neo4j-graphql-skill

## When to Use

- Creating a GraphQL API from a Neo4j graph schema with `@neo4j/graphql`
- Writing type definitions with `@relationship`, `@cypher`, `@authorization` directives
- Using OGM for server-side programmatic Neo4j access (bypasses GraphQL auth)
- Configuring auto-generated queries, mutations, subscriptions
- Securing types/fields with JWT or JWKS-based `@authorization` rules
- Migrating from v5/v6 to v7 (breaking changes below)

## When NOT to Use

- **Raw Cypher queries outside GraphQL resolvers** → `neo4j-cypher-skill`
- **Spring Data Neo4j / Java entity mapping** → `neo4j-spring-data-skill`
- **Generic GraphQL without Neo4j** — outside scope

---

## Version Matrix

| Version | Status | Notes |
|---|---|---|
| v7 | Current | `@node` required; `options` removed; explicit `eq` syntax |
| v5 | LTS | Older syntax; `options: {limit, offset, sort}` still valid |

Default to v7 unless codebase is on v5.

---

## Step 1 — Install

```bash
npm install @neo4j/graphql neo4j-driver graphql @apollo/server
```

For subscriptions (CDC required):
```bash
npm install ws graphql-ws express body-parser cors
```

---

## Step 2 — Minimal Server Setup

```javascript
import { ApolloServer } from '@apollo/server';
import { startStandaloneServer } from '@apollo/server/standalone';
import { Neo4jGraphQL } from '@neo4j/graphql';
import neo4j from 'neo4j-driver';

const typeDefs = `#graphql
  type Movie @node {
    id: ID! @id
    title: String!
    actors: [Person!]! @relationship(type: "ACTED_IN", direction: IN)
  }

  type Person @node {
    id: ID! @id
    name: String!
    movies: [Movie!]! @relationship(type: "ACTED_IN", direction: OUT)
  }
`;

const driver = neo4j.driver(
  process.env.NEO4J_URI,
  neo4j.auth.basic(process.env.NEO4J_USERNAME, process.env.NEO4J_PASSWORD)
);

const neoSchema = new Neo4jGraphQL({ typeDefs, driver });

// assertIndexesAndConstraints syncs @id → UNIQUE constraints; wrap in try/catch
await neoSchema.assertIndexesAndConstraints({ options: { create: true } });

const server = new ApolloServer({ schema: await neoSchema.getSchema() });

const { url } = await startStandaloneServer(server, {
  context: async ({ req }) => ({ token: req.headers.authorization }),
  listen: { port: 4000 },
});
```

`assertIndexesAndConstraints` throws if constraints missing. Use `{ create: true }` to auto-create, or run `CREATE CONSTRAINT` manually and retry.

---

## Key Directives

### @node (v7 required)

Every GraphQL type representing a Neo4j node must have `@node`. Without it, v7 ignores the type.

```graphql
type Product @node {
  id: ID! @id
  name: String!
}

# Custom label (default = type name)
type Article @node(labels: ["Post", "Content"]) {
  title: String!
}
```

### @relationship — Full Syntax

```graphql
type Person @node {
  # direction: OUT = (this)-[:KNOWS]->(other)
  friends: [Person!]! @relationship(type: "KNOWS", direction: OUT)

  # direction: IN = (other)-[:ACTED_IN]->(this)
  actedIn: [Movie!]! @relationship(type: "ACTED_IN", direction: IN)

  # direction: UNDIRECTED = matches both directions (use sparingly — double-counts)
  colleagues: [Person!]! @relationship(type: "COLLEAGUE_OF", direction: UNDIRECTED)

  # Relationship with properties — reference an @relationshipProperties interface
  reviews: [Movie!]! @relationship(type: "REVIEWED", direction: OUT, properties: "ReviewedProps")
}

interface ReviewedProps @relationshipProperties {
  rating: Int!
  date: Date
}
```

Direction rule: `OUT` = arrow leaves this node. `IN` = arrow enters this node. Both sides of a relationship must declare opposite directions.

### Querying Relationship Properties — Connection API

For each relationship with `properties:`, a `{field}Connection` field is auto-generated. Access rel properties via `actorsConnection.edges.properties`, not via `actors`:

```graphql
query {
  movies(where: { title: { eq: "The Matrix" } }) {
    title
    actorsConnection {
      edges {
        properties { role }   # maps to @relationshipProperties interface
        node { name }
      }
    }
  }
}
```

### @cypher — Custom Resolver

```graphql
type Person @node {
  name: String!

  # columnName must exactly match the RETURN alias — mismatch returns null silently
  friendCount: Int
    @cypher(
      statement: "MATCH (this)-[:KNOWS]->(f:Person) RETURN count(f) AS friendCount"
      columnName: "friendCount"
    )

  recommendedMovies: [Movie!]!
    @cypher(
      statement: """
        MATCH (this)-[:WATCHED]->(m:Movie)<-[:WATCHED]-(o:Person)-[:WATCHED]->(rec:Movie)
        WHERE NOT (this)-[:WATCHED]->(rec)
        RETURN rec
      """
      columnName: "rec"
    )
}

# @cypher on Query field — custom top-level query
type Query {
  topRatedMovies(limit: Int = 10): [Movie!]!
    @cypher(
      statement: "MATCH (m:Movie) WHERE m.rating IS NOT NULL RETURN m ORDER BY m.rating DESC LIMIT $limit"
      columnName: "m"
    )
}
```

`this` refers to the current node in field-level @cypher. Parameters are passed as `$paramName`.

### @cypher — Field Arguments and extend type

```graphql
# extend type adds computed fields without modifying the base type definition
extend type Movie @node {
  avgRating: Float
    @cypher(statement: "MATCH (this)<-[r:RATED]-(:User) RETURN avg(r.rating) AS result", columnName: "result")

  # Field arguments passed as Cypher params; always provide default to avoid null
  recommended(limit: Int = 3): [Movie!]!
    @cypher(
      statement: "MATCH (this)<-[:RATED]-(u:User)-[:RATED]->(rec:Movie) WITH rec, COUNT(u) AS score ORDER BY score DESC RETURN rec LIMIT $limit"
      columnName: "rec"
    )
}
```

### @id and @timestamp

```graphql
type Post @node {
  id: ID! @id                          # auto-generates UUID; creates UNIQUE constraint
  createdAt: DateTime! @timestamp(operations: [CREATE])
  updatedAt: DateTime @timestamp(operations: [CREATE, UPDATE])
  title: String!
}
```

### @alias — Map GraphQL field to Neo4j property

```graphql
type User @node {
  id: ID! @id
  email: Stri