Bug Report: Cyclic Dependency with Self-Referential Relations in Delegate Models

[2234839]

Bug Report: Cyclic Dependency with Self-Referential Relations in Delegate Models

Description and expected behavior

Bug: When using @@delegate inheritance with self-referential relations, Zenstack throws a Cyclic dependency error during the topological sort phase. This prevents models that extend a base class with @@delegate from having self-referencing relationships.

Expected Behavior: Models using @@delegate inheritance should support self-referential relations (e.g., parent-child, reply chains) just like regular models do. The schema should compile successfully without circular dependency errors.

Self-referential relations are a common and essential pattern in database modeling for:

• Comment/reply threads
• Organizational hierarchies
• Category trees
• Social media features (posts with replies)

Environment (please complete the following information)

• ZenStack version: 3.4.2
• Database type: SQLite (sql.js v1.14.0)
• Node.js version: v24.3.0
• Package manager: pnpm

Steps to Reproduce

Repository: https://github.com/2234839/zplayground/tree/bug/delegate-self-relation-circular-dependency

A minimal reproduction case is available in the above repository. The schema in zenstack/schema.zmodel demonstrates the issue.

1. Create a schema with @@delegate and self-referential relation

datasource db {
    provider = 'sqlite'
    url = 'file:./dev.db'
}

enum ContentType {
    POST
    ARTICLE
    QUESTION
}

model Content {
    id   Int         @id @default(autoincrement())
    type ContentType
    @@delegate(type)
}

model Post extends Content {
    post1s   Post1[]
    replies  Post[]  @relation("PostReplies")
    parentId Int?
    parent   Post?   @relation("PostReplies", fields: [parentId], references: [id])
}

model Post1 extends Content {
    post   Post @relation(fields: [postId], references: [id])
    postId Int
}

2. Run generation

npx zenstack generate
# or
pnpm dev

Actual Behavior

The application crashes with the following error:

Error: Cyclic dependency, node was:{"name":"Post","baseModel":"Content","fields":{...}}
    at visit (/node_modules/.pnpm/toposort@2.0.2/node_modules/toposort/index.js:45:13)

The error occurs during the topological sort phase when Zenstack tries to resolve model dependencies.

Additional context

Self-Referential Relations Work Without @@delegate

Regular models without @@delegate support self-referential relations without issues. This is tested and working:

// This works fine - from Zenstack's own test suite
model User {
    id        Int     @id @default(autoincrement())
    teacherId Int?
    teacher   User?   @relation("TeacherStudents", fields: [teacherId], references: [id])
    students  User[]  @relation("TeacherStudents")
}

Reference: tests/integration/tests/enhancements/with-policy/self-relation.test.ts

Root Cause Analysis

The issue appears to be in how Zenstack builds the dependency graph for topological sorting. When a model uses @@delegate inheritance AND has a self-referential relation, the dependency resolver treats the self-reference as a cross-model dependency, creating a cycle:

Post → (extends) → Content
Post → (relation) → Post (self-reference detected as cycle)

The topological sort algorithm detects this as a cycle and fails, even though self-referential relations are valid and should be handled specially (similar to how they work for regular models).

[ymc9]

Hi @2234839 , thanks for filing this. Just wanted to let you know that the toposort issue is exposed when you call db.$pushSchema. This api is for test purposes only and should not be used in production. I'll make a fix for the crash.

[2234839]

Well, I understand, I won't use this for production, mainly I want to report another problem to you, but I want to write a demo to demonstrate this problem, so I refer to the method used in the official example.

[ymc9]

Fixed in 3.4.4