generator-helper: schema attribute is not exposed to generators when using multiSchema

[duniul]

This was also reported in the feature feedback thread, but I thought it could be worth tracking separately.

Bug description

@prisma/generator-helper does not expose any information about a model's schema, preventing generators like https://github.com/notiz-dev/prisma-dbml-generator or https://github.com/valtyr/prisma-kysely to generate proper table names without workarounds.

It's missing from both the type (DMMF.Model) and the model objects provided to generatorHandler's onGenerate function (options.dmmf.datamodel.models).

How to reproduce

1. Create a simple generator with @prisma/generator-helper and log the output.

   import { GeneratorOptions, generatorHandler } from "@prisma/generator-helper";
   
   generatorHandler({
     onGenerate: async (options: GeneratorOptions) => {
       console.log(options.dmmf.datamodel.models);
     },
   });

2. Add a prisma/schema.prisma file with multiSchema enabled that uses the generator.
3. Run prisma generate and look at the log - models do not include any schema info.

Expected behavior

That a model's schema is included on the DMMF.Model object, e.g. like:

interface Model {
    name: string;
    dbName: string | null;
    schema: string | null; // <-- e.g. like this
    fields: Field[];
    uniqueFields: string[][];
    uniqueIndexes: uniqueIndex[];
    documentation?: string;
    primaryKey: PrimaryKey | null;
    [key: string]: any;
}

Prisma information

Example Prisma schema:

generator client {
    provider        = "prisma-client-js"
    previewFeatures = ["multiSchema"]
}

datasource db {
    provider = "postgresql"
    schemas  = ["mammals", "birds"]
    url      = env("DATABASE_URL")
}

model Dog {
    id   Int    @id
    name String

    @@schema("mammals")
}

model Parrot {
    id   Int    @id
    name String

    @@schema("birds")
}

Environment & setup

• OS: macOS
• Database: PostgreSQL
• Node.js version: v18.15.0

Prisma Version

prisma                  : 4.16.1
@prisma/client          : Not found
Current platform        : darwin-arm64
Query Engine (Node-API) : libquery-engine b20ead4d3ab9e78ac112966e242ded703f4a052c (at node_modules/@prisma/engines/libquery_engine-darwin-arm64.dylib.node)
Migration Engine        : migration-engine-cli b20ead4d3ab9e78ac112966e242ded703f4a052c (at node_modules/@prisma/engines/migration-engine-darwin-arm64)
Format Wasm             : @prisma/prisma-fmt-wasm 4.16.0-66.b20ead4d3ab9e78ac112966e242ded703f4a052c
Default Engines Hash    : b20ead4d3ab9e78ac112966e242ded703f4a052c
Studio                  : 0.484.0
Preview Features        : multiSchema