What is the `file` Service Configuration in Symfony For?

Question

Short Version: What does the Symfony file: SomeFile.php service configuration do?

Recently I entered an invalid service definition in a service.yaml file while working in a Symfony project. I was greeted by this super useful error message

The configuration key "foo" is unsupported for definition "App\Services\ServiceA" in "/Users/alanstorm/Sites/symfony-4/my-project/config/services.yaml". Allowed configuration keys are "alias", "parent", "class", "shared", "synthetic", "lazy", "public", "abstract", "deprecated", "factory", "file", "arguments", "properties", "configurator", "calls", "tags", "decorates", "decoration_inner_name", "decoration_priority", "autowire", "autoconfigure", "bind" in /Users/alanstorm/Sites/symfony-4/my-project/config/services.yaml (which is loaded in resource "/Users/alanstorm/Sites/symfony-4/my-project/config/services.yaml").

I don't think I'd ever seen every valid configuration for a Symfony service listed somewhere before. I'm trying to understand what the file configuration is for and how to use it.

I tried configuration a service using it

App\Services\ServiceA:
    file: SomeFile.php

and Symfony complained

Warning: include_once(SomeFile.php): failed to open stream: No such file or directory

I tried placing a file named SomeFile.php at `src/SomeFile.php, and Symfony complained

The autoloader expected class "App\SomeFile" to be defined in file "/Users/alanstorm/Sites/symfony-4/my-project/vendor/composer/../../src/SomeFile.php". The file was found but the class was not in it, the class name or namespace probably has a typo in /Users/alanstorm/Sites/symfony-4/my-project/config/services.yaml (which is loaded in resource "/Users/alanstorm/Sites/symfony-4/my-project/config/services.yaml").

So I defined a class named App\SomeFile in src/SomeFile.php

#File: src/SomeFile.php
namespace App;
class SomeFile {
}

and Symfony loaded this file -- but when back to complaining

Warning: include_once(SomeFile.php): failed to open stream: No such file or directory in var/cache/dev/ContainerG6s3qUD/getServiceA2Service.php (line 11)

So finally, I checked out the `` file and saw it included this line

#File: var/cache/dev/ContainerG6s3qUD/getServiceA2Service.php
//...
include_once 'SomeFile.php';
//...

So, best I can tell is this file configuration is some sort of alternative to the composer autoloader -- but I can't find any docs on how to confirm thy suspicions or how to use it.

Can anyone help me understand that this configuration field is for?

Just recently the Symfony errors started to become more verbose. Not sure how helpful this is since most people ignore them anyways. That said, the file attribute is discussed here: symfony.com/doc/current/service_container/… Not something that get used much. — Cerad
@Cerad FWIW I've found the new error messages to be helpful. I bet a lot of people do read them -- you just only hear from the people that don't :) — Alan Storm

Alan Storm Alan Storm · Accepted Answer · 2019-02-10T16:24:53

Thanks to a little help from some internet friends, who were able to dig up some old documentation, I now know that the file service configuration is for including a PHP immediately before the service gets loaded.

There's a few things that tripped me up. First -- you need to use the %kernel.root_dir% parameter in order for this to work

App\Services\ServiceA:
    public: true
    file: "%kernel.root_dir%/foo.php"

The underlying container code expects this to be a full path.

Extra tricky was the following exception message

The autoloader expected class "App\SomeFile" to be defined in file "/Users/alanstorm/Sites/symfony-4/my-project/vendor/composer/../../src/SomeFile.php".

It turns out this didn't have anything to do with my file configuration. Instead, this error message was the result of the following default service.yaml configuration

_defaults:
    autowire: true
    public: true

App\:
    resource: '../src/*'
    exclude: '../src/{DependencyInjection,Entity,Migrations,Tests,Kernel.php}'

Because my included file was in src, Symfony's resource configuration seem to be trying to load it as a class file. When it wasn't a class file, it complained. Then, when the file loader tried to load a path without the %kernel.root_dir%, things were still sad.

If you're going to use these two configuration patterns together, you'll want to be sure to exclude your file file

    exclude: '../src/{DependencyInjection,Entity,Migrations,Tests,Kernel.php,foo.php}'

What is the `file` Service Configuration in Symfony For?

1 Answers