Usable wasm browser apps build output with WasmBundlerFriendlyBootConfig=true by ArcadeMode · Pull Request #125192 · dotnet/runtime

ArcadeMode · 2026-03-04T21:51:25Z

It is currently not possible to use the output of a Wasm Browser App's dotnet build when WasmBundlerFriendlyBootConfig=true.

Hotreload is still referenced from the generated boot.config.json. However there wont be a server involved to provide the files, nor are they present on disk.
Static assets are not copied from wwwroot to the output directory

These two points make it so that builds will fail when passed into an npm project.

Secondary 'issues' (rather improvements)

Compression is also enabled by default, slowing the build down while the js bundler most likely wont be using these files.
Fingerprinting is also enabled by default, which the bundler can to (and often does) by itself.

Changes

defaulted the aforementioned properties to false when building bundler friendly
ammended static asset sdk 'default items' Content with instruction to also copy to the output directory on build.

Test are updated to always run an npm build when building bundler friendly, so multiple tests verify that this works. A new test was added to explicitly test for the absence of hot reload from the boot json.

Effect

The proposed changes make it no longer necessary to go through a dev cycle with publish + npm builds, instead the (faster) builds can be used for the npm builds. Once ready its ofcourse still possible to publish for a release build (a more typical development flow).

…nfig true

Copilot

Pull request overview

This PR aims to make WasmBundlerFriendlyBootConfig=true usable in Debug builds by preventing hot reload from being referenced in the generated boot config when no dev server/files are available (e.g., when bundling with a JS bundler).

Changes:

Adds MSBuild logic to set WasmEnableHotReload=false when WasmBundlerFriendlyBootConfig=true (under certain conditions).

...nuget/Microsoft.NET.Sdk.WebAssembly.Pack/build/Microsoft.NET.Sdk.WebAssembly.Browser.targets

…nfig

Copilot

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 4 comments.

src/mono/wasm/Wasm.Build.Tests/Blazor/BlazorWasmTestBase.cs

src/mono/wasm/Wasm.Build.Tests/LibraryInitializerTests.cs

ArcadeMode · 2026-03-06T23:38:52Z

@pavelsavara could you look at this if you have a moment?

I added a build test to confirm the hotreload references are omitted when building bundler friendly, just in case.

Copilot

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

src/mono/wasm/Wasm.Build.Tests/Blazor/BlazorWasmTestBase.cs

src/mono/wasm/Wasm.Build.Tests/LibraryInitializerTests.cs

ArcadeMode · 2026-03-07T12:06:55Z

Converted to draft, I was doing some things wrong. Will undraft when I got the tests working properly

…nfig

Copilot

Pull request overview

Copilot reviewed 6 out of 6 changed files in this pull request and generated 3 comments.

src/mono/wasm/Wasm.Build.Tests/DebugLevelTests.cs

...nuget/Microsoft.NET.Sdk.WebAssembly.Pack/build/Microsoft.NET.Sdk.WebAssembly.Browser.targets

Copilot

Pull request overview

Copilot reviewed 6 out of 6 changed files in this pull request and generated 2 comments.

src/mono/wasm/Wasm.Build.Tests/Blazor/BlazorWasmTestBase.cs

src/mono/wasm/Wasm.Build.Tests/DebugLevelTests.cs

Copilot

Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

...nuget/Microsoft.NET.Sdk.WebAssembly.Pack/build/Microsoft.NET.Sdk.WebAssembly.Browser.targets

…nfig

Copilot

Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

...nuget/Microsoft.NET.Sdk.WebAssembly.Pack/build/Microsoft.NET.Sdk.WebAssembly.Browser.targets

src/mono/wasm/Wasm.Build.Tests/DebugLevelTests.cs

ArcadeMode · 2026-03-13T15:27:23Z

@maraf This is ready for another review. I think there's been some good improvements.

…nfig

Copilot

Pull request overview

Copilot reviewed 6 out of 6 changed files in this pull request and generated 2 comments.

...nuget/Microsoft.NET.Sdk.WebAssembly.Pack/build/Microsoft.NET.Sdk.WebAssembly.Browser.targets


+  <Target Name="EnsureProjectAssetsInOutputDirectoryForBundlerFriendlyBuild"
+          BeforeTargets="ResolveBuildStaticWebAssets"
+          Condition="'$(WasmBundlerFriendlyBootConfig)' == 'true' and '$(IsPublishing)' != 'true'">


...nuget/Microsoft.NET.Sdk.WebAssembly.Pack/build/Microsoft.NET.Sdk.WebAssembly.Browser.targets

+  <Target Name="EnsurePublishAssetsInOutputDirectoryForBundlerFriendlyBuild"
+          AfterTargets="_SplitStaticWebAssetsByCopyOptions"
+          BeforeTargets="_BuildCopyStaticWebAssetsPreserveNewest;_BuildCopyStaticWebAssetsAlways;_BuildCopyStaticWebAssetsIfDifferent"
+          Condition="'$(WasmBundlerFriendlyBootConfig)' == 'true' and '$(IsPublishing)' != 'true'">


ArcadeMode added 2 commits March 4, 2026 22:02

disable wasmhotreload if not explicitly set and bundlerfriendlybootco…

2512418

…nfig true

casing

3b65b19

ArcadeMode requested review from akoeplinger and lewing as code owners March 4, 2026 21:51

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github-actions bot added the area-Build-mono label Mar 4, 2026

dotnet-policy-service bot added the community-contribution Indicates that the PR has been added by a community member label Mar 4, 2026

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build-analysis bot mentioned this pull request Mar 5, 2026

Wasm build terminated with exit code 137 #108299

Open

add build test no hotreload in bootjson

2f96dcb

ArcadeMode requested review from ilonatommy and maraf as code owners March 6, 2026 22:45

Merge branch 'main' into wasm-no-hotreload-with-bundlerfriendlybootco…

34fa937

…nfig

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ArcadeMode added 2 commits March 7, 2026 00:39

aot is not relevant here

f809af2

pass explicitly no build props

43d8563

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ArcadeMode marked this pull request as draft March 7, 2026 12:05

ArcadeMode added 4 commits March 10, 2026 22:50

disable compression, hotreload and fingerprinting when bundlerfriendly

862aeb3

update test to work

d01a074

allow pdbs as file in rollup

23435bc

Merge branch 'main' into wasm-no-hotreload-with-bundlerfriendlybootco…

ffef895

…nfig

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ArcadeMode added 2 commits March 11, 2026 20:48

dont include content, update staticwebassets to get copied to outdir

ba4e664

change order, ensure fingerprint and compression remain disabled

247615c

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This was referenced Mar 12, 2026

BlazorWasm AOT not requiring trimming #125233

Open

BlazorWasm_CannotAOT_InDebug test failure #125244

Open

ArcadeMode added 2 commits March 12, 2026 21:48

bundler friendly builds treat assets as they are during publish

1c1f5b5

refactor private field + public method

ba717c2

Copilot AI review requested due to automatic review settings March 12, 2026 20:51

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ArcadeMode added 2 commits March 12, 2026 22:28

add update attribute

0ce730c

Merge branch 'main' into wasm-no-hotreload-with-bundlerfriendlybootco…

4d63607

…nfig

Copilot AI review requested due to automatic review settings March 12, 2026 21:28

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Copilot started reviewing on behalf of ArcadeMode March 12, 2026 21:51 View session

fix bad condition causing unwanted fingerprint disabling

faf2368

ArcadeMode requested a review from maraf March 13, 2026 15:25

only run test when building bundler-friendly

ecd01f0

Copilot AI review requested due to automatic review settings March 13, 2026 16:49

Merge branch 'main' into wasm-no-hotreload-with-bundlerfriendlybootco…

badc32e

…nfig

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This was referenced Mar 13, 2026

The Operation will be canceled. The next steps may not contain expected logs. dotnet/dnceng#3008

Open

[android-arm64] The Operation will be canceled. The next steps may not contain expected logs. dotnet/dnceng#6408

Open

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ArcadeMode commented Mar 6, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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ArcadeMode commented Mar 4, 2026 •

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