GHC API question: resolving dependencies for modules

Hello! I’m trying to use GHC as a library. And my goal is to be able to gather information about where each function or data type came from. I’ve started by simply calling `getNamesInScope` function and observing its result. Here is my code: * Main.hs: https://lpaste.net/9026688686753841152 https://lpaste.net/9026688686753841152 And here is the code for my test modules: * test/X.hs: https://lpaste.net/6844657232357883904 https://lpaste.net/6844657232357883904 * test/Y.hs: https://lpaste.net/8673289058127970304 https://lpaste.net/8673289058127970304 Unfortunately, my implementation doesn't work since I’m not very familiar with GHC API. And I see the following errors after executing my `Main.hs` file (I’m using ghc-8.2.2): * error messages: https://lpaste.net/3316737208131518464 https://lpaste.net/3316737208131518464 Could you please point me to places or parts of GHC API or some documentation about module dependencies and how to make ghc see imports of other modules? I can’t find simple and small enough usage example of this part of the library. Thanks in advance, Dmitrii Kovanikov

This doesn't answer your question directly but if you want to gather
information about a module then using a source plugin would probably
be easier and more robust than using the GHC API.
You need to write a function of type:
```
ModSummary -> TcGblEnv -> TcM TcGblEnv
```
In `TcGblEnv` you will find `tcg_rdr_env` which contains all top-level
things and describes how they came to be in scope.
Source plugins will be in GHC 8.6.
Cheers,
Matt
On Thu, Jun 21, 2018 at 10:06 AM, Dmitriy Kovanikov
Hello!
I’m trying to use GHC as a library. And my goal is to be able to gather information about where each function or data type came from. I’ve started by simply calling `getNamesInScope` function and observing its result. Here is my code:
* Main.hs: https://lpaste.net/9026688686753841152
And here is the code for my test modules:
* test/X.hs: https://lpaste.net/6844657232357883904 * test/Y.hs: https://lpaste.net/8673289058127970304
Unfortunately, my implementation doesn't work since I’m not very familiar with GHC API. And I see the following errors after executing my `Main.hs` file (I’m using ghc-8.2.2):
* error messages: https://lpaste.net/3316737208131518464
Could you please point me to places or parts of GHC API or some documentation about module dependencies and how to make ghc see imports of other modules? I can’t find simple and small enough usage example of this part of the library.
Thanks in advance, Dmitrii Kovanikov
_______________________________________________ ghc-devs mailing list ghc-devs@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs

Thanks a lot for your suggestion! I’ve looked into GHC source plugins. And, specifically, into your `hashtag-coerce` example: * https://github.com/mpickering/hashtag-coerce https://github.com/mpickering/hashtag-coerce As far as I can see, this allows only to analyse source code (to produce warnings or errors). While my actual goal is actually to refactor code automatically. And I would like to avoid full compilation process to make it work faster. Thanks, Dmitrii
On 21 Jun 2018, at 5:51 PM, Matthew Pickering
wrote: This doesn't answer your question directly but if you want to gather information about a module then using a source plugin would probably be easier and more robust than using the GHC API.
You need to write a function of type:
``` ModSummary -> TcGblEnv -> TcM TcGblEnv ```
In `TcGblEnv` you will find `tcg_rdr_env` which contains all top-level things and describes how they came to be in scope.
Source plugins will be in GHC 8.6.
Cheers,
Matt
On Thu, Jun 21, 2018 at 10:06 AM, Dmitriy Kovanikov
wrote: Hello!
I’m trying to use GHC as a library. And my goal is to be able to gather information about where each function or data type came from. I’ve started by simply calling `getNamesInScope` function and observing its result. Here is my code:
* Main.hs: https://lpaste.net/9026688686753841152
And here is the code for my test modules:
* test/X.hs: https://lpaste.net/6844657232357883904 * test/Y.hs: https://lpaste.net/8673289058127970304
Unfortunately, my implementation doesn't work since I’m not very familiar with GHC API. And I see the following errors after executing my `Main.hs` file (I’m using ghc-8.2.2):
* error messages: https://lpaste.net/3316737208131518464
Could you please point me to places or parts of GHC API or some documentation about module dependencies and how to make ghc see imports of other modules? I can’t find simple and small enough usage example of this part of the library.
Thanks in advance, Dmitrii Kovanikov
_______________________________________________ ghc-devs mailing list ghc-devs@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs

Dmitriy Kovanikov
Thanks a lot for your suggestion! I’ve looked into GHC source plugins. And, specifically, into your `hashtag-coerce` example:
* https://github.com/mpickering/hashtag-coerce https://github.com/mpickering/hashtag-coerce
As far as I can see, this allows only to analyse source code (to produce warnings or errors).
It depends upon which type of source plugin you are using. There are a few points in the compilation pipeline that source plugins allow you to plug in to. Some of these allow the plugin to modify the AST while others only allow inspection. See the users guide [1] for details. Cheers, - Ben [1] https://github.com/ghc/ghc/blob/master/docs/users_guide/extending_ghc.rst#so...

I'm sorry of my poor form for not really answering your question here
but it's because no one really knows how to use the GHC API.
If you are stuck on this path then you could look at how GHC uses the
API or an existing user of the API like haddock or haskell-indexer.
However, these solutions are not going to be as robust as using a
plugin and you will end up with writing a lot of code probably in
order to get it to work.
Cheers,
Matt
On Mon, Jun 25, 2018 at 9:34 AM, Dmitriy Kovanikov
Thanks a lot for your suggestion! I’ve looked into GHC source plugins. And, specifically, into your `hashtag-coerce` example:
* https://github.com/mpickering/hashtag-coerce
As far as I can see, this allows only to analyse source code (to produce warnings or errors). While my actual goal is actually to refactor code automatically. And I would like to avoid full compilation process to make it work faster.
Thanks, Dmitrii
On 21 Jun 2018, at 5:51 PM, Matthew Pickering
wrote: This doesn't answer your question directly but if you want to gather information about a module then using a source plugin would probably be easier and more robust than using the GHC API.
You need to write a function of type:
``` ModSummary -> TcGblEnv -> TcM TcGblEnv ```
In `TcGblEnv` you will find `tcg_rdr_env` which contains all top-level things and describes how they came to be in scope.
Source plugins will be in GHC 8.6.
Cheers,
Matt
On Thu, Jun 21, 2018 at 10:06 AM, Dmitriy Kovanikov
wrote: Hello!
I’m trying to use GHC as a library. And my goal is to be able to gather information about where each function or data type came from. I’ve started by simply calling `getNamesInScope` function and observing its result. Here is my code:
* Main.hs: https://lpaste.net/9026688686753841152
And here is the code for my test modules:
* test/X.hs: https://lpaste.net/6844657232357883904 * test/Y.hs: https://lpaste.net/8673289058127970304
Unfortunately, my implementation doesn't work since I’m not very familiar with GHC API. And I see the following errors after executing my `Main.hs` file (I’m using ghc-8.2.2):
* error messages: https://lpaste.net/3316737208131518464
Could you please point me to places or parts of GHC API or some documentation about module dependencies and how to make ghc see imports of other modules? I can’t find simple and small enough usage example of this part of the library.
Thanks in advance, Dmitrii Kovanikov
_______________________________________________ ghc-devs mailing list ghc-devs@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs

| I'm sorry of my poor form for not really answering your question here but
| it's because no one really knows how to use the GHC API.
That may be true, but it's alarming if true.
The GHC API has grown rather than being consciously and carefully designed. It would be Really Good if someone cares about using the API would like to write down the API they'd *like*, and agree it with others. Then we could implement it!
Simon
| -----Original Message-----
| From: ghc-devs
participants (4)
-
Ben Gamari
-
Dmitriy Kovanikov
-
Matthew Pickering
-
Simon Peyton Jones