Implement encoding and decoding for Windows-invalid characters in file names

- Added `encode_path_name` and `decode_path_name` functions to handle encoding and decoding of invalid characters.
- Updated `SyncbackRules` to include an option for encoding Windows-invalid characters during syncback.
- Modified `name_for_inst` to conditionally encode invalid characters based on the new option.
- Adjusted `ServeSession` and `InstanceContext` to support the new encoding feature.
- Updated tests and snapshots to reflect changes in encoding behavior.

src/json.rs

@@ -166,19 +166,6 @@ pub fn to_vec_pretty_sorted<T: Serialize>(value: &T) -> anyhow::Result<Vec<u8>>
     serde_json::to_vec_pretty(&sorted_value).context("Failed to serialize to JSON")
 }
 
-/// Serialize a value to a pretty-printed JSON string with sorted keys.
-///
-/// This ensures deterministic output by sorting all object keys alphabetically,
-/// which is especially useful for version control and syncback operations.
-///
-/// # Errors
-///
-/// Returns an error if the value cannot be serialized to JSON.
-pub fn to_string_pretty_sorted<T: Serialize>(value: &T) -> anyhow::Result<String> {
-    let json_value = serde_json::to_value(value).context("Failed to convert to JSON value")?;
-    let sorted_value = sort_json_value(json_value);
-    serde_json::to_string_pretty(&sorted_value).context("Failed to serialize to JSON")
-}
 
 #[cfg(test)]
 mod tests {
@@ -380,25 +367,6 @@ mod tests {
         assert!(mango_pos < zebra_pos);
     }
 
-    #[test]
-    fn test_to_string_pretty_sorted() {
-        use indexmap::IndexMap;
-
-        let mut map: IndexMap<String, i32> = IndexMap::new();
-        map.insert("zebra".to_string(), 1);
-        map.insert("apple".to_string(), 2);
-        map.insert("mango".to_string(), 3);
-
-        let output = to_string_pretty_sorted(&map).unwrap();
-
-        // Keys should be in alphabetical order
-        let apple_pos = output.find("apple").unwrap();
-        let mango_pos = output.find("mango").unwrap();
-        let zebra_pos = output.find("zebra").unwrap();
-        assert!(apple_pos < mango_pos);
-        assert!(mango_pos < zebra_pos);
-    }
-
     #[test]
     fn test_sorted_nested_objects() {
         use serde::Serialize;
@@ -413,7 +381,7 @@ mod tests {
         inner.insert("a".to_string(), 2);
 
         let nested = Nested { inner };
-        let output = to_string_pretty_sorted(&nested).unwrap();
+        let output = String::from_utf8(to_vec_pretty_sorted(&nested).unwrap()).unwrap();
 
         // Inner keys should also be sorted
         let a_pos = output.find("\"a\"").unwrap();

src/lib.rs

@@ -14,6 +14,7 @@ mod json;
 mod lua_ast;
 mod message_queue;
 mod multimap;
+pub mod path_encoding;
 mod path_serializer;
 mod project;
 mod resolution;

src/path_encoding.rs

@@ -0,0 +1,157 @@
+//! Encoding and decoding utilities for Windows-invalid filename characters.
+//!
+//! Windows does not allow the following characters in file names:
+//! < > : " / \ | ? *
+//!
+//! Windows also does not allow leading/trailing spaces in file names.
+//!
+//! This module provides functions to encode these characters using a %NAME%
+//! format (e.g., `<` becomes `%LT%`) and decode them back.
+
+/// Mapping of Windows-invalid characters to their encoded representations.
+const CHAR_ENCODINGS: &[(&str, &str)] = &[
+    ("<", "%LT%"),
+    (">", "%GT%"),
+    (":", "%COLON%"),
+    ("\"", "%QUOTE%"),
+    ("/", "%SLASH%"),
+    ("\\", "%BACKSLASH%"),
+    ("|", "%PIPE%"),
+    ("?", "%QUESTION%"),
+    ("*", "%STAR%"),
+];
+
+const SPACE_ENCODING: &str = "%SPACE%";
+
+/// Encodes Windows-invalid characters in a file name.
+///
+/// This replaces characters like `<`, `>`, `:`, `"`, `/`, `\`, `|`, `?`, `*`
+/// with their encoded representations like `%LT%`, `%GT%`, etc.
+/// Leading and trailing spaces are encoded as `%SPACE%`.
+pub fn encode_path_name(name: &str) -> String {
+    // Count leading and trailing spaces first (before any modifications)
+    let leading_spaces = name.len() - name.trim_start_matches(' ').len();
+    let trailing_spaces = name.len() - name.trim_end_matches(' ').len();
+
+    // Get the middle part (without leading/trailing spaces)
+    let middle = &name[leading_spaces..name.len() - trailing_spaces];
+
+    // Encode invalid characters in the middle part
+    let mut encoded_middle = middle.to_string();
+    for (char, encoded) in CHAR_ENCODINGS {
+        encoded_middle = encoded_middle.replace(char, encoded);
+    }
+
+    // Build final result with encoded spaces
+    let encoded_prefix = SPACE_ENCODING.repeat(leading_spaces);
+    let encoded_suffix = SPACE_ENCODING.repeat(trailing_spaces);
+
+    format!("{}{}{}", encoded_prefix, encoded_middle, encoded_suffix)
+}
+
+/// Decodes encoded Windows-invalid characters back to their original form.
+///
+/// This replaces encoded representations like `%LT%`, `%GT%`, etc. back
+/// to their original characters `<`, `>`, etc.
+/// `%SPACE%` at the start/end is decoded back to spaces.
+pub fn decode_path_name(name: &str) -> String {
+    let mut result = name.to_string();
+
+    // Count and strip leading %SPACE%
+    let mut leading_spaces = 0;
+    while result.starts_with(SPACE_ENCODING) {
+        leading_spaces += 1;
+        result = result[SPACE_ENCODING.len()..].to_string();
+    }
+
+    // Count and strip trailing %SPACE%
+    let mut trailing_spaces = 0;
+    while result.ends_with(SPACE_ENCODING) {
+        trailing_spaces += 1;
+        result = result[..result.len() - SPACE_ENCODING.len()].to_string();
+    }
+
+    // Decode invalid characters in the middle
+    for (char, encoded) in CHAR_ENCODINGS {
+        result = result.replace(encoded, char);
+    }
+
+    // Rebuild with actual spaces
+    let prefix = " ".repeat(leading_spaces);
+    let suffix = " ".repeat(trailing_spaces);
+    format!("{}{}{}", prefix, result, suffix)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_encode_all_chars() {
+        let input = r#"<>:"/\|?*"#;
+        let expected = "%LT%%GT%%COLON%%QUOTE%%SLASH%%BACKSLASH%%PIPE%%QUESTION%%STAR%";
+        assert_eq!(encode_path_name(input), expected);
+    }
+
+    #[test]
+    fn test_decode_all_chars() {
+        let input = "%LT%%GT%%COLON%%QUOTE%%SLASH%%BACKSLASH%%PIPE%%QUESTION%%STAR%";
+        let expected = r#"<>:"/\|?*"#;
+        assert_eq!(decode_path_name(input), expected);
+    }
+
+    #[test]
+    fn test_roundtrip() {
+        let original = "Test<File>With:Special\"Chars/And\\More|Stuff?Here*End";
+        let encoded = encode_path_name(original);
+        let decoded = decode_path_name(&encoded);
+        assert_eq!(decoded, original);
+    }
+
+    #[test]
+    fn test_no_special_chars() {
+        let input = "NormalFileName";
+        assert_eq!(encode_path_name(input), input);
+        assert_eq!(decode_path_name(input), input);
+    }
+
+    #[test]
+    fn test_leading_spaces() {
+        let input = "  LeadingSpaces";
+        let encoded = encode_path_name(input);
+        assert_eq!(encoded, "%SPACE%%SPACE%LeadingSpaces");
+        assert_eq!(decode_path_name(&encoded), input);
+    }
+
+    #[test]
+    fn test_trailing_spaces() {
+        let input = "TrailingSpaces  ";
+        let encoded = encode_path_name(input);
+        assert_eq!(encoded, "TrailingSpaces%SPACE%%SPACE%");
+        assert_eq!(decode_path_name(&encoded), input);
+    }
+
+    #[test]
+    fn test_both_spaces() {
+        let input = " Both Spaces ";
+        let encoded = encode_path_name(input);
+        assert_eq!(encoded, "%SPACE%Both Spaces%SPACE%");
+        assert_eq!(decode_path_name(&encoded), input);
+    }
+
+    #[test]
+    fn test_middle_spaces_unchanged() {
+        let input = "Middle Spaces Here";
+        let encoded = encode_path_name(input);
+        assert_eq!(encoded, "Middle Spaces Here");
+        assert_eq!(decode_path_name(&encoded), input);
+    }
+
+    #[test]
+    fn test_roundtrip_with_spaces() {
+        let original = "  <Test>  ";
+        let encoded = encode_path_name(original);
+        let decoded = decode_path_name(&encoded);
+        assert_eq!(decoded, original);
+    }
+}

src/serve_session.rs

@@ -106,8 +106,15 @@ impl ServeSession {
 
         let root_id = tree.get_root_id();
 
-        let instance_context =
+        let decode_windows_invalid_chars = root_project
+            .syncback_rules
+            .as_ref()
+            .map(|rules| rules.encode_windows_invalid_chars())
+            .unwrap_or(false);
+
+        let mut instance_context =
             InstanceContext::with_emit_legacy_scripts(root_project.emit_legacy_scripts);
+        instance_context.set_decode_windows_invalid_chars(decode_windows_invalid_chars);
 
         log::trace!("Generating snapshot of instances from VFS");
         let snapshot = snapshot_from_vfs(&instance_context, &vfs, start_path)?;

src/snapshot/metadata.rs

@@ -145,6 +145,11 @@ pub struct InstanceContext {
     pub emit_legacy_scripts: bool,
     #[serde(skip_serializing_if = "Vec::is_empty")]
     pub sync_rules: Vec<SyncRule>,
+    /// Whether to decode Windows-invalid characters in file names.
+    /// Characters like `%LT%`, `%GT%`, `%COLON%`, etc. will be decoded
+    /// back to `<`, `>`, `:`, etc. in instance names sent to the plugin.
+    #[serde(default)]
+    pub decode_windows_invalid_chars: bool,
 }
 
 impl InstanceContext {
@@ -153,6 +158,7 @@ impl InstanceContext {
             path_ignore_rules: Arc::new(Vec::new()),
             emit_legacy_scripts: emit_legacy_scripts_default().unwrap(),
             sync_rules: Vec::new(),
+            decode_windows_invalid_chars: false,
         }
     }
 
@@ -165,6 +171,10 @@ impl InstanceContext {
         }
     }
 
+    pub fn set_decode_windows_invalid_chars(&mut self, decode: bool) {
+        self.decode_windows_invalid_chars = decode;
+    }
+
     /// Extend the list of ignore rules in the context with the given new rules.
     pub fn add_path_ignore_rules<I>(&mut self, new_rules: I)
     where

src/snapshot/tests/snapshots/librojo__snapshot__tests__apply__add_property.snap

@@ -13,6 +13,7 @@ metadata:
   relevant_paths: []
   context:
     emit_legacy_scripts: true
+    decode_windows_invalid_chars: false
   specified_id: ~
   middleware: ~
   schema: ~

src/snapshot/tests/snapshots/librojo__snapshot__tests__apply__remove_property_after_patch.snap

@@ -11,6 +11,7 @@ metadata:
   relevant_paths: []
   context:
     emit_legacy_scripts: true
+    decode_windows_invalid_chars: false
   specified_id: ~
   middleware: ~
   schema: ~

src/snapshot/tests/snapshots/librojo__snapshot__tests__apply__remove_property_initial.snap

@@ -13,6 +13,7 @@ metadata:
   relevant_paths: []
   context:
     emit_legacy_scripts: true
+    decode_windows_invalid_chars: false
   specified_id: ~
   middleware: ~
   schema: ~

src/snapshot/tests/snapshots/librojo__snapshot__tests__apply__set_name_and_class_name.snap

@@ -11,6 +11,7 @@ metadata:
   relevant_paths: []
   context:
     emit_legacy_scripts: true
+    decode_windows_invalid_chars: false
   specified_id: ~
   middleware: ~
   schema: ~

src/snapshot/tests/snapshots/librojo__snapshot__tests__compute__add_child.snap

@@ -12,6 +12,7 @@ added_instances:
         relevant_paths: []
         context:
           emit_legacy_scripts: true
+          decode_windows_invalid_chars: false
         specified_id: ~
         middleware: ~
         schema: ~

src/snapshot_middleware/dir.rs

@@ -172,6 +172,11 @@ pub fn syncback_dir_no_meta<'sync>(
                 );
                 continue;
             }
+            // Skip instances matching ignoreTrees
+            if snapshot.should_ignore_tree(*new_child_ref) {
+                old_child_map.remove(new_child.name.as_str());
+                continue;
+            }
             if let Some(old_child) = old_child_map.remove(new_child.name.as_str()) {
                 if old_child.metadata().relevant_paths.is_empty() {
                     log::debug!(
@@ -223,6 +228,10 @@ pub fn syncback_dir_no_meta<'sync>(
                 );
                 continue;
             }
+            // Skip instances matching ignoreTrees
+            if snapshot.should_ignore_tree(*new_child_ref) {
+                continue;
+            }
             children.push(snapshot.with_joined_path(*new_child_ref, None)?);
         }
     }

src/snapshot_middleware/mod.rs

@@ -30,6 +30,7 @@ use serde::{Deserialize, Serialize};
 
 use crate::{
     glob::Glob,
+    path_encoding::decode_path_name,
     project::DEFAULT_PROJECT_NAMES,
     syncback::{SyncbackReturn, SyncbackSnapshot},
 };
@@ -74,13 +75,19 @@ pub fn snapshot_from_vfs(
 
     if meta.is_dir() {
         let (middleware, dir_name, init_path) = get_dir_middleware(vfs, path)?;
+        // Decode directory name if the flag is set
+        let decoded_name = if context.decode_windows_invalid_chars {
+            decode_path_name(dir_name)
+        } else {
+            dir_name.to_string()
+        };
         // TODO: Support user defined init paths
         // If and when we do, make sure to go support it in
         // `Project::set_file_name`, as right now it special-cases
         // `default.project.json` as an `init` path.
         match middleware {
-            Middleware::Dir => middleware.snapshot(context, vfs, path, dir_name),
+            Middleware::Dir => middleware.snapshot(context, vfs, path, &decoded_name),
-            _ => middleware.snapshot(context, vfs, &init_path, dir_name),
+            _ => middleware.snapshot(context, vfs, &init_path, &decoded_name),
         }
     } else {
         let file_name = path
@@ -152,19 +159,23 @@ fn snapshot_from_path(
     vfs: &Vfs,
     path: &Path,
 ) -> anyhow::Result<Option<InstanceSnapshot>> {
+    // Helper to decode name if the flag is set
+    let decode_name = |name: &str| -> String {
+        if context.decode_windows_invalid_chars {
+            decode_path_name(name)
+        } else {
+            name.to_string()
+        }
+    };
+
     if let Some(rule) = context.get_user_sync_rule(path) {
-        return rule
+        let name = decode_name(rule.file_name_for_path(path)?);
-            .middleware
+        return rule.middleware.snapshot(context, vfs, path, &name);
-            .snapshot(context, vfs, path, rule.file_name_for_path(path)?);
     } else {
         for rule in default_sync_rules() {
             if rule.matches(path) {
-                return rule.middleware.snapshot(
+                let name = decode_name(rule.file_name_for_path(path)?);
-                    context,
+                return rule.middleware.snapshot(context, vfs, path, &name);
-                    vfs,
-                    path,
-                    rule.file_name_for_path(path)?,
-                );
             }
         }
     }

src/snapshot_middleware/snapshots/librojo__snapshot_middleware__csv__test__csv_from_vfs.snap

@@ -13,6 +13,7 @@ metadata:
     - /foo.meta.jsonc
   context:
     emit_legacy_scripts: true
+    decode_windows_invalid_chars: false
   specified_id: ~
   middleware: ~
   schema: ~

src/snapshot_middleware/snapshots/librojo__snapshot_middleware__csv__test__csv_init.snap

@@ -20,6 +20,7 @@ metadata:
     - /root/init.meta.jsonc
   context:
     emit_legacy_scripts: true
+    decode_windows_invalid_chars: false
   specified_id: ~
   middleware: ~
   schema: ~

src/snapshot_middleware/snapshots/librojo__snapshot_middleware__csv__test__csv_init_with_meta.snap

@@ -20,6 +20,7 @@ metadata:
     - /root/init.meta.jsonc
   context:
     emit_legacy_scripts: true
+    decode_windows_invalid_chars: false
   specified_id: manually specified
   middleware: ~
   schema: ~

src/snapshot_middleware/snapshots/librojo__snapshot_middleware__csv__test__csv_with_meta.snap

@@ -13,6 +13,7 @@ metadata:
     - /foo.meta.jsonc
   context:
     emit_legacy_scripts: true
+    decode_windows_invalid_chars: false
   specified_id: ~
   middleware: ~
   schema: ~

src/snapshot_middleware/snapshots/librojo__snapshot_middleware__dir__test__empty_folder.snap

@@ -20,6 +20,7 @@ metadata:
     - /foo/init.meta.jsonc
   context:
     emit_legacy_scripts: true
+    decode_windows_invalid_chars: false
   specified_id: ~
   middleware: ~
   schema: ~

src/snapshot_middleware/snapshots/librojo__snapshot_middleware__dir__test__folder_in_folder.snap

@@ -20,6 +20,7 @@ metadata:
     - /foo/init.meta.jsonc
   context:
     emit_legacy_scripts: true
+    decode_windows_invalid_chars: false
   specified_id: ~
   middleware: ~
   schema: ~
@@ -45,6 +46,7 @@ children:
         - /foo/Child/init.meta.jsonc
       context:
         emit_legacy_scripts: true
+        decode_windows_invalid_chars: false
       specified_id: ~
       middleware: dir
       schema: ~

src/snapshot_middleware/snapshots/librojo__snapshot_middleware__json__test__instance_from_vfs.snap

@@ -13,6 +13,7 @@ metadata:
     - /foo.meta.jsonc
   context:
     emit_legacy_scripts: true
+    decode_windows_invalid_chars: false
   specified_id: ~
   middleware: ~
   schema: ~

src/snapshot_middleware/snapshots/librojo__snapshot_middleware__json__test__with_metadata.snap

@@ -13,6 +13,7 @@ metadata:
     - /foo.meta.jsonc
   context:
     emit_legacy_scripts: true
+    decode_windows_invalid_chars: false
   specified_id: manually specified
   middleware: ~
   schema: ~

src/snapshot_middleware/snapshots/librojo__snapshot_middleware__json_model__test__model_from_vfs.snap

@@ -11,6 +11,7 @@ metadata:
     - /foo.model.json
   context:
     emit_legacy_scripts: true
+    decode_windows_invalid_chars: false
   specified_id: ~
   middleware: ~
   schema: ~
@@ -26,6 +27,7 @@ children:
       relevant_paths: []
       context:
         emit_legacy_scripts: true
+        decode_windows_invalid_chars: false
       specified_id: ~
       middleware: ~
       schema: ~

src/snapshot_middleware/snapshots/librojo__snapshot_middleware__json_model__test__model_from_vfs_legacy.snap

@@ -11,6 +11,7 @@ metadata:
     - /foo.model.json
   context:
     emit_legacy_scripts: true
+    decode_windows_invalid_chars: false
   specified_id: ~
   middleware: ~
   schema: ~
@@ -26,6 +27,7 @@ children:
       relevant_paths: []
       context:
         emit_legacy_scripts: true
+        decode_windows_invalid_chars: false
       specified_id: ~
       middleware: ~
       schema: ~

src/snapshot_middleware/snapshots/librojo__snapshot_middleware__lua__test__class_client_from_vfs.snap

@@ -13,6 +13,7 @@ metadata:
     - /foo.meta.jsonc
   context:
     emit_legacy_scripts: true
+    decode_windows_invalid_chars: false
   specified_id: ~
   middleware: ~
   schema: ~

src/snapshot_middleware/snapshots/librojo__snapshot_middleware__lua__test__class_module_from_vfs.snap

@@ -13,6 +13,7 @@ metadata:
     - /foo.meta.jsonc
   context:
     emit_legacy_scripts: true
+    decode_windows_invalid_chars: false
   specified_id: ~
   middleware: ~
   schema: ~

src/snapshot_middleware/snapshots/librojo__snapshot_middleware__lua__test__class_module_with_meta.snap

@@ -13,6 +13,7 @@ metadata:
     - /foo.meta.jsonc
   context:
     emit_legacy_scripts: true
+    decode_windows_invalid_chars: false
   specified_id: ~
   middleware: ~
   schema: ~

src/snapshot_middleware/snapshots/librojo__snapshot_middleware__lua__test__class_script_disabled.snap

@@ -13,6 +13,7 @@ metadata:
     - /bar.meta.jsonc
   context:
     emit_legacy_scripts: true
+    decode_windows_invalid_chars: false
   specified_id: ~
   middleware: ~
   schema: ~

src/snapshot_middleware/snapshots/librojo__snapshot_middleware__lua__test__class_script_with_meta.snap

@@ -13,6 +13,7 @@ metadata:
     - /foo.meta.jsonc
   context:
     emit_legacy_scripts: true
+    decode_windows_invalid_chars: false
   specified_id: ~
   middleware: ~
   schema: ~

src/snapshot_middleware/snapshots/librojo__snapshot_middleware__lua__test__class_server_from_vfs.snap

@@ -13,6 +13,7 @@ metadata:
     - /foo.meta.jsonc
   context:
     emit_legacy_scripts: true
+    decode_windows_invalid_chars: false
   specified_id: ~
   middleware: ~
   schema: ~

src/snapshot_middleware/snapshots/librojo__snapshot_middleware__lua__test__init_module_from_vfs.snap

@@ -20,6 +20,7 @@ metadata:
     - /root/init.meta.jsonc
   context:
     emit_legacy_scripts: true
+    decode_windows_invalid_chars: false
   specified_id: ~
   middleware: ~
   schema: ~

src/snapshot_middleware/snapshots/librojo__snapshot_middleware__lua__test__init_module_from_vfs_with_meta.snap

@@ -20,6 +20,7 @@ metadata:
     - /root/init.meta.jsonc
   context:
     emit_legacy_scripts: true
+    decode_windows_invalid_chars: false
   specified_id: manually specified
   middleware: ~
   schema: ~

src/snapshot_middleware/snapshots/librojo__snapshot_middleware__lua__test__plugin_module_from_vfs.snap

@@ -13,6 +13,7 @@ metadata:
     - /foo.meta.jsonc
   context:
     emit_legacy_scripts: false
+    decode_windows_invalid_chars: false
   specified_id: ~
   middleware: ~
   schema: ~

src/snapshot_middleware/snapshots/librojo__snapshot_middleware__lua__test__runcontext_client_from_vfs.snap

@@ -13,6 +13,7 @@ metadata:
     - /foo.meta.jsonc
   context:
     emit_legacy_scripts: false
+    decode_windows_invalid_chars: false
   specified_id: ~
   middleware: ~
   schema: ~

src/snapshot_middleware/snapshots/librojo__snapshot_middleware__lua__test__runcontext_module_from_vfs.snap

@@ -13,6 +13,7 @@ metadata:
     - /foo.meta.jsonc
   context:
     emit_legacy_scripts: false
+    decode_windows_invalid_chars: false
   specified_id: ~
   middleware: ~
   schema: ~

src/snapshot_middleware/snapshots/librojo__snapshot_middleware__lua__test__runcontext_module_with_meta.snap

@@ -13,6 +13,7 @@ metadata:
     - /foo.meta.jsonc
   context:
     emit_legacy_scripts: false
+    decode_windows_invalid_chars: false
   specified_id: ~
   middleware: ~
   schema: ~

src/snapshot_middleware/snapshots/librojo__snapshot_middleware__lua__test__runcontext_script_disabled.snap

@@ -13,6 +13,7 @@ metadata:
     - /bar.meta.jsonc
   context:
     emit_legacy_scripts: false
+    decode_windows_invalid_chars: false
   specified_id: ~
   middleware: ~
   schema: ~

src/snapshot_middleware/snapshots/librojo__snapshot_middleware__lua__test__runcontext_script_with_meta.snap

@@ -13,6 +13,7 @@ metadata:
     - /foo.meta.jsonc
   context:
     emit_legacy_scripts: false
+    decode_windows_invalid_chars: false
   specified_id: ~
   middleware: ~
   schema: ~

src/snapshot_middleware/snapshots/librojo__snapshot_middleware__lua__test__runcontext_server_from_vfs.snap

@@ -13,6 +13,7 @@ metadata:
     - /foo.meta.jsonc
   context:
     emit_legacy_scripts: false
+    decode_windows_invalid_chars: false
   specified_id: ~
   middleware: ~
   schema: ~

src/snapshot_middleware/snapshots/librojo__snapshot_middleware__meta_file__test__adjacent_read_json.snap

@@ -10,6 +10,7 @@ metadata:
     - /foo/bar.meta.jsonc
   context:
     emit_legacy_scripts: true
+    decode_windows_invalid_chars: false
   specified_id: manually specified
   middleware: ~
   schema: ~

src/snapshot_middleware/snapshots/librojo__snapshot_middleware__meta_file__test__adjacent_read_jsonc.snap

@@ -10,6 +10,7 @@ metadata:
     - /foo/bar.meta.jsonc
   context:
     emit_legacy_scripts: true
+    decode_windows_invalid_chars: false
   specified_id: manually specified
   middleware: ~
   schema: ~

src/snapshot_middleware/snapshots/librojo__snapshot_middleware__meta_file__test__directory_read_json.snap

@@ -10,6 +10,7 @@ metadata:
     - /foo/init.meta.jsonc
   context:
     emit_legacy_scripts: true
+    decode_windows_invalid_chars: false
   specified_id: manually specified
   middleware: ~
   schema: ~

src/snapshot_middleware/snapshots/librojo__snapshot_middleware__meta_file__test__directory_read_jsonc.snap

@@ -10,6 +10,7 @@ metadata:
     - /foo/init.meta.jsonc
   context:
     emit_legacy_scripts: true
+    decode_windows_invalid_chars: false
   specified_id: manually specified
   middleware: ~
   schema: ~

src/snapshot_middleware/snapshots/librojo__snapshot_middleware__project__test__no_name_project.snap

@@ -11,6 +11,7 @@ metadata:
     - /foo/default.project.json
   context:
     emit_legacy_scripts: true
+    decode_windows_invalid_chars: false
   specified_id: ~
   middleware: ~
   schema: ~

src/snapshot_middleware/snapshots/librojo__snapshot_middleware__project__test__project_from_direct_file.snap

@@ -11,6 +11,7 @@ metadata:
     - /foo/hello.project.json
   context:
     emit_legacy_scripts: true
+    decode_windows_invalid_chars: false
   specified_id: ~
   middleware: ~
   schema: ~

src/snapshot_middleware/snapshots/librojo__snapshot_middleware__project__test__project_path_property_overrides.snap

@@ -12,6 +12,7 @@ metadata:
     - /foo/default.project.json
   context:
     emit_legacy_scripts: true
+    decode_windows_invalid_chars: false
   specified_id: ~
   middleware: project
   schema: ~

src/snapshot_middleware/snapshots/librojo__snapshot_middleware__project__test__project_with_children.snap

@@ -11,6 +11,7 @@ metadata:
     - /foo.project.json
   context:
     emit_legacy_scripts: true
+    decode_windows_invalid_chars: false
   specified_id: ~
   middleware: ~
   schema: ~
@@ -31,6 +32,7 @@ children:
       relevant_paths: []
       context:
         emit_legacy_scripts: true
+        decode_windows_invalid_chars: false
       specified_id: ~
       middleware: ~
       schema: ~

src/snapshot_middleware/snapshots/librojo__snapshot_middleware__project__test__project_with_path_to_project.snap

@@ -12,6 +12,7 @@ metadata:
     - /foo/default.project.json
   context:
     emit_legacy_scripts: true
+    decode_windows_invalid_chars: false
   specified_id: ~
   middleware: project
   schema: ~

src/snapshot_middleware/snapshots/librojo__snapshot_middleware__project__test__project_with_path_to_project_with_children.snap

@@ -12,6 +12,7 @@ metadata:
     - /foo/default.project.json
   context:
     emit_legacy_scripts: true
+    decode_windows_invalid_chars: false
   specified_id: ~
   middleware: project
   schema: ~
@@ -32,6 +33,7 @@ children:
       relevant_paths: []
       context:
         emit_legacy_scripts: true
+        decode_windows_invalid_chars: false
       specified_id: ~
       middleware: ~
       schema: ~

src/snapshot_middleware/snapshots/librojo__snapshot_middleware__project__test__project_with_path_to_txt.snap

@@ -14,6 +14,7 @@ metadata:
     - /foo/default.project.json
   context:
     emit_legacy_scripts: true
+    decode_windows_invalid_chars: false
   specified_id: ~
   middleware: text
   schema: ~

src/snapshot_middleware/snapshots/librojo__snapshot_middleware__project__test__project_with_resolved_properties.snap

@@ -11,6 +11,7 @@ metadata:
     - /foo.project.json
   context:
     emit_legacy_scripts: true
+    decode_windows_invalid_chars: false
   specified_id: ~
   middleware: ~
   schema: ~

src/snapshot_middleware/snapshots/librojo__snapshot_middleware__project__test__project_with_unresolved_properties.snap

@@ -11,6 +11,7 @@ metadata:
     - /foo.project.json
   context:
     emit_legacy_scripts: true
+    decode_windows_invalid_chars: false
   specified_id: ~
   middleware: ~
   schema: ~

src/snapshot_middleware/snapshots/librojo__snapshot_middleware__toml__test__instance_from_vfs.snap

@@ -13,6 +13,7 @@ metadata:
     - /foo.meta.jsonc
   context:
     emit_legacy_scripts: true
+    decode_windows_invalid_chars: false
   specified_id: ~
   middleware: ~
   schema: ~

src/snapshot_middleware/snapshots/librojo__snapshot_middleware__toml__test__with_metadata.snap

@@ -13,6 +13,7 @@ metadata:
     - foo.meta.jsonc
   context:
     emit_legacy_scripts: true
+    decode_windows_invalid_chars: false
   specified_id: manually specified
   middleware: ~
   schema: ~

src/snapshot_middleware/snapshots/librojo__snapshot_middleware__txt__test__instance_from_vfs.snap

@@ -13,6 +13,7 @@ metadata:
     - /foo.meta.jsonc
   context:
     emit_legacy_scripts: true
+    decode_windows_invalid_chars: false
   specified_id: ~
   middleware: ~
   schema: ~

src/snapshot_middleware/snapshots/librojo__snapshot_middleware__txt__test__with_metadata.snap

@@ -13,6 +13,7 @@ metadata:
     - /foo.meta.jsonc
   context:
     emit_legacy_scripts: true
+    decode_windows_invalid_chars: false
   specified_id: manually specified
   middleware: ~
   schema: ~

src/snapshot_middleware/snapshots/librojo__snapshot_middleware__yaml__test__instance_from_vfs.snap

@@ -13,6 +13,7 @@ metadata:
     - /foo.meta.jsonc
   context:
     emit_legacy_scripts: true
+    decode_windows_invalid_chars: false
   specified_id: ~
   middleware: ~
   schema: ~

src/snapshot_middleware/snapshots/librojo__snapshot_middleware__yaml__test__with_metadata.snap

@@ -13,6 +13,7 @@ metadata:
     - foo.meta.jsonc
   context:
     emit_legacy_scripts: true
+    decode_windows_invalid_chars: false
   specified_id: manually specified
   middleware: ~
   schema: ~

src/syncback/file_names.rs

@@ -6,12 +6,15 @@ use std::borrow::Cow;
 use anyhow::Context;
 use rbx_dom_weak::Instance;
 
-use crate::{snapshot::InstanceWithMeta, snapshot_middleware::Middleware};
+use crate::{
+    path_encoding::encode_path_name, snapshot::InstanceWithMeta, snapshot_middleware::Middleware,
+};
 
 pub fn name_for_inst<'old>(
     middleware: Middleware,
     new_inst: &Instance,
     old_inst: Option<InstanceWithMeta<'old>>,
+    encode_invalid_chars: bool,
 ) -> anyhow::Result<Cow<'old, str>> {
     if let Some(old_inst) = old_inst {
         if let Some(source) = old_inst.metadata().relevant_paths.first() {
@@ -35,13 +38,37 @@ pub fn name_for_inst<'old>(
             | Middleware::CsvDir
             | Middleware::ServerScriptDir
             | Middleware::ClientScriptDir
-            | Middleware::ModuleScriptDir => Cow::Owned(new_inst.name.clone()),
+            | Middleware::ModuleScriptDir => {
+                let name = if encode_invalid_chars {
+                    let encoded = encode_path_name(&new_inst.name);
+                    // Validate for issues not fixed by encoding (trailing space/dot, control chars, reserved names)
+                    validate_file_name(&encoded).with_context(|| {
+                        format!("name '{}' (encoded from '{}') is not legal to write to the file system", encoded, new_inst.name)
+                    })?;
+                    encoded
+                } else {
+                    validate_file_name(&new_inst.name).with_context(|| {
+                        format!("name '{}' is not legal to write to the file system", new_inst.name)
+                    })?;
+                    new_inst.name.clone()
+                };
+                Cow::Owned(name)
+            }
             _ => {
                 let extension = extension_for_middleware(middleware);
-                let name = &new_inst.name;
+                let name = if encode_invalid_chars {
-                validate_file_name(name).with_context(|| {
+                    let encoded = encode_path_name(&new_inst.name);
-                    format!("name '{name}' is not legal to write to the file system")
+                    // Validate for issues not fixed by encoding (trailing space/dot, control chars, reserved names)
-                })?;
+                    validate_file_name(&encoded).with_context(|| {
+                        format!("name '{}' (encoded from '{}') is not legal to write to the file system", encoded, new_inst.name)
+                    })?;
+                    encoded
+                } else {
+                    validate_file_name(&new_inst.name).with_context(|| {
+                        format!("name '{}' is not legal to write to the file system", new_inst.name)
+                    })?;
+                    new_inst.name.clone()
+                };
                 Cow::Owned(format!("{name}.{extension}"))
             }
         })

src/syncback/mod.rs

@@ -409,6 +409,12 @@ pub struct SyncbackRules {
     /// generally a better UX.
     #[serde(skip_serializing_if = "Option::is_none")]
     create_ignore_dir_paths: Option<bool>,
+    /// Whether to encode Windows-invalid characters in file names during
+    /// syncback. Characters like `<`, `>`, `:`, `"`, `/`, `\`, `|`, `?`, `*`
+    /// will be encoded as `%LT%`, `%GT%`, `%COLON%`, etc.
+    /// Defaults to `false`.
+    #[serde(skip_serializing_if = "Option::is_none")]
+    encode_windows_invalid_chars: Option<bool>,
 }
 
 impl SyncbackRules {
@@ -432,6 +438,13 @@ impl SyncbackRules {
 
         Ok(globs)
     }
+
+    /// Returns whether Windows-invalid characters should be encoded in file
+    /// names during syncback. Defaults to `false`.
+    #[inline]
+    pub fn encode_windows_invalid_chars(&self) -> bool {
+        self.encode_windows_invalid_chars.unwrap_or(false)
+    }
 }
 
 fn is_valid_path(globs: &Option<Vec<Glob>>, base_path: &Path, path: &Path) -> bool {

src/syncback/snapshot.rs

@@ -44,7 +44,13 @@ impl<'sync> SyncbackSnapshot<'sync> {
             middleware: None,
         };
         let middleware = get_best_middleware(&snapshot);
-        let name = name_for_inst(middleware, snapshot.new_inst(), snapshot.old_inst())?;
+        let encode_invalid_chars = self.encode_windows_invalid_chars();
+        let name = name_for_inst(
+            middleware,
+            snapshot.new_inst(),
+            snapshot.old_inst(),
+            encode_invalid_chars,
+        )?;
         snapshot.path = self.path.join(name.as_ref());
 
         Ok(snapshot)
@@ -70,7 +76,13 @@ impl<'sync> SyncbackSnapshot<'sync> {
             middleware: None,
         };
         let middleware = get_best_middleware(&snapshot);
-        let name = name_for_inst(middleware, snapshot.new_inst(), snapshot.old_inst())?;
+        let encode_invalid_chars = self.encode_windows_invalid_chars();
+        let name = name_for_inst(
+            middleware,
+            snapshot.new_inst(),
+            snapshot.old_inst(),
+            encode_invalid_chars,
+        )?;
         snapshot.path = base_path.join(name.as_ref());
 
         Ok(snapshot)
@@ -224,6 +236,34 @@ impl<'sync> SyncbackSnapshot<'sync> {
             .map(|classes| classes.iter().any(|c| c == class_name))
             .unwrap_or(false)
     }
+
+    /// Checks if an instance should be ignored based on ignoreTrees rules.
+    /// Takes a Ref to check against the new tree's instance path.
+    #[inline]
+    pub fn should_ignore_tree(&self, referent: Ref) -> bool {
+        if let Some(ignore_trees) = self.ignore_tree() {
+            let path = inst_path(self.new_tree(), referent);
+            for ignored in ignore_trees {
+                if path.starts_with(ignored.as_str()) {
+                    log::debug!("Ignoring {path} because it matches ignoreTrees entry: {ignored}");
+                    return true;
+                }
+            }
+        }
+        false
+    }
+
+    /// Returns whether Windows-invalid characters should be encoded in file
+    /// names during syncback.
+    #[inline]
+    pub fn encode_windows_invalid_chars(&self) -> bool {
+        self.data
+            .project
+            .syncback_rules
+            .as_ref()
+            .map(|rules| rules.encode_windows_invalid_chars())
+            .unwrap_or(false)
+    }
 }
 
 pub fn filter_out_property(inst: &Instance, prop_name: &str) -> bool {