#line annotations no longer generated with relative paths with dotnet-t4

[mwadams]

In our JSON Schema code generation project, we use T4 to generate code at build time.

There is a fair bit of code to generate, and we do this "one time" and commit the results to our repo, rather than running the template generation with every build, and check in the product.

We are currently running T4 text template processor version 2.3.1+932110915c from an orchestrating batch file which looks like this:

REM Runs all the template build commands
cd Corvus.Json.CodeGeneration.6\Corvus.Json.CodeGeneration.Draft6
start cmd.exe /C BuildTemplates.cmd
cd ..\..\Corvus.Json.CodeGeneration.7\Corvus.Json.CodeGeneration.Draft7
start cmd.exe /C BuildTemplates.cmd
cd ..\..\Corvus.Json.CodeGeneration.201909\Corvus.Json.CodeGeneration.Draft201909
start cmd.exe /C BuildTemplates.cmd
cd ..\..\Corvus.Json.CodeGeneration.202012\Corvus.Json.CodeGeneration.Draft202012
start cmd.exe /C BuildTemplates.cmd
cd ..\..\Corvus.Json.ExtendedTypes\Corvus.Json
start cmd.exe /C BuildTemplates.cmd
cd ..\..

The individual batch files contain a set of commands that look like this:

t4 -o Generators/CodeGenerator.Array.Add.cs -c Corvus.Json.CodeGeneration.Generators.Draft6.CodeGeneratorArrayAdd ../../Corvus.Json.CodeGeneration.Abstractions/SharedTemplates/CodeGenerator.Array.Add.tt

With previous versions of the dotnet-t4 tool (prior to 2.3.0), we used to get relative paths in the #line annotations.

#line 123 "../../Corvus.Json.CodeGeneration.Abstractions/SharedTemplates/CodeGenerator.Array.Add.tt"

But in the 2.3.0 and 2.3.1 versions we see

#line 123 "C:\Users\BLAH\source\repos\Corvus.JsonSchema\Solutions\Corvus.Json.CodeGeneration.Abstractions\SharedTemplates\CodeGenerator.Array.Add.tt"

This is a problem for our scenario because it ties those annotations to the machine on which it was generated [and incidentally generates hundreds of spurious file changes when there are only small numbers of actual changes]

[mwadams]

I can see that this is because there is a new option UseRelativeLinePragmas in Mono.TextTemplating/Mono.TextTemplating/TemplateGenerator.cs

However this defaults to false when the original behaviour was to default to true.

[mwadams]

There doesn't seem to be any way of controlling this from the dotnet-t4 tool.

[mwadams]

A workaround is to install version 2.2.1+650c1854cb explicitly.