Sort JSDoc @param completions by argument position

Fixes #20183

When triggering completions after `@param` in a JSDoc comment, parameter
suggestions are now sorted by their position in the function signature
rather than alphabetically.

Before: For `function foo(z, a) {}`, completions showed `a`, `z`
After: Completions now show `z`, `a` (matching argument order)

The fix uses the parameter index to generate a unique sortText value,
ensuring the IDE displays parameters in the order they appear in the
function definition. This makes it easier to document parameters in
the correct order.

Co-authored-by: Cursor <cursoragent@cursor.com>

Author: murataslan1

src/services/jsDoc.ts

@@ -420,7 +420,7 @@ export function getJSDocParameterNameCompletions(tag: JSDocParameterTag): Comple
     const fn = jsdoc.parent;
     if (!isFunctionLike(fn)) return [];
 
-    return mapDefined(fn.parameters, param => {
+    return mapDefined(fn.parameters, (param, index) => {
         if (!isIdentifier(param.name)) return undefined;
 
         const name = param.name.text;
@@ -431,7 +431,9 @@ export function getJSDocParameterNameCompletions(tag: JSDocParameterTag): Comple
             return undefined;
         }
 
-        return { name, kind: ScriptElementKind.parameterElement, kindModifiers: "", sortText: Completions.SortText.LocationPriority };
+        // Use parameter index as sortText suffix to maintain argument order in completions
+        const sortText = (Completions.SortText.LocationPriority + String(index).padStart(4, "0")) as Completions.SortText;
+        return { name, kind: ScriptElementKind.parameterElement, kindModifiers: "", sortText };
     });
 }
 

tests/cases/fourslash/jsdocParameterNameCompletion.ts

@@ -1,5 +1,8 @@
 ///<reference path="fourslash.ts" />
 
+// Tests that @param completions are sorted by argument position (not alphabetically).
+// See https://github.com/microsoft/TypeScript/issues/20183
+
 /////**
 //// * @param /*0*/
 //// */
@@ -22,8 +25,27 @@
 //// */
 ////function i(foo, bar) {}
 
+// sortText uses LocationPriority ("11") + zero-padded index to maintain argument order
+const locationPriority = completion.SortText.LocationPriority;
 verify.completions(
-    { marker: ["0", "3", "4"], exact: ["foo", "bar"] },
-    { marker: "1", exact: "bar" },
-    { marker: "2", exact: ["canary", "canoodle"] },
+    {
+        marker: ["0", "3", "4"],
+        exact: [
+            { name: "foo", sortText: locationPriority + "0000" },
+            { name: "bar", sortText: locationPriority + "0001" },
+        ],
+    },
+    {
+        marker: "1",
+        // bar is the second parameter (index 1), already documented foo is filtered out
+        exact: { name: "bar", sortText: locationPriority + "0001" },
+    },
+    {
+        marker: "2",
+        // canary is index 1, canoodle is index 2 (cat=0, cantaloupe=3 filtered)
+        exact: [
+            { name: "canary", sortText: locationPriority + "0001" },
+            { name: "canoodle", sortText: locationPriority + "0002" },
+        ],
+    },
 );