Right now I don't have time to look into your issue with failed CI.

There's no need, I only added the comment to make sure it was clear why I made the change. The error is the same that you raised in #610 (comment) and that I fixed in a2d1823.

With regard to multiple inheritance think of it like this. Say you have a JSON syntax, and then a bunch of helper syntaxes where the first overrides JSON to add optional trailing commas in arrays and objects, the second adds support for single-quoted strings, the third adds support for null as an additional value, the fourth adds support for line and block comments. Now JSON has syntax flavors like GeoJSON, HJSON, JSON5, JSONC (with Comments), JSON.NET. So for JSONC as an example you would need to do the following: (1) add multiple inheritance where (2) the comments helper syntax goes into the list of syntaxes for the extends key before (3) the trailing commas helper syntax. syntect should produce an error (as does Sublime) if (1) not all entries in the list extend from the same syntax or (2) you add the base syntax to the list, which is the same as (1) but I just wanted to reiterate that explicitely in case it wasn't obvious.

Are you saying this pointing to some specific flaw in the PR?

Thanks for the detailed review!

some behavior with regard to addressing syntax v1 vs. v2 changed. I saw you addressing the stacking of meta_scopes. The complete list is here as a reference. I haven't checked if you addressed all, yet.

I went through the compatibility list after your comment. The latest two commits add tests covering the remaining gaps I found and fix the ones that were failing: specifically, set in v2 no longer applies the parent context's meta_content_scope to the matched text, and the escape pattern in a v2 embed now correctly sees the embed_scope (which is the context's meta_content_scope). The v1/v2 differences that were already handled (e.g. clear_scopes stacking on multi-push, capture group scoping) continue to pass.

I saw you checking if each syntax in an extends list value exists. I didn't see you checking if whatever they extend from themselves: exists, and is the same for all, and has the same syntax version between the parents and their common base, and has the same syntax version between the parents and the source

The "exists" case was already covered: unresolvable parents cause the child to remain in the unresolved set, which produces a warning at the end of the fixed-point loop. The other three were missing — the latest commits add them:

• Same root for all parents: if parents don't share a common ancestor syntax, the extends is skipped with a warning.
• Version consistency: the version check is enforced at each resolution step — parents must have the same version as the child extending them. Since this applies transitively throughout the chain, it covers both the parents-vs-common-base and source-vs-parents cases.

In all error cases syntect emits a warning (via eprintln!) and skips applying the extends, leaving the child syntax in its unextended state.

I hadn't thought about local relative paths explicitly. I looked into it, the current find_parent_index implementation already handles this: it normalizes the extends value and checks whether any loaded syntax path ends with it (after prepending /). So a relative path like syntaxes/json-feature-comments.sublime-syntax will match against the full loaded path Packages/JSON/syntaxes/json-feature-comments.sublime-syntax. I added a test in 74e4476 to make sure this keeps working.

Is there some way in which I can facilitate the review process? 🙂

My comments above were addressed, marked them as "resolved". Looks good so far.

@keith-hall maybe you can take a look if you have a min?