that's fine for now

Cargo.lock

@@ -2,11 +2,44 @@
 # It is not intended for manual editing.
 version = 4
 
+[[package]]
+name = "addr2line"
+version = "0.24.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "dfbe277e56a376000877090da837660b4427aad530e3028d44e0bffe4f89a1c1"
+dependencies = [
+ "gimli",
+]
+
+[[package]]
+name = "adler2"
+version = "2.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "512761e0bb2578dd7380c6baaa0f4ce03e84f95e960231d1dec8bf4d7d6e2627"
+
 [[package]]
 name = "anyhow"
 version = "1.0.97"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "dcfed56ad506cb2c684a14971b8861fdc3baaaae314b9e5f9bb532cbe3ba7a4f"
+dependencies = [
+ "backtrace",
+]
+
+[[package]]
+name = "backtrace"
+version = "0.3.74"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8d82cb332cdfaed17ae235a638438ac4d4839913cc2af585c3c6746e8f8bee1a"
+dependencies = [
+ "addr2line",
+ "cfg-if",
+ "libc",
+ "miniz_oxide",
+ "object",
+ "rustc-demangle",
+ "windows-targets",
+]
 
 [[package]]
 name = "bitflags"
@@ -54,6 +87,12 @@ dependencies = [
  "wasi",
 ]
 
+[[package]]
+name = "gimli"
+version = "0.31.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "07e28edb80900c19c28f1072f2e8aeca7fa06b23cd4169cefe1af5aa3260783f"
+
 [[package]]
 name = "libc"
 version = "0.2.171"
@@ -75,6 +114,30 @@ dependencies = [
  "tempfile",
 ]
 
+[[package]]
+name = "memchr"
+version = "2.7.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "78ca9ab1a0babb1e7d5695e3530886289c18cf2f87ec19a575a0abdce112e3a3"
+
+[[package]]
+name = "miniz_oxide"
+version = "0.8.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8e3e04debbb59698c15bacbb6d93584a8c0ca9cc3213cb423d31f760d8843ce5"
+dependencies = [
+ "adler2",
+]
+
+[[package]]
+name = "object"
+version = "0.36.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "62948e14d923ea95ea2c7c86c71013138b66525b86bdc08d2dcc262bdb497b87"
+dependencies = [
+ "memchr",
+]
+
 [[package]]
 name = "once_cell"
 version = "1.21.1"
@@ -87,6 +150,12 @@ version = "5.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "74765f6d916ee2faa39bc8e68e4f3ed8949b48cccdac59983d287a7cb71ce9c5"
 
+[[package]]
+name = "rustc-demangle"
+version = "0.1.24"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "719b953e2095829ee67db738b3bfa9fa368c94900df327b3f07fe6e794d2fe1f"
+
 [[package]]
 name = "rustix"
 version = "1.0.3"

Cargo.toml

@@ -12,7 +12,7 @@ name = "lk"
 path = "src/main.rs"
 
 [dependencies]
-anyhow = { version = "1.0.97" }
+anyhow = { version = "1.0.97", features = ["backtrace"] }
 camino = "1.1.9"
 
 [dev-dependencies]

src/main.rs

@@ -1,4 +1,5 @@
-use anyhow::{Context as _, Result};
+use anyhow::{Context as _, Result, anyhow};
+use camino::{Utf8Path, Utf8PathBuf};
 use std::{
     borrow::Cow,
     fs,
@@ -14,7 +15,7 @@ fn main() -> Result<()> {
 struct App {
     is_terminal: bool,
     lk: Option<Lk>,
-    paths: Vec<Cow<'static, str>>,
+    paths: Vec<Cow<'static, Utf8Path>>,
     path_index: usize,
 }
 
@@ -27,15 +28,20 @@ impl App {
         let _exe_name = args.next().context("How do we not have an exe name?")?;
         let mut paths = vec![];
         for arg in args {
-            paths.push(arg.into());
+            paths.push(Cow::Owned(Utf8PathBuf::from(arg)));
         }
         let paths = if paths.is_empty() {
-            vec![".".into()]
+            vec![Cow::Borrowed(Utf8Path::new("."))]
         } else {
             paths
         };
 
-        Ok(App { is_terminal, lk: None, paths, path_index: 0 })
+        Ok(App {
+            is_terminal,
+            lk: None,
+            paths,
+            path_index: 0,
+        })
     }
 
     fn poll(&mut self) -> Result<Option<Rc<[u8]>>> {
@@ -45,12 +51,14 @@ impl App {
             }
             let path = &self.paths[self.path_index];
             match self.lk.as_mut() {
-                Some(lk) => if let Some(buf) = lk.poll()? {
+                Some(lk) => {
+                    if let Some(buf) = lk.poll()? {
                         return Ok(Some(buf));
                     } else {
                         self.lk = None;
                         self.path_index += 1;
                     }
+                }
                 None => {
                     self.lk = Some(Lk::try_new(path)?);
                 }
@@ -72,7 +80,7 @@ enum Lk {
 }
 
 impl Lk {
-    fn try_new(path: &str) -> Result<Self> {
+    fn try_new(path: &Utf8Path) -> Result<Self> {
         let metadata = fs::metadata(path)?;
         if metadata.is_dir() {
             Self::try_new_ls(path)
@@ -81,14 +89,15 @@ impl Lk {
         }
     }
 
-    fn try_new_cat(path: &str) -> Result<Self> {
+    fn try_new_cat(path: &Utf8Path) -> Result<Self> {
         Ok(Self::Cat(Cat::try_new(path)?))
     }
 
-    fn try_new_ls(path: &str) -> Result<Self> {
+    fn try_new_ls(path: &Utf8Path) -> Result<Self> {
         Ok(Self::Ls(Ls::try_new(path)?))
     }
 
+    // I don't understand why, but using `Rc` here instead of `Cow` satisfies the borrow checker.
     fn poll(&mut self) -> Result<Option<Rc<[u8]>>> {
         match self {
             Lk::Cat(x) => x.poll(),
@@ -103,7 +112,7 @@ struct Cat {
 }
 
 impl Cat {
-    fn try_new(path: &str) -> Result<Self> {
+    fn try_new(path: &Utf8Path) -> Result<Self> {
         let f = fs::File::open(path)?;
         let buf = vec![0u8; 4_096];
         Ok(Self { f, buf })
@@ -120,34 +129,80 @@ impl Cat {
 }
 
 struct Ls {
-    d: fs::ReadDir,
+    names: Vec<String>,
+    name_index: usize,
 }
 
 impl Ls {
-    fn try_new(path: &str) -> Result<Self> {
+    fn try_new(path: &Utf8Path) -> Result<Self> {
         let d = fs::read_dir(path)?;
-        Ok(Self { d })
+        let mut names = vec![];
+        for entry in d {
+            let entry = entry?;
+            names.push(
+                entry
+                    .file_name()
+                    .into_string()
+                    .map_err(|_| anyhow!("name is not UTF-8"))?,
+            );
+        }
+        names.sort();
+        Ok(Self {
+            names,
+            name_index: 0,
+        })
     }
 
     fn poll(&mut self) -> Result<Option<Rc<[u8]>>> {
-        let Some(entry) = self.d.next() else {
+        if self.name_index >= self.names.len() {
             return Ok(None);
-        };
+        }
-        let entry = entry?;
+        let name = &self.names[self.name_index];
-        let path = entry.file_name();
+        self.name_index += 1;
-        let path = path.to_str().context("file name is not valid Unicode")?;
+        Ok(Some(format!("{name}\n").into_bytes().into()))
-        Ok(Some(format!("{path}\n").into_bytes().into()))
     }
 }
 
 #[cfg(test)]
 mod tests {
     use super::*;
+    use std::path::Path;
 
     #[test]
     fn test() -> Result<()> {
         let dir = tempfile::tempdir()?;
+        let dir = dir.as_ref();
+        fs::write(dir.join("alfa.txt"), "alfa\n")?;
+        fs::write(dir.join("bravo.txt"), "bravo\n")?;
+
+        for (input, expected) in [
+            (vec![dir], b"alfa.txt\nbravo.txt\n".to_vec()),
+            (
+                vec![&dir.join("alfa.txt"), &dir.join("bravo.txt")],
+                b"alfa\nbravo\n".to_vec(),
+            ),
+        ] {
+            assert_eq!(lk(input)?, expected);
+        }
 
         Ok(())
     }
+
+    fn lk(paths: Vec<&Path>) -> Result<Vec<u8>> {
+        let paths = paths
+            .iter()
+            .map(|p| Cow::Owned(Utf8PathBuf::from_path_buf(p.to_path_buf()).unwrap()))
+            .collect();
+        let mut app = App {
+            is_terminal: false,
+            lk: None,
+            paths,
+            path_index: 0,
+        };
+        let mut out = vec![];
+        while let Some(buf) = app.poll()? {
+            out.write_all(&buf)?;
+        }
+        Ok(out)
+    }
 }