* [Caml-list] Information for writting a ppx
@ 2016-06-17 17:10 Xavier Van de Woestyne
2016-06-20 14:15 ` Anton Bachin
0 siblings, 1 reply; 5+ messages in thread
From: Xavier Van de Woestyne @ 2016-06-17 17:10 UTC (permalink / raw)
To: caml-list
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Hello,
I have writted some ppx extension but I have a question,
Is there a proper way to add a start "file" structure.
I have try using the "structure" member of the mapper :
`
let new_mapper =
Ast_mapper.{
default_mapper with
structure = general_structure
}`
Where general_structure is just a
`my_begining_structure :: List.map (...)` but my begining
structure is repeated into each module. It is logic but I need
to add my own structure only at the begining of my file. In an
other project, I use a mandatory attribute ([@@@active_this_ppx]
for example), but imho, it is not a good approach.
Thanks a lot for your feedback and advices !
Xavier Van de Woestyne
Développeur à Derniercri.io
http://derniercri.io
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^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [Caml-list] Information for writting a ppx
2016-06-17 17:10 [Caml-list] Information for writting a ppx Xavier Van de Woestyne
@ 2016-06-20 14:15 ` Anton Bachin
2016-06-20 15:01 ` Xavier Van de Woestyne
0 siblings, 1 reply; 5+ messages in thread
From: Anton Bachin @ 2016-06-20 14:15 UTC (permalink / raw)
To: Xavier Van de Woestyne; +Cc: caml-list
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Hi Xavier,
Bisect_ppx does this by looking at the location of each module it sees in “structure". The file names are stored in a set. If a file name is not yet in the set, Bisect_ppx assumes that the module is the top-level module of a file. We haven’t had any problems with it.
You can see it here: https://github.com/aantron/bisect_ppx/blob/afa95d9f02ab4c95df3af283641c73ec1dc8cfb1/src/syntax/instrumentPpx.ml#L480 <https://github.com/aantron/bisect_ppx/blob/afa95d9f02ab4c95df3af283641c73ec1dc8cfb1/src/syntax/instrumentPpx.ml#L480>
The code is a bit old, but there it is.
Best,
Anton
> On Jun 17, 2016, at 12:10, Xavier Van de Woestyne <xavier@derniercri.io> wrote:
>
> Hello,
> I have writted some ppx extension but I have a question,
> Is there a proper way to add a start "file" structure.
> I have try using the "structure" member of the mapper :
>
> `
> let new_mapper =
> Ast_mapper.{
> default_mapper with
> structure = general_structure
> }`
>
> Where general_structure is just a
> `my_begining_structure :: List.map (...)` but my begining
> structure is repeated into each module. It is logic but I need
> to add my own structure only at the begining of my file. In an
> other project, I use a mandatory attribute ([@@@active_this_ppx]
> for example), but imho, it is not a good approach.
>
> Thanks a lot for your feedback and advices !
>
> Xavier Van de Woestyne
> Développeur à Derniercri.io
> http://derniercri.io
>
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^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [Caml-list] Information for writting a ppx
2016-06-20 14:15 ` Anton Bachin
@ 2016-06-20 15:01 ` Xavier Van de Woestyne
2016-06-20 15:31 ` Marc Lasson
0 siblings, 1 reply; 5+ messages in thread
From: Xavier Van de Woestyne @ 2016-06-20 15:01 UTC (permalink / raw)
To: Anton Bachin; +Cc: caml-list
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Thanks a lot, Mr Marc L explain me how to do that :
```
(* Mapper for all transformation *)
let general_mapper = Ast_mapper.{ default_mapper with structure = structure }
(* New Mapper only for the toplevel *)
let toplevel_mapper =
Ast_mapper.{
default_mapper with
structure = fun _ str ->
let pl = Ast_helper.Str.eval (Ppx.Fabric.print_endline "Hello World") in
pl :: (general_mapper.structure general_mapper str)
}
```
Xavier Van de Woestyne
http://xvw.github.io
On juin 20 2016, at 4:16 pm, Anton Bachin <antronbachin@gmail.com>
wrote:
> Hi Xavier,
>
>
>
>
> Bisect_ppx does this by looking at the location of each module it sees in
“structure". The file names are stored in a set. If a file name is not yet in
the set, Bisect_ppx assumes that the module is the top-level module of a file.
We haven’t had any problems with it.
>
>
>
>
> You can see it here:
[https://github.com/aantron/bisect_ppx/blob/afa95d9f02ab4c95df3af283641c73ec1dc8cfb1/src/syntax/instrumentPpx.ml#L480](https://github.com/aantron/bisect_ppx/blob/afa95d9f02ab4c95df3af283641c73ec1dc8cfb1/src/syntax/instrumentPpx.ml#L480&r=Y2FtbC1saXN0QGlucmlhLmZy)
>
>
>
>
> The code is a bit old, but there it is.
>
>
>
>
> Best,
>
> Anton
>
>
>
>
>> On Jun 17, 2016, at 12:10, Xavier Van de Woestyne
<[xavier@derniercri.io](mailto:xavier@derniercri.io)> wrote:
>>
>>
>
>>
>> Hello,
>>
>> I have writted some ppx extension but I have a question,
>>
>> Is there a proper way to add a start "file" structure.
>
>>
>> I have try using the "structure" member of the mapper :
>>
>>
>
>>
>> `
>>
>> let new_mapper =
>>
>> Ast_mapper.{
> default_mapper with
> structure = general_structure
> }`
>>
>>
>
>>
>> Where general_structure is just a
>>
>> `my_begining_structure :: List.map (...)` but my begining
>>
>> structure is repeated into each module. It is logic but I need
>>
>> to add my own structure only at the begining of my file. In an
>>
>> other project, I use a mandatory attribute ([@@@active_this_ppx]
>>
>> for example), but imho, it is not a good approach.
>>
>>
>
>>
>> Thanks a lot for your feedback and advices !
>>
>>
>
>>
>> Xavier Van de Woestyne
>>
>> Développeur à Derniercri.io
>>
>> [http://derniercri.io](http://derniercri.io&r=Y2FtbC1saXN0QGlucmlhLmZy)
>>
>> 
>
>
>
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^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [Caml-list] Information for writting a ppx
2016-06-20 15:01 ` Xavier Van de Woestyne
@ 2016-06-20 15:31 ` Marc Lasson
2016-06-20 15:33 ` Xavier Van de Woestyne
0 siblings, 1 reply; 5+ messages in thread
From: Marc Lasson @ 2016-06-20 15:31 UTC (permalink / raw)
To: caml-list
To paraphrase the code, I just advised Xavier to use a mapper that does
recursively not call itself.
> (* Mapper for all transformation *)
> let general_mapper = Ast_mapper.{ default_mapper with structure =
> structure }
>
> (* New Mapper only for the toplevel *)
> let toplevel_mapper =
> Ast_mapper.{
> default_mapper with
> structure = fun _ str ->
> let pl = Ast_helper.Str.eval (Ppx.Fabric.print_endline "Hello
> World") in
> pl :: (general_mapper.structure general_mapper str)
> }
> ```
Note that if you do not plan to extend general_mapper with a mapper that
actually does something you could simply write :
let toplevel_mapper =
Ast_mapper.{
default_mapper with
structure = fun _ str ->
let pl = Ast_helper.Str.eval (Ppx.Fabric.print_endline "Hello
World") in
pl :: str
}
Also, if the ppx is also applied to compile mli interfaces, then this
will be structures occurring within the toplevel signature (eg. in the
payloads of attributes). So to be "safe", you should probably do :
let toplevel_mapper =
Ast_mapper.{
default_mapper with
signature = fun _ -> default_mapper.signature default_mapper;
structure = fun _ str ->
let pl = Ast_helper.Str.eval (Ppx.Fabric.print_endline "Hello
World") in
pl :: str
}
--
Marc.
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2016-06-17 17:10 [Caml-list] Information for writting a ppx Xavier Van de Woestyne
2016-06-20 14:15 ` Anton Bachin
2016-06-20 15:01 ` Xavier Van de Woestyne
2016-06-20 15:31 ` Marc Lasson
2016-06-20 15:33 ` Xavier Van de Woestyne
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