handle circular references

src/yamler/yamler.ts

@@ -56,8 +56,13 @@ export default class YamlER {
     if (!this.parentFile) {
       // expressions can return an expression or reference an attribute wiith an expression later in the
       // object that hasn't been evaluated yet so we parse expressions in a loop until there are no more
-      while (await this.parseAllExpressions())
-        ;
+      const maxIterations = 100 // prevent infinite loops
+      let iterations = 0
+
+      while (await this.parseAllExpressions()) {
+        if (++iterations >= maxIterations)
+          throw new Error(`Maximum expression parsing iterations (${maxIterations}) exceeded. Possible circular reference in expressions.`)
+      }
     }
 
     return this.attributes

tests/fixtures/circular_expressions.staxfile

@@ -0,0 +1,4 @@
+stax:
+  vars:
+    value1: ${{ get stax.vars.value2 }}
+    value2: ${{ get stax.vars.value1 }}

tests/unit/yamler.test.js

@@ -52,4 +52,11 @@ describe('YamlER', () => {
   it('handles expressions that return an expression', () => {
     expect(yaml.stax.vars.value5).toBe('some_service')
   })
+
+  it('throws an error when expressions have circular references', async () => {
+    const circularYaml = resolve(fixturesDir, 'circular_expressions.staxfile')
+    const promise = loadFile(circularYaml, expressionCallback)
+
+    await expect(promise).rejects.toThrow('Maximum expression parsing iterations (100) exceeded. Possible circular reference in expressions.')
+  })
 })