fix(lsp): re-sync full-document changes as didClose+didOpen (avoid at least Roslyn C# LSP crash) - #2927
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…Roslyn crash A `range: None` content change is a full-document replacement, valid only when the server negotiated FULL text sync. Strict servers — notably Roslyn (Microsoft.CodeAnalysis.LanguageServer) — negotiate INCREMENTAL and throw a NullReferenceException in ProtocolConversions.RangeToLinePositionSpan on the null range. That faults the request queue and closes the server's stdout (EOF), so edits stop syncing and completion/hover die on the line being typed (hover still works on unedited code, which made it look like the server was fine). Fresh emits full-document changes from several paths (file reload, workspace restore, plugin edits, event_apply resync). handle_did_change_sequential is the single chokepoint every didChange (live and queued-replay) flows through; it now detects a full-document change and, when the negotiated sync kind isn't FULL, re-syncs via didClose + didOpen — didOpen carries the whole text with no range, so it is correct under any sync kind. Per-keystroke ranged incremental edits are unaffected. Adds a negotiated_change_sync_kind() helper and a unit test covering every TextDocumentSync capability shape (Kind/Options/None). Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
The fix re-routes a `range: None` change to didClose+didOpen when the server negotiated a sync kind other than FULL. Drive that path directly: under INCREMENTAL the tracked document version resets to 0 (proving the close+open), while a ranged change passes through as a didChange (version bumps). A second test pins the other side of the condition — under FULL sync a full-document change stays a didChange. Fails without the fix (the full-document change bumps the version to 2 instead of resetting). Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
sfjohansson
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August 7, 2026 14:58
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Bug: Roslyn negotiates INCREMENTAL sync, then throws
NullReferenceExceptionon a full-document change (range: None). That faults its request queue and closes stdout — completion/hover die on the line you're typing, while hover still works on untouched code, so the server looks healthy.Fix: in
handle_did_change_sequential(the single chokepoint for every didChange) — when a change hasrange: Noneand the negotiated sync kind isn't FULL, re-sync as didClose + didOpen. didOpen carries the whole text with no range, valid under any sync kind.event_applyresync.Tests: unit test over every
TextDocumentSynccapability shape, plus a behavioural one — under INCREMENTAL a full-document change resets the tracked version to 0 (proving close+open), a ranged change still bumps it, and under FULL it stays a didChange. Both fail without the fix.Refs: LSP 3.17 — Text Document Synchronization · Roslyn
ProtocolConversions.cs