Support --mode flag in astro dev command

[yacoubb]

Body

Summary

Support passing the --mode flag when running astro dev

Background & Motivation

Following on from withastro/astro#10509
Vite has the incredibly useful --mode flag which allows you to load different .env.[MODE] files. This flag is supported by vite build and vite serve.

astro dev does not use the --mode flag, import.meta.env.MODE is always development and only .env and .env.development are loaded.

Switching between development and staging environments when running astro locally is especially difficult because of this limitation. The best solution at the moment seems to be renaming .env.development to swap out the variables needed for development/staging 🤢
Coming from vite, this seems like a step backwards.

Goals

• astro dev command supports passing --mode flag
• --mode flag updates import.meta.env.MODE
• --mode flag controls which .env.[MODE] file is loaded

Example

With an app that logs import.meta.env.MODE on startup:

astro dev
...
> 'development'

astro dev --mode staging
...
> 'staging'

[blikblum]

I second that feature request.

In my apps i have a script that runs a custom dev build that access remote database instead of local database

I accomplish that with vite setting mode to "remote"

In .env.remote i set a env variable "REMOTE_DATA"

In app i check import.meta.env.REMOTE_DATA to connect to remote data even in dev build

With astro this is not possible currently

Also, the astro docs (https://docs.astro.build/en/guides/environment-variables/) is misleading as it states that can use "any methods supported by vite" to load env variables which is not true

BTW setting env inline in the script command is a poor solution in my case since i develop both in windows and linux

[nkneupper]

Definitely support this feature request too. I went down quite a rabbit hole on this only to find out it's not implemented in Astro, especially since the official astro docs state that the --mode flag with astro dev is possible. https://docs.astro.build/en/guides/environment-variables/#env-files

[ematipico]

It is implemented https://docs.astro.build/en/reference/programmatic-reference/#mode

[ematipico]

https://docs.astro.build/en/reference/programmatic-reference/#mode