fix(client): $transaction type fallback (#5794)

src/packages/client/src/__tests__/integration/happy/exhaustive-schema/__snapshots__/test.ts.snap

@@ -300,8 +300,9 @@ exports[`exhaustive-schema: generatedTypeScript 1`] = `
 import * as runtime from '@prisma/client/runtime';
 declare const prisma: unique symbol
 export type PrismaPromise<A> = Promise<A> & {[prisma]: true}
+type UnwrapPromise<P extends any> = P extends Promise<infer R> ? R : P
 type UnwrapTuple<Tuple extends readonly unknown[]> = {
-  [K in keyof Tuple]: K extends \`\${number}\` ? Tuple[K] extends PrismaPromise<infer X> ? X : never : never
+  [K in keyof Tuple]: K extends \`\${number}\` ? Tuple[K] extends PrismaPromise<infer X> ? X : UnwrapPromise<Tuple[K]> : UnwrapPromise<Tuple[K]>
 };
 
 

src/packages/client/src/__tests__/types/$transaction/test.ts

@@ -1,4 +1,4 @@
-import { PrismaClient } from '@prisma/client'
+import { PrismaClient, User } from '@prisma/client'
 
 // tslint:disable
 
@@ -21,6 +21,12 @@ async function main() {
     prisma.$queryRaw`SELECT 1`,
     prisma.$executeRaw(''),
   ])
+  // Test Type Fallback
+  const txs = [
+    prisma.user.findMany(),
+    prisma.user.findFirst()
+  ]
+  const res: (User | User[] | null)[] = await prisma.$transaction(txs)
 }
 
 main().catch((e) => {

src/packages/client/src/generation/TSClient/common.ts

@@ -102,8 +102,9 @@ export const commonCodeTS = ({
   tsWithoutNamespace: () => `import * as runtime from '${runtimePath}';
 declare const prisma: unique symbol
 export type PrismaPromise<A> = Promise<A> & {[prisma]: true}
+type UnwrapPromise<P extends any> = P extends Promise<infer R> ? R : P
 type UnwrapTuple<Tuple extends readonly unknown[]> = {
-  [K in keyof Tuple]: K extends \`\$\{number\}\` ? Tuple[K] extends PrismaPromise<infer X> ? X : never : never
+  [K in keyof Tuple]: K extends \`\$\{number\}\` ? Tuple[K] extends PrismaPromise<infer X> ? X : UnwrapPromise<Tuple[K]> : UnwrapPromise<Tuple[K]>
 };
 `,
   ts: (hideFetcher?: boolean) => `export import DMMF = runtime.DMMF