Overriding DATABASE_URL for migration example doesn't work

[garethlau]

Hey! I found this example from this page. I did as the docs suggested, adding an override to the DATABASE_URL environment variable in package.json. I couldn't get it to work so I tried this example repository and also found that it failed to run the migrations.

I cloned the data-proxy branch and added a .env file with two variables:

DATABASE_URL=prisma://<stuff>
MIGRATE_DATABASE_URL=postgresql://<stuff>

Then I ran yarn run prisma:migrate script and got the following error:

$ DATABASE_URL="$MIGRATE_DATABASE_URL" prisma migrate deploy
Environment variables loaded from .env
Prisma schema loaded from prisma/schema.prisma
Error: Schema validation error - Error (query-engine-node-api library)
Error code: P1012
error: Error validating datasource `db`: You must provide a nonempty URL. The environment variable `DATABASE_URL` resolved to an empty string.
  -->  schema.prisma:7
   |
 6 |   provider = "postgresql"
 7 |   url      = env("DATABASE_URL")
   |

Validation Error Count: 1
[Context: getConfig]

Prisma CLI Version : 4.4.0
error Command failed with exit code 1.
info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.

Any ideas?