docs: refine the loggert tutorials

[xieyuschen]

Changes

• add a LoggerT monad transformer usage in example
  Previously, the tutorial uses the WithLog env SimpleMsg m => m () function only for usingLoggerT. In my opinion, it's better for the tutorial to state the WithLog env SimpleMsg m => m () and LoggerT SimpleMsg m () is equivalent.
  Hence, I refined this tutorial.
• update the docs to run the tutorial as the cabal file requires a new flag

Note

• the LoggerT example cannot print the location correctly. I guess it's normal as inside co-log does additional work for it. I haven't checked further so please correct me if i'm wrong and I will fix the example as well.

Regards

[alaendle]

Hello @xieyuschen, thanks for your contribution and please excuse the late reply. To be honest I'm not really sure if this improves the documentation around LoggerT - on the one hand, yes, it really tries to build up examples around the transformer; on the other hand, no, it complicates things for newcomer and might be confusing. Unfortunately I still haven't found time to take a deeper look; but I also don't want to delay a reaction further - so please take this as some kind of interim feedback. Regarding the missing location - WithLog enforces HasCallStack - just add HasCallStack as an additional constraint and the location of the log statement should get visible.

[alaendle]

@xieyuschen - one again, thanks for your contribution - I've changed a few small things - if you still like it, I think we should merge it 👍 otherwise feel free to further improve this PR 😉

[xieyuschen]

Hello @xieyuschen, thanks for your contribution and please excuse the late reply. To be honest I'm not really sure if this improves the documentation around LoggerT - on the one hand, yes, it really tries to build up examples around the transformer; on the other hand, no, it complicates things for newcomer and might be confusing. Unfortunately I still haven't found time to take a deeper look; but I also don't want to delay a reaction further - so please take this as some kind of interim feedback. Regarding the missing location - WithLog enforces HasCallStack - just add HasCallStack as an additional constraint and the location of the log statement should get visible.

Hi @alaendle . sorry for late reply. The motivation of this tutorial is to show the equivalent of LoggerT and the monad decorated by WithLog. When I tried to learn about the colog library, I got confused why it provides a LoggerT but rarely uses it in the example. Instead, we use the WithLog more frequently.

I'm not sure whether I miss some haskell knowledges that leads the confusion, or colog misses some documentation about them. I prefer the latter, hence I created a PR for appending this detail.

[xieyuschen]

@xieyuschen - one again, thanks for your contribution - I've changed a few small things - if you still like it, I think we should merge it 👍 otherwise feel free to further improve this PR 😉

sure, thanks for your kindly help. I will check it:)

[alaendle]

I hope it was okay that I already merged - it's better to have a lot of small progress rather than being stuck 😃