I had the same problem and found that even though the DATABASE_URL is being loaded correctly as a string, the PrismaPg adapter fails to properly extract the password when the url option is used. I fixed this by using connectionString instead of url when configuring the adapter.

import { Injectable } from '@nestjs/common';
import { ConfigService } from '@nestjs/config';
import { PrismaPg } from '@prisma/adapter-pg';
import { PrismaClient } from 'generated/prisma/client';
import { Pool } from 'pg';

@Injectable()
export class PrismaService extends PrismaClient {
  constructor(configService: ConfigService) {
    const databaseUrl = configService.get<string>('DATABASE_URL');

    const pool = new Pool({
      connectionString: databaseUrl,
    });

    const adapter = new PrismaPg(pool);
    super({ adapter, log: ['info', 'warn', 'error'] });
  }
}