Re: [Caml-list] Test coverage of generated lexers/parsers

[Anton Bachin <antonbachin@yahoo.com>]

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If there is a good, general, alternative approach for this, we can support it in Bisect_ppx. Unfortunately, I don’t know enough about Menhir to be able to propose anything specific at this point.

Best,
Anton

> On Mar 6, 2016, at 16:53, Gabriel Scherer <gabriel.scherer@gmail.com> wrote:
> 
> This is an interesting question and, as far as I know, there is no good solution using existing versions of the interacting tools.
> 
> Below very simple patch that will add (*BISECT-IGNORE*) in front of every line of code generated by Menhir, except those written by the programmer (the "strecthes" in Menhir-speak). It applies cleanly on top of the latest released Menhir archive,
>   http://gallium.inria.fr/~fpottier/menhir/menhir-20160303.tar.gz <http://gallium.inria.fr/~fpottier/menhir/menhir-20160303.tar.gz>
> 
> The patch as-is is obviously a hack: it would need to be a configuration option when running menhir, and hard-coding Bisect (or bisect_ppx)'s syntax into Menhir is not elegant. One could try to have a configuration option to let users write a fixed string (or comment) at the beginning of each generated code line, but I'm not sure whether François Pottier (in cc:) would consider this is elegant enough. François, would you comment on whether this is a direction that seems acceptable to you?
> 
> (Bisect support ignoring entire regions at once by using (*BISECT-IGNORE-BEGIN*) and (*BISECT-IGNORE-END*); we could try to implement that instead of a per-line change, but I suspect that it would be slightly harder to implement (you have to hook the beginning of input, end of input, and around each user-code insertion) for no real gain.)
> 
> Toggling code-coverage semantics by inserting comments is not a very nice interface (although rather logical when you think of the level of generality required), so it's a bit frustrating that parser generators would have to play at this level. It would be better to have a more structured, unified interface supported by all the code-coverage tools, but to my knowledge no such thing exists.
> 
> 
> From d595ba5149a314c56623e1735af7678f5f62d525 Mon Sep 17 00:00:00 2001
> From: Gabriel Scherer <gabriel.scherer@gmail.com <mailto:gabriel.scherer@gmail.com>>
> Date: Sun, 6 Mar 2016 17:43:14 -0500
> Subject: [PATCH] output (*BISECT-IGNORE*) in front of each
>  non-programmer-written line
> 
> EXPERIMENTAL PATCH: this should of course be turned into an explicit option
> ---
>  src/printer.ml <http://printer.ml/> | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/src/printer.ml <http://printer.ml/> b/src/printer.ml <http://printer.ml/>
> index ea978bc..714bb08 100644
> --- a/src/printer.ml <http://printer.ml/>
> +++ b/src/printer.ml <http://printer.ml/>
> @@ -46,6 +46,7 @@ let rawnl f =
>  
>  let nl f =
>    rawnl f;
> +  output_string f "(*BISECT-IGNORE*)";
>    output_substring f whitespace 0 !indentation
>  
>  let indent ofs producer f x =
> -- 
> 2.5.0
> 
> 
> 
> On Sun, Mar 6, 2016 at 2:53 PM, Vincent Jacques <vincent@vincent-jacques.net <mailto:vincent@vincent-jacques.net>> wrote:
> Hello,
> 
> Does somebody have experience measuring test coverage of generated lexers/parsers?
> 
> I'm using ocamllex/ocamlyacc [1] (but I can switch to Menhir [2]) to generate a lexer/parser. In my tests, I simply check that some input strings give the ASTs I expect.
> 
> I usually use Bisect [3] to make sure that my tests cover the code I intended to cover, but in that configuration, Bisect is lost between the .mll/.mly files and the generated .ml files and produces useless reports.
> 
> How would you measure test coverage in that case?
> 
> Thanks,
> 
> [1] http://caml.inria.fr/pub/docs/manual-ocaml/lexyacc.html <http://caml.inria.fr/pub/docs/manual-ocaml/lexyacc.html>
> [2] http://gallium.inria.fr/~fpottier/menhir/ <http://gallium.inria.fr/~fpottier/menhir/>
> [3] http://bisect.x9c.fr/ <http://bisect.x9c.fr/>
> -- 
> Vincent Jacques
> http://vincent-jacques.net <http://vincent-jacques.net/>
> 
> "S'il n'y a pas de solution, c'est qu'il n'y a pas de problème"
>             Devise Shadock
> 
> <0001-output-BISECT-IGNORE-in-front-of-each-non-programmer.patch>


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