fix (generator): fix type issue on schemas containing relations (#727)

This PR fixes the problem where the generated client may contain type
errors for models containing relations.
This is a known problem with Zod and Prisma and is described here:
chrishoermann/zod-prisma-types#98. That issue
also proposes a solution with a dirty type cast:
chrishoermann/zod-prisma-types#98 (comment)
which is implemented in this PR.

This PR removes the need for pinning the version of Zod
(#700).

Author: kevin-dp

.changeset/weak-years-explode.md

@@ -0,0 +1,5 @@
+---
+"@electric-sql/prisma-generator": patch
+---
+
+Fix type issue in generated client for DB schemas containing relations.

generator/src/functions/contentWriters/writeOutputObjectType.ts

@@ -1,8 +1,19 @@
 import { writeSelect } from './writeSelect'
 import { writeNonScalarType, writeScalarType, writeSpecialType } from '..'
-import { ExtendedDMMFSchemaField } from '../../classes'
+import { ExtendedDMMF, ExtendedDMMFSchemaField } from '../../classes'
 import { type ContentWriterOptions } from '../../types'
 
+function modelHasRelation(
+  model: ExtendedDMMFSchemaField['modelType'],
+  dmmf: ExtendedDMMF
+): boolean {
+  if (typeof model === 'string') {
+    const maybeModel = dmmf.datamodel.models.find((m) => m.name === model)
+    return maybeModel?.hasRelationFields ?? false
+  }
+  return false
+}
+
 export const writeOutputObjectType = (
   { fileWriter, dmmf, getSingleFileContent = false }: ContentWriterOptions,
   field: ExtendedDMMFSchemaField
@@ -120,7 +131,14 @@ export const writeOutputObjectType = (
         writer.newLine()
       })
     })
-    .write(`).strict()`)
+    .write(`).strict() `)
+    // There is a typing bug that occurs only with models that have relations.
+    // a dirty fix here is to typecast the value to the expected type:
+    // cf. https://github.com/chrishoermann/zod-prisma-types/issues/98#issuecomment-1800112669
+    .conditionalWrite(
+      modelHasRelation(field.modelType, dmmf),
+      `as ${field.customArgType}`
+    )
 
   if (useMultipleFiles && !getSingleFileContent) {
     writer.blankLine().writeLine(`export default ${field.argName}Schema;`)

generator/src/functions/writeSingleFileArgTypeStatements.ts

@@ -15,7 +15,8 @@ export const writeSingleFileArgTypeStatements: WriteStatements = (
 
   fileWriter.writeHeading(`ARGS`, 'FAT')
 
-  dmmf.schema.outputObjectTypes.argTypes.forEach((outputType) => {
+  const types = dmmf.schema.outputObjectTypes
+  types.argTypes.forEach((outputType) => {
     outputType.prismaActionFields.forEach((field) => {
       writeOutputObjectType({ dmmf, fileWriter }, field)
     })