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[browser][coreCLR] use WASMFS - #130141
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Pull request overview
This PR shifts the browser/CoreCLR WASM stack toward using Emscripten WASMFS by moving VFS population and working-directory setup from the JavaScript FS.* APIs into native open/mkdir/chdir-based helpers, and adjusts WASM platform I/O behavior accordingly.
Changes:
- Update
System.NativeWASM behavior: trust browser/WASMFSdirent.d_type, treat WASI as unreliable, and avoidO_NOCTTYon WASM where WASMFS rejects unknown flags. - Replace JS-side
FS.createPath/createDataFile/chdirusage with new native exports (BrowserHost_WriteFileToVfs,BrowserHost_SetWorkingDirectory) and corresponding TS type updates. - Enable WASMFS in the native build, add a WASMFS root override for corerun (node/shell path), and export
emscripten_stack_get_currentwhere needed.
Reviewed changes
Copilot reviewed 15 out of 15 changed files in this pull request and generated 2 comments.
Show a summary per file
| File | Description |
|---|---|
| src/native/libs/System.Native/pal_io.c | Adjust WASM dirent d_type handling and skip O_NOCTTY on WASM to match WASMFS constraints. |
| src/native/libs/System.Native.Browser/native/index.ts | Remove JS-side working directory creation/chdir from preInit. |
| src/native/libs/System.Native.Browser/libSystem.Native.Browser.Utils.footer.js | Add emscripten_stack_get_current as an explicit dependency. |
| src/native/libs/Common/JavaScript/types/internal.ts | Extend module internal typing with onRuntimeInitialized. |
| src/native/libs/Common/JavaScript/types/ems-ambient.ts | Add ambient typings for new BrowserHost exports; remove typed FS surface. |
| src/native/libs/Common/JavaScript/host/host.ts | Call native working-directory setter during CoreCLR initialization. |
| src/native/libs/Common/JavaScript/host/assets.ts | Route VFS file installation/PDB registration through native file-write export. |
| src/native/corehost/browserhost/libBrowserHost.footer.js | Export new BrowserHost entrypoints for file write + working directory. |
| src/native/corehost/browserhost/browserhost.cpp | Implement native VFS write and working-directory setup using open/mkdir/chdir. |
| src/coreclr/hosts/corerun/wasm/wasmfs_root_override.cpp | Provide WASMFS root backend override (node backend). |
| src/coreclr/hosts/corerun/wasm/libCorerun.js | Add emscripten_stack_get_current dependency for corerun wasm JS library. |
| src/coreclr/hosts/corerun/wasm/corerun.html | Update corerun browser sample invocation (args/core-root). |
| src/coreclr/hosts/corerun/CMakeLists.txt | Wire in WASMFS root override for node/shell corerun builds and remove NODERAWFS link option. |
| eng/native/configureplatform.cmake | Enable WASMFS link options for CoreCLR browser builds. |
| eng/native.wasm.targets | Export _emscripten_stack_get_current from the WASM build. |
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| const workingDirPtr = _ems_.dotnetBrowserUtilsExports.stringToUTF8Ptr(loaderConfig.virtualWorkingDirectory!) as any; | ||
| _ems_._BrowserHost_SetWorkingDirectory(workingDirPtr); | ||
| _ems_._free(workingDirPtr); |
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| extern "C" int BrowserHost_WriteFileToVfs(const char* path, const void* data, int32_t length) | ||
| { | ||
| BrowserHost_EnsureParentDirs(path); | ||
|
|
||
| int fd = open(path, O_CREAT | O_WRONLY | O_TRUNC, 0644); | ||
| if (fd < 0) | ||
| { | ||
| std::fprintf(stderr, "BrowserHost_WriteFileToVfs: open('%s') failed - errno %d\n", path, errno); | ||
| return -1; | ||
| } |
This was referenced Jul 3, 2026
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This was referenced Jul 3, 2026
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| const loaderConfig = _ems_.dotnetApi.getConfig(); | ||
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| const workingDirPtr = _ems_.dotnetBrowserUtilsExports.stringToUTF8Ptr(loaderConfig.virtualWorkingDirectory!) as any; | ||
| _ems_._BrowserHost_SetWorkingDirectory(workingDirPtr); | ||
| _ems_._free(workingDirPtr); | ||
|
|
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| [ConditionalTheory(typeof(Directory_CreateDirectory), nameof(NoMaxComponentLength))] | ||
| [MemberData(nameof(PathsWithComponentLongerThanMaxComponent))] | ||
| public void DirectoryWithComponentLongerThanMaxComponentAsPath_BrowserDoesNotThrowException(string path) | ||
| { |
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Remove the remaining legacy JavaScript filesystem dependencies and propagate native working-directory setup failures. Avoid linking Emscripten's NODERAWFS root hook when CoreRun provides its own root mapping. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
This was referenced Oct 1, 2026
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Summary
JavaScript
FSAPI to nativeopen,mkdir, andchdiroperations.conflicting NODERAWFS root hook.
/usr/shareforSpecialFolder.CommonApplicationDataand propagatenative working-directory setup failures.
behavior from CoreCLR's WASMFS behavior.
Testing
.\build.cmd -bl -os browser -subset clr+libs+host -c Debug /p:RuntimeFlavor=CoreCLR.\dotnet.cmd build -bl /p:TargetOS=browser /p:TargetArchitecture=wasm /p:Configuration=Debug /p:RuntimeFlavor=CoreCLR /t:RunSample src\mono\sample\wasm\console-nodeHello World!output..\dotnet.cmd build -bl /p:TargetOS=browser /p:TargetArchitecture=wasm /p:Configuration=Debug /p:RuntimeFlavor=CoreCLR /t:Test /p:Scenario=WasmTestOnChrome /p:InstallChromeForTests=false /p:XUnitClassName=System.IO.Tests.Directory_CreateDirectory .\src\libraries\System.Runtime\tests\System.IO.FileSystem.Tests\System.IO.FileSystem.Tests.csprojcase was skipped.
FilesToIncludeInFileSystemTestswas not completed locally becauseVBCSCompiler held
hostfxr.dllopen while the workload SDK was beingreinstalled.
Note
This pull request description was generated with GitHub Copilot.