Dune: [RFC] Improving the CLI

[jeremiedimino]

I propose to change the CLI as follow:

• when the first argument starts with a letter, it is always considered as a command name (as now)
• otherwise, the build command is implicitly assumed if at least one ancestor directory contains a dune, dune-project or dune-workspace file

The idea is to allow the user to type simply dune or dune @all rather than dune build or dune build @all. The first rule prevents ambiguities and the condition on the second rule is to make sure that dune doesn't crawl the whole hard drive when called outside a project.

[trefis]

Does that imply that dune --help would show me the manpage of the build command instead of the manpage listing the available commands?

[jeremiedimino]

That's a good point. I don't think it should, it should be the same as the current dune --help. However, we should extend this man page to document the new behaviour.

[ksromanov]

I checked selection of OPAM packages (1472 packages, Github-only), out of them:

1. 126 use _dune_ only
2. 643 use _make_ only
3. 451 use both _make_ and _dune_

Among these 451, default _Makefile_ targets about 445 are various flavors of dune build <args>. Most common are:

• dune build (236)
• dune build @install (74)
• dune build @install --profile=release (16)
• dune build --profile release (10)
• various jbuilder build ... (20, half of which have --dev, half - not).

These are rough numbers, since I discarded about 1/3 of repos (there was 2288 repos in OPAM in total).

[hcarty]

@ksromanov Does dune exec do what you're looking for?

[avsm]

I'm generally in favour of simpler consistency for the CLI, subcommands since higher level tools (e.g. VSCode rules, or Makefiles) invoke dune directly. For them, calling dune build @all isn't a burden at all.

[ksromanov]

@hcarty

@ksromanov Does dune exec do what you're looking for?

Unfortunately it does not :-(. But yes, you are right - I missed exec. Updating comment above. The idea is to reduce command-line boilerplate.

[jeremiedimino]

@ksromanov I feel like we are diverging from the original conversation. Please open a separate ticket to discuss improvements to dune exec.

[Chris00]

If the motivation is to type less, wouldn't a shell completion mode be better?

[jeremiedimino]

That's a fair point. In particular, I wonder how much we would still want the shorter command line if we add shell completion. Linking the ticket for shell completion: #126

[rgrinberg]

I also think that shell completion would be far more effective and that adding any kind of cleverness is gratuitous. If we make a few straight forward improvements to polling mode, that would cut down on the dune invocations by 90% for me. And as Anil said, proper integration would make this even less relevant.