How to pass variables accessible from VsCode devcontainer.json to docker-compose.yml

Question

In devcontainer.json we have access to these variables:

${localWorkspaceFolder}
${containerWorkspaceFolder}
${localWorkspaceFolderBasename}
${containerWorkspaceFolderBasename}

I have tried making these variables available in .devcontainer.json like this:

{
    "dockerComposeFile": "docker-compose.yml",
    "service": "my-devcontainer",
    "containerEnv": {
          "THING_I_WANT_TO_PASS": "${localWorkspaceFolderBasename}",
      },
      "remoteEnv": {
          "THING_I_WANT_TO_PASS": "${localWorkspaceFolderBasename}",
      },
}

So that they can be used in my docker-compose.yml like so:

services:
  my-devcontainer:
    container_name: "${THING_I_WANT_TO_PASS}-just-example"

But I still get this error VsCode attempts to build the container:

level=warning msg="The "THING_I_WANT_TO_PASS" variable is not set. Defaulting to a blank string.

Lindsay-Needs-Sleep · Accepted Answer · 2025-04-24 06:16:56Z

0

It's not great, but you can create an .env file during initializeCommand that will be used by docker-compose.yml.

In .devcontainer.json:

{
    "dockerComposeFile": "docker-compose.yml",
    "service": "my-devcontainer",
    "initializeCommand": "echo THING_I_WANT_TO_PASS=${localWorkspaceFolderBasename} > .devcontainer/.env"
}

answered Apr 24 at 6:16

Lindsay-Needs-Sleep

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