Further F# Interop
This evening, I merged another F# PR in the same project as last time. The first PR covered downloading; in this PR, I moved most of the code related to user settings to the F# library project.
As part of this, I had the opportunity to work with JSON serialization and deserialization in an F# context. Here’s a sample of the new code:
[<CompiledName("Read")>]
let read filePath =
let (FilePath path) = filePath
let verify settings =
let isEmpty str = String.IsNullOrWhiteSpace str
let dirMissing str = not <| (Directory.Exists str)
match settings with
| { WorkingDirectory = w } when isEmpty w -> Error $"No working directory was specified."
| { WorkingDirectory = w } when dirMissing w -> Error $"Working directory \"{w}\" is missing."
| { MoveToDirectory = m } when isEmpty m -> Error $"No move-to directory was specified."
| { MoveToDirectory = m } when dirMissing m -> Error $"Move-to directory \"{m}\" is missing."
| _ -> Ok settings
try
path
|> File.ReadAllText
|> JsonSerializer.Deserialize<UserSettings>
|> verify
with
| :? FileNotFoundException -> Error $"\"{path}\" was not found."
| :? JsonException -> Error $"Could not parse JSON in \"{path}\" to settings."
| e -> Error $"Settings unexpectedly could not be read from \"{path}\": {e.Message}"
It might not be amazing F#, but I’m pretty fond of it. The backward pipe into not, the matching, the argument-free try pipeline, even the exception handling—it was fun!
Incidentally, [<CompiledName("Read")>] sets how the function name will appear in the C# project, which pulls in the library as a reference. Since method and function names in C# are Pascal case, this helps reduce any visual dissonance induced via lowercase function names.
A small downside of this move is that I still have a C# wrapper class that handles calling the F# code, which is less than ideal, but I can look into that more later. I also need to think about how much of the tool I want to port over to F#. Honestly, unless I get distracted or otherwise pulled away, I might just keep transferring more and more of the C# over to F#. Thus far, it’s been both educational and entertaining!