How To Get Around Elm Make Error On `getAppUserDataDirectory`?

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1

I am trying to use the elm executable release to compile an elm app to javascript.

I am using the elm.exe contained in https://github.com/elm/compiler/releases/download/0.19.0/installer-for-windows.exe

To compile an elm app, I start the elm executable with a .net c# program like this:

var process = new System.Diagnostics.Process
{
    StartInfo = new ProcessStartInfo
    {
        WorkingDirectory = workingDirectory,
        FileName = executableFilePath,
        Arguments = "make CounterWebApp.elm --output=\"file-for-elm-make-output.js\"",
        UseShellExecute = false,
        RedirectStandardOutput = true,
        RedirectStandardError = true,
    },
};

process.Start();
var standardOutput = process.StandardOutput.ReadToEnd();
var standardError = process.StandardError.ReadToEnd();

process.WaitForExit();
var exitCode = process.ExitCode;
process.Close();

This works on a development machine, but when I use this approach on an azure app, elm make fails with following output:

  • Exit Code: 1
  • Standard Output: contains 0 characters
  • Standard Error: elm.exe: getAppUserDataDirectory:sHGetFolderPath: illegal operation (unsupported operation)

How do I use elm make without dependency on getAppUserDataDirectory?

How can I configure my system so that elm make works?

I am not familiar with the internals of the elm compiler, I guess that the dependency is used for caching on the default file system.
I ran elm make --help to see if I can use an argument to avoid this, but only get this:

The `make` command compiles Elm code into JS or HTML:

    elm19 make <zero-or-more-elm-files>

For example:

    elm make src/Main.elm

This tries to compile an Elm file named src/Main.elm, putting the resulting
JavaScript code in an elm.js file.

You can customize this command with the following flags:

    --debug
        Turn on the time-travelling debugger. It allows you to rewind and replay
        events. The events can be imported/exported into a file, which makes for
        very precise bug reports!

    --optimize
        Turn on optimizations to make code smaller and faster. For example, the
        compiler renames record fields to be as short as possible and unboxes
        values to reduce allocation.

    --output=<output-file>
        Specify the name of the resulting JS file. For example
        --output=assets/elm.js to generate the JS at assets/elm.js or
        --output=/dev/null to generate no output at all!

    --report=<report-type>
        You can say --report=json to get error messages as JSON. This is only
        really useful if you are an editor plugin. Humans should avoid it!

    --docs=<json-file>
        Generate a JSON file of documentation for a package. Eventually it will
        be possible to preview docs with `reactor` because it is quite hard to
        deal with these JSON files directly.
2

In other thread it was mentioned that you can set home directory with ELM_HOME.

2 Likes
3

Awesome, setting ELM_HOME seems to solve the problem:

var elmHomeDirectory = Path.Combine(workingDirectory, "elm-make-home-directory");
Directory.CreateDirectory(elmHomeDirectory);
process.StartInfo.Environment["ELM_HOME"] = elmHomeDirectory;
4

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