From 7c0e4646d694c384fd1c1932182a65731d600979 Mon Sep 17 00:00:00 2001
From: Ivan Towlson <github@hestia.cc>
Date: Mon, 16 Sep 2024 15:17:34 +1200
Subject: [PATCH] Fix watch with workdir not working on Windows

Signed-off-by: itowlson <ivan.towlson@fermyon.com>
---
 src/commands/watch/filters.rs | 44 ++++++++++++++++++++++++++++++++++-
 1 file changed, 43 insertions(+), 1 deletion(-)

diff --git a/src/commands/watch/filters.rs b/src/commands/watch/filters.rs
index 11f4777b8d..970266697f 100644
--- a/src/commands/watch/filters.rs
+++ b/src/commands/watch/filters.rs
@@ -125,7 +125,7 @@ fn create_source_globs(cid: &str, c: &v2::Component) -> Option<Vec<String>> {
             build
                 .watch
                 .iter()
-                .filter_map(|w| Path::new(workdir).join(w).to_str().map(String::from))
+                .map(|w| concatenate_glob_friendly(workdir, w))
                 .collect()
         })
         .unwrap_or_else(|| build.watch.clone());
@@ -137,6 +137,20 @@ fn create_source_globs(cid: &str, c: &v2::Component) -> Option<Vec<String>> {
     }
 }
 
+/// Using Path::join on Windows correctly joins with a backslash. But the watchexec glob
+/// engines hates backslashes. So we must always use forward slashes in glob expressions,
+/// and in workdirs, and for concatenating the two. (We could use Path::join on Unix but
+/// the signature ends up a bit different because to_str returns an Option, so...)
+fn concatenate_glob_friendly(workdir: &str, watch_glob: &str) -> String {
+    if PathBuf::from(watch_glob).is_absolute() {
+        watch_glob.to_string()
+    } else if workdir.ends_with('/') {
+        format!("{workdir}{watch_glob}")
+    } else {
+        format!("{workdir}/{watch_glob}")
+    }
+}
+
 #[async_trait]
 impl FilterFactory for ManifestFilterFactory {
     async fn build_filter(
@@ -207,3 +221,31 @@ impl watchexec::filter::Filterer for CompositeFilterer {
         Ok(false)
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn joining_workdir_always_uses_forward_slash() {
+        assert_eq!(
+            "work/src/**/*.rs",
+            concatenate_glob_friendly("work", "src/**/*.rs")
+        );
+        assert_eq!(
+            "work/src/**/*.rs",
+            concatenate_glob_friendly("work/", "src/**/*.rs")
+        );
+
+        #[cfg(not(target_os = "windows"))]
+        assert_eq!(
+            "/global/src/**/*.rs",
+            concatenate_glob_friendly("work", "/global/src/**/*.rs")
+        );
+        #[cfg(target_os = "windows")]
+        assert_eq!(
+            "D:/global/src/**/*.rs",
+            concatenate_glob_friendly("work", "D:/global/src/**/*.rs")
+        );
+    }
+}