Nixify ffi CI

[benalleng]

I realized adding the specific needs for the JS bindings into the global dev shell was mostly a time waster so I opted to refactor the recent additions from #1572 and instead use a javascript specific dev shell, the same applies for the addition of csharp and dart here

Unfortunately a windows build is not really feasibly nixify-able at this time.

Pull Request Checklist

Please confirm the following before requesting review:

• I have disclosed my use of
  AI
  in the body of this PR.
• I have read CONTRIBUTING.md and rebased my branch to produce hygienic commits.

[coveralls]

Coverage Report for CI Build 26466302919

Coverage remained the same at 85.14%

Details

• Coverage remained the same as the base build.
• Patch coverage: No coverable lines changed in this PR.
• No coverage regressions found.

Uncovered Changes

No uncovered changes found.

Coverage Regressions

No coverage regressions found.

---

Coverage Stats

Relevant Lines:	13701
Covered Lines:	11665
Line Coverage:	85.14%
Coverage Strength:	394.86 hits per line

---

💛 - Coveralls

[caarloshenriq]

tACK b3d667b on NixOS with act

Approach is clean. Just flagging that 3f76cc7 (DO NOT MERGE test) is still in the branch and left a stray test line in payjoin-ffi/README.md. Worth squashing before merging.

[chavic]

What happens if we stick to dotnet 10? The previous PR touching this file assumed we needed to have donnet 8 compatibility, but we're gonna upgrade BTCPay and the Plugin to use dotnet 10 from now on....

I'm wondering if this had to be brought back because of a regression?

[benalleng]

The error I was getting was due to the inability to find the net_8 apphost file while using the he 1.0 sdk when running ./payjoin-ffi/csharp/contrib/test.sh I think it must have to do with some build step misconfiguration on my end.

/nix/store/60wblmm28bvni14276vvmi3p77hmxw79-dotnet-sdk-10.0.203/share/dotnet/sdk/10.0.203/Microsoft.Common.CurrentVersion.targets(5395,5): error MSB3030: Could not copy the file "/home/runner/work/rust-payjoin/rust-payjoin/payjoin-ffi/csharp/obj/Debug/net8.0/apphost" because it was not found. [/home/runner/work/rust-payjoin/rust-payjoin/payjoin-ffi/csharp/Payjoin.Tests.csproj]

[benalleng]

Found in this CI run https://github.com/payjoin/rust-payjoin/actions/runs/26295972437/job/77408538246?pr=1574#step:6:1000

[chavic]

Confirmed we can avoid bringing back .NET 8 entirely. I tested the stricter path: move the C# test project to net10.0, drop runtime_8_0 from the Nix shell, and update CI to install .NET 10.

Suggested change:

diff --git a/flake.nix b/flake.nix
@@
-        dotnetSdk = pkgs.dotnetCorePackages.combinePackages [
-          pkgs.dotnetCorePackages.sdk_10_0
-          pkgs.dotnetCorePackages.runtime_8_0
-        ];
+        dotnetSdk = pkgs.dotnetCorePackages.sdk_10_0;

diff --git a/payjoin-ffi/csharp/Payjoin.Tests.csproj b/payjoin-ffi/csharp/Payjoin.Tests.csproj
@@
-    <TargetFramework>net8.0</TargetFramework>
+    <TargetFramework>net10.0</TargetFramework>

diff --git a/.github/workflows/csharp.yml b/.github/workflows/csharp.yml
@@
-      - name: Install .NET 8 SDK
+      - name: Install .NET 10 SDK
         uses: actions/setup-dotnet@v4
         with:
-          dotnet-version: "8.0.x"
+          dotnet-version: "10.0.x"

Local verification passes:

• nix develop -c dotnet --info shows only .NET 10 SDK/runtime
• nix develop -c bash payjoin-ffi/csharp/contrib/test.sh passes: 27 tests under net10.0
• git diff --check
• nix fmt -- --ci

[benalleng]

Got it, the last missing step was the global.json config specifying the sdk version as 8.0.100