From efcd91aca1a74715d690312c828984533446c631 Mon Sep 17 00:00:00 2001
From: alexion <contact@alexion.dev>
Date: Sat, 19 Sep 2026 20:14:49 -0400
Subject: [PATCH] refactor(xatu): retain node parsing scaffolding

---
 Cargo.lock          |   1 +
 src/xatu/BUILD      |   1 +
 src/xatu/Cargo.toml |   1 +
 src/xatu/ast.rs     |  46 +++++++++++++++
 src/xatu/parser.rs  | 133 +++++++++++++++++++++++++++++++++++++++++---
 src/xatu/rules.rs   |   9 ++-
 6 files changed, 181 insertions(+), 10 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index 50f9989..bedb295 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -401,6 +401,7 @@ dependencies = [
  "googletest",
  "monorepo",
  "rnix",
+ "rowan",
  "status",
 ]
 
diff --git a/src/xatu/BUILD b/src/xatu/BUILD
index 3466168..4a72c08 100644
--- a/src/xatu/BUILD
+++ b/src/xatu/BUILD
@@ -14,6 +14,7 @@ rust_library(
     deps = [
         "//src/status:status",
         "//third_party/crates:rnix",
+        "//third_party/crates/rowan-0.16.1:rowan",
     ],
 )
 
diff --git a/src/xatu/Cargo.toml b/src/xatu/Cargo.toml
index ce0e581..d12e186 100644
--- a/src/xatu/Cargo.toml
+++ b/src/xatu/Cargo.toml
@@ -14,6 +14,7 @@ path = "xatu_main.rs"
 clap = { workspace = true, features = ["derive"] }
 monorepo = { workspace = true }
 rnix = { workspace = true }
+rowan = { workspace = true }
 status = { workspace = true }
 
 [dev-dependencies]
diff --git a/src/xatu/ast.rs b/src/xatu/ast.rs
index 8fb0c90..1addbf4 100644
--- a/src/xatu/ast.rs
+++ b/src/xatu/ast.rs
@@ -3,10 +3,17 @@ use crate::FileId;
 #[derive(Debug)]
 pub struct ParsedFile {
     pub file_id: FileId,
+    pub nodes: Vec<Node>,
     pub tokens: Vec<Token>,
     pub errors: Vec<ParseError>,
 }
 
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct Node {
+    pub range: SourceRange,
+    pub data: NodeData,
+}
+
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub struct SourceRange {
     pub start: usize,
@@ -19,6 +26,45 @@ impl std::fmt::Display for SourceRange {
     }
 }
 
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub enum NodeData {
+    Apply(Apply),
+    LetIn(LetIn),
+    Inherit(Inherit),
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct Apply {
+    pub function: Expr,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub enum Expr {
+    Ident(Ident),
+    Select(Box<Select>),
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct Ident {
+    pub name: String,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct Select {
+    pub receiver: Expr,
+    pub attrs: Vec<Ident>,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct LetIn {
+    pub binding_count: usize,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct Inherit {
+    pub attr_count: usize,
+}
+
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct Token {
     pub range: SourceRange,
diff --git a/src/xatu/parser.rs b/src/xatu/parser.rs
index bdc89dc..e92f605 100644
--- a/src/xatu/parser.rs
+++ b/src/xatu/parser.rs
@@ -1,12 +1,18 @@
+use rnix::ast::HasEntry;
+use rowan::ast::AstNode;
+
 use crate::{FileId, ast};
 
 pub fn parse_file(file_id: FileId, source: &str) -> ast::ParsedFile {
     let parse = rnix::Root::parse(source);
     let source_len = source.len();
 
+    let (nodes, tokens) = convert_syntax(parse.syntax());
+
     ast::ParsedFile {
         file_id,
-        tokens: convert_tokens(parse.syntax()),
+        nodes,
+        tokens,
         errors: parse
             .errors()
             .iter()
@@ -15,14 +21,125 @@ pub fn parse_file(file_id: FileId, source: &str) -> ast::ParsedFile {
     }
 }
 
-fn convert_tokens(syntax: rnix::SyntaxNode) -> Vec<ast::Token> {
-    syntax
-        .descendants_with_tokens()
-        .filter_map(|element| match element {
-            rnix::NodeOrToken::Token(token) => convert_token(token),
-            _ => None,
+fn convert_syntax(syntax: rnix::SyntaxNode) -> (Vec<ast::Node>, Vec<ast::Token>) {
+    let mut nodes = Vec::new();
+    let mut tokens = Vec::new();
+
+    for element in syntax.descendants_with_tokens() {
+        match element {
+            rnix::NodeOrToken::Node(node) => nodes.extend(convert_node(node)),
+            rnix::NodeOrToken::Token(token) => tokens.extend(convert_token(token)),
+        }
+    }
+
+    (nodes, tokens)
+}
+
+fn convert_node(node: rnix::SyntaxNode) -> Option<ast::Node> {
+    match node.kind() {
+        rnix::SyntaxKind::NODE_APPLY => convert_apply(node),
+        rnix::SyntaxKind::NODE_LET_IN => convert_let_in(node),
+        rnix::SyntaxKind::NODE_INHERIT => convert_inherit(node),
+        _ => None,
+    }
+}
+
+fn convert_apply(node: rnix::SyntaxNode) -> Option<ast::Node> {
+    let apply = rnix::ast::Apply::cast(node)?;
+    let range = apply.syntax().text_range().into();
+    let data = apply.try_into().ok()?;
+
+    Some(ast::Node {
+        range,
+        data: ast::NodeData::Apply(data),
+    })
+}
+
+impl TryFrom<rnix::ast::Apply> for ast::Apply {
+    type Error = ();
+
+    fn try_from(apply: rnix::ast::Apply) -> Result<Self, Self::Error> {
+        Ok(Self {
+            function: apply.lambda().ok_or(())?.try_into()?,
         })
-        .collect()
+    }
+}
+
+impl TryFrom<rnix::ast::Expr> for ast::Expr {
+    type Error = ();
+
+    fn try_from(expr: rnix::ast::Expr) -> Result<Self, Self::Error> {
+        match expr {
+            rnix::ast::Expr::Ident(ident) => Ok(Self::Ident(ident.into())),
+            rnix::ast::Expr::Select(select) => Ok(Self::Select(Box::new(select.try_into()?))),
+            _ => Err(()),
+        }
+    }
+}
+
+impl From<rnix::ast::Ident> for ast::Ident {
+    fn from(ident: rnix::ast::Ident) -> Self {
+        Self {
+            name: ident.to_string(),
+        }
+    }
+}
+
+impl TryFrom<rnix::ast::Select> for ast::Select {
+    type Error = ();
+
+    fn try_from(select: rnix::ast::Select) -> Result<Self, Self::Error> {
+        Ok(Self {
+            receiver: select.expr().ok_or(())?.try_into()?,
+            attrs: select
+                .attrpath()
+                .ok_or(())?
+                .attrs()
+                .map(|attr| match attr {
+                    rnix::ast::Attr::Ident(ident) => Ok(ident.into()),
+                    _ => Err(()),
+                })
+                .collect::<Result<Vec<_>, _>>()?,
+        })
+    }
+}
+
+fn convert_let_in(node: rnix::SyntaxNode) -> Option<ast::Node> {
+    let let_in = rnix::ast::LetIn::cast(node)?;
+
+    Some(ast::Node {
+        range: let_in.syntax().text_range().into(),
+        data: ast::NodeData::LetIn(let_in.into()),
+    })
+}
+
+impl From<rnix::ast::LetIn> for ast::LetIn {
+    fn from(let_in: rnix::ast::LetIn) -> Self {
+        Self {
+            binding_count: let_in.attrpath_values().count()
+                + let_in
+                    .inherits()
+                    .map(|inherit| inherit.attrs().count())
+                    .sum::<usize>(),
+        }
+    }
+}
+
+fn convert_inherit(node: rnix::SyntaxNode) -> Option<ast::Node> {
+    let inherit = rnix::ast::Inherit::cast(node)?;
+
+    Some(ast::Node {
+        range: inherit.syntax().text_range().into(),
+        data: ast::NodeData::Inherit(inherit.into()),
+    })
+}
+
+impl From<rnix::ast::Inherit> for ast::Inherit {
+    fn from(inherit: rnix::ast::Inherit) -> Self {
+        Self {
+            attr_count: inherit.attrs().count(),
+        }
+    }
 }
 
 fn convert_token(token: rnix::SyntaxToken) -> Option<ast::Token> {
diff --git a/src/xatu/rules.rs b/src/xatu/rules.rs
index e88003b..890aca9 100644
--- a/src/xatu/rules.rs
+++ b/src/xatu/rules.rs
@@ -37,10 +37,15 @@ pub trait TokenRule {
 }
 
 pub fn run_rules(file: &ast::ParsedFile) -> Vec<Diagnostic> {
-    file.tokens
+    let node_diagnostics = file.nodes.iter().flat_map(|_| std::iter::empty());
+    let token_diagnostics = file
+        .tokens
         .iter()
         .flat_map(|token| [run_token_rule::<UnquotedUri>(token)])
-        .flatten()
+        .flatten();
+
+    node_diagnostics
+        .chain(token_diagnostics)
         .map(|finding| Diagnostic {
             file_id: file.file_id,
             finding,