How to merge openapi schemas under different namespaces?

[g-borgulya]

I'm putting together a GraphQL backend gateway for two HTTP REST APIs. The backend gateway does more than routing, like for example authorization related functions. For that reason I can't simply expose the HTTP REST APIs directly, I'm adding some custom logic between the externally-facing GraphQL API and the HTTP REST calls.

I found out that I can use the graphql-mesh openapi plugin together with graphql-codegenerator, to generate a merged schema from the two openapi specifications. My problem is that the two openapis have some naming conflicts. Which leads to my question: is it possible to use namespaces for each openapis?

This is what I'm trying to do in the codegen.yml:

schema:
  API1:
    loader: '@omnigraph/openapi'
    source: "./schemas/api1_openapi.json"
    ignoreErrorResponses: true
    # namespace: API1  # <--- I'm looking for something like this
  API2:
    loader: '@omnigraph/openapi'
    source: "./schemas/api2_openapi.json"
    ignoreErrorResponses: true
    # namespace: API2  # <--- I'm looking for something like this
generates:
  ./src/__generated__/resolvers-types.ts:
    plugins:
      - "typescript"
      - "typescript-resolvers"
    config:
      useIndexSignature: true
      contextType: "../resolver_context#ResolverContext"
  ./schemas/__generated__/merged.graphql:
    plugins:
      - schema-ast

Without the namespaces this is the error what I get when running codegen:

  ❯ Generate to ./src//__generated__/resolvers-types.ts
    ✖
      Failed to load schema from API1,API2:
      Unable to merge GraphQL type "Query": Field "list" already defined with a different type.  ...
      ...

Is there any existing solution / setting for this problem?

[ardatan]

You can use prefix transforms in a same Mesh configuration. Using omnigraph won't work as expected since it merges schemas barely.

[g-borgulya]

Thanks for the direction! I have a completely different, probably unrelated problem when I'm trying to use mesh, and couldn't find anything on that either.

If I start with this very simple .meshrc.yaml:

sources:
  - name: API
    handler:
      openapi:
        source: ./schemas/openapi.json

Then I get this error:

🐛 🕸️  Mesh - API Attaching execution directives to the schema
🐛 🕸️  Mesh - API Building the executable schema.
💥 🕸️  Mesh - API Failed to generate the schema TypeError [ERR_UNKNOWN_FILE_EXTENSION]: Unknown file extension ".ts" for /.../.mesh/sources/API/schemaWithAnnotations.ts
    at new NodeError (node:internal/errors:399:5)
    at Object.getFileProtocolModuleFormat [as file:] (node:internal/modules/esm/get_format:79:11)
    at defaultGetFormat (node:internal/modules/esm/get_format:121:38)
    at defaultLoad (node:internal/modules/esm/load:81:20)
    at nextLoad (node:internal/modules/esm/loader:163:28)
    at ESMLoader.load (node:internal/modules/esm/loader:605:26)
    at ESMLoader.moduleProvider (node:internal/modules/esm/loader:457:22)
    at new ModuleJob (node:internal/modules/esm/module_job:64:26)
    at ESMLoader.#createModuleJob (node:internal/modules/esm/loader:480:17)
    at ESMLoader.getModuleJob (node:internal/modules/esm/loader:434:34)

And I couldn't find any ways to resolve that. The problem only occurs when I'm trying to use the openapi handler. It works fine with the graphql handler with a local file as the source.

This is my latest tsconfig.json:

{
  "compilerOptions": {
    "allowJs": true,
    "allowSyntheticDefaultImports": true,
    "baseUrl": "src",
    "rootDirs": ["src", ".mesh"],
    "outDir": "./build",
    "declaration": true,
    "esModuleInterop": false,
    "lib": ["ES2022"],
    "module": "ES2022",
    "moduleResolution": "node",
    "noImplicitReturns": true,
    "removeComments": true,
    "skipLibCheck": true,
    "sourceMap": true,
    "strict": true,
    "target": "ES2022",
    "types": ["node"],
    "useDefineForClassFields": true
  },
  "include": ["src/**/*", ".mesh/**/*"],
  "exclude": ["node_modules", "**/*.spec.ts"],
  "ts-node": {
    "esm": true,
    "experimentalSpecifierResolution": "node"
  }
}

May I ask for clarification on this, so that I can try the transformation with Mesh?

[ardatan]

I see you are trying to use ESM which is currently experimental in Mesh. But you can find an example like below;
https://github.com/Urigo/graphql-mesh/tree/master/examples/hello-world-esm

If you don't really need ESM, we don't recommend an ESM configuration and use a simpler tsconfig file like in our basic examples.

If you still have issues, please create a reproduction on CodeSandbox. Thanks!

[g-borgulya]

I really appreciate your help. Changing the tsconfig.json didn't help either.

Here's the CodeSandbox with a very much simplified project but the same error:
https://codesandbox.io/p/sandbox/amazing-tu-kyobl9

I'm trying to run:

$ DEBUG=1 npx mesh build

And getting the same error:

🐛 🕸️  Mesh - API Building the executable schema.
💥 🕸️  Mesh - API Failed to generate the schema TypeError [ERR_UNKNOWN_FILE_EXTENSION]: Unknown file extension ".ts" for /project/home/gborgulya/workspace/.mesh/sources/API/schemaWithAnnotations.ts

[ardatan]

But you still have "type: module" in your package.json. As i said earlier, you should either remove it or use the command as in the example I send above.

[g-borgulya]

Thanks a ton for your help! Seems to work fine!

For the namespace question seemingly I can use the encapsulate transformation.