CSV TP behaviour has changed for local files?

[isaacabraham]

I opened an old project of mine today which uses the CSV provider, having upgraded to the latest version of FSharp.Data (2.4.6).

I have a local CSV file.

type Football = CsvProvider< @"\..\Data\FootballResults.csv">

When I create the CSV Provider, it "works" inside the code editor (with intellisense etc.), but when I execute in FSI, it shows no rows are read (with a empty seq).

If I change the code to as follows, it then starts working:

[<Literal>]
let Path = __SOURCE_DIRECTORY__ + @"\..\Data\FootballResults.csv"
type Football = CsvProvider<Path>

Is this a change in behaviour from the TP? Or something about upgrading to VS2017? Or just something I'm doing wrong? I've tried the usual trick of Environment.CurrentDirectory <- __SOURCE_DIRECTORY__ but that didn't help either.

[isaacabraham]

Investigating a bit more, this might also be to do with the way I'm referencing the type provider now - using Paket's load scripts feature rather than directly reference the type provider assembly as a #r. cc: @forki any thoughts?

[ovatsus]

The path resolution is something that's not 100% right, but it's a tricky thing to change, and whenever we change it we end up breaking more things. But in any case feel free to debug this further and propose a change

[github-actions]

🤖 This is an automated response from Repo Assist.

This is a well-known path resolution quirk with FSharp.Data type providers (see also #818 for a related discussion).

Root cause: Type providers resolve relative paths in two different contexts:

• Design-time (in the IDE / at compile time): the path is resolved relative to the source file's directory (__SOURCE_DIRECTORY__).
• Runtime (when you actually call .Load() or .GetSample()): the path is resolved relative to AppDomain.BaseDirectory, which is typically the application output directory (e.g. bin/Debug/) — not your source folder.

Solutions:

1. Use ResolutionFolder (recommended for scripts and projects):

   type Football = CsvProvider<"..\\Data\\FootballResults.csv", ResolutionFolder=__SOURCE_DIRECTORY__>

   This tells the provider to use your source directory as the base at both design-time and runtime.

2. Use __SOURCE_DIRECTORY__ for the load path (what you discovered works):

   let path = __SOURCE_DIRECTORY__ + @"\..\\Data\\FootballResults.csv"
   let data = Football.Load(path)

3. Copy the data file to the output directory and use a relative path — this matches AppDomain.BaseDirectory at runtime.

The maintainer's comment from 2018 ("whenever we change it we end up breaking more things") still applies; the ResolutionFolder parameter is the intentional escape hatch for this situation. Option 1 is the cleanest fix.

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