From 6b72672d29f0cde481fc1c582c41e0231725bd3b Mon Sep 17 00:00:00 2001
From: Olivier <olivier@librepush.net>
Date: Fri, 11 Aug 2023 20:24:59 +0100
Subject: [PATCH] Fix bug in path iteration leading to bug in gradual scans

---
 yama/src/scan.rs      | 38 ++++++++++++++++++++------------------
 yama_pile/src/tree.rs |  4 +++-
 2 files changed, 23 insertions(+), 19 deletions(-)

diff --git a/yama/src/scan.rs b/yama/src/scan.rs
index eca4209..370bfbb 100644
--- a/yama/src/scan.rs
+++ b/yama/src/scan.rs
@@ -265,15 +265,7 @@ pub fn prepopulate_unmodified(
                             );
 
                             // Pull out parent directories so our subset always contains the parents for their children.
-                            let mut path_fragment = path.as_bytes();
-                            while let Some((index, _)) = path_fragment
-                                .iter()
-                                .enumerate()
-                                .rev()
-                                .find(|(_idx, char_byte)| **char_byte == b'/')
-                            {
-                                path_fragment = &path_fragment[0..index];
-
+                            for path_fragment in iterate_dirs_upwards(path.as_bytes()) {
                                 if let Some(directory) = pruned_scan_entry_map.remove(path_fragment)
                                 {
                                     prepopulated_scan_entry_map.insert(path_fragment, directory);
@@ -345,15 +337,7 @@ pub fn limit_scan_entry_map_to_size(
             accum_size += size_of_entry;
 
             // Pull out parent directories so our subset always contains the parents for their children.
-            let mut path_fragment = &path_bytes[..];
-            while let Some((index, _)) = path_fragment
-                .iter()
-                .enumerate()
-                .rev()
-                .find(|(_idx, char_byte)| **char_byte == b'/')
-            {
-                path_fragment = &path_bytes[0..index];
-
+            for path_fragment in iterate_dirs_upwards(&path_bytes) {
                 if let Some(directory) = unincluded_directories.remove(path_fragment) {
                     result.insert(path_fragment, directory);
                     accum_size += 4096;
@@ -375,6 +359,24 @@ pub fn limit_scan_entry_map_to_size(
     result
 }
 
+/// Returns a list of all the parent paths of the given path (in bytes),
+/// including the root, in order from leaf to root.
+pub fn iterate_dirs_upwards(path_bytes: &[u8]) -> Vec<&[u8]> {
+    let mut result = Vec::new();
+    let mut path_fragment = &path_bytes[..];
+    while let Some((index, _)) = path_fragment
+        .iter()
+        .enumerate()
+        .rev()
+        .find(|(_idx, char_byte)| **char_byte == b'/')
+    {
+        path_fragment = &path_bytes[0..index];
+        result.push(path_fragment);
+    }
+    result.push(&path_bytes[0..0]);
+    result
+}
+
 #[cfg(test)]
 mod tests {
     use crate::scan::limit_scan_entry_map_to_size;
diff --git a/yama_pile/src/tree.rs b/yama_pile/src/tree.rs
index e908990..cda68ca 100644
--- a/yama_pile/src/tree.rs
+++ b/yama_pile/src/tree.rs
@@ -417,7 +417,9 @@ pub fn assemble_tree_from_scan_entries(
                     // note: for the root, this inserts the root file entry as a child called "" within a fake root 'directory'.
                     // That's fine. We'll patch this up later.
                     dirs.get_mut(parent_dir_name)
-                        .context("bad PMap: parent not seen first")?
+                        .with_context(|| {
+                            format!("bad PMap: parent {parent_dir_name} not seen first")
+                        })?
                         .insert(
                             child_name.to_owned(),
                             TreeNode::NormalFile {