showed error on unresolved alias

src/languageservice/services/validation/unused-anchors.ts

@@ -16,6 +16,7 @@ export class UnusedAnchorsValidator implements AdditionalValidator {
     const result = [];
     const anchors = new Set<Scalar | YAMLMap | YAMLSeq>();
     const usedAnchors = new Set<Node>();
+    const unIdentifiedAlias = new Set<Node>();
     const anchorParent = new Map<Scalar | YAMLMap | YAMLSeq, Node | Pair>();
 
     visit(yamlDoc.internalDocument, (key, node, path) => {
@@ -27,7 +28,11 @@ export class UnusedAnchorsValidator implements AdditionalValidator {
         anchorParent.set(node, path[path.length - 1] as Node);
       }
       if (isAlias(node)) {
-        usedAnchors.add(node.resolve(yamlDoc.internalDocument));
+        if (!node.resolve(yamlDoc.internalDocument)) {
+          unIdentifiedAlias.add(node);
+        } else {
+          usedAnchors.add(node.resolve(yamlDoc.internalDocument));
+        }
       }
     });
 
@@ -46,6 +51,17 @@ export class UnusedAnchorsValidator implements AdditionalValidator {
       }
     }
 
+    unIdentifiedAlias.forEach((node) => {
+      const nodeRange = node.range;
+      if (nodeRange) {
+        const startOffset = nodeRange[0];
+        const endOffset = nodeRange[1];
+        const range = Range.create(document.positionAt(startOffset), document.positionAt(endOffset));
+        const warningDiagnostic = Diagnostic.create(range, `Unresolved alias "${node}"`, DiagnosticSeverity.Hint, 0);
+        warningDiagnostic.tags = [DiagnosticTag.Unnecessary];
+        result.push(warningDiagnostic);
+      }
+    });
     return result;
   }
   private getAnchorNode(parentNode: YamlNode, node: Node): CST.SourceToken | undefined {

test/yamlValidation.test.ts

@@ -84,7 +84,7 @@ some:
 ee: *g`;
       const result = await parseSetup(yaml);
       expect(result).is.not.empty;
-      expect(result.length).to.be.equal(4);
+      expect(result.length).to.be.equal(5);
       expect(result).to.include.deep.members([
         createUnusedAnchorDiagnostic('Unused anchor "&bar"', 0, 5, 0, 9),
         createUnusedAnchorDiagnostic('Unused anchor "&a"', 4, 2, 4, 4),
@@ -94,6 +94,16 @@ ee: *g`;
     });
   });
 
+  describe('Unresolved alias diagnostics', () => {
+    it('should report unresolved alias', async () => {
+      const yaml = 'foo: *bar';
+      const result = await parseSetup(yaml);
+      expect(result).is.not.empty;
+      expect(result.length).to.be.equal(1);
+      expect(result[0]).deep.equal(createUnusedAnchorDiagnostic('Unresolved alias "*bar"', 0, 5, 0, 9));
+    });
+  });
+
   describe(`YAML styles test`, () => {
     it('should not report flow style', async () => {
       const yaml = `host: phl-42