Re: [Caml-list] Go Oracle like facility for Ocaml?

[Gabriel Scherer <gabriel.scherer@gmail.com>]

(One can find a description of Go oracle's design in
  https://docs.google.com/document/d/1WmMHBUjQiuy15JfEnT8YBROQmEv-7K6bV-Y_K53oi5Y/view
and its user manual in
  https://docs.google.com/document/d/1SLk36YRjjMgKqe490mSRzOPYEDe0Y_WQNRv-EiFYUyw/view#heading=h.kthq8ap0mdwi
)

The ecosystem of OCaml tooling is not as refined as Go's (but
contributions are welcome). There is no centralized tool provider with
a common interface, but several contributors have developped separate
tool to anayze different aspects of OCaml programs:

- ocamlspotter: https://bitbucket.org/camlspotter/ocamlspot
- ocp-index: http://typerex.ocamlpro.com/ocp-index.html
- pfff: https://github.com/facebook/pfff
- merlin: http://the-lambda-church.github.io/merlin/

These tool provide a relatively complete coverage of the information
that can easily be retrieved from the typedtree of a program (>=4.01
versions of the OCaml compiler have the option to generate a reified
typedtree for external tools): the occurences of a declared/defined
name, the definition place of a name, the type of an expression, etc.
As far as I'm aware, there is not much in the direction of the more
advanced static analysis feature Go's oracle supports: points-to
information, "who may update this mutable field", etc. I'm not
familiar with Pfff's capabilities, it may be the more advanced in this
regard.

(There is also more experimental work going on, for example Thomas
Blanc's work on static analysis of exception flow at OCamlPro:
https://github.com/OCamlPro/socaml-analyzer )

I think merlin is the best-positioned tool to deal with
partially-incorrect files (typical of an edition session) and
incrementality. It also incorporates some query/analysis feature, but
it's unclear whether those should grow inside a monolithic tool (eg.
it could encompass the current feature set of ocp-index and
ocamlspotter, if it does not already), or rather try to communicate
with external analysis/query plugins. It also interacts with existing
editors through a reasonable query-answer interface, but does not
provide a direct command-line interface (anyone interested in this
could work on it, it may be relatively easy to implement).

There are fairly orthogonal aspects to a "answering questions about
programs" toolbox, among which:
1) user-interface, interactive use, and interface with existing editors
2) support for incrementality and robustness under partially-incorrect files
3) knowledge of what the "project", or whole program, is; which
dependencies are required to understand the work? (build system
knowledge)
4) implementation of various program analyses and transformations

Is it possible to provide them in separate programs and have them
interact to form a useful whole? Or would it be easier, faster and
more robust to implement them all in a monolithic program? What are
the necessary interdependence between these aspects and what interface
should them provide to each other?

On Tue, Nov 18, 2014 at 6:00 AM, Kenneth Adam Miller
<kennethadammiller@gmail.com> wrote:
> If anybody knows what Go's oracle is you'll know that its a great
> accelerator for your time; it allows expressive and meaningful searches to
> be done over a source repository. It's fast and dead useful. Opengrok is
> much the same, but to a lesser extent (having links is nice, but not quite
> as powerful as oracle, I could be wrong).
>
> Is there anything like this for OCaml?