feat: use lockfiles to dedup recompilation

cli/loader/Cargo.toml

@@ -18,6 +18,7 @@ wasm = ["tree-sitter/wasm"]
 anyhow = "1.0"
 cc = "^1.0.58"
 dirs = "3.0"
+fs4 = "0.7.0"
 libloading = "0.7"
 once_cell = "1.7"
 regex = "1"

cli/loader/src/lib.rs

@@ -1,6 +1,7 @@
 #![doc = include_str!("../README.md")]
 
 use anyhow::{anyhow, Context, Error, Result};
+use fs4::FileExt;
 use libloading::{Library, Symbol};
 use once_cell::unsync::OnceCell;
 use regex::{Regex, RegexBuilder};
@@ -371,9 +372,27 @@ impl Loader {
             library_path.set_extension("wasm");
         }
 
-        let recompile = needs_recompile(&library_path, &parser_path, scanner_path.as_deref())
+        let mut recompile = needs_recompile(&library_path, &parser_path, scanner_path.as_deref())
             .with_context(|| "Failed to compare source and binary timestamps")?;
 
+        let lock_path = if env::var("CROSS_RUNNER").is_ok() {
+            PathBuf::from("/tmp")
+                .join("tree-sitter")
+                .join("lock")
+                .join(format!("{name}.lock"))
+        } else {
+            dirs::cache_dir()
+                .ok_or(anyhow!("Cannot determine cache directory"))?
+                .join("tree-sitter")
+                .join("lock")
+                .join(format!("{name}.lock"))
+        };
+
+        if let Ok(lock_file) = fs::OpenOptions::new().write(true).open(&lock_path) {
+            recompile = false;
+            lock_file.lock_exclusive()?;
+        }
+
         #[cfg(feature = "wasm")]
         if let Some(wasm_store) = self.wasm_store.lock().unwrap().as_mut() {
             if recompile {
@@ -394,11 +413,26 @@ impl Loader {
 
         {
             if recompile {
+                fs::create_dir_all(lock_path.parent().unwrap()).with_context(|| {
+                    format!(
+                        "Failed to create directory {:?}",
+                        lock_path.parent().unwrap()
+                    )
+                })?;
+                let lock_file = fs::OpenOptions::new()
+                    .create(true)
+                    .truncate(true)
+                    .write(true)
+                    .open(&lock_path)?;
+                lock_file.lock_exclusive()?;
+
                 self.compile_parser_to_dylib(
                     header_paths,
                     &parser_path,
                     &scanner_path,
                     &library_path,
+                    &lock_file,
+                    &lock_path,
                 )?;
             }
 
@@ -421,6 +455,8 @@ impl Loader {
         parser_path: &Path,
         scanner_path: &Option<PathBuf>,
         library_path: &PathBuf,
+        lock_file: &fs::File,
+        lock_path: &Path,
     ) -> Result<(), Error> {
         let mut config = cc::Build::new();
         config
@@ -494,6 +530,10 @@ impl Loader {
         let output = command
             .output()
             .with_context(|| "Failed to execute C compiler")?;
+
+        lock_file.unlock()?;
+        fs::remove_file(lock_path)?;
+
         if !output.status.success() {
             return Err(anyhow!(
                 "Parser compilation failed.\nStdout: {}\nStderr: {}",
@@ -687,6 +727,7 @@ impl Loader {
 
         fs::rename(src_path.join(output_name), output_path)
             .context("failed to rename wasm output file")?;
+
         Ok(())
     }