Completion improvements

dbuenzli commented 5 years ago

As mentioned in the manual completion support is rather crude at the moment.

Here are a few directions that could be taken:

Patch #directory directives via Topdirs to collect which directories are included and pass corresponding -I arguments to ocp-index. This doesn't however allow us to determine which modules are opened and we miss those -I option that may have been specified on the ocaml invocation. Best for this would be to solve point 2. in this issue upstream as this would have benefits for other projects aswell (ocamlfind, utop, omod).
Along with working on the various points in https://github.com/ocaml/ocaml/issues/7589, try to convince merlin authors to provide support for toplevel sessions via the cli. @pqwy mentioned almost getting to something with ocamlmerlin single complete-prefix, but that "it falls short because it heavily assumes you are editing a file in a project".

In general it seems better to isolate completion via the cli and try to improve the Toploop API so that compiler-libs is not needed (also using compiler-libs in ocamlnat is a no-go). This allows down to work for the rest (readline, history, sessions) even though the underlying completion engine may not have been updated for the latest version of the compiler.

ghost commented 5 years ago

I was thinking as well that it would be nice to use merlin in utop for completion. I remember talking briefly about it with @let-def once. IIRC, we concluded that there was no fundamental blocker.

nojb commented 4 months ago

This is somewhat orthogonal to the ideas in this issue, but I recently played with reimplementing completion using compiler-libs: https://github.com/nojb/down/commit/4c7d77fca535c0e7013d846dd0dd26ecfd84f101 (it is a proof of concept, so not complete and a little rough around the edges).

Upsides:

No dependency on any other tool
Faster than invoking an external tool
Makes use of the current environment (opens, local variables, etc)

Downsides:

Depends on compiler-libs (=> one need to build a non-expunged toplevel) (*)
For documentation, either the .cmis need to have been produced with -keep-docs or one needs to use .cmt files (not done in the proof of concept)

(*) is probably a blocker for an external project such as this, but it would disappear if this code was ever upstreamed into OCaml itself :)

Cheers!

dbuenzli commented 4 months ago

Depends on compiler-libs (=> one need to build a non-expunged toplevel) (*)

I would love for the expunge process to go. I can appreciate and understand its idea but since we need to improve ocaml outside of the system it has rather lead to code I would have liked not to have written. However as I noted there it's not necessarily about compiler libs but providing the right bits in Toploop.

The other problem is that AFAIR loading compiler-libs in ocamlnat is a no-go. Not sure if something has changed on that front since them.

dbuenzli commented 4 months ago

A propos @nojb if these things are in the ocaml executable anyways it may be possible to expose bits from upstream in the Toploop API. Even if not used by ocaml itself, this can be benificial for other contexts (e.g. js_of_ocaml topevels).

dbuenzli commented 4 months ago

The other problem is that AFAIR loading compiler-libs in ocamlnat is a no-go. Not sure if something has changed on that front since them.

But it seems ocamlnat is not expunged:

> ocamlnat
OCaml version 4.14.2 - native toplevel
Enter #help;; for help.

Down v0.3.0-7-ge3a4f38 loaded. Type Down.help () for more info.
Omod v0.0.4-3-gb0d2684 loaded. Type Omod.help () for more info.
# Config.version;;
- : string = "4.14.2"

dbuenzli / down

Completion improvements #11