Which environment variables do we want to expose in configuration?

[cristiano-belloni]

Let's discuss what env variables we want to add to our Modular configuration in v4.

@AlbertoBrusa has identified an exhaustive list of all ENV variables we read in Modular as part of this PR - #2227

We believe that only things that affect build/production should be configurable by file, while the rest should only be ENV_VARIABLES

Variable	Description	CRA	Configurable
NODE_ENV		No	No
NODE_PATH		No	No
HTTPS	Development server in HTTPS mode	Yes	No
SSL_CRT_FILE		No	No
SSL_KEY_FILE		No	No
HOST	Specify different host to localhost	Yes	No
PORT	Specify port to run on	Yes	No
BROWSER	Specify browser to override default	Yes	No
BROWSER_ARGS	Arguments passed to browser when opening	Yes	No
SKIP_PREFLIGHT_CHECK	Skip all the modular repo checks	No	No
USE_MODULAR_WEBPACK	Removed	No	No
USE_MODULAR_ESBUILD	Use esbuild instead of Webpack	No	Yes
EXTERNAL_CDN_TEMPLATE	URL template to query a CDN	No	Yes
PUBLIC_URL	Force assets to be referenced verbatim to the url you provide	Yes	Yes
EXTERNAL_BLOCK_LIST	Specifies which dependencies are allowed to be rewritten to the CDN. Default is none	No	Yes
EXTERNAL_ALLOW_LIST	Specifies which dependencies are not allowed to be rewritten to the CDN. Default is all	No	Yes
MODULAR_LOGGER_DEBUG	Turn on Debug logs	No	No
MODULAR_LOGGER_MUTE	Mute all logs	No	No
BROWSERSLIST_ENV	Pass env to browserlist command	No	No
SKIP_MODULAR_STARTUP_CHECK	Skip modular startup checks (Always skipped in CI)	No	No
NO_HEADLESS_TESTS	Force tests to not run headless	No	No
GIT_AUTHOR_EMAIL		No	No
GIT_AUTHOR_NAME		No	No
MODULAR_LINT_FIX		No	No
REACT_EDITOR		Yes	No
VISUAL		No	No
EDITOR		No	No
WDS_SOCKET_PATH	When set, Create React App will run the development server with a custom websocket path for hot module reloading. Normally, webpack-dev-server defaults to /ws for the SockJS pathname. You may use this variable to start local development on more than one Create React App project at a time. See webpack-dev-server documentation for more details.	Yes	No
WDS_SOCKET_HOST	When set, Create React App will run the development server with a custom websocket hostname for hot module reloading. Normally, webpack-dev-server defaults to window.location.hostname for the SockJS hostname. You may use this variable to start local development on more than one Create React App project at a time. See webpack-dev-server documentation for more details.	Yes	No
WDS_SOCKET_PORT	When set, Create React App will run the development server with a custom websocket port for hot module reloading. Normally, webpack-dev-server defaults to window.location.port for the SockJS port. You may use this variable to start local development on more than one Create React App project at a time. See webpack-dev-server documentation for more details.	Yes	No
DANGEROUSLY_DISABLE_HOST_CHECK		No	No
INLINE_RUNTIME_CHUNK	Some apps do not need the benefits of saving a web request, so not inlining the chunk makes for a smoother build process	Yes	No
GENERATE_SOURCEMAP	Source maps are resource heavy and can cause out of memory issue for large source files. We need to make it configurable everywhere we currently set it	Yes	Yes
IMAGE_INLINE_SIZE_LIMIT	This one is Webpack-only	Yes	No

[AlbertoBrusa]

To start off the discussion, I feel like anything that users might expect to be configurable coming from CRA should easily be configurable in modular through the config:
HTTPS
HOST
PORT
BROWSER
BROWSER_ARGS
PUBLIC_URL

[cristiano-belloni]

EXTERNAL_BLOCK_LIST and EXTERNAL_ALLOW_LIST should be configurable, with a default value of undefined

[AlbertoBrusa]

Agreed - I've kept the the default as ['**'] for allow and [] for block as is already the case

[cristiano-belloni]

Even better!

[cristiano-belloni]

@AlbertoBrusa look for variables that are determined by destructuring process.env too; for example, HTTPS is useless without SSL_CRT_FILE and SSL_KEY_FILE:

const { SSL_CRT_FILE, SSL_KEY_FILE, HTTPS } = process.env;

[AlbertoBrusa]

Good catch, will add them in

[AlbertoBrusa]

Looking at the code HTTPS can be provided and is still useful without the other two, so we need to decide if we want to configure all three by the file, for now I've done HTTPS

[cristiano-belloni]

SOCKER -> SOCKET

[AlbertoBrusa]

Finalised list of configuration options we want to expose via a configuration file:

Variable	Description
USE_MODULAR_ESBUILD	Use esbuild instead of Webpack
EXTERNAL_CDN_TEMPLATE	URL template to query a CDN
PUBLIC_URL	Force assets to be referenced verbatim to the url you provide
EXTERNAL_BLOCK_LIST	Specifies which dependencies are allowed to be rewritten to the CDN. Default is none. Discourage use
EXTERNAL_ALLOW_LIST	Specifies which dependencies are not allowed to be rewritten to the CDN. Default is all. Discourage use
GENERATE_SOURCEMAP	Source maps are resource heavy and can cause out of memory issue for large source files. We need to make it configurable everywhere we currently set it regardless of if it currently uses ENV variable