[DI][Improvement] Allow to define a default value on environment variables #25129

vincentchalamon · 2017-11-23T09:29:56Z

Q	A
Bug report?	no
Feature request?	yes
BC Break report?	no
RFC?	no
Symfony version	3.4

Since Symfony 3.4, it's now possible to parse environment variables using %env()% tool: https://goo.gl/8Zsed6

But in some environment, I don't have the right environment variables set, so the application is not bootable (on Insight analysis for instance). To fix it, I need to define the environment variable on a parameter key:

parameters:
    db_hostname: '%env(DB_HOSTNAME)%'
    env(DB_HOSTNAME): db

doctrine:
    dbal:
        host: '%db_hostname%'

It should be interesting to parse a default value directly on the %env()% tool:

doctrine:
    dbal:
        host: '%env(default:db:DB_HOSTNAME)%'

The text was updated successfully, but these errors were encountered:

nicolas-grekas · 2017-11-23T10:25:57Z

That should actually be quite easy, as a new processor. The actual syntax would need a swap:
%env(default:FOO:defaultvalue)%, so that the default value could contain a colon.
BUT, this would actually be of limited use, since the allowed characters between env(...) is quite limited (and it shouldn't be widened.)

You can simplify your example a bit if you want:

parameters:
    env(DB_HOSTNAME): db

doctrine:
    dbal:
        host: '%env(DB_HOSTNAME)%'

vincentchalamon · 2017-11-23T10:32:16Z

But what about resolve (for instance)? Should I declare exactly the same in parameters?:

parameters:
    env(resolve:DB_HOSTNAME): db

doctrine:
    dbal:
        host: '%env(resolve:DB_HOSTNAME)%'

This also ask a good question: if we allow default keyword, we should also allow multiple keywords usage, like: %env(default:resolve:DB_HOSTNAME:defaultvalue)%

nicolas-grekas · 2017-11-23T10:44:15Z

Should I declare exactly the same in parameter

nope

should also allow multiple keywords usage

it's already allowed

nicolas-grekas · 2017-11-23T10:45:08Z

should also allow multiple keywords usage

OK, no, in fact it should be reversed: resolve:default:DB_HOSTNAME:defaultvalue

vincentchalamon · 2017-11-23T10:46:15Z

OK, thanks for your feedback. I'll try to open a PR soon for this default value improvement

javiereguiluz · 2017-11-23T10:53:54Z

@vincentchalamon I don't understand this:

But what about resolve (for instance)? Should I declare exactly the same in parameters?:

Resolve is needed in env vars because they can't interpolate the container parameters. But that's not a problem in your example:

parameters:
    # use container params here without doing anything special
    env(DB_HOSTNAME): '%kernel.project_dir%/db'

doctrine:
    dbal:
        host: '%env(resolve:DB_HOSTNAME)%'

I don't think Symfony needs to change anything about this behavior. Could you please share some realistic config that it's impossible to do with Symfony? Thanks!

vincentchalamon · 2017-11-23T11:00:00Z

@javiereguiluz

But what about resolve (for instance)? Should I declare exactly the same in parameters?:

I was thinking about following syntax:

parameters:
    env(resolve:DB_HOSTNAME): 'foo'

But I was wrong, the right syntax is what you wrote. Thanks :-)

In this improvement/question issue, the idea is to simplify the configuration and not having to declare a parameter key for the default value:

doctrine:
    dbal:
        host: '%env(resolve:default:DB_HOSTNAME:%kernel.project_dir%/db)%'

nicolas-grekas · 2017-11-23T11:09:38Z

host: '%env(resolve:default:DB_HOSTNAME:%kernel.project_dir%/db)%'

What I said before: this won't work, as / is not allowed between env().
Which means I'm personally not sure it's a good idea.

vincentchalamon · 2017-11-23T11:16:23Z

In this case, you're right (I was also afraid about % or other characters not allowed in env()), and I should declare a parameter as default value of my environment variable.

But I think the default value in env() could be useful for more simple variables to don't declare them all as parameters just for a default value. For instance, in my current project, I should declare 18 parameters as default values for my 18 environment variables. So the ideal configuration should be like (using env(default…) idea):

parameters:
    locale: en
    env(DB_HOST): %kernel.project_dir%/db

doctrine:
    dbal:
        driver:   "%env(default:DATABASE_DRIVER:pdo_mysql)%"
        host:     "%env(resolve:DATABASE_HOSTNAME)%"
        port:     "%env(int:default:DATABASE_PORT:3306)%"
        dbname:   "%env(default:DATABASE_NAME:api_platform)%"
        user:     "%env(default:DATABASE_USER:api_platform)%"
        password: "%env(default:DATABASE_PASSWORD:api_platform)%"
        charset: "%env(default:DATABASE_CHARSET:utf-8)%"
        server_version: "%env(default:DATABASE_SERVER_VERSION:5.7)%"

swiftmailer:
    transport: '%env(default:MAILER_TRANSPORT:smtp)%'
    host: '%env(default:MAILER_HOST:127.0.0.1)%'
    username: '%env(default:MAILER_USER:null)%'
    password: '%env(default:MAILER_PASSWORD:null)%'

etc. for each environment variable used in my configuration (JWT Token Paths, CORS Allow Origin…).

nicolas-grekas · 2017-11-23T11:20:14Z

you're asking for much more: I guess that by "null", you're expecting null, not "null".
Basically this is asking to have a runtime parser for env vars.
Solving the simple case will create a situation where ppl will expect / to be allowed, and as such generate negative feedback for sure (because it doesn't work). Better teach ppl the proper way, that is feature full...

javiereguiluz · 2017-11-23T11:25:45Z

@vincentchalamon I think that the real problem is that you are using env vars where you don't need to use env vars. Regular config params still work in Symfony.

Remove some or all the env vars if you don't need them ... but if you really need them, there's a price to pay for env vars (define default values for them, propagate them to the production servers, etc.)

vincentchalamon · 2017-11-23T12:06:56Z

OK, understood. Thanks for your feedbacks @nicolas-grekas @javiereguiluz

xabbuh added DependencyInjection Feature labels Nov 23, 2017

vincentchalamon closed this as completed Nov 23, 2017

bpolaszek mentioned this issue Jan 3, 2019

Nullable environment variable processor #29767

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[DI][Improvement] Allow to define a default value on environment variables #25129

[DI][Improvement] Allow to define a default value on environment variables #25129

[DI][Improvement] Allow to define a default value on environment variables #25129

[DI][Improvement] Allow to define a default value on environment variables #25129

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