GraphQL Schema拼接后cmsMetaData返回null问题求助

已将两个远程GraphQL Schema拼接并部署在本地服务器，查询主Product类型下的cmsMetaData字段始终返回null。使用@graphql-tools/stitch完成Schema拼接，扩展Product类型添加cmsMetaData字段关联Strapi_Product，配置了解析器通过delegateToSchema从第二个Schema获取数据，但结果仍为null。以下是相关代码、查询语句及类型定义：

相关代码 #

主API路由文件 #

import { ApolloServer } from 'apollo-server-micro';
import { ApolloServerPluginInlineTraceDisabled, ApolloServerPluginLandingPageLocalDefault } from "apollo-server-core";
import { stitchSchemas } from '@graphql-tools/stitch';
import { delegateToSchema } from '@graphql-tools/delegate';
import { RenameTypes, RenameRootFields } from '@graphql-tools/wrap';

import createRemoteSchema from '../../utils/createRemoteExecutor';

// Configuration for Next.js API Routes
export const config = {
    api: {
        bodyParser: false,
    },
};

// Export as a Next.js API Route
export default async (req, res) => {
    
    // Setup subschema configurations
    const productsSubschema = await createRemoteSchema({
        url: 'https://schema1.com/graphql/'
    });
    
    const cmsSubschema = await createRemoteSchema({
        url: 'https://schema2.com/graphql/',
        transforms: [
            new RenameRootFields(
                (operationName, fieldName, fieldConfig) => `strapi_${fieldName}`,
            ),
            new RenameTypes((name) => `Strapi_${name}`),
        ],
    });
    
    // Build the combined schema and set up the extended schema and resolver
    const schema = stitchSchemas({
        subschemas: [productsSubschema, cmsSubschema],
        typeDefs: `
        extend type Product {
            cmsMetaData: Strapi_Product
        }
        `,
        resolvers: {
            Product: {
                cmsMetaData: {
                    selectionSet: `{ id }`,
                    resolve(product, args, context, info) {
                        
                        // Get the data for the extended type from the subschema for Strapi
                        return delegateToSchema({
                            schema: cmsSubschema,
                            operation: 'query',
                            fieldName: 'strapi_product',
                            args: { where: { SaleorID: product.id } },
                            context,
                            info,
                        });
                    },
                },
            },
        },
    });

    // Set up the GraphQL server
    const apolloServer = new ApolloServer({
        schema,
        plugins: [
            ApolloServerPluginInlineTraceDisabled(),
            ApolloServerPluginLandingPageLocalDefault({ embed: true }),
        ],
    });
    await apolloServer.start();
    const apolloServerHandler = apolloServer.createHandler({
        path: '/api/graphql',
    });

    // Return the GraphQL endpoint
    return apolloServerHandler(req, res);
};

utils/createRemoteExecutor.js #

import { introspectSchema, wrapSchema } from '@graphql-tools/wrap';
import { print } from 'graphql';

// Builds a remote schema executor function,
// customize any way that you need (auth, headers, etc).
// Expects to recieve an object with "document" and "variable" params,
// and asynchronously returns a JSON response from the remote.
export default async function createRemoteSchema({ url, ...filters }) {
    const executor = async ({ document, variables }) => {
        const query = print(document);
        const fetchResult = await fetch(url, {
            method: 'POST',
            headers: {
                // We can also do Authentication here
                'Content-Type': 'application/json',
            },
            body: JSON.stringify({ query, variables }),
        });
        return fetchResult.json();
    };

    return wrapSchema({
        schema: await introspectSchema(executor),
        executor,
        ...filters,
    });
}

查询语句 #

products(first: 100, channel: "default-channel")
{
    edges
    {
        node
        {
            id
            name        
            cmsMetaData
            {
                Title
                SaleorID
            }
        }
    }
}

生成的类型定义 #

export type Product = Node & ObjectWithMetadata & {
    __typename?: 'Product';
    ... 
    cmsMetaData?: Maybe<Array<Maybe<Strapi_Product>>>;
    ...
}

export type Strapi_Product = {
    __typename?: 'Strapi_Product';
    SaleorID?: Maybe<Scalars['String']>;
    Title?: Maybe<Scalars['String']>;
    createdAt?: Maybe<Scalars['Strapi_DateTime']>;
    publishedAt?: Maybe<Scalars['Strapi_DateTime']>;
    updatedAt?: Maybe<Scalars['Strapi_DateTime']>;
};

查询结果 #

{
  "data": {
    "products": {
      "edges": [
        {
          "node": {
            "id": "UHJvZHVjdDoxMjc=",
            "name": "52-00 Base Plate",
            "cmsMetaData": null
          }
        },
        {
          "node": {
            "id": "UHJvZHVjdDoxMjg=",
            "name": "52-01HD Weigh Module",
            "cmsMetaData": null
          }
        }
      ]
    }
  }
}

排查方向 #

• 字段类型不匹配：类型定义中cmsMetaData是数组类型Maybe<Array<Maybe<Strapi_Product>>>，但扩展类型时定义为单个Strapi_Product，类型不匹配会导致数据无法映射返回null。需统一类型：要么修改扩展类型为[Strapi_Product]，要么调整解析器处理数组结果。
• 关联字段格式不一致：主Schema的product.id是Base64编码值（如UHJvZHVjdDoxMjc=解码后为Product:127），需确认Strapi侧SaleorID存储的是原始ID还是编码后的值，若格式不同需在解析器中解码product.id后再传入参数。
• 远程查询字段错误：手动请求Strapi的GraphQL端点，验证strapi_product字段是否存在，以及where: { SaleorID: xxx }是否能返回有效数据。
• 解析器参数传递问题：在解析器中添加日志打印product.id和传入的args，确认参数是否正确传递到远程查询；同时检查delegateToSchema的schema是否指向正确的cmsSubschema。
• 远程权限缺失：若Strapi需要认证才能查询，需在createRemoteSchema的fetch请求headers中添加认证字段（如Authorization: Bearer xxx）。
• 错误捕获缺失：在解析器中添加try-catch块，捕获delegateToSchema可能抛出的错误，排查是否存在网络错误、字段不存在等问题。

内容的提问来源于stack exchange，提问作者Laurence Cope