`-no-build-nodejs` without `/p:SkipTestBuild=true` fails build

[dougbu]

I accidentally hit this in #21487. See https://dev.azure.com/dnceng/public/_build/results?buildId=974989 for example. The following errors occur in that build

/datadisks/disk1/workspace/_work/1/s/.dotnet/sdk/6.0.100-preview.1.21073.4/Sdks/Microsoft.NET.Sdk.BlazorWebAssembly/targets/Microsoft.NET.Sdk.BlazorWebAssembly.Current.targets(258,5): error MSB3954: Failed to compute hash for file '/datadisks/disk1/workspace/_work/1/s/src/Components/Web.JS/dist/Release/blazor.webassembly.js' because it does not exist or is inaccessible. [/datadisks/disk1/workspace/_work/1/s/src/Components/WebAssembly/testassets/StandaloneApp/StandaloneApp.csproj]
/datadisks/disk1/workspace/_work/1/s/.dotnet/sdk/6.0.100-preview.1.21073.4/Sdks/Microsoft.NET.Sdk.BlazorWebAssembly/targets/Microsoft.NET.Sdk.BlazorWebAssembly.Current.targets(258,5): error MSB3954: Failed to compute hash for file '/datadisks/disk1/workspace/_work/1/s/src/Components/Web.JS/dist/Release/blazor.webassembly.js' because it does not exist or is inaccessible. [/datadisks/disk1/workspace/_work/1/s/src/Components/WebAssembly/testassets/Wasm.Authentication.Client/Wasm.Authentication.Client.csproj]
/datadisks/disk1/workspace/_work/1/s/.dotnet/sdk/6.0.100-preview.1.21073.4/Sdks/Microsoft.NET.Sdk.BlazorWebAssembly/targets/Microsoft.NET.Sdk.BlazorWebAssembly.Current.targets(258,5): error MSB3954: Failed to compute hash for file '/datadisks/disk1/workspace/_work/1/s/src/Components/Web.JS/dist/Release/blazor.webassembly.js' because it does not exist or is inaccessible. [/datadisks/disk1/workspace/_work/1/s/src/Components/WebAssembly/testassets/HostedInAspNet.Client/HostedInAspNet.Client.csproj]
/datadisks/disk1/workspace/_work/1/s/.dotnet/sdk/6.0.100-preview.1.21073.4/Sdks/Microsoft.NET.Sdk.BlazorWebAssembly/targets/Microsoft.NET.Sdk.BlazorWebAssembly.Current.targets(258,5): error MSB3954: Failed to compute hash for file '/datadisks/disk1/workspace/_work/1/s/src/Components/Web.JS/dist/Release/blazor.webassembly.js' because it does not exist or is inaccessible. [/datadisks/disk1/workspace/_work/1/s/src/Components/WebAssembly/testassets/CustomBasePathApp/CustomBasePathApp.csproj]
/datadisks/disk1/workspace/_work/1/s/.dotnet/sdk/6.0.100-preview.1.21073.4/Sdks/Microsoft.NET.Sdk.BlazorWebAssembly/targets/Microsoft.NET.Sdk.BlazorWebAssembly.Current.targets(258,5): error MSB3954: Failed to compute hash for file '/datadisks/disk1/workspace/_work/1/s/src/Components/Web.JS/dist/Release/blazor.webassembly.js' because it does not exist or is inaccessible. [/datadisks/disk1/workspace/_work/1/s/src/Components/benchmarkapps/Wasm.Performance/TestApp/Wasm.Performance.TestApp.csproj]
/datadisks/disk1/workspace/_work/1/s/.dotnet/sdk/6.0.100-preview.1.21073.4/Sdks/Microsoft.NET.Sdk.BlazorWebAssembly/targets/Microsoft.NET.Sdk.BlazorWebAssembly.Current.targets(258,5): error MSB3954: Failed to compute hash for file '/datadisks/disk1/workspace/_work/1/s/src/Components/Web.JS/dist/Release/blazor.webassembly.js' because it does not exist or is inaccessible. [/datadisks/disk1/workspace/_work/1/s/src/Components/test/testassets/GlobalizationWasmApp/GlobalizationWasmApp.csproj]
/datadisks/disk1/workspace/_work/1/s/.dotnet/sdk/6.0.100-preview.1.21073.4/Sdks/Microsoft.NET.Sdk.BlazorWebAssembly/targets/Microsoft.NET.Sdk.BlazorWebAssembly.Current.targets(258,5): error MSB3954: Failed to compute hash for file '/datadisks/disk1/workspace/_work/1/s/src/Components/Web.JS/dist/Release/blazor.webassembly.js' because it does not exist or is inaccessible. [/datadisks/disk1/workspace/_work/1/s/src/Components/test/testassets/BasicTestApp/BasicTestApp.csproj]

The problem is the test assets projects attempt to use the Release version of blazor.webassembly.js which (because of -no-build-nodejs) doesn't exist. Options include

1. Fail fast (with a much clearer error message) when those projects attempt to build and blazor.webassembly.js doesn't exist
2. Fall back to the Debug version of the file (which is checked in) when the Release version doesn't exist

Thoughts @dotnet/aspnet-blazor-eng❔

[dougbu]

As a side note

aspnetcore/src/Components/Web.JS/Microsoft.AspNetCore.Components.Web.JS.npmproj

Lines 10 to 11 in 70a880f

	<BuildOutputFiles Include="dist\release\blazor.server.js" />
	<BuildOutputFiles Include="dist\release\blazor.webassembly.js" />

will never match real files on Linux systems because "Release" is always capitalized. That <ItemGroup> may however just be redundant given

aspnetcore/eng/targets/Npm.Common.targets

Line 29 in 70a880f

<BuildOutputFiles Include="dist\**\*.js" />

[dougbu]

Bug causing the current low-level error (which should at least mention building with node when in our repo) is unconditional nature of setting at

aspnetcore/src/Components/Directory.Build.targets

Line 3 in 70a880f

<BlazorWebAssemblyJSPath>$(RepoRoot)src\Components\Web.JS\dist\$(Configuration)\blazor.webassembly.js</BlazorWebAssemblyJSPath>

That line is fine in most local builds (whether building w/ node or not) because those default to Debug builds. Problem is visible in local builds with -configuration Release and --no-build-nodejs (or -noBuildNodeJS on Windows) after cleaning the repo e.g.

git clean -dfx -e .vs/ -e .vscode/ -e .dotnet/ -e .tools/
.\build.cmd -configuration Release -noBuildNodeJS

On machines lacking node, -noBuildNodeJS or --no-build-nodejs isn't needed to see the problem.

The warning without node installed or with its use disabled mentions "Building NodeJS is disabled so the managed projects will fallback to using the output from previous builds." but that's irrelevant when there is no "previous build" done with node. This should probably be fixed as well.

[captainsafia]

In the Directory.Build.targets above, can we do something like:

<BlazorWebAssemblyJSPath>$(RepoRoot)src\Components\Web.JS\dist\$(Configuration)\blazor.webassembly.js</BlazorWebAssemblyJSPath> 
<BlazorWebAssemblyJSPath Condition="!Exists(BlazorWebAssemblyJSPath)">$(RepoRoot)src\Components\Web.JS\dist\Debug\blazor.webassembly.js</BlazorWebAssemblyJSPath> 

to fallback to the Debug version in the event the Release version is not available?

[dougbu]

fallback to the Debug version

Yeah, that's my second option in the original description. I can handle the fix if that's the direction you want to go. Should the build emit warnings when it does this❔

And, what about the redundant bit mentioned in https://github.com/dotnet/aspnetcore/issues/29944#issuecomment-774340127❔

[dougbu]

After some offline discussion, we're going with the "fail fast" option because there is no checked-in blazor.webassembly.js file anymore. Specifically, I'll add an <Error> if Microsoft.AspNetCore.Components.WebAssembly.csproj is packed and a <Warning> if any $(UsingMicrosoftNETSdkBlazorWebAssembly) (test) project is built when the file doesn't exist.

I'll also change the Microsoft.AspNetCore.Web.JS.npmproj project to use $(Configuration) instead of release because that's what dependant projects consume.

[dougbu]

@mkArtakMSFT assigned dougbu 1 hour ago

😀