Fix LSP crash on unparseable cell option YAML by handling null lint result

apps/lsp/src/quarto.ts

@@ -50,7 +50,9 @@ export async function initializeQuarto(context: QuartoContext): Promise<Quarto>
     getAttrCompletions: initializeAttrCompletionProvider(
       context.resourcePath
     ),
-    getYamlDiagnostics: quartoModule.getLint,
+    // the external getLint() resolves to null when linting fails
+    getYamlDiagnostics: async (context) =>
+      (await quartoModule.getLint(context)) ?? [],
     getHover: quartoModule.getHover
   };
 
@@ -168,7 +170,7 @@ function normalizedValue(value: string, simpleDiv: boolean) {
 
 interface QuartoYamlModule {
   getCompletions(context: EditorContext): Promise<CompletionResult>;
-  getLint(context: EditorContext): Promise<Array<LintItem>>;
+  getLint(context: EditorContext): Promise<Array<LintItem> | null>;
   getHover?: (context: EditorContext) => Promise<HoverResult | null>;
 }
 

apps/vscode/CHANGELOG.md

@@ -5,6 +5,7 @@
 - In Positron, running a Python cell in a knitr document now respects the `quarto.cells.useReticulate` setting, instead of always routing it through reticulate on the R console (<https://github.com/quarto-dev/quarto/pull/1116>).
 - In Positron, when Positron serves language features for code cells itself (the `quarto.embeddedLanguageFeatures.native` setting), the extension no longer serves them from virtual document temp files (<https://github.com/quarto-dev/quarto/pull/1115>).
 - In Positron, fixed how the "Render on Save" checkbox works in the visual editor (<https://github.com/quarto-dev/quarto/pull/1121>).
+- Fixed a crash of the Quarto language server on save when a code cell contained unparseable YAML options (e.g. an unquoted `fig-cap` value containing a colon) (<https://github.com/quarto-dev/quarto/pull/1123>).
 
 ## 1.137.0 (Release on 2026-09-04)