Re: [Caml-list] [ANN] Beta-release of Merlin

[Simon Cruanes <simon.cruanes.2007@m4x.org>]

I started using Merlin a few days ago, on vim, and I must say it's a
pleasure to have direct access to completion/type checking/type
querying. Per-project configuration is really simple (just define a list
of source directories, build directories, and ocamlfind-able packages);
then completion and type-checking work seamlessly even with external
code. Maybe that's no big deal for emacs users, but on vim I think this
is quite a big improvement.

It's already very useful for me, so I'd like to thank the authors :)

Cheers,

Simon

On 02/21/2013 10:20 AM, Gabriel Scherer wrote:
> I looked into Merlin in the last few days, so here is a bit more
> information if you, like me, are interested in design information about
> projects before deciding whether to use (and potentially contribute to)
> them.
> 
> Interface-wise: using Merlin (at least on emacs) feels a lot like
> ProofGeneral (or CoqIde): there is a "checked zone" from the start of
> the buffer to the first error, and reliable type information is
> available in all this checked zone. The interface is rather simple and
> easy to use.
> 
> (If you're considering porting Merlin to another editor: merlin is an
> OCaml program that inputs and outputs JSON queries, so it seems rather
> easy to port to any editor having plugin support in any language with
> JSON support. Given its youth, you should however expect Merlin's
> protocol to evolve over the next development period, so editor plugin
> developers would need to follow Merlin's internal changes for now.)
> 
> The major difference between Merlin and -annot-based tools such as
> Ocamlspotter or Typerex2 is that Merlin does the work of parsing OCaml
> sentences into chunks and sending them incrementally to the
> type-checker, instead of sending the whole buffer at once and using the
> output. This means that Merlin is much more robust with respect to files
> that have errors and cannot be compiled as a whole: you'll get reliable
> type information from the start of the file upto the first error (and
> some resilience heuristic to have more after). The OCaml type-checker is
> in fact able to provide some typing information even for incorrect
> programs, so -annot-based tools do support some of those features, but
> in a less reliable and more coarse-grained way.
> The design trade-off is that Merlin has to copy/adapt more logic from
> the compiler: it embeds an OCaml parser derived from the compiler's one
> (you won't get parsing bugs as with regexpy elisp modes), and currently
> also copies and slightly modifies the type-checker (I hope this can be
> changed in the future, possibly by adding some flexibility to the
> type-checker regarding eg. production of warnings). This means more
> maintenance work to port Merlin to future OCaml versions. On the other
> hand, it's probably not reasonable to expect the compiler type-checker
> to be re-engineered for optimal incrementality support, so having an
> external implementation of incrementality that piggybacks on the batch
> typer interface makes sense.
> 
> My personal intuition is that Merlin's design is a good long-term choice
> for an editor service (as opposed to code-analysis services). You want
> tools such as ocamldoc, dead code analysis, or everything concerned with
> analysis of an existing correct codebase to be based on -bin-annot and
> work on the typedtrees directly (without local support for parsing and
> typing programs). You want tools designed to work on incomplete programs
> in the process of being created to embed incrementality logic (insofar
> as it hasn't been pushed into the compiler), understanding partial files
> and local modifications to cleverly control the parsing&typing process
> with reactivity in mind. The One True Editor Mode will merge both
> aspects, working on .cmt of already-compiled dependencies on one side,
> and partial/incremental information in edition buffers on the other.
> Merlin can evolve in this way, as its type-directed analyses (those
> performed in the "checked zone") work directly on the typedtree, so
> could work with .cmt files.
> 
> On Thu, Feb 21, 2013 at 12:10 AM, Frédéric Bour
> <frederic.bour@lakaban.net <mailto:frederic.bour@lakaban.net>> wrote:
> 
>     We are very pleased to announce the beta release of Merlin. Merlin
>     is a tool
>     which provides smart completion, among other things, in your
>     favorite editor.
>     As of today, Vim and Emacs are supported.
> 
>     See it at work:
>     https://github.com/def-lkb/__merlin#screenshots
>     <https://github.com/def-lkb/merlin#screenshots>
> 
>     Its features include:
>     - completion of values, constructorsand modules based on local scope
>     - retrieving type of identifiers and/or expressions under cursor
>     - integration of findlib to manage buildpath
>     - highlighting of syntax errors, type errors and warnings inside the
>     editor
>     - to a certain amount, resilience to syntax and type errors
> 
>     It works only with Ocaml 4.00.1 (may works with newer versions).
> 
>     If you happen to have an opam installation with the right version
>     (opam switch 4.00.1), you can try it right away with:
> 
>     $ opam remote add kiwi http://kiwi.iuwt.fr/~asmanur/__opam/.git
>     <http://kiwi.iuwt.fr/~asmanur/opam/.git>
>     <http://kiwi.iuwt.fr/%__7Easmanur/opam/.git
>     <http://kiwi.iuwt.fr/%7Easmanur/opam/.git>>
>     $ opam install merlin
> 
>     Then to get started and set-up your editor:
>     - https://github.com/def-lkb/__merlin#setting-up-vim
>     <https://github.com/def-lkb/merlin#setting-up-vim>
>     - https://github.com/def-lkb/__merlin#emacs-interface
>     <https://github.com/def-lkb/merlin#emacs-interface>
> 
>     Check it out at: https://github.com/def-lkb/__merlin
>     <https://github.com/def-lkb/merlin>
> 
>     The current version still needs to be tested under various systems and
>     configurations, your feedback iswelcome.
> 
> 
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