settings: accept trailing commas (#2606)

Z-2357

I've found a crate that handles both comments and trailing commas in
JSON. It is a fork of `serde_json`, but it is maintained & up-to-date.
Sadly RawValue seems to not play nicely with it; I've ran into
deserialisation issues around use of RawValue. For this PR I've migrated
to `Value` API.

Obviously this is just a point of discussion, not something I'd merge
straight away. There may be better solutions to this particular problem.

I've also noticed that `serde_json_lenient` does not handle trailing
commas after bindings array. I'm not sure how big of an issue that is.

Release Notes:
- Improved handling of trailing commas in settings files.
[#1322](https://github.com/zed-industries/community/issues/1322)

crates/settings/src/keymap_file.rs

@@ -1,5 +1,5 @@
 use crate::{settings_store::parse_json_with_comments, SettingsAssets};
-use anyhow::{Context, Result};
+use anyhow::{anyhow, Context, Result};
 use collections::BTreeMap;
 use gpui::{keymap_matcher::Binding, AppContext};
 use schemars::{
@@ -8,7 +8,7 @@ use schemars::{
     JsonSchema,
 };
 use serde::Deserialize;
-use serde_json::{value::RawValue, Value};
+use serde_json::Value;
 use util::{asset_str, ResultExt};
 
 #[derive(Deserialize, Default, Clone, JsonSchema)]
@@ -24,7 +24,7 @@ pub struct KeymapBlock {
 
 #[derive(Deserialize, Default, Clone)]
 #[serde(transparent)]
-pub struct KeymapAction(Box<RawValue>);
+pub struct KeymapAction(Value);
 
 impl JsonSchema for KeymapAction {
     fn schema_name() -> String {
@@ -37,11 +37,12 @@ impl JsonSchema for KeymapAction {
 }
 
 #[derive(Deserialize)]
-struct ActionWithData(Box<str>, Box<RawValue>);
+struct ActionWithData(Box<str>, Value);
 
 impl KeymapFile {
     pub fn load_asset(asset_path: &str, cx: &mut AppContext) -> Result<()> {
         let content = asset_str::<SettingsAssets>(asset_path);
+
         Self::parse(content.as_ref())?.add_to_cx(cx)
     }
 
@@ -54,18 +55,27 @@ impl KeymapFile {
             let bindings = bindings
                 .into_iter()
                 .filter_map(|(keystroke, action)| {
-                    let action = action.0.get();
+                    let action = action.0;
 
                     // This is a workaround for a limitation in serde: serde-rs/json#497
                     // We want to deserialize the action data as a `RawValue` so that we can
                     // deserialize the action itself dynamically directly from the JSON
                     // string. But `RawValue` currently does not work inside of an untagged enum.
-                    if action.starts_with('[') {
-                        let ActionWithData(name, data) = serde_json::from_str(action).log_err()?;
-                        cx.deserialize_action(&name, Some(data.get()))
+                    if let Value::Array(items) = action {
+                        let Ok([name, data]): Result<[serde_json::Value; 2], _> = items.try_into() else {
+                            return Some(Err(anyhow!("Expected array of length 2")));
+                        };
+                        let serde_json::Value::String(name) = name else {
+                            return Some(Err(anyhow!("Expected first item in array to be a string.")))
+                        };
+                        cx.deserialize_action(
+                            &name,
+                            Some(data),
+                        )
+                    } else if let Value::String(name) = action {
+                        cx.deserialize_action(&name, None)
                     } else {
-                        let name = serde_json::from_str(action).log_err()?;
-                        cx.deserialize_action(name, None)
+                        return Some(Err(anyhow!("Expected two-element array, got {:?}", action)));
                     }
                     .with_context(|| {
                         format!(
@@ -118,3 +128,24 @@ impl KeymapFile {
         serde_json::to_value(root_schema).unwrap()
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use crate::KeymapFile;
+
+    #[test]
+    fn can_deserialize_keymap_with_trailing_comma() {
+        let json = indoc::indoc! {"[
+              // Standard macOS bindings
+              {
+                \"bindings\": {
+                  \"up\": \"menu::SelectPrev\",
+                },
+              },
+            ]
+                  "
+
+        };
+        KeymapFile::parse(json).unwrap();
+    }
+}

crates/settings/src/settings_store.rs

@@ -834,11 +834,8 @@ fn to_pretty_json(value: &impl Serialize, indent_size: usize, indent_prefix_len:
 }
 
 pub fn parse_json_with_comments<T: DeserializeOwned>(content: &str) -> Result<T> {
-    Ok(serde_json::from_reader(
-        json_comments::CommentSettings::c_style().strip_comments(content.as_bytes()),
-    )?)
+    Ok(serde_json_lenient::from_str(content)?)
 }
-
 #[cfg(test)]
 mod tests {
     use super::*;