Linking via an alias --alias forces the use of _URL as the environment variable suffix

[suwyn]

Description of problem

When linking a postgres database to an app using the --link-flags argument, the plugin appends _URL to the environment variable name specified in the argument.

This causes an issue when the application you are linking does not use _URL as the suffix of the DSN URL. In our case that is Metabase, which uses MB_DB_CONNECTION_URI

Steps to Reproduce

1. Create an application.
2. Create a postgres database.
3. Link the postgres database to the app by specifying an alias. dokku postgres:link metabase metabase -a MB_DB_CONNECTION_URI

Actual Results

Sets the environment variable MB_DB_CONNECTION_URI_URL on the metabase application

Expected Results

MB_DB_CONNECTION_URI would have been set.

The work around is to set the environment variable via the app config. e.g. dokku config:set metabase MB_DB_CONNECTION_URI=$(dokku postgres:info metabase --dsn)

[josegonzalez]

I'll post the potential fix here (from a discussion in discord):

TL;DR: We need a new flag called --env-name that tracks the alternative env-name. If set, we use that, otherwise, fallback to existing behavior.

• and adding a new flag to track the env-name value: https://github.com/dokku/dokku-redis/blob/master/common-functions#L701
• add a new config_set call to all the places where we currently do that in this file: https://github.com/dokku/dokku-redis/blob/master/common-functions#L635
  • you'd only want to add the config_set call if there is an SERVICE_ENV_NAME environment variable value
• running bin/generate (assuming you updated the docblock on the link subcommand here) would be enough
• add a bats test here: https://github.com/dokku/dokku-redis/blob/master/tests/service_link.bats

That should make it generic enough that this is a copy-paste process for me to get this implemented on all datastores. You could implement the above on any datastore and I can take it from there, no need to focus on redis specifically.

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This has been requested a few times and as I don't want to break existing behavior, I think the above is a good balance between desired functionality and backwards compatibility.