Support parsing cargo metadata by string(JSON ...) for cmake >= 3.19

[crabtw]

New feature for #70

[jschwe]

First of all thanks for this PR! I have only skimmed the PR and will have a closer look and test it tomorrow, but I have left some comments already.

[jschwe]

I don't think generating CMake code with file(APPEND ${out_file} is actually necessary for the new CorrosionGenerator, since it is just included later anyway.
Unless I'm missing something, I would ask you to just write the code normally there, instead of writing to a file and then including it. This was necessary for the generator written in rust, but can be avoided here.

Also, I merged #130. so it would be great if you could also add the PROFILE option to the new CorrosionGenerator.

[crabtw]

I don't think generating CMake code with file(APPEND ${out_file} is actually necessary for the new CorrosionGenerator, since it is just included later anyway. Unless I'm missing something, I would ask you to just write the code normally there, instead of writing to a file and then including it. This was necessary for the generator written in rust, but can be avoided here.

Also, I merged #130. so it would be great if you could also add the PROFILE option to the new CorrosionGenerator.

Done, thanks.

[jschwe]

Thanks for the changes! I've had time for a more thorough look now and I think it looks fine.
I left some more minor comments.

Also I would prefer if you would rename CORROSION_PARSE_METADATA_BY_CMAKE to CORROSION_EXPERIMENTAL_PARSER and add the option to the README.md under Usage->Options->Advanced explaining what the option does.

I tested the new generator with our project at work and it doesn't seem to break anything for us, so I'm fine with approving this MR. @ogoffart Do you want to do a second review?

[crabtw]

@jschwe Done, thanks!

[housel]

This commit seems to break the PROPERTY CORROSION_ENVIRONMENT_VARIABLES feature for me on CMake 3.22

[jschwe]

Hi @housel, thanks for the report! Could you open an issue describing in a bit more detail what problem you are facing?
For me CORROSION_ENVIRONMENT_VARIABLES appear to work on CMake 3.22, and we also have the envvar test, which is passing.