Fix optional property quick info showing redundant '| undefined'

Author: sw1tch3roo

src/services/symbolDisplay.ts

@@ -57,6 +57,7 @@ import {
     isNameOfFunctionDeclaration,
     isNewExpressionTarget,
     isObjectBindingPattern,
+    isOptionalChain,
     isTaggedTemplateExpression,
     isThisInTypeQuery,
     isTransientSymbol,
@@ -322,6 +323,12 @@ function getSymbolDisplayPartsDocumentationAndSymbolKindWorker(
         let signature: Signature | undefined;
         type ??= isThisExpression ? typeChecker.getTypeAtLocation(location) : typeChecker.getTypeOfSymbolAtLocation(symbol, location);
 
+        // For optional symbols, use the non-optional type to avoid showing both '?' and '| undefined'
+        // but only when not in optional chaining contexts where '| undefined' is semantically meaningful
+        if (symbol.flags & SymbolFlags.Optional && type && !isOptionalChain(location)) {
+            type = typeChecker.getNonOptionalType(type);
+        }
+
         if (location.parent && location.parent.kind === SyntaxKind.PropertyAccessExpression) {
             const right = (location.parent as PropertyAccessExpression).name;
             // Either the location is on the right of a property access, or on the left and the right is missing

tests/cases/fourslash/quickInfoOptionalPropertyConsistency.ts

@@ -0,0 +1,28 @@
+/// <reference path='fourslash.ts'/>
+
+//// interface Options {
+////     width?: number;
+////     height?: number;
+////     color?: ColorOptions;
+////     border?: BorderOptions;
+//// }
+////
+//// interface ColorOptions {
+////     primary: string;
+////     secondary: string;
+//// }
+////
+//// interface BorderOptions {
+////     style: string;
+////     width: number;
+//// }
+////
+//// function processOptions(options: Options) {
+////     return options.wi/*1*/dth + options.he/*2*/ight + options.co/*3*/lor + options.bo/*4*/rder;
+//// }
+
+// Test that optional properties show consistently with '?' and not '| undefined'
+verify.quickInfoAt("1", "(property) Options.width?: number");
+verify.quickInfoAt("2", "(property) Options.height?: number"); 
+verify.quickInfoAt("3", "(property) Options.color?: ColorOptions");
+verify.quickInfoAt("4", "(property) Options.border?: BorderOptions");