Allow references in .env file

[Flamefire]

Currently the .env file is not a real dot-env-file because it is a simple list of name=value pairs. However "real" .env supports string references: see https://marketplace.visualstudio.com/items?itemName=mikestead.dotenv

Why is this important?

I set up my PYTHONPATH in the .env file to mirror runtime set env variables so I can use the integrated debugger. This becomes quite lengthy so I tried:

REPO="/home/user/git/foobar"
PYTHONPATH="${REPO}/foo:${REPO}/bar"
# Or
PYTHONPATH="${REPO}/foo"
PYTHONPATH="${PYTHONPATH}:${REPO}/bar"

Would be great, if this was allowed.

[DonJayamanne]

• Use https://www.npmjs.com/package/dotenv-expand to expand variables
• Ensure ${workspaceFolder} gets expanded to current workspace folder
• Ensure we support multi-root workspace folders (all you need to do is use current resource when expanding ${workspaceFolder})

@ericsnowcurrently pointed out that ${xxx} values for env variables will get expanded in the shell (applies to Pwsh, bash, etc). I.e. when using env files in shells, then we don't need to expand them.
However when not using a shell, then we will need this.

[ericsnowcurrently]

Considering that this is an app-specific .env file, we can dictate the format for substitution and stick with what is the defacto standard (regardless of platform or shell). The substitution will happen in IEnvironmentVariablesService.parseFile(), so the terminal case is not impacted.

[ericsnowcurrently]

FTR...

There are three sorts of `env' files out there:

• system-level
  • e.g. /etc/environment
  • used by pam_env
  • must be simple VARIABLE=value lines
  • shell-agnostic, so no substitution syntax supported
  • https://help.ubuntu.com/community/EnvironmentVariables#A.2Fetc.2Fenvironment
  • https://www.ibm.com/support/knowledgecenter/ssw_aix_72/com.ibm.aix.osdevice/etc_env_file.htm
• shell-level
  • e.g. ~/.env
  • used as part of shell startup (a la .profile)
  • shell-specific
  • may or may not support substitution
  • https://www.ibm.com/support/knowledgecenter/en/ssw_aix_72/com.ibm.aix.osdevice/env_file.htm
• app-level
  • e.g. $PROJECT_ROOT/.env
  • format is app-specific, but de facto standard follows NAME=VALUE with simple $NAME and ${NAME} substitution
  • often used to hold sensitive details out of the app (e.g. passwords)

In the extension:

• https://code.visualstudio.com/docs/python/environments#_environment-variable-definitions-file
• https://github.com/Microsoft/vscode-python/blob/master/src/client/common/variables/environment.ts#L24

Highlighting in VSCode:

• https://marketplace.visualstudio.com/items?itemName=mikestead.dotenv

Node:

• https://www.npmjs.com/package/dotenv
• https://github.com/motdotla/dotenv-expand

[ericsnowcurrently]

There should be a docs update to go along with this. @DonJayamanne, how do I get that rolling?

[DonJayamanne]

how do I get that rolling?

File an issue on https://github.com/Microsoft/vscode-docs

[ericsnowcurrently]

FWIW, the philosophy on .env files from the dotenv module isn't compatible with our needs. This became clear in conversations on upstream PRs:

• motdotla/dotenv#371
• motdotla/dotenv#372
• motdotla/dotenv#373
• motdotla/dotenv#374