symfony/symfony

[Router] Declaring route with host and environment variable works in dev but not in prod

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#62,111 opened on Oct 19, 2025

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BugHelp wantedRoutingStatus: Needs Review

Description

Symfony version(s) affected

all

Description

Hi, I spend some time to figure about a bug on generating URL when parameter (ex: route.host.app) is used in Route::host argument.

No issue during the development because the cache is correctly rebuilt with the env var value. But when i build docker image, i explicitly build the symfony cache (to avoid building the cache each time containers start) and the cache file url_generating_routes.php contains empty value for host tokens.

I see the usage of env var is explicitly forbidden by the PR: https://github.com/symfony/symfony/pull/20687/files but when the env var is used through a parameter, the check didn't apply.

I'm not sure how we can add a check to help developers to see an error during development and not when deploying in production.

How to reproduce

Set route.host.app value is %env(resolve:ROUTE_HOST_APP)%

Declare route host like this

app:
    resource:
        path: ../src/Controller/
        namespace: App\Controller
    type: attribute
    host: '%route.host.app%'
    prefix: /

Possible Solution

No response

Additional Context

No response

Contributor guide

Tech stack
None
Domain
backend
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
Symfony routingenvironment variable handlingDocker image build
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
35
Research direction
Investigate the referenced PR #20687 to understand the existing check for env var usage in routes. Examine the url generating routes.php cache file and how host tokens are resolved. Look at the Routing component's route compiler and url generator to identify where a parameter resolved from an env var could be detected during compilation to throw an error or warning.