prisma/prisma

Prisma schema (PSL)

The user-facing schema file (schema.prisma) is written in PSL (Prisma Schema Language). It's a small declarative DSL with three top-level block types: datasource, generator, and model. PSL is parsed, validated, and formatted by @prisma/prisma-schema-wasm (compiled from Rust).

Block types

datasource db {
  provider = "postgresql"
}

generator client {
  provider = "prisma-client"
  output   = "../generated"
}

model Post {
  id        Int     @id @default(autoincrement())
  title     String
  content   String?
  published Boolean @default(false)
  author    User?   @relation(fields: [authorId], references: [id])
  authorId  Int?
}

model User {
  id    Int     @id @default(autoincrement())
  email String  @unique
  name  String?
  posts Post[]
}

In Prisma 7, datasource URLs no longer live in the schema. Connection details come from prisma.config.ts instead. The datasource block stays, but it only declares the provider.

Models, fields, attributes

Models declare:

Scalar fields with builtin types (Int, String, Boolean, DateTime, Decimal, Bytes, Json, …)
Relation fields (User?, Post[])
Enum fields
Composite type fields (Mongo only)

Attributes (@id, @unique, @default, @relation, @@index, @@map) modify field or model behavior. The full reference is in Prisma docs, not in this wiki — this page focuses on what's relevant for working on Prisma itself.

Multi-file schemas

@prisma/schema-files-loader handles split schemas — multiple .prisma files combined into one logical schema. This is the recommended pattern for large projects. The loader assembles the files, deduplicates, and hands a single textual representation to the parser.

Parsing pipeline

graph LR
    Files[schema.prisma + extras] --> Loader[schema-files-loader]
    Loader --> Text[Combined schema text]
    Text --> Wasm[prisma-schema-wasm parser]
    Wasm --> AST[Internal AST]
    AST --> Validate[Validation]
    Validate --> DMMF[DMMF JSON]
    Validate --> Errors[Diagnostics]

Errors come back from Wasm as structured objects; rendering happens in @prisma/internals.

Formatting

prisma format calls into the same Wasm artifact:

graph LR
    File[schema.prisma] --> Read
    Read --> Wasm[prisma-schema-wasm formatter]
    Wasm --> Formatted[Formatted text]
    Formatted --> Write[overwrite file]

Implementation: packages/cli/src/Format.ts. It's a pure text-in/text-out call.

Validation

prisma validate is similarly thin:

graph LR
    File[schema.prisma] --> Wasm[prisma-schema-wasm validator]
    Wasm -->|ok| Exit0[exit 0]
    Wasm -->|errors| Render[render diagnostics]
    Render --> Exit1[exit 1]

Implementation: packages/cli/src/Validate.ts.

Forced panics for testing

FORCE_PANIC_PRISMA_SCHEMA=1 npx prisma format
FORCE_PANIC_GET_DMMF=1 npx prisma validate
FORCE_PANIC_GET_CONFIG=1 npx prisma validate

These trigger panics in the Wasm parser to verify error-rendering paths in @prisma/internals.