Modern Fortran support for environment variables in settings.json

Help Visual Studio Code
1

I am unable to use the following syntax in settings.json

“fortran.linter.compilerPath”: “${env:MY_GCC_ROOT}/bin/gfortran”,
”fortran.fortls.path”:”{env:HOME}/.local/bin/fortls”

The output console shows it failed to locate gfortran, and to initialize fortls. However, if I use the expanded path, both work.

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Thank you

@gnikit

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2

I am not a Visual Studio user, but standard JSON does not support variables. You would have to use some work-around importing the file and then stringifying and expanding it or having bash expand it in a here document or some work-around normally. Perhaps Visual Studio runs the file through a preprocessor or has some other work-around built in so I cannot say there is not a ready solution, but pure standard JSON would need expanded names.

3

json files supports strings, how the strings are parsed is application dependent.

For example, launch.json and task.json support the ${workspaceFolder} syntax within VScode

I do not think it is a JSON issue. It is an application issue.

4

I had a similar issue when dealing with VSCode gfortran on Windows but it didn’t seem to be an issue on WSL. I can’t remember if I did anything different.

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5

Are you using Windows? I had issues with Windows vs Linux paths. Maybe the variables contain Windows style paths. Does it work if you change the hard-coded portion to Windows? Remember to double the backslashes.

“fortran.linter.compilerPath”: “${env:MY_GCC_ROOT}\\bin\\gfortran”,”fortran.fortls.path”:”{env:HOME}\\.local\\bin\\fortls.exe”
6

Working on Linux at the moment.

Similar string, like $HOME/.local/bin/fortls works just fine

Thank you.

7

Update:

–> ”fortran.fortls.path”:”{env:HOME}/.local/bin/fortls” ←– WORKS.

I verified vscode was fixed Aug 1, 2025

Unfortunately, it seems that
”fortran.linter.compilerPath”:”${env:HOME}/.local/bin/gfortran”
does not work, while “fortran.fortls.path” does.

It seems the problem is in the Modern Fortran extension handling of the settings entry. If I expand ${env:HOME} explicitly, it works.

Looking at the Modern Fortran extension in github, it seems (I am not familiar with the VSCode extensions API) that it is reading the json attributes literally,

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Looking into the handling for the language server path, fortls, which works, it seems it is missing the resolution of the variables in the string via a ResolveVariables (from util/tools) call

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It would be great to “resolve those environment variables”

@gnikit