I am interested in this issue. But it is a year old. Is any planing or research on this subject done?

Not that anyone has shared with me.

Hello there, i've started work on this over at my fork on branch feat/sourcemap-javascript.

It's not in a place where I want to submit it for review, but so far I've managed to produce a basic sourcemap for a test Gleam module. This is it, visualized.

I was able to make debugging work through vscode-js-debug on neovim, using the following DAP config :

{
    type = "pwa-node",
    request = "launch",
    name = "Debug gleam program",
    -- NOTE: This wont work if the project's name doesnt match the folder name
    -- This should ideally be the name variable in the Gleam.toml manifest
    program = "${workspaceFolder}/build/dev/javascript/${workspaceFolderBasename}/gleam.main.mjs",
    cwd = "${workspaceFolder}",
    outFiles = {"${workspaceFolder}/**/*.mjs"},
    resolveSourceMapLocations = {"${workspaceFolder}/build/dev/javascript/**/*.map"},
    sourceMaps = true,
    pauseForSourceMap = true,
}

Is anyone actively interested in this, and willing to provide feedback ?

I think people are interested for sure!