Fable: Problem with reflection info of delegate types

[nilshelmig]

Description

I've updated all my dependencies to their latest version and upgrade from fable-loader 2.0 to 2.1 and installed fable-compiler.

// Edit: I've also removed dotnet-fable and changed my build targets to call webpack directly

Since then I got the build error:

ERROR in ./WebUI.Fable/material_ui.fs
Module Error (from ./node_modules/fable-loader/index.js):
D:/Repositories/P-PLUS/WebUI.All/WebUI.Fable/material_ui.fs(1,1): error FABLE: Cannot get type info of generic parameter, please inline or inject a type resolver
 @ ./WebUI.Fable/pplus_common.fs 1:0-2063 5:31-72 6:31-72 7:30-65 8:36-75 9:33-68 10:43-79 11:51-84 12:40-74 13:40-75 14:35-71 15:52-85 16:46-79 17:34-68 18:34-70 19:34-68 20:34-68 21:29-62 22:33-67 23:30-64 24:31-63 25:30-65 26:38-72 27:39-74 28:34-68 31:46-79 32:49-81 36:17-56 37:12-46 38:31-69 39:30-65 40:19-55 41:20-58 42:10-45 43:32-67 44:37-75 45:12-46 46:22-56 47:18-52 48:36-69 51:13-47 52:12-46 53:9-41 56:8-42 57:7-40
 @ ./WebUI.Fable/WebUI_Fable.fs
 @ ./WebUI.Fable/WebUI.Fable.fsproj
 @ ./src/WebUI.js

Everything is fine if I open the material_ui.fs or pplus_common.fs in Visual Studio or VsCode. The lines which are marked as errors from the output are empty or the middle part of a function or value binding.

Related information

fable-loader: 2.1.2
fable-compiler: 2.1.8
webpack: 4.28.3
Operation System: Windows 10

[MangelMaxime]

You won't see an F#/intellisense error here because it's a Fable requirement when working with generic types.

If your code or the library is using reflection, the function needs to be inlined or have an [<Inject>] variable in it. For example: https://github.com/MangelMaxime/Thoth/blob/master/src/Thoth.Json/Decode.fs#L1017-L1020

You should check if your code or the library is using reflection somewhere.

[nilshelmig]

@MangelMaxime And how do I know which function I need to inline or add the [<Inject>] attribute? The line numbers in the error message points to an emtpy line or code fragments

// Edit: Is there an editor plugin which give me the ability to see those errors with intellisense?

[MangelMaxime]

By looking at the code and seeing which code is using reflection. Or isolating the problem in a small repro case to isolate the function.

I don't know why Fable isn't show the correct line however.

[nilshelmig]

I don't see any code with reflection in the given files (material_ui.fs & pplus_common.fs). There are just type and function definitions with concrete types as arguments. No generic types or refelction

I will now downgrade to Fable 2.0.11

If I can help you in any way, just aks me :)

// Edit: In the file material_ui.fs I have a lot of function calls like this

let teal500 : Color = importMember<string> "material-ui/styles/colors"

or

let private _Place = importDefault<RCom> "material-ui/svg-icons/maps/place"
let place (color : string) = R.from _Place (createObj [ "color" ==> color ]) []

[alfonsogarciacaro]

Hmm, may be related to #1655. Are you using any reflection in material_ui.fs like typeof<'T>.FullName? Would it be possible to share the contents of that file (maybe through a private message) so I can have a look?

[nilshelmig]

@alfonsogarciacaro here you go https://gist.github.com/nilshelmig/1d8a203c89665e78d5fcf48be088ddd0

[alfonsogarciacaro]

Thanks @nilshelmig! Which version of Fable.React are you using?

[nilshelmig]

My current dependencies (Fable related)

Fable.Core - 2.0.3
Fable.Elmish - 2.0.3
Fable.Elmish.Browser - 2.1
Fable.Elmish.Debugger - 2.0.2
Fable.Elmish.React - 2.1
Fable.React - 4.1.3

[mvsmal]

@nilshelmig Just curiosity, do you really need the deprecated material-ui npm package? There is a fable-material-ui package with bindings for the latest @material-ui/core.

[nilshelmig]

@mvsmal I know, but we are stuck to the legacy material-ui package 😭

[alfonsogarciacaro]

Hmm, unfortunately I cannot find any hint in the code for that file 😕 Would it be possible to share the project somehow or create a minimal version that I can use to reproduce the problem?

If this is not possible, I can try to release a Fable version with more logs so you can run it and see if it helps to spot the error.

[nilshelmig]

@alfonsogarciacaro Sharing the project is not possible, but I can run a version with additional logs for you and publish the results, if I can not find the error by myself

[nilshelmig]

@alfonsogarciacaro
I've got a minimal project which reproduces the bug

https://github.com/nilshelmig/minimal-fable-bug-example

Hope this will help 😃

[alfonsogarciacaro]

It does! Thanks a lot for this, I could finally find the cause of the problem 🙌 and I believe I managed to fix it. I will soon publish a new fable-compiler version with the fix :+1:

[nilshelmig]

It works! 🎉 😃
Thank you very much