Mix should use Checksums for recompilation

[l...@expert360.com]

The default mix compile to determine if something is stale is to use the last-modified time on each file.

https://github.com/elixir-lang/elixir/blob/v1.5.2/lib/mix/lib/mix/utils.ex#L141

A checksum should be used instead to determine if a file has changed rather than the last modified time as I have been experiencing issues which cause everything to be recompiled when the file hasn't changed.

[José Valim]

Can you please provide more information on this scenario? When does it happen? Why does it trigger? How to reproduce it?

Please try to describe the problem as detailed as possible without focusing on a possible solution.

Using checksums makes the cost of noop much higher, since we need to read files and compute MD5s, and that would be harmful to development.

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José Valim

www.plataformatec.com.br

Founder and 

Director of R&D

[l...@expert360.com]

I can't. I'm hoping there is a way to add debug logs for the mix compilation task? Or someway for me to try and get to the bottom of why it thinks it needs to recompile?

[Xavier Noria]

On Thu, 28 Dec 2017 at 00:42, <l...@expert360.com> wrote:

I can't. I'm hoping there is a way to add debug logs for the mix compilation task? Or someway for me to try and get to the bottom of why it thinks it needs to recompile?

Let me just say in case it helps that running a patched Mix or Elixir compiler is very easy: Just checkout the project, add traces, make compile, and use the executables under bin. Those executables use relative paths so they’ll pick your modifications.

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[José Valim]

There is MIX_DEBUG=1 as well as "mix compile --verbose" which will spit more info but it won't say the reason why recompilation was triggered.

José Valim

www.plataformatec.com.br

Founder and 

Director of R&D

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