Building in VS from aspnetcore repo, .razor files failing with CS0649 (Field is never assigned to) and RZ9991 (Attribute names could not be inferred)

[SteveSandersonMS]

This seems to be a new issue since yesterday, as far as I can tell. Note that it works fine when building from the command line.

Repro: Open ComponentsNoDeps.slnf in Visual Studio and try to build BasicTestApp

2>------ Build started: Project: BasicTestApp, Configuration: Debug Any CPU ------
2>C:\dir\aspnetcore\src\Components\test\testassets\BasicTestApp\FormsTest\InputFileComponent.razor(8,170,8,182): error RZ9991: The attribute names could not be inferred from bind attribute 'bind-value'. Bind attributes should be of the form 'bind' or 'bind-value' along with their corresponding optional parameters like 'bind-value:event', 'bind:format' etc.
2>C:\dir\aspnetcore\src\Components\test\testassets\BasicTestApp\FormsTest\InputFileComponent.razor(13,283,13,299): error RZ9991: The attribute names could not be inferred from bind attribute 'bind-value'. Bind attributes should be of the form 'bind' or 'bind-value' along with their corresponding optional parameters like 'bind-value:event', 'bind:format' etc.
2>C:\dir\aspnetcore\src\Components\test\testassets\BasicTestApp\VirtualizationComponent.razor(3,87,3,95): error RZ9991: The attribute names could not be inferred from bind attribute 'bind-value'. Bind attributes should be of the form 'bind' or 'bind-value' along with their corresponding optional parameters like 'bind-value:event', 'bind:format' etc.
2>C:\dir\aspnetcore\src\Components\test\testassets\BasicTestApp\GlobalizationBindCases.razor(15,640,15,660): error RZ9991: The attribute names could not be inferred from bind attribute 'bind-value'. Bind attributes should be of the form 'bind' or 'bind-value' along with their corresponding optional parameters like 'bind-value:event', 'bind:format' etc.
2>C:\dir\aspnetcore\src\Components\test\testassets\BasicTestApp\GlobalizationBindCases.razor(27,1126,27,1153): error RZ9991: The attribute names could not be inferred from bind attribute 'bind-value'. Bind attributes should be of the form 'bind' or 'bind-value' along with their corresponding optional parameters like 'bind-value:event', 'bind:format' etc.
2>C:\dir\aspnetcore\src\Components\test\testassets\BasicTestApp\GlobalizationBindCases.razor(39,1612,39,1634): error RZ9991: The attribute names could not be inferred from bind attribute 'bind-value'. Bind attributes should be of the form 'bind' or 'bind-value' along with their corresponding optional parameters like 'bind-value:event', 'bind:format' etc.
2>C:\dir\aspnetcore\src\Components\test\testassets\BasicTestApp\GlobalizationBindCases.razor(52,2217,52,2244): error RZ9991: The attribute names could not be inferred from bind attribute 'bind-value'. Bind attributes should be of the form 'bind' or 'bind-value' along with their corresponding optional parameters like 'bind-value:event', 'bind:format' etc.
2>C:\dir\aspnetcore\src\Components\test\testassets\BasicTestApp\BindCasesComponent.razor(22,1131,22,1161): error RZ9991: The attribute names could not be inferred from bind attribute 'bind-value'. Bind attributes should be of the form 'bind' or 'bind-value' along with their corresponding optional parameters like 'bind-value:event', 'bind:format' etc.
2>C:\dir\aspnetcore\src\Components\test\testassets\BasicTestApp\BindCasesComponent.razor(24,1366,24,1396): error RZ9991: The attribute names could not be inferred from bind attribute 'bind-value'. Bind attributes should be of the form 'bind' or 'bind-value' along with their corresponding optional parameters like 'bind-value:event', 'bind:format' etc.
2>C:\dir\aspnetcore\src\Components\test\testassets\BasicTestApp\BindCasesComponent.razor(37,1894,37,1917): error RZ9991: The attribute names could not be inferred from bind attribute 'bind-value'. Bind attributes should be of the form 'bind' or 'bind-value' along with their corresponding optional parameters like 'bind-value:event', 'bind:format' etc.
2>C:\dir\aspnetcore\src\Components\test\testassets\BasicTestApp\BindCasesComponent.razor(67,3213,67,3230): error RZ9991: The attribute names could not be inferred from bind attribute 'bind-value'. Bind attributes should be of the form 'bind' or 'bind-value' along with their corresponding optional parameters like 'bind-value:event', 'bind:format' etc.
2>C:\dir\aspnetcore\src\Components\test\testassets\BasicTestApp\BindCasesComponent.razor(91,4297,91,4316): error RZ9991: The attribute names could not be inferred from bind attribute 'bind-value'. Bind attributes should be of the form 'bind' or 'bind-value' along with their corresponding optional parameters like 'bind-value:event', 'bind:format' etc.
2>C:\dir\aspnetcore\src\Components\test\testassets\BasicTestApp\BindCasesComponent.razor(136,6411,136,6439): error RZ9991: The attribute names could not be inferred from bind attribute 'bind-value'. Bind attributes should be of the form 'bind' or 'bind-value' along with their corresponding optional parameters like 'bind-value:event', 'bind:format' etc.
2>C:\dir\aspnetcore\src\Components\test\testassets\BasicTestApp\BindCasesComponent.razor(166,8113,166,8139): error RZ9991: The attribute names could not be inferred from bind attribute 'bind-value'. Bind attributes should be of the form 'bind' or 'bind-value' along with their corresponding optional parameters like 'bind-value:event', 'bind:format' etc.
2>C:\dir\aspnetcore\src\Components\test\testassets\BasicTestApp\BindCasesComponent.razor(178,8819,178,8852): error RZ9991: The attribute names could not be inferred from bind attribute 'bind-value'. Bind attributes should be of the form 'bind' or 'bind-value' along with their corresponding optional parameters like 'bind-value:event', 'bind:format' etc.
2>C:\dir\aspnetcore\src\Components\test\testassets\BasicTestApp\BindCasesComponent.razor(283,14378,283,14419): error RZ9991: The attribute names could not be inferred from bind attribute 'bind-value'. Bind attributes should be of the form 'bind' or 'bind-value' along with their corresponding optional parameters like 'bind-value:event', 'bind:format' etc.
2>C:\dir\aspnetcore\src\Components\test\testassets\BasicTestApp\BindCasesComponent.razor(297,15089,297,15122): error RZ9991: The attribute names could not be inferred from bind attribute 'bind-value'. Bind attributes should be of the form 'bind' or 'bind-value' along with their corresponding optional parameters like 'bind-value:event', 'bind:format' etc.
2>C:\dir\aspnetcore\src\Components\test\testassets\BasicTestApp\BindCasesComponent.razor(311,15740,311,15772): error RZ9991: The attribute names could not be inferred from bind attribute 'bind-value'. Bind attributes should be of the form 'bind' or 'bind-value' along with their corresponding optional parameters like 'bind-value:event', 'bind:format' etc.
2>C:\dir\aspnetcore\src\Components\test\testassets\BasicTestApp\BindCasesComponent.razor(325,16455,325,16491): error RZ9991: The attribute names could not be inferred from bind attribute 'bind-value'. Bind attributes should be of the form 'bind' or 'bind-value' along with their corresponding optional parameters like 'bind-value:event', 'bind:format' etc.
2>C:\dir\aspnetcore\src\Components\test\testassets\BasicTestApp\SignalRClientComponent.razor(31,31,31,44): error CS0649: Field 'SignalRClientComponent.transportType' is never assigned to, and will always have its default value
2>C:\dir\aspnetcore\src\Components\test\testassets\BasicTestApp\MultipleChildContent.razor(24,10,24,20): error CS0649: Field 'MultipleChildContent.ShowFooter' is never assigned to, and will always have its default value false
2>C:\dir\aspnetcore\src\Components\test\testassets\BasicTestApp\EventCustomArgsComponent.razor(80,10,80,38): error CS0649: Field 'EventCustomArgsComponent.customKeyDownStopPropagation' is never assigned to, and will always have its default value false
2>C:\dir\aspnetcore\src\Components\test\testassets\BasicTestApp\EventBubblingComponent.razor(81,10,81,31): error CS0649: Field 'EventBubblingComponent.targetStopPropagation' is never assigned to, and will always have its default value false
2>C:\dir\aspnetcore\src\Components\test\testassets\BasicTestApp\EventBubblingComponent.razor(83,10,83,26): error CS0649: Field 'EventBubblingComponent.preventOnKeyDown' is never assigned to, and will always have its default value false
2>C:\dir\aspnetcore\src\Components\test\testassets\BasicTestApp\HttpClientTest\CookieCounterComponent.razor(19,12,19,29): error CS0649: Field 'CookieCounterComponent.testServerBaseUrl' is never assigned to, and will always have its default value null
2>C:\dir\aspnetcore\src\Components\test\testassets\BasicTestApp\EventBubblingComponent.razor(80,10,80,37): error CS0649: Field 'EventBubblingComponent.intermediateStopPropagation' is never assigned to, and will always have its default value false
2>C:\dir\aspnetcore\src\Components\test\testassets\BasicTestApp\EventBubblingComponent.razor(82,10,82,32): error CS0649: Field 'EventBubblingComponent.ancestorPreventDefault' is never assigned to, and will always have its default value false
2>C:\dir\aspnetcore\src\Components\test\testassets\BasicTestApp\CascadingValueTest\CascadingValueSupplier.razor(26,10,26,27): error CS0649: Field 'CascadingValueSupplier.currentFlagValue2' is never assigned to, and will always have its default value false
2>C:\dir\aspnetcore\src\Components\test\testassets\BasicTestApp\RouterTest\PreventDefaultCases.razor(36,10,36,30): error CS0649: Field 'PreventDefaultCases.targetPreventDefault' is never assigned to, and will always have its default value false
2>C:\dir\aspnetcore\src\Components\test\testassets\BasicTestApp\CascadingValueTest\CascadingValueSupplier.razor(25,10,25,27): error CS0649: Field 'CascadingValueSupplier.currentFlagValue1' is never assigned to, and will always have its default value false
2>C:\dir\aspnetcore\src\Components\test\testassets\BasicTestApp\RouterTest\PreventDefaultCases.razor(37,10,37,34): error CS0649: Field 'PreventDefaultCases.descendantPreventDefault' is never assigned to, and will always have its default value false
2>C:\dir\aspnetcore\src\Components\test\testassets\BasicTestApp\DynamicComponentRendering.razor(31,20,31,35): error CS0649: Field 'DynamicComponentRendering.currentCaseName' is never assigned to, and will always have its default value null
2>C:\dir\aspnetcore\src\Components\test\testassets\BasicTestApp\SignalRClientComponent.razor(30,20,30,26): error CS0649: Field 'SignalRClientComponent.hubUrl' is never assigned to, and will always have its default value null
2>C:\dir\aspnetcore\src\Components\test\testassets\BasicTestApp\EventCustomArgsComponent.razor(79,10,79,37): error CS0649: Field 'EventCustomArgsComponent.customKeyDownPreventDefault' is never assigned to, and will always have its default value false
2>C:\dir\aspnetcore\src\Components\test\testassets\BasicTestApp\RouterTest\PreventDefaultCases.razor(35,10,35,32): error CS0649: Field 'PreventDefaultCases.ancestorPreventDefault' is never assigned to, and will always have its default value false
2>Done building project "BasicTestApp.csproj" -- FAILED.
========== Build: 1 succeeded, 1 failed, 6 up-to-date, 0 skipped ==========

This happens in other sample projects too if I add a [Parameter] property.

I'm unsure why this would only affect building inside VS and not the command line. Might it be something to do with source generator changes? I tried the following VS versions:

• 16.10.0 Preview 1.0
• 16.10.0 Preview 2.0 [31117.304.main]

... with the same results on both.

[SteveSandersonMS]

cc @pranavkm and @captainsafia for opinions on whether this might be related to source generator work, or @NTaylorMullen in case this is a known issue in the VS Razor tooling

[SteveSandersonMS]

Update It's not only on VS. It happens in command line builds too, but only sometimes! What I'm getting at the moment is:

• When running build.cmd from src\Components, it's all OK
• When running dotnet build inside a specific sample project on the command line (e.g., BasicTestApp), it sometimes succeeds and sometimes fails with the errors above. It's not purely random, since if you immediately re-run dotnet build then whatever it did last time it will do again this time, but I'm not sure what causes it to transition between the "works" and "doesn't work" states.

[captainsafia]

@SteveSandersonMS It looks like you might've run into #30720.

I'd marked that as investigate until I could get a reliable repro out of it, but it looks like it's reproing reliably now for you.

Can you share the SDK version you're on? The delta between the version I last tried to repro on and the current one might have made the repro more reliable.

Edit: Nevermind. Just saw that you're doing this on the aspnetcore repo so I can pull out the SDK version.

[pranavkm]

Dupe of #30720. I think it's got something to do with the compiler that gets used. Killing the compiler seems to fix it at times, but don't quote me on it.

[SteveSandersonMS]

Can you share the SDK version you're on? The delta between the version I last tried to repro on and the current one might have made the repro more reliable.
Edit: Nevermind. Just saw that you're doing this on the aspnetcore repo so I can pull out the SDK version.

Yeah, it's currently 6.0.100-preview.3.21160.5 for me.

[SteveSandersonMS]

Dupe of #30720

Ah, thanks! I did search for an existing issue but none came up. Perhaps... because... in #30720, somebody put the error message in a screenshot instead of pasting the text 😆

Thanks for contacting us.
We're moving this issue to the Next sprint planning milestone for future evaluation / consideration. We will evaluate the request when we are planning the work for the next milestone. To learn more about what to expect next and how this issue will be handled you can read more about our triage process here.

[SteveSandersonMS]

A further data point. I got into this state again just now, this time on the command line. I tried following @pranavkm's suggestion to kill all running .NET Core processes on the machine (including by closing all VS + VS Code instances, and terminating related processes like rzls). However, the errors still happened. It was only after I killed all the .NET processes and removed the bin/obj directories from artifacts that the problem went away. So maybe there's some aspect of this where the bad state is held in files on disk.