = { version = "x.y.z", features = ["fancy"] }
```
```rust
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.
```
### Features
* `span` (default) - Includes spans in the various document-related structs.
* `v1` - Adds support for v1 parsing. This will pull in the entire previous
version of `kdl-rs`, and so may be fairly heavy.
* `v1-fallback` - Implies `v1`. Makes it so the various `*::parse()` and
`FromStr` implementations try to parse their inputs as `v2`, and, if that
fails, try again with `v1`. For `KdlDocument`, a heuristic will be applied
if both `v1` and `v2` parsers fail, to pick which error(s) to return. For
other types, only the `v2` parser's errors will be returned.
### Quirks
#### Properties
Multiple properties with the same name are allowed, and all duplicated
**will be preserved**, meaning those documents will correctly round-trip.
When using `node.get()`/`node["key"]` & company, the _last_ property with
that name's value will be returned (as per spec).
#### Numbers
KDL itself does not specify a particular representation for numbers and
accepts just about anything valid, no matter how large and how small. This
means a few things:
* Numbers without a decimal point are interpreted as [`i128`].
* Numbers with a decimal point are interpreted as [`f64`].
* The keywords `#inf`, `#-inf`, and `#nan` evaluate to [`f64::INFINITY`],
[`f64::NEG_INFINITY`], and [`f64::NAN`].
* The original _representation/text_ of these numbers will be preserved,
unless you [`KdlDocument::autoformat`] in which case the original
representation will be thrown away and the actual value will be used when
serializing.
### Minimum Supported Rust Version
You must be at least `1.70.0` tall to get on this ride.
### License
The code in this repository is covered by [the Apache-2.0
License](./LICENSE).
[`KdlDocument`]: https://docs.rs/kdl/latest/kdl/struct.KdlDocument.html
[`KdlNode`]: https://docs.rs/kdl/latest/kdl/struct.KdlNode.html
[`KdlEntry`]: https://docs.rs/kdl/latest/kdl/struct.KdlEntry.html
[`KdlIdentifier`]: https://docs.rs/kdl/latest/kdl/struct.KdlIdentifier.html
[`KdlError`]: https://docs.rs/kdl/latest/kdl/struct.KdlError.html
[`miette::Diagnostic`]: https://docs.rs/miette/latest/miette/trait.Diagnostic.html
[`miette::Result`]: https://docs.rs/miette/latest/miette/type.Result.html