docs(rust-style): order declarations by dependency

src/skills/style/rust/rules/declarations.md

@@ -0,0 +1,38 @@
+# Declaration rules
+
+## Order declarations by dependency
+
+### Rule
+
+Order Rust declarations in depth-first dependency order.
+Place each function, struct, and enum before private declarations that support it.
+For structs and enums, order supporting declarations by field or variant order.
+For functions, order helper declarations by first use in the function body.
+Apply the same rule recursively to each supporting declaration.
+
+### Rationale
+
+Dependency order lets readers start at the public operation or type.
+Readers can then continue downward into the declarations that explain each part.
+
+### Examples
+
+```rust
+pub struct Report {
+    files: FileStore,
+    diagnostics: Vec<Diagnostic>,
+}
+
+struct FileStore {
+    files: Vec<SourceFile>,
+}
+
+struct SourceFile {
+    path: PathBuf,
+    source: String,
+}
+
+struct Diagnostic {
+    message: String,
+}
+```

src/xatu/rules.rs

@@ -38,20 +38,6 @@ pub trait NodeRule {
     fn check(node: &Self::Node) -> Option<&'static str>;
 }
 
-fn run_node_rule<R>(node: &ast::Node) -> Option<Finding>
-where
-    R: NodeRule,
-{
-    let typed_node = R::select(&node.data)?;
-    let message = R::check(typed_node)?;
-
-    Some(Finding {
-        rule_id: R::ID,
-        range: node.range,
-        message,
-    })
-}
-
 pub fn run_rules(file: &ast::ParsedFile) -> Vec<Diagnostic> {
     file.nodes
         .iter()
@@ -69,3 +55,17 @@ pub fn run_rules(file: &ast::ParsedFile) -> Vec<Diagnostic> {
         })
         .collect()
 }
+
+fn run_node_rule<R>(node: &ast::Node) -> Option<Finding>
+where
+    R: NodeRule,
+{
+    let typed_node = R::select(&node.data)?;
+    let message = R::check(typed_node)?;
+
+    Some(Finding {
+        rule_id: R::ID,
+        range: node.range,
+        message,
+    })
+}

src/xatu/xatu_main.rs

@@ -4,28 +4,45 @@ use std::path::{Path, PathBuf};
 use std::process::ExitCode;
 use xatu::{Report, SourceFile};
 
-fn is_nix_file(path: &Path) -> bool {
-    path.extension().is_some_and(|extension| extension == "nix")
+fn main() -> ExitCode {
+    match analyze(Args::parse()) {
+        Ok(report) if report.is_clean() => {
+            println!("No findings.");
+            ExitCode::SUCCESS
+        }
+        Ok(report) => {
+            print!("{report}");
+            ExitCode::from(1)
+        }
+        Err(error) => {
+            eprintln!("{error}");
+            ExitCode::from(2)
+        }
+    }
 }
 
-// TODO: Add configurable exclusions.
-fn is_excluded_dir(path: &Path) -> bool {
-    path.file_name()
-        .and_then(|name| name.to_str())
-        .is_some_and(|name| {
-            matches!(
-                name,
-                ".git"
-                    | "bazel-bin"
-                    | "bazel-dev"
-                    | "bazel-out"
-                    | "bazel-testlogs"
-                    | "target"
-                    | "testdata"
-                    | "third_party"
-            ) || name == "result"
-                || name.starts_with("result-")
-        })
+fn analyze(args: Args) -> status::Result<Report> {
+    let paths: Vec<PathBuf> = args
+        .paths
+        .into_iter()
+        .map(monorepo::workspace::resolve_workspace_path)
+        .collect();
+
+    let files: Vec<SourceFile> = paths
+        .iter()
+        .map(|path| collect_source_files(path))
+        .collect::<status::Result<Vec<_>>>()?
+        .into_iter()
+        .flatten()
+        .collect();
+
+    xatu::future_sight(files)
+}
+
+#[derive(Debug, Parser)]
+struct Args {
+    #[arg(value_name = "PATH", default_value = ".")]
+    paths: Vec<PathBuf>,
 }
 
 fn collect_source_files(path: &Path) -> status::Result<Vec<SourceFile>> {
@@ -61,43 +78,26 @@ fn collect_source_files(path: &Path) -> status::Result<Vec<SourceFile>> {
     Ok(Vec::new())
 }
 
-#[derive(Debug, Parser)]
-struct Args {
-    #[arg(value_name = "PATH", default_value = ".")]
-    paths: Vec<PathBuf>,
+// TODO: Add configurable exclusions.
+fn is_excluded_dir(path: &Path) -> bool {
+    path.file_name()
+        .and_then(|name| name.to_str())
+        .is_some_and(|name| {
+            matches!(
+                name,
+                ".git"
+                    | "bazel-bin"
+                    | "bazel-dev"
+                    | "bazel-out"
+                    | "bazel-testlogs"
+                    | "target"
+                    | "testdata"
+                    | "third_party"
+            ) || name == "result"
+                || name.starts_with("result-")
+        })
 }
 
-fn analyze(args: Args) -> status::Result<Report> {
-    let paths: Vec<PathBuf> = args
-        .paths
-        .into_iter()
-        .map(monorepo::workspace::resolve_workspace_path)
-        .collect();
-
-    let files: Vec<SourceFile> = paths
-        .iter()
-        .map(|path| collect_source_files(path))
-        .collect::<status::Result<Vec<_>>>()?
-        .into_iter()
-        .flatten()
-        .collect();
-
-    xatu::future_sight(files)
-}
-
-fn main() -> ExitCode {
-    match analyze(Args::parse()) {
-        Ok(report) if report.is_clean() => {
-            println!("No findings.");
-            ExitCode::SUCCESS
-        }
-        Ok(report) => {
-            print!("{report}");
-            ExitCode::from(1)
-        }
-        Err(error) => {
-            eprintln!("{error}");
-            ExitCode::from(2)
-        }
-    }
+fn is_nix_file(path: &Path) -> bool {
+    path.extension().is_some_and(|extension| extension == "nix")
 }