From 02b3bb9b7856f5e308b3ff1f92ec3059c1ac672b Mon Sep 17 00:00:00 2001
From: Christian Dietrich <christian.dietrich.opensource@gmail.com>
Date: Tue, 15 Aug 2023 17:11:49 +0200
Subject: [PATCH] add implicit ID rule call for cross refs to
 getAllReachableRules

Fixes #1151

Signed-off-by: Christian Dietrich <christian.dietrich.opensource@gmail.com>
---
 packages/langium/src/utils/grammar-util.ts    |  6 ++-
 .../langium/test/utils/grammar-util.test.ts   | 42 ++++++++++++++++++-
 2 files changed, 46 insertions(+), 2 deletions(-)

diff --git a/packages/langium/src/utils/grammar-util.ts b/packages/langium/src/utils/grammar-util.ts
index ef018bfc0..c41ef0ac7 100644
--- a/packages/langium/src/utils/grammar-util.ts
+++ b/packages/langium/src/utils/grammar-util.ts
@@ -1,5 +1,5 @@
 /******************************************************************************
- * Copyright 2021-2022 TypeFox GmbH
+ * Copyright 2021-2023 TypeFox GmbH
  * This program and the accompanying materials are made available under the
  * terms of the MIT License, which is available in the project root.
  ******************************************************************************/
@@ -75,6 +75,10 @@ function ruleDfs(rule: ast.AbstractRule, visitedSet: Set<string>, allTerminals:
             if (refRule && !visitedSet.has(refRule.name)) {
                 ruleDfs(refRule, visitedSet, allTerminals);
             }
+        } else if (ast.isCrossReference(node)) {
+            if (node.terminal === undefined) {
+                visitedSet.add("ID")
+            }
         }
     });
 }
diff --git a/packages/langium/test/utils/grammar-util.test.ts b/packages/langium/test/utils/grammar-util.test.ts
index 5a4b7b46c..f75a4683d 100644
--- a/packages/langium/test/utils/grammar-util.test.ts
+++ b/packages/langium/test/utils/grammar-util.test.ts
@@ -1,5 +1,5 @@
 /******************************************************************************
- * Copyright 2022 TypeFox GmbH
+ * Copyright 2022-2023 TypeFox GmbH
  * This program and the accompanying materials are made available under the
  * terms of the MIT License, which is available in the project root.
  ******************************************************************************/
@@ -36,4 +36,44 @@ describe('Grammar Utils', () => {
         expect(reachableRules).toContain('Ws');
     });
 
+    test('ID implicit called should be returned by getAllReachableRules', async () => {
+        // [A] is short for [A:ID] thus the ID rule is needed by the parser and getAllReachableRules should return ID
+        const input = `
+            grammar HelloWorld
+
+            entry Model: A|B;
+            A: name=STRING;
+            B: ref=[A];
+            terminal ID: /[_a-zA-Z][\w_]*/;
+            terminal STRING: /"(\\.|[^"\\])*"|'(\\.|[^'\\])*'/;
+        `;
+        const output = await parse(input);
+
+        // act
+        const reachableRules = [...getAllReachableRules(output.parseResult.value, true)].map(r => r.name);
+
+        // assert
+        expect(reachableRules).toContain('ID');
+    });
+
+    test('ID not implicit called should not be returned by getAllReachableRules', async () => {
+        // no implicit ID rule call in cross ref
+        const input = `
+            grammar HelloWorld
+
+            entry Model: A|B;
+            A: name=STRING;
+            B: ref=[A:STRING];
+            terminal ID: /[_a-zA-Z][\w_]*/;
+            terminal STRING: /"(\\.|[^"\\])*"|'(\\.|[^'\\])*'/;
+        `;
+        const output = await parse(input);
+
+        // act
+        const reachableRules = [...getAllReachableRules(output.parseResult.value, true)].map(r => r.name);
+
+        // assert
+        expect(reachableRules).not.toContain('ID');
+    });
+
 });