Add fs::exists helper to xtask (#302)

crates/xtask/src/fs.rs

@@ -43,6 +43,10 @@ fn create_parent(path: impl AsRef<Path>) -> Result<()> {
     Ok(())
 }
 
+pub fn exists(path: impl AsRef<Path>) -> bool {
+    path.as_ref().exists()
+}
+
 pub fn metadata(path: impl AsRef<Path>) -> Result<Metadata> {
     let name = path.as_ref().display();
     std::fs::metadata(path.as_ref()).with_context(|| format!("reading {name} metadata"))
@@ -59,7 +63,7 @@ pub fn remove_file(path: impl AsRef<Path>) -> Result<()> {
 }
 
 pub fn touch(path: impl AsRef<Path>) -> Result<()> {
-    if path.as_ref().exists() {
+    if exists(path.as_ref()) {
         return Ok(());
     }
     write(path, "")

crates/xtask/src/main.rs

@@ -18,7 +18,6 @@ use std::collections::BinaryHeap;
 use std::fmt::Display;
 use std::num::ParseIntError;
 use std::os::unix::prelude::CommandExt;
-use std::path::Path;
 use std::process::{Command, Output};
 use std::str::FromStr;
 
@@ -285,7 +284,7 @@ impl AppletOptions {
         } else {
             format!("examples/{}/{}", self.lang, self.name)
         };
-        ensure!(Path::new(&dir).exists(), "{dir} does not exist");
+        ensure!(fs::exists(&dir), "{dir} does not exist");
         let native = match (main.native, &main.native_target, command) {
             (_, Some(target), command) => {
                 if let Some(AppletCommand::Runner(x)) = command {
@@ -509,8 +508,8 @@ impl RunnerOptions {
         cargo.current_dir(format!("crates/runner-{}", self.name));
         fs::touch("target/wasefire/applet.wasm")?;
         if run && self.name == "host" {
-            let path = Path::new("target/wasefire/storage.bin");
-            if self.erase_flash && path.exists() {
+            let path = "target/wasefire/storage.bin";
+            if self.erase_flash && fs::exists(path) {
                 fs::remove_file(path)?;
             }
             replace_command(cargo);
@@ -672,23 +671,21 @@ fn wrap_command() -> Result<Command> {
 ///
 /// Returns whether the copy took place.
 fn copy_if_changed(src: &str, dst: &str) -> Result<bool> {
-    let dst_file = format!("{dst}.hash");
+    let dst_hash = format!("{dst}.hash");
     let src_hash = Sha256::digest(fs::read(src)?);
-    let dst_path = Path::new(dst);
-    let changed =
-        !dst_path.exists() || !Path::new(&dst_file).exists() || fs::read(&dst_file)? != *src_hash;
+    let changed = !fs::exists(dst) || !fs::exists(&dst_hash) || fs::read(&dst_hash)? != *src_hash;
     if changed {
         println!("cp {src} {dst}");
         fs::copy(src, dst)?;
-        fs::write(&dst_file, src_hash)?;
+        fs::write(&dst_hash, src_hash)?;
     }
     Ok(changed)
 }
 
 fn ensure_assemblyscript() -> Result<()> {
     const ASC_VERSION: &str = "0.27.17"; // scripts/upgrade.sh relies on this name
     const PATH: &str = "examples/assemblyscript/node_modules/assemblyscript/package.json";
-    if Path::new(PATH).exists() {
+    if fs::exists(PATH) {
         let mut sed = Command::new("sed");
         sed.args(["-n", r#"s/^  "version": "\(.*\)",$/\1/p"#, PATH]);
         if read_output_line(&mut sed)? == ASC_VERSION {