src/natu/ast.rs

@@ -49,6 +49,7 @@ pub enum Expr {
     Ident(Ident),
     Select(Select),
     Let {
+        range: SourceRange,
         bindings: Vec<Binding>,
         body: Box<Expr>,
     },

src/natu/natu.rs

@@ -1,3 +1,5 @@
+use std::collections::HashSet;
+
 mod ast;
 mod file_store;
 mod parser;
@@ -23,7 +25,45 @@ impl Report {
 
 impl std::fmt::Display for Report {
     fn fmt(&self, formatter: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let mut reported_let_order_files = HashSet::new();
+
         for diagnostic in &self.diagnostics {
+            if diagnostic.finding.rule_id == "let_order" {
+                if !reported_let_order_files.insert(diagnostic.file_id) {
+                    continue;
+                }
+
+                let file = self.files.get(diagnostic.file_id);
+                writeln!(
+                    formatter,
+                    "{} [let_order] Let bindings must follow dependency order",
+                    file.path.display()
+                )?;
+
+                let mut findings = self
+                    .diagnostics
+                    .iter()
+                    .filter(|candidate| {
+                        candidate.file_id == diagnostic.file_id
+                            && candidate.finding.rule_id == "let_order"
+                    })
+                    .collect::<Vec<_>>();
+                findings.sort_by_key(|finding| finding.finding.range.start);
+
+                for finding in findings {
+                    let (start, _) = line_range(&file.source, finding.finding.range);
+                    let expected_order =
+                        finding.finding.expected_order.as_ref().expect("let order");
+                    writeln!(
+                        formatter,
+                        "  let at line {start}: {}",
+                        expected_order.join(", ")
+                    )?;
+                }
+
+                continue;
+            }
+
             let file = self.files.get(diagnostic.file_id);
             let (start, end) = line_range(&file.source, diagnostic.finding.range);
             let location = if start == end {

src/natu/natu_test.rs

@@ -50,7 +50,18 @@ fn natu_reports_out_of_order_let_bindings() -> googletest::Result<()> {
         .iter()
         .filter(|diagnostic| diagnostic.finding.rule_id == "let_order")
         .count();
-    expect_that!(let_order_count, eq(4));
+    expect_that!(let_order_count, eq(2));
+    expect_that!(
+        report.to_string(),
+        eq(concat!(
+            "testdata/lint_findings.nix:11 [manual_inherit] Use `inherit` for this assignment\n",
+            "testdata/lint_findings.nix:12 [manual_inherit_from] Use `inherit` for this selected attribute\n",
+            "testdata/lint_findings.nix:13 [unquoted_uri] URI literals should be quoted\n",
+            "testdata/lint_findings.nix [let_order] Let bindings must follow dependency order\n",
+            "  let at line 1: first, second, nested\n",
+            "  let at line 4: nestedSecond, nestedFirst\n",
+        ))
+    );
     Ok(())
 }
 

src/natu/parser.rs

@@ -43,6 +43,7 @@ fn convert_expr(expr: rnix::ast::Expr) -> ast::Expr {
     match expr {
         rnix::ast::Expr::Ident(ident) => ast::Expr::Ident(ident.into()),
         rnix::ast::Expr::LetIn(let_in) => ast::Expr::Let {
+            range: let_in.syntax().text_range().into(),
             bindings: let_in
                 .attrpath_values()
                 .filter_map(convert_binding_ast)

src/natu/rules.rs

@@ -22,6 +22,7 @@ pub struct Finding {
     pub range: ast::SourceRange,
     pub message: &'static str,
     pub binding: Option<String>,
+    pub expected_order: Option<Vec<String>>,
 }
 
 impl std::fmt::Display for Diagnostic {
@@ -79,7 +80,8 @@ pub fn run_rules(file: &ast::ParsedFile, graph: &ScopeGraph) -> Vec<Diagnostic>
         rule_id: "let_order",
         range: finding.range,
         message: "Let bindings must follow dependency order",
-        binding: Some(finding.binding),
+        binding: None,
+        expected_order: Some(finding.expected_order),
     });
 
     node_diagnostics
@@ -104,6 +106,7 @@ where
         range: node.range,
         message,
         binding: None,
+        expected_order: None,
     })
 }
 
@@ -119,5 +122,6 @@ where
         range: token.range,
         message,
         binding: None,
+        expected_order: None,
     })
 }

src/natu/rules/let_order.rs

@@ -5,7 +5,7 @@ use crate::{
 
 pub struct Finding {
     pub range: ast::SourceRange,
-    pub binding: String,
+    pub expected_order: Vec<String>,
 }
 
 pub fn check(graph: &ScopeGraph) -> Vec<Finding> {
@@ -14,26 +14,26 @@ pub fn check(graph: &ScopeGraph) -> Vec<Finding> {
         .iter()
         .flat_map(|let_scope| {
             let expected = expected_order(graph, let_scope);
-            let positions = expected
-                .iter()
-                .enumerate()
-                .map(|(position, declaration)| (*declaration, position))
-                .collect::<Vec<_>>();
+            let is_ordered = expected.iter().enumerate().all(|(position, declaration)| {
+                let_scope
+                    .bindings
+                    .get(position)
+                    .is_some_and(|binding| binding.declaration == *declaration)
+            });
 
-            let_scope
-                .bindings
-                .iter()
-                .enumerate()
-                .filter_map(move |(position, binding)| {
-                    positions
-                        .iter()
-                        .find(|(declaration, _)| *declaration == binding.declaration)
-                        .filter(|(_, expected_position)| position != *expected_position)
-                        .map(|_| Finding {
-                            range: binding.range,
-                            binding: binding.name.clone(),
-                        })
-                })
+            (!is_ordered).then(|| Finding {
+                range: let_scope.range,
+                expected_order: expected
+                    .iter()
+                    .filter_map(|declaration| {
+                        let_scope
+                            .bindings
+                            .iter()
+                            .find(|binding| binding.declaration == *declaration)
+                            .map(|binding| binding.name.clone())
+                    })
+                    .collect(),
+            })
         })
         .collect()
 }

src/natu/scope_graph.rs

@@ -26,7 +26,11 @@ impl ScopeGraph {
     fn build_expr(&mut self, expr: &ast::Expr, scope: NodeId) -> Vec<NodeId> {
         match expr {
             ast::Expr::Ident(ident) => vec![self.add_reference(&ident.name, scope)],
-            ast::Expr::Let { bindings, body } => self.build_let(bindings, body, scope),
+            ast::Expr::Let {
+                range,
+                bindings,
+                body,
+            } => self.build_let(*range, bindings, body, scope),
             ast::Expr::AttrSet(bindings) => bindings
                 .iter()
                 .flat_map(|binding| self.build_expr(&binding.value, scope))
@@ -48,6 +52,7 @@ impl ScopeGraph {
 
     fn build_let(
         &mut self,
+        range: ast::SourceRange,
         bindings: &[ast::Binding],
         body: &ast::Expr,
         parent: NodeId,
@@ -59,7 +64,6 @@ impl ScopeGraph {
                 declaration: self.add_declaration(&binding.key.name, scope),
                 name: binding.key.name.clone(),
                 references: Vec::new(),
-                range: binding.range,
             })
             .collect::<Vec<_>>();
 
@@ -74,6 +78,7 @@ impl ScopeGraph {
             .chain(entry_references.iter().copied())
             .collect();
         self.lets.push(LetScope {
+            range,
             bindings: graph_bindings,
             entry_references,
         });
@@ -181,6 +186,7 @@ struct Edge {
 
 #[derive(Debug)]
 pub(crate) struct LetScope {
+    pub(crate) range: ast::SourceRange,
     pub(crate) bindings: Vec<Binding>,
     pub(crate) entry_references: Vec<NodeId>,
 }
@@ -190,5 +196,4 @@ pub(crate) struct Binding {
     pub(crate) declaration: NodeId,
     pub(crate) name: String,
     pub(crate) references: Vec<NodeId>,
-    pub(crate) range: ast::SourceRange,
 }