Fable.System.IO

Fable.System.IO is a no-dependency, F#-only implementation of certain parts of the System.IO API. At the moment, this library only implements most of the methods in System.IO.Path. This library is built to be completely Fable-compatible, and behave exactly the same whether targetting .NET or Javascript.

To use the library, reference the Fable.System.IO nuget package. When targetting Fable, you also need the platform-detect NPM package, installed like so:

npm install platform-detect@3.0.1

Or:

yarn add platform-detect@3.0.1

Then, replace all occurrences of open System.IO with open Fable.System.IO.

Fable.System.IO will behave the same as the browser's current platform, as detected by platform-detect. In other words, when running in a Unix agent, it will use / as the directory separator; and in a Windows agent, it will use \ instead.

Choosing OS to emulate

By default, this library will emulate the path behavior for the current detected operating system. If you want to force Windows path behavior, you can open Fable.Windows.System.IO. Likewise, to force Unix path behavior, open Fable.Unix.System.IO. For example:

open Fable
open Fable.Unix.System.IO

printfn "Path.Combine(\"foo\", \"bar\") = \"%s\"" (Path.Combine ("foo", "bar"))

// This will output "foo/bar" on all systems

Supported APIs

Here is a list of currently implemented APIs in Fable.System.IO:

• System.IO
  • Path (click here for Microsoft docs)
    • GetInvalidFileNameChars()
    • GetInvalidPathChars()
    • IsPathRooted(string)
    • Combine(string[])
    • Join(string, string)
    • GetRelativePath(string, string)
    • GetDirectoryName(string)
    • GetFileName(string)
    • GetFileNameWithoutExtension(string)
    • GetExtension(string)
    • HasExtension(string)
    • DirectorySeparatorChar : string
    • AltDirectorySeparatorChar : string

Development

You can open the Fable.System.IO.sln directly in your favorite .NET IDE.

You can run all tests (.NET and Javascript) with:

dotnet tool restore
dotnet paket restore
dotnet fable build -t Test

All the .NET tests include "Oracle" tests cases, which test the API against the BCL implementation. Therefore, for complete testing, one should make sure to run the test suite under a Windows system and a Unix system. The GitHub CI runs the full test suite under Windows and Ubuntu.