tarpaulin causes constant rebuilds

[vmiklos]

Hi,

First, thanks a lot for making tarpaulin. I was scared that the only decent way to get rust code coverage is via some nightly-only flag and then found this project. :-)

The issue I ran into is: it seems tarpaulin somehow causes unexpected rebuilds. My workflow is that I change the code, then cargo build, some manual testing then cargo tarpaulin --out Lcov to run the tests + check coverage. Here are the times I get for a small project:

• cargo build: 47,308s, then 0,203s
• cargo tarpaulin --out Lcov: 55,252s, then 3,771s

Is this a usage error on my end? Why does building causes a complete tarpaulin rebuild and vice versa?

My hope would be that once I ran both build and tarpaulin, re-running both of them after a tiny code change would not cause a rebuild of dependencies, etc.

Any ideas?

Thanks,

Miklos

[xd009642]

So currently on the latest alpha it was found that there are incremental compilation issues with -Clink-dead-code is used meaning that without a clean incremental compilation could cause cargo to hang when building the tests. With 0.16.0 which is the last stable release it had to change the relocation model when linking which I believe internally to the rust compiler also causes a rebuild.

Some people tackle this by having a separate target directory for tarpaulin built binaries and using the --target-dir flag. And then if on the latest alpha you can use --skip-clean to then disable the clean.

[vmiklos]

Aha, adding --target-dir $PWD/target-cov to my cargo tarpaulin invocation fixes the problem. Thanks! :-)