Add a lock around parse, to prevent concurrent access to the underlying parse tree. (simonbs#367)

* Add a lock around parse, as we can have both the OperationQueue-based parse and this parse happen at the same time

* Fixes SwiftLint violation

---------

Co-authored-by: Simon Støvring <mail@simonbs.dk>

Author: migueldeicaza

Sources/Runestone/TextView/SyntaxHighlighting/Internal/TreeSitter/TreeSitterInternalLanguageMode.swift

@@ -16,6 +16,7 @@ final class TreeSitterInternalLanguageMode: InternalLanguageMode {
     private let lineManager: LineManager
     private let rootLanguageLayer: TreeSitterLanguageLayer
     private let operationQueue = OperationQueue()
+    private let parseLock = NSLock()
 
     init(language: TreeSitterInternalLanguage, languageProvider: TreeSitterLanguageProvider?, stringView: StringView, lineManager: LineManager) {
         self.stringView = stringView
@@ -37,7 +38,9 @@ final class TreeSitterInternalLanguageMode: InternalLanguageMode {
     }
 
     func parse(_ text: NSString) {
-        rootLanguageLayer.parse(text)
+        parseLock.withLock {
+            rootLanguageLayer.parse(text)
+        }
     }
 
     func parse(_ text: NSString, completion: @escaping ((Bool) -> Void)) {