Add failing test for empty node scenario

actions-languageservice/src/utils/find-token.test.ts

@@ -174,4 +174,18 @@ jobs:
       token: ["job", TokenType.String, "runs-"]
     });
   });
+
+  it("empty node", () => {
+    expect(
+      testFindToken(`on: push
+jobs:
+  build:
+    concurrency:
+    runs-on: ubu|`)
+    ).toEqual({
+      parent: ["job-factory", TokenType.Mapping],
+      key: [null, TokenType.String, "runs-on"],
+      token: ["runs-on", TokenType.String, "ubu"]
+    });
+  });
 });

actions-languageservice/src/utils/find-token.ts

@@ -67,6 +67,7 @@ export function findToken(pos: Position, root?: TemplateToken): TokenResult {
         for (let i = 0; i < mappingToken.count; i++) {
           const {key, value} = mappingToken.get(i);
 
+          // If the position is within the key, immediately return it as the token.
           if (posInToken(pos, key)) {
             return {
               parent: mappingToken,
@@ -75,7 +76,7 @@ export function findToken(pos: Position, root?: TemplateToken): TokenResult {
             };
           }
 
-          // Empty nodes positions won't always match the cursor, so check if we're on the same line
+          // If the value is an empty node (null, empty string)
           if (emptyNode(value)) {
             return {
               parent: mappingToken,