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| 1 | +# Converting a SpacetimeDB 2.0.x project to use NativeAOT-LLVM |
| 2 | + |
| 3 | +This guide provides instructions on taking an existing C# module that targets the public-released SpacetimeDB CLI, and guides you through the necessary steps to enable `NativeAOT-LLVM` use. |
| 4 | + |
| 5 | +## Overview |
| 6 | +In order to use `NativeAOT-LLVM` on a C# module, we'll need to set the `EXPERIMENTAL_WASM_AOT` environment variable to `1` which SpacetimeDB will check during publishing of a module. |
| 7 | +For the module to work, we'll also need the `NuGet.Config` and `.csproj` files with the required package sources and references. |
| 8 | + |
| 9 | +### Prerequisites: |
| 10 | +- **.NET SDK 8.x** (same version used by SpacetimeDB) |
| 11 | +- **Emscripten SDK (EMSDK)** installed (must contain `upstream/emscripten/emcc.bat`) |
| 12 | +- **(Optional) Binaryen (wasm-opt)** installed and on `PATH` (recommended: `version_116`) |
| 13 | + |
| 14 | +## Steps |
| 15 | + |
| 16 | +1. **Install EMSDK** |
| 17 | + - Download and extract the `https://github.com/emscripten-core/emsdk` release. |
| 18 | + - Example path: `D:\Tools\emsdk` |
| 19 | + |
| 20 | +2. **Set environment variables** |
| 21 | + |
| 22 | + ```powershell |
| 23 | + $env:EXPERIMENTAL_WASM_AOT=1 |
| 24 | + $env:EMSDK="D:\Tools\emsdk" |
| 25 | + ``` |
| 26 | + |
| 27 | +3. **Ensure NuGet feed is configured** |
| 28 | + NativeAOT-LLVM packages currently come from **dotnet-experimental**: |
| 29 | + - Add the `dotnet-experimental` feed to a project-local `NuGet.Config` |
| 30 | + ```xml |
| 31 | + <add key="dotnet-experimental" value="https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet-experimental/nuget/v3/index.json" /> |
| 32 | + ``` |
| 33 | + This should be a `NuGet.Config` placed in the root directory of your module folder (next to the `.csproj`). You can simply add the above line to the `packageSources` of your existing file, or if you need to create a minimal one, you can use: |
| 34 | + |
| 35 | + ```xml |
| 36 | + <?xml version="1.0" encoding="utf-8"?> |
| 37 | + <configuration> |
| 38 | + <packageSources> |
| 39 | + <clear /> |
| 40 | + <add key="dotnet-experimental" value="https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet-experimental/nuget/v3/index.json" /> |
| 41 | + <add key="nuget.org" value="https://api.nuget.org/v3/index.json" /> |
| 42 | + </packageSources> |
| 43 | + </configuration> |
| 44 | + ``` |
| 45 | + |
| 46 | +4. **Ensure NativeAOT emits a `.wasm` output** |
| 47 | + - For LLVM AOT builds, the CLI currently accepts `dotnet.wasm` under `bin/Release/net8.0/wasi-wasm/publish/`. |
| 48 | + - In the module `.csproj`, ensure the AOT package references include: |
| 49 | + |
| 50 | + ```xml |
| 51 | + <ItemGroup Condition="'$(EXPERIMENTAL_WASM_AOT)' == '1'"> |
| 52 | + <PackageReference Include="Microsoft.NET.ILLink.Tasks" Version="8.0.0-*" Condition="'$(ILLinkTargetsPath)' == ''" /> |
| 53 | + <PackageReference Include="Microsoft.DotNet.ILCompiler.LLVM" Version="8.0.0-*" /> |
| 54 | + <PackageReference Include="runtime.$(NETCoreSdkPortableRuntimeIdentifier).Microsoft.DotNet.ILCompiler.LLVM" Version="8.0.0-*" /> |
| 55 | + </ItemGroup> |
| 56 | + ``` |
| 57 | + |
| 58 | + The contents of your `.csproj` should look something like this: |
| 59 | + |
| 60 | + ```xml |
| 61 | + <Project Sdk="Microsoft.NET.Sdk"> |
| 62 | + <PropertyGroup> |
| 63 | + <TargetFramework>net8.0</TargetFramework> |
| 64 | + <RuntimeIdentifier>wasi-wasm</RuntimeIdentifier> |
| 65 | + <ImplicitUsings>enable</ImplicitUsings> |
| 66 | + <Nullable>enable</Nullable> |
| 67 | + </PropertyGroup> |
| 68 | + <ItemGroup> |
| 69 | + <PackageReference Include="SpacetimeDB.Runtime" Version="2.0.*" /> |
| 70 | + </ItemGroup> |
| 71 | + <ItemGroup Condition="'$(EXPERIMENTAL_WASM_AOT)' == '1'"> |
| 72 | + <PackageReference Include="Microsoft.NET.ILLink.Tasks" Version="8.0.0-*" Condition="'$(ILLinkTargetsPath)' == ''" /> |
| 73 | + <PackageReference Include="Microsoft.DotNet.ILCompiler.LLVM" Version="8.0.0-*" /> |
| 74 | + <PackageReference Include="runtime.$(NETCoreSdkPortableRuntimeIdentifier).Microsoft.DotNet.ILCompiler.LLVM" Version="8.0.0-*" /> |
| 75 | + </ItemGroup> |
| 76 | + </Project> |
| 77 | + ``` |
| 78 | + |
| 79 | + - **NU1504 warning**: Because the runtime targets also add these LLVM packages, you may see a duplicate PackageReference warning. It is non-blocking. |
| 80 | + |
| 81 | +5. **(Optional) Install wasm-opt (Binaryen)** |
| 82 | + This step is optional, but provides performance improvements, and therefore is recommended. |
| 83 | + - Download Binaryen `https://github.com/WebAssembly/binaryen/releases/tag/version_116` for Windows and extract it, e.g. `D:\Tools\binaryen`. |
| 84 | + - Add `D:\Tools\binaryen\bin` to `PATH`. |
| 85 | + - Verify: |
| 86 | + |
| 87 | + ```powershell |
| 88 | + wasm-opt --version |
| 89 | + ``` |
| 90 | + |
| 91 | +6. **Publish module** |
| 92 | + - Use the SpacetimeDB CLI to publish from the module directory. |
| 93 | + - With `EXPERIMENTAL_WASM_AOT=1`, publish should attempt LLVM AOT. |
| 94 | + - Ensure the local server is running if publishing to `local`. |
| 95 | + |
| 96 | +## Troubleshooting |
| 97 | + |
| 98 | +### Package source mapping enabled |
| 99 | +If you have **package source mapping** enabled in `NuGet.Config`, you must add mappings for the LLVM packages or restores will fail. |
| 100 | +Place the following in `NuGet.Config` inside the `configuration` section: |
| 101 | +```xml |
| 102 | +<packageSourceMapping> |
| 103 | + <packageSource key="bsatn-runtime"> |
| 104 | + <package pattern="SpacetimeDB.BSATN.Runtime" /> |
| 105 | + </packageSource> |
| 106 | + <packageSource key="SpacetimeDB.Runtime"> |
| 107 | + <package pattern="SpacetimeDB.Runtime" /> |
| 108 | + </packageSource> |
| 109 | + <packageSource key="dotnet-experimental"> |
| 110 | + <package pattern="Microsoft.DotNet.ILCompiler.LLVM" /> |
| 111 | + <package pattern="runtime.*" /> |
| 112 | + </packageSource> |
| 113 | + <packageSource key="nuget.org"> |
| 114 | + <package pattern="*" /> |
| 115 | + </packageSource> |
| 116 | +</packageSourceMapping> |
| 117 | +``` |
| 118 | + |
| 119 | +### wasi-experimental workload install fails |
| 120 | +If the CLI cannot install the `wasi-experimental` workload automatically, install it manually: |
| 121 | + |
| 122 | +```powershell |
| 123 | +dotnet workload install wasi-experimental |
| 124 | +``` |
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