add kdl v2 support

This adds v2 support with fallback to v1 for legacy configs.
It might be a bit bumpy at first but I'm hoping it works ok.
Probably worth treating as experimental for now.

niri-config/Cargo.toml

@@ -10,8 +10,9 @@ repository.workspace = true
 [dependencies]
 bitflags.workspace = true
 csscolorparser = "0.7.0"
+kdl = { version = "6.3.3", features = ["v1-fallback"] }
 knuffel = "3.2.0"
-miette = { version = "5.10.0", features = ["fancy-no-backtrace"] }
+miette = { version = "7.5.0", features = ["fancy-no-backtrace"] }
 niri-ipc = { version = "25.1.0", path = "../niri-ipc" }
 regex = "1.11.1"
 smithay = { workspace = true, features = ["backend_libinput"] }

niri-config/src/lib.rs

@@ -9,6 +9,7 @@ use std::str::FromStr;
 use std::time::Duration;
 
 use bitflags::bitflags;
+use kdl::{KdlDocument, KdlError};
 use knuffel::errors::DecodeError;
 use knuffel::Decode as _;
 use layer_rule::LayerRule;
@@ -2042,9 +2043,12 @@ impl Config {
         Ok(config)
     }
 
-    pub fn parse(filename: &str, text: &str) -> Result<Self, knuffel::Error> {
+    pub fn parse(filename: &str, text: &str) -> Result<Self, KdlError> {
         let _span = tracy_client::span!("Config::parse");
-        knuffel::parse(filename, text)
+        let mut doc: KdlDocument = text.parse()?;
+        doc.ensure_v1();
+        Ok(knuffel::parse(filename, text)
+            .expect("This should always succeed, if it passed the first time."))
     }
 }