`${containerEnv:ENV_VAR:default_value}` not working

[aeschli]

Testing #7100

• open a new folder, create a new devcontainer file (e.g. Ubuntu)
• add "postCreateCommand": "echo XXX ${localEnv:PATH:NO_PATH} ${localEnv:PATH1:NO_PATH1}",
• run the container. Works

[5207 ms] Start: Run in container: /bin/sh -c echo XXX /home/aeschli/.local/bin:/home/aeschli/.... NO_PATH1
XXX /home/aeschli/.local/bin:/home/aeschli/... NO_PATH1

change localEnv to containerEnv:
"postCreateCommand": "echo XXX ${containerEnv:PATH:NO_PATH} ${containerEnv:PATH1:NO_PATH1}",

• rebuild container

[5199 ms] Start: Run in container: /bin/sh -c echo XXX ${containerEnv:PATH:NO_PATH} ${containerEnv:PATH1:NO_PATH1}
/bin/sh: 1: Bad substitution

[tvenhaus]

I just tested version v0.250.0 using the VSCode Insiders build and observed that container environment variables (i.e. ${containerEnv:ENV_VAR:default_value) are still not working when used within the "mounts" property.

"mounts": [
	"source=${containerEnv:SOME_VAR},target=/some/folder,type=bind,consistency=cached"
],

This results in the following error:

docker: Error response from daemon: invalid mount config for type "bind": invalid mount path: '${containerEnv:SOME_VAR}' mount path must be absolute.

[aeschli]

Verified with v0.252.0