`ALTER TYPE` enum migrations fail in PostgreSQL

Bug description

Using migrations from version 2.14, I updated an enum to add a few more values.

That generated the following migration.

-- AlterEnum
ALTER TYPE "account_type_enum" ADD VALUE 'Giving';
ALTER TYPE "account_type_enum" ADD VALUE 'Parent';
ALTER TYPE "account_type_enum" ADD VALUE 'Saving';
ALTER TYPE "account_type_enum" ADD VALUE 'Spending';

-- AlterTable
ALTER TABLE "account" ALTER COLUMN "type" SET DEFAULT E'Spending';

Unfortunately, when running this, I get the following error from Postgres.

Database error: Error querying the database: db error: ERROR: ALTER TYPE ... ADD cannot run inside a transaction block
   0: sql_migration_connector::flavour::postgres::sql_schema_from_migration_history
             at migration-engine/connectors/sql-migration-connector/src/flavour/postgres.rs:174
   1: sql_migration_connector::sql_database_migration_inferrer::validate_migrations
             at migration-engine/connectors/sql-migration-connector/src/sql_database_migration_inferrer.rs:89
   2: migration_core::api::DiagnoseMigrationHistory
             at migration-engine/core/src/api.rs:109

I can confirm that reducing the migration to a single ALTER TYPE solves the issue.

How to reproduce

1. Use Postgres
2. Create an enum
3. Add multiple new values
4. Generate a migration
5. Run the migration

Expected behavior

New enum values should be added.

Environment & setup

• OS: Mac OS
• Database: PostgreSQL 11
• Node.js version: 4.15
• Prisma version:

@prisma/cli          : 2.14.0
@prisma/client       : 2.14.0
Current platform     : darwin
Query Engine         : query-engine 5d491261d382a2a5ffdc71de17072b0e409f1cc1 (at node_modules/@prisma/engines/query-engine-darwin)
Migration Engine     : migration-engine-cli 5d491261d382a2a5ffdc71de17072b0e409f1cc1 (at node_modules/@prisma/engines/migration-engine-darwin)
Introspection Engine : introspection-core 5d491261d382a2a5ffdc71de17072b0e409f1cc1 (at node_modules/@prisma/engines/introspection-engine-darwin)
Format Binary        : prisma-fmt 5d491261d382a2a5ffdc71de17072b0e409f1cc1 (at node_modules/@prisma/engines/prisma-fmt-darwin)
Studio               : 0.332.0

[pimeys]

It seems that this restriction is not valid anymore for PostgreSQL versions higher than 11. On versions 12 and 13 I can successfully execute this migration.

[albertoperdomo]

Created https://github.com/prisma/prisma/issues/5543 for us to add a comment with a warning, suggesting users of PostgreSQL 11 and earlier versions to only add one ENUM value at a time in each migration.