Miniscript support?

[joemphilips]

Hi

I've been trying to port rust-miniscript into F#

https://github.com/joemphilips/FNBItcoin/tree/master/src/FNBitcoin

My original idea is to make this library as a wrapper for NBitcoin, but I'm wondering if this should be included in this repository when it is finished. Any opinion ?

(It is almost done besides 1. decompiler is not finished, and 2. want to add more property tests to asssure the behaviour will be exactly the same with rust-miniscript in all case. )

reasons to merge into this repo is

1. more fluent ScriptBuilder class will be possible
2. PSBT could support arbitrary script for finalization (currently it is only for simple multisig)
3. PSBT can parse the script into human readable format and users could see if it is in the right form

reasons to not merge is

1. It is written in F# and does not align well with other source code.

• I have no clue how to write this kind of software (parser, compiler) with C#

2. spec of miniscript itself is not formalized and might change slightly in the future

• I don't think this is a big problem since 1) optimizing the compilation process seems to have done well and more optimization sounds like over-engineering. 2) it is likely to change in the future anyway, when MuSig and Graftroot comes out.

[joemphilips]

Oh yeah, one more reason to not include is

1. If it is possible to compile rust-miniscript to wasm and load that directly, that will be much better in any sense.

[NicolasDorier]

I think making a library for miniscript in F# or C# is a great idea. The logic should not be that hard, and mistakes are not so hard to find and damaging as if it was a cryptographic mistake so the WASM route seems not necessary.

That said, I would advise to add it in the main NBitcoin project instead of separate library or dependency.
Converting F# to C# can be done 95% via automated tools. (one solution, which is probably not the best, is use ilspy to decompile the F# assembly and convert the IL to C#)

I am quite sure I can find around converters that work at the abstract syntax tree level instead of IL level.

If you want I can do it once you think your library is ready.

[NicolasDorier]

Another idea actually which would work great, is that you just use extensions method in your MiniScript library.

By doing this you can "add helper methods" to Script / PSBT without changing NBitcoin.

If you need to access internal state of those classes to do your stuff, we can just change NBitcoin to make the classes more extensible.

[knocte]

Converting F# to C# can be done 95% via automated tools

Why are you mentioning this? what's the point of converting F# to C#?

[NicolasDorier]

@knocte for including Miniscript directly into NBitcoin project, without any dependency.

[knocte]

Mmm, sorry but I still don't find the point. I assumed the N in "NBitcoin" stands for ".NET", not for C#. An F# library in a .NET nuget package wouldn't hinder it or add dependencies.

[NicolasDorier]

I mean I am pretty happy with NBitcoin being 1 big library as opposed to 35 decoupled packages.
It makes so much things simpler.

So I don't want NBitcoin library to have a direct dependency to a MiniScript nuget library.
There is lot's of cool methods that can added to NBitcoin with MiniScript, but because NBitcoin will not reference the MiniScript package (and can't because this would be a circular dependency), then the best way seems to include MiniScript directly in C# inside NBitcoin.

Extensions method at Miniscript level are good, but the problem is that people referencing NBitcoin have no way to know it exists.

[NicolasDorier]

There is no good reason to include the Miniscript F# library directly into NBitcoin IMHO.

This will not increase discovery of Miniscript library, while needlessly blocking @joemphilips progress as I will need to manage releases.

[knocte]

Nuget packages can supply more than 1 library (dll). Then it's just a matter of namespace discoverability, just as any other feature in NBitcoin.

[NicolasDorier]

Nuget package can have several libraries? I was unaware of this.

[knocte]

Yes, you just need to list several <file> elements in the nuspec file. An example: https://github.com/nblockchain/JsonRpcSharp/blob/master/build/JsonRpcSharp.nuspec

[NicolasDorier]

Ok. So the idea would be including F# lib inside the NBitcoin nuget package and rely on extensions method?

This seems good.

[NicolasDorier]

If we go extension method route, which namespace NBitcoin.Miniscript should put the extension methods?

NBitcoin seems the best for discovery. NBitcoin.Extensions seems best to follow Microsoft best practicies.

[NicolasDorier]

@knocte I don't think <file> will automatically reference the assembly.

[NicolasDorier]

There might have another solution like ILMerge. But afaik this does not work on .NET Core.