Fix false positive multiplicity validation (#1559)

Author: msujew

package-lock.json

@@ -15,7 +15,7 @@
         "langium:watch": "langium generate --watch"
     },
     "dependencies": {
-        "langium": "~3.1.0"
+        "langium": "~3.1.1"
     },
     "devDependencies": {
         "@types/node": "^18.0.0",

packages/generator-langium/templates/core/.package.json

@@ -1,7 +1,7 @@
 {
   "name": "langium-vscode",
   "publisher": "langium",
-  "version": "3.1.0",
+  "version": "3.1.1",
   "displayName": "Langium",
   "description": "Support for the Langium Grammar Language",
   "homepage": "https://langium.org",
@@ -95,7 +95,7 @@
     "lint": "eslint src --ext ts"
   },
   "dependencies": {
-    "langium": "3.1.0",
+    "langium": "3.1.1",
     "langium-railroad": "3.1.0",
     "vscode-languageserver": "~9.0.1",
     "ignore": "~5.2.4"

packages/langium-vscode/package.json

@@ -1,6 +1,6 @@
 {
   "name": "langium",
-  "version": "3.1.0",
+  "version": "3.1.1",
   "description": "A language engineering tool for the Language Server Protocol",
   "homepage": "https://langium.org",
   "engines": {

packages/langium/package.json

@@ -23,7 +23,6 @@ import * as ast from '../../languages/generated/ast.js';
 import { getTypeNameWithoutError, hasDataTypeReturn, isPrimitiveGrammarType, isStringGrammarType, resolveImport, resolveTransitiveImports } from '../internal-grammar-util.js';
 import { typeDefinitionToPropertyType } from '../type-system/type-collector/declared-types.js';
 import { flattenPlainType, isPlainReferenceType } from '../type-system/type-collector/plain-types.js';
-import { AstUtils } from '../../index.js';
 
 export function registerValidationChecks(services: LangiumGrammarServices): void {
     const registry = services.validation.ValidationRegistry;
@@ -731,20 +730,26 @@ export class LangiumGrammarValidator {
             }
             return result;
         };
-        // Locate called rule, ensure it is not a fragment.
-        const refersToFragment = call.rule.ref !== undefined && call.rule.ref.fragment;
-        // Data type rules do not cause problems, too.
-        const callInDataTypeRule = (AstUtils.getContainerOfType(call, ast.isParserRule))?.dataType !== undefined;
-        if (refersToFragment || callInDataTypeRule) {
+        const ref = call.rule.ref;
+        // Parsing an unassigned terminal rule is fine.
+        if (!ref || ast.isTerminalRule(ref)) {
+            return;
+        }
+        // Fragment or data type rules are fine too.
+        if (ref.fragment || isDataTypeRule(ref)) {
+            return;
+        }
+        // Multiple unassigned calls if inside a data type rule is fine too.
+        const parentRule = getContainerOfType(call, ast.isParserRule);
+        if (!parentRule || isDataTypeRule(parentRule)) {
             return;
         }
 
         const appearsMultipleTimes = findContainerWithCardinality(call) !== undefined;
-        const hasAssignment = AstUtils.getContainerOfType(call, ast.isAssignment) !== undefined;
+        const hasAssignment = getContainerOfType(call, ast.isAssignment) !== undefined;
         if (appearsMultipleTimes && !hasAssignment) {
-            accept('error', `Rule call ${call.rule.$refText} requires assignment when used with multiplicity.`, {
-                node: call,
-                property: 'cardinality'
+            accept('error', `Rule call '${ref.name}' requires assignment when parsed multiple times.`, {
+                node: call
             });
         }
     }

packages/langium/src/grammar/validation/validator.ts

@@ -156,7 +156,6 @@ describe('Langium grammar validation', () => {
             Plus+;
         List3:
             Exp+;
-        // addresses https://github.com/eclipse-langium/langium/pull/1437#pullrequestreview-1994232830
         List4:
             elems += (Minus | Div);
         
@@ -171,13 +170,36 @@ describe('Langium grammar validation', () => {
 
         const validationResult = await validate(grammar);
         expect(validationResult.diagnostics).to.have.length(2);
-        expectError(validationResult, 'Rule call Mult requires assignment when used with multiplicity.', {
-            property: 'cardinality'
+        expectError(validationResult, "Rule call 'Mult' requires assignment when parsed multiple times.", {
+            property: undefined
         });
-        expectError(validationResult, 'Rule call Plus requires assignment when used with multiplicity.', {
-            property: 'cardinality'
+        expectError(validationResult, "Rule call 'Plus' requires assignment when parsed multiple times.", {
+            property: undefined
         });
     });
+
+    test('Rule calls with multiplicity - negative', async () => {
+        const grammar = `
+        grammar Test
+
+        entry Main:
+            // Fragment rule
+            Body*
+            // Data type rule
+            FQN*
+            // Terminal rule
+            ID*;
+        fragment Body:
+            value+='test';
+        FQN returns string:
+            ID ('.' ID)*;
+        
+        terminal ID: /[_a-zA-Z][\\w_]*/;
+        `.trim();
+
+        const validationResult = await validate(grammar);
+        expectNoIssues(validationResult);
+    });
 });
 
 describe('Data type rule return type', () => {