chore: detect circular aliases

stoplightio · Jun 28, 2021 · 7b7ddf0 · 7b7ddf0
1 parent fd4bb00
commit 7b7ddf0
Show file tree

Hide file tree

Showing 2 changed files with 36 additions and 1 deletion.
diff --git a/packages/core/src/ruleset/__tests__/ruleset.test.ts b/packages/core/src/ruleset/__tests__/ruleset.test.ts
@@ -1011,6 +1011,32 @@ describe('Ruleset', () => {
       ).toThrowError(ReferenceError('Alias "PathItem-" does not exist'));
     });
 
+    it('given circular alias, should throw', () => {
+      expect(
+        print.bind(
+          null,
+          new Ruleset({
+            aliases: {
+              Root: '#Info',
+              Info: '#Root.test',
+              Contact: '#Info',
+              Test: '#Contact.test',
+            },
+            rules: {
+              'valid-path': {
+                given: '#Test',
+                then: {
+                  function: truthy,
+                },
+              },
+            },
+          }),
+        ),
+      ).toThrowError(
+        ReferenceError('Alias "Test" is circular. Resolution stack: Test -> Contact -> Info -> Root -> Info'),
+      );
+    });
+
     it('should refuse to resolve externally defined aliases', () => {
       expect(
         print.bind(

diff --git a/packages/core/src/ruleset/rule/rule.ts b/packages/core/src/ruleset/rule/rule.ts
@@ -90,13 +90,22 @@ export class Rule implements IRule {
   #resolveAlias(this: Rule, expr: string): string {
     let resolvedExpr = expr;
 
+    const stack = new Set<string>();
+
     while (resolvedExpr.startsWith('#')) {
       const alias = ALIAS.exec(resolvedExpr)?.[1];
 
       if (alias === void 0 || alias === null) {
-        throw new ReferenceError(`"${this.name}" references an invalid alias`);
+        throw new ReferenceError(`"${this.name}" rule references an invalid alias`);
+      }
+
+      if (stack.has(alias)) {
+        const _stack = [...stack, alias];
+        throw new ReferenceError(`Alias "${_stack[0]}" is circular. Resolution stack: ${_stack.join(' -> ')}`);
       }
 
+      stack.add(alias);
+
       if (this.owner.aliases === null || !(alias in this.owner.aliases)) {
         throw new ReferenceError(`Alias "${alias}" does not exist`);
       }