GraphQL schema/codegen fails: “Schema must contain uniquely named types … multiple types named Bool”

[usama-liaqat]

Describe the bug

I’m using GraphQL Code Generator against a GraphQL endpoint backed by MongooseIM (URL below). Codegen fails while loading the schema with:

Schema must contain uniquely named types but contains multiple types named "Bool".

This prevents generating TS types.

Steps to reproduce

1. Configure GraphQL Code Generator to load schema from the endpoint(s) below.
2. Run graphql-codegen.

Example config:

schema:
  - <uri>
generates:
  ./src/__graphql__/generated/min-types.ts:
    plugins:
      - typescript

Generate to ./src/__graphql__/generated/min-types.ts
✖ Failed to load schema from https://stage-api.nsuna.com/query,https://stage-mim.nsuna.com/api/graphql:
  Schema must contain uniquely named types but contains multiple types named "Bool".
  Error: Schema must contain uniquely named types but contains multiple types named "Bool".
  at new GraphQLSchema (.../node_modules/graphql/type/schema.js:219:15)
  at Object.mapSchema (.../node_modules/@graphql-tools/utils/cjs/mapSchema.js:15:12)
  at createWrappingSchema (.../node_modules/@graphql-tools/wrap/dist/index.cjs:87:16)
  at wrapSchema2 (.../node_modules/@graphql-tools/wrap/dist/index.cjs:82:18)
  at memoized (.../node_modules/@graphql-tools/utils/cjs/memoize.js:15:30)
  at UrlLoader.load (.../node_modules/@graphql-tools/url-loader/cjs/index.js:219:51)

[tomaszwojcikowski]

Thanks for the report! I checked the schema as generated by MongooseIM locally (in-memory endpoint built from priv/graphql/schemas/* via mongoose_graphql:init/0) using an introspection query { __schema { types { name } } } and the result contains Bool only once.

Given your codegen config loads two schemas (https://stage-api.nsuna.com/query and https://stage-mim.nsuna.com/api/graphql) in a single run, the error Schema must contain uniquely named types ... multiple types named "Bool" is consistent with the merged schema containing Bool twice (i.e. both endpoints expose a Bool scalar/type).

Could you try reproducing with only the MongooseIM endpoint (remove the other URL) and confirm whether codegen succeeds? If it only fails when both URLs are provided, this is likely a schema-merge/stitching issue on the client side (graphql-tools/url-loader) rather than MongooseIM returning a self-conflicting schema.

If you can share the introspection JSON from the MongooseIM endpoint alone (or a minimal SDL excerpt that defines Bool twice), we can dig further.

[usama-liaqat]

here is my codegenfile codegen.ts

import type { CodegenConfig } from "@graphql-codegen/cli";

const config: CodegenConfig = {
    schema: process.env.MIM_GQL_URL,
    documents: ["src/__graphql__/mim/documents/**/*.{ts,tsx,graphql,gql}"],
    generates: {
        "./src/__graphql__/generated/types.ts": {
            plugins: [
                "typescript",
            ],
            config: {
                typesPrefix: "I",
                enumPrefix: false
            }
        }
    },
    hooks: { afterAllFileWrite: ["prettier --write"] },
    ignoreNoDocuments: true
};
export default config;

i am still getting this error

✔ Parse Configuration
⚠ Generate outputs
  ❯ Generate to ./src/__graphql__/generated/types.ts
    ✖ Failed to load schema from https://stage-mim.nsuna.com/api/graphql:
      Schema must contain uniquely named types but contains multiple types named "Bool".
      Error: Schema must contain uniquely named types but contains multiple types named "Bool".
      at new GraphQLSchema (/Volumes/Storage/Projects/ProjectX/projectx-nsuna-mobile-app/node_modules/graphql/type/schema.js:219:15)
      at Object.mapSchema (/Volumes/Storage/Projects/ProjectX/projectx-nsuna-mobile-app/node_modules/@graphql-tools/utils/cjs/mapSchema.js:15:12)
      at createWrappingSchema (/Volumes/Storage/Projects/ProjectX/projectx-nsuna-mobile-app/node_modules/@graphql-tools/wrap/dist/index.cjs:87:16)
      at wrapSchema2 (/Volumes/Storage/Projects/ProjectX/projectx-nsuna-mobile-app/node_modules/@graphql-tools/wrap/dist/index.cjs:82:18)
      at memoized (/Volumes/Storage/Projects/ProjectX/projectx-nsuna-mobile-app/node_modules/@graphql-tools/utils/cjs/memoize.js:15:30)
      at UrlLoader.load (/Volumes/Storage/Projects/ProjectX/projectx-nsuna-mobile-app/node_modules/@graphql-tools/url-loader/cjs/index.js:219:51)
      at process.processTicksAndRejections (node:internal/process/task_queues:105:5)
      at async /Volumes/Storage/Projects/ProjectX/projectx-nsuna-mobile-app/node_modules/@graphql-tools/load/cjs/load-typedefs/load-file.js:15:39
      at async Promise.all (index 5)
      at async loadFile (/Volumes/Storage/Projects/ProjectX/projectx-nsuna-mobile-app/node_modules/@graphql-tools/load/cjs/load-typedefs/load-file.js:13:9)
      at async /Volumes/Storage/Projects/ProjectX/projectx-nsuna-mobile-app/node_modules/@graphql-tools/load/cjs/load-typedefs/collect-sources.js:200:25

      GraphQL Code Generator supports:

      - ES Modules and CommonJS exports (export as default or named export "schema")
      - Introspection JSON File
      - URL of GraphQL endpoint
      - Multiple files with type definitions (glob expression)
      - String in config file

      Try to use one of above options and run codegen again.

    ◼ Load GraphQL documents
    ◼ Generate

[tomaszwojcikowski]

I manage to reproduce your issue. The problem is as follows:

• MongooseIM's schema includes both a custom Bool scalar AND the standard Boolean scalar
• When @graphql-tools/wrap (used by the URL loader) processes the schema, it creates a duplicate "Bool" type during the wrapping transformation

The workaround I can suggest is to use introspection JSON file directly (instead of URL).

[usama-liaqat]

Yeah, it’s working well with the introspection file. I think we should also fix the type-conflict issues so the codegen works directly with the server.