Artem Pianykh fcce3c0659 [RFC][build] Use dune environments and profiles instead of contexts ... Summary: With profiles and `(env ...)` stanza it's possible to consolidate various ocamlc/ocamlopt/etc setups in a single place. Where previously we needed to append `dune.common` to every dune file and specify `flags` and `ocamlopt_flags` now the flags are specified in `env` and applied accross the board. This allows to 1. simplify build definitions, 2. avoid the need to generate dune files, 3. use plain sexps instead of OCaml and JBuilder plugin in build files. (I'll try to address 2 and 3 in the followup patches). Existing `make` targets should continue working as before. Also, we can use dune CLI like so: ``` infer/src$ dune printenv --profile opt # <- very useful for introspection infer/src$ dune build check infer/src$ dune build check --profile test infer/src$ dune build infer.exe --profile dev infer/src$ dune build infer.exe --profile opt ``` Also, with just 1 context something like `dune runtest` will run unit tests only once instead of N times, where N is the number of contexts. Now, there's one difference compared to the previous setup with contexts: - Previously, each context had its own build folder, and building infer in opt context didn't invalidate any of the build artifacts in default context. Therefore, alternating between `make` and `make opt` had low overhead at the expense of having N copies of all build artifacts (1 for every context). - Now, there's just 1 build folder and switching between profiles does invalidate some artifacts (but not all) and rebuild takes a bit more time. So, if you're alternating like crazy between profiles your experience may get worse (but not necessarily, more on that below). If you want to trigger an opt build occasionally, you shouldn't notice much difference. For those who are concerned about slower build times when alternating between different build profiles, there's a solution: [dune cache](https://dune.readthedocs.io/en/stable/caching.html). You can enable it by creating a file `~/.config/dune/config` with the following contents: ``` (lang dune 2.0) (cache enabled) ``` With cache enabled switching between different build profiles (but also branches and commits) has ~0 overhead. Dune cache works fine on Linux, but unfortunately there are [certain problems with MacOS](https://github.com/ocaml/dune/issues/3233) (hopefully, those will be fixed soon and then there will be no downsides to using profiles compared to contexts for our case). Reviewed By: jvillard Differential Revision: D20247864 fbshipit-source-id: 5f8afa0db		5 years ago
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Dockerfile	[RFC][build] Use dune environments and profiles instead of contexts	5 years ago