Client generation

[colonelpanic8]

This builds on #12 with support for client generation

Fixes #3, #14

[colonelpanic8]

hlint error is due to ndmitchell/hlint#332

[colonelpanic8]

Here is a diff that excludes the changes from #12

https://github.com/rblaze/haskell-dbus/pull/15/files/fd544aaddce4cccd1e183575ed5f069ac544204b..6eeecf73a88aa580c91d10c6674539a87a1ad361

[rblaze]

Ivan, first, thanks again for your contribution! But I feel we need to get a bit more organized here: with 40 commits this becomes longest email thread in my inbox this year. And it is quite hard to review, I don't even know when to start.

Could you please make all the intermediate changes in the forked repo, squash changes and send one-diff pull requests, self-contained and ready to merge? It would also help a lot if each pull request will have complete, but relatively small scope: it is much easier to review three 50-line diffs than one 150-line.

By the way, feel free to drop support for ghc versions before 7.10.3, just remove them from travis config.

[colonelpanic8]

Could you please make all the intermediate changes in the forked repo, squash changes and send one-diff pull requests, self-contained and ready to merge? It would also help a lot if each pull request will have complete, but relatively small scope: it is much easier to review three 50-line diffs than one 150-line.

I can squash the commits, but this change depends on the new properties functions in #12 so its scope really can't be made much smaller, unfortunately.

The diff from the tip of #12 (This is what the diff would look like if #12 were merged) is actually not SO bad:
https://github.com/rblaze/haskell-dbus/pull/15/files/5d8e670161cbdb943242313ddd7a41d87a795888..74d94a000937da3d9960c0e2bdbe3ded956ec39c

You'll notice that almost all of the diff is the addition of a new file: lib/DBus/Generation.hs, and that there are actually only 3 lines that are deleted (changed) which should make this change very safe.

Basically, what this change does is add facilities to generate clients and signal/emission/registration functions. I would recommend that you not even try to review lib/DBus/Generation.hs, as reading template haskell code can be very difficult. I did add a test in tests/DBusTests/Client.hs that should give you some confidence that the code actually works. The new files tests/DBusTests/Generation.hs and tests/DBusTests/TH.hs are simply to support that test. They have to be in separate files becuase of annoying limitations of template haskell.

You may also want to check out
https://github.com/IvanMalison/status-notifier-item which is using all of the new generations facilities quite a lot.

In https://github.com/IvanMalison/status-notifier-item/blob/master/src/StatusNotifier/Item/Constants.hs we load an xml file from which bindings for the client are created in
https://github.com/IvanMalison/status-notifier-item/blob/master/src/StatusNotifier/Item/Client.hs

I've included gists of the output that is produced by the generations calls here. Looking at these might help give you a sense of what generation is doing.

Client: https://gist.github.com/2df87d651b3f78da87e3198b457054fc
Signals: https://gist.github.com/a49868a2eff677ac42b3751a4098a7c2
(Tip: The raw versions are easier to read)

[colonelpanic8]

Also, if it would be helpful, I would be happy to get on a skype call or something like that to walk you through the changes.

[colonelpanic8]

@rblaze This should be a bit easier to review now that #12 is merged :)

The template haskell parts are all completely new, so shouldn't affect any existing stuff anyway.

[colonelpanic8]

@rblaze Is there anything I can do to help out here? I'd really like to get this merged so that I can make new releases of several projects.

[rblaze]

Looks good, but I have a few style issues.

[rblaze]

/home/travis/build/rblaze/haskell-dbus/lib/DBus/Generation.hs:96:3: warning: [-Wmissing-fields]
• Fields of ‘GenerationParams’ not initialised: useDBusR
• In the expression:
GenerationParams
{genBusName = Nothing, genInterfaceName = fromString "",
getTHType = defaultGetTHType, genObjectPath = Nothing,
genTakeSignalErrorHandler = False}

[rblaze]

There are multiple warnings like this:
This pattern-binding binds no variables:
$(varP methodCallN) = $setMethodCallParamsE

I'm not familiar with template haskell, is this compiler misunderstanding something or a genuine issue?

[colonelpanic8]

Yes, this is a known issue. See this thread https://mail.haskell.org/pipermail/haskell-cafe/2014-December/117437.html

[rblaze]

The qualified import of ‘DBus.Introspection’ is redundant
  except perhaps to import instances from ‘DBus.Introspection’
To import instances alone, use: import DBus.Introspection()

[rblaze]

Looks like generated code isn't very clean:
Top-level binding with no type signature: signalForPropertiesChanged :: DBus.Internal.Message.Signal
Top-level binding with no type signature: methodCallForInterfaces :: DBus.Internal.Message.MethodCall
Defined but not used: ‘replySuccess’
etc...

Can you make sure it compiles without warnings? It is very annoying when library adds a lot of warning noise.

[colonelpanic8]

I got rid of all of these except for the replySuccess not being used. That one only comes up when there are no return values for a method. Getting rid of it would require a lot more code.

[rblaze]

Can't we use Reader from transformers? Using mtl and transformers in the same library looks counterintuitive.

[colonelpanic8]

yep. good catch.

[colonelpanic8]

Not sure why the build errored.

If you take a look at the output of the build here:

https://travis-ci.org/rblaze/haskell-dbus/jobs/357683407

the only thing there is the no bindings for pattern and the (existing) orphan instance issues.

[rblaze]

It timed out. It happens sometimes, restarting build helps usually (you need to login to travis with github account for this). I'll do it now.

[rblaze]

I'm looking into changing library license from GPL to Apache, to make it easier to use in non-GPL projects. Are you okay with releasing your changes under Apache license?

[colonelpanic8]

sure