From 48ee942c4fa75a61342471c788ef0ea8305d1900 Mon Sep 17 00:00:00 2001
From: WillLillis <wlillis@umass.edu>
Date: Sun, 28 Dec 2025 01:51:35 -0500
Subject: [PATCH] fix(cli): canonicalize build `--output` path

This fixes a potential issue with the new lock file hashing mechanism,
in which two different path literals pointing to the same location would
hash to separate lock files, allowing a race condition.

(cherry picked from commit 93d793d24920db614b560c251b7ddff822597f21)
---
 crates/cli/src/main.rs      | 14 ++++++++++++--
 crates/loader/src/loader.rs | 10 +++++-----
 2 files changed, 17 insertions(+), 7 deletions(-)

diff --git a/crates/cli/src/main.rs b/crates/cli/src/main.rs
index af4f13a7..35d8fcb7 100644
--- a/crates/cli/src/main.rs
+++ b/crates/cli/src/main.rs
@@ -955,11 +955,21 @@ impl Build {
         } else {
             let output_path = if let Some(ref path) = self.output {
                 let path = Path::new(path);
-                if path.is_absolute() {
+                let full_path = if path.is_absolute() {
                     path.to_path_buf()
                 } else {
                     current_dir.join(path)
-                }
+                };
+                let parent_path = full_path
+                    .parent()
+                    .context("Output path must have a parent")?;
+                let name = full_path
+                    .file_name()
+                    .context("Ouput path must have a filename")?;
+                fs::create_dir_all(parent_path).context("Failed to create output path")?;
+                let mut canon_path = parent_path.canonicalize().context("Invalid output path")?;
+                canon_path.push(name);
+                canon_path
             } else {
                 let file_name = grammar_path
                     .file_stem()
diff --git a/crates/loader/src/loader.rs b/crates/loader/src/loader.rs
index a6f10d54..11c8b673 100644
--- a/crates/loader/src/loader.rs
+++ b/crates/loader/src/loader.rs
@@ -1098,11 +1098,11 @@ impl Loader {
 
         // Ensure the dynamic library exists before trying to load it. This can
         // happen in race conditions where we couldn't acquire the lock because
-        // another process was compiling but it still haven't finished by the
+        // another process was compiling but it still hasn't finished by the
         // time we reach this point, so the output file still doesn't exist.
         //
-        // Instead of complaining about library load failure in `load_language`,
-        // inform the user about the precise issue.
+        // Instead of allowing the `load_language` call below to fail, return a
+        // clearer error to the user here.
         if !output_path.exists() {
             let msg = format!(
                 "Dynamic library `{}` not found after build attempt. \
@@ -1110,10 +1110,10 @@ impl Loader {
                 output_path.display()
             );
 
-            return Err(LoaderError::IO(IoError::new(
+            Err(LoaderError::IO(IoError::new(
                 std::io::Error::new(std::io::ErrorKind::NotFound, msg),
                 Some(output_path.as_path()),
-            )));
+            )))?;
         }
 
         Self::load_language(&output_path, &language_fn_name)