Explicit DocumentationFile=path instead of GenerateDocumentationFile=true leads to build race

[nguerrera]

Previously, C# projects would set an explicit intermediate path for the documentation file. This leads to using the same intermediate path for different TFMs that are built in parallel. We implemented GenerateDocumentationFile=true, but users porting existing projects might not know about it.

While the fix is simple (use GenerateDocumentationFile), the error is intermittent and doesn't at all hint at the fix: "cannot write to obj\Debug\Something.xml: already in use".

We should detect when the DocumentationFile is going to be written to the intermediate output path minus TFM in a multi-targeted project and issue an error. Alternatively, we could implement a fixup to insert the TFM in to the DocumentationFile path.

See also:

• Fix build parallelism issue with documentation file generation roslyn#22232
• GenerateDocumentationFile=true breaks DebugSymbolsProjectOutputGroup in VB projects #1598

[KalleOlaviNiemitalo]

@vlada-shubina, did you close this by mistake? d8bb6c2 seems to relate to dotnet/templating#1599 and not to this #1599.

[vlada-shubina]

@vlada-shubina, did you close this by mistake? d8bb6c2 seems to relate to dotnet/templating#1599 and not to this #1599.

yes, it was incorrectly closed. I will check what else might be affected shortly