Initial Retrie plugin

[pepeiborra]

Supports RULES, functions and type synonyms

Future work:

• Handling names properly (when Matching of qualified names facebookincubator/retrie#10 is fixed)
• Suggestions for pattern synonyms (when Allow rewriting with pattern synonyms facebookincubator/retrie#15 is released)
• Refactorings: rename, extract, move, etc..
• Automatically add imports when unfolding
• Proper support for workspace folders

Closes #103

/cc @xich

[lukel97]

Does this mean we can build hls with -fghc-lib now? That might solve the hlint ghc-lib mismatch issue @jneira

[pepeiborra]

I don't know about that, I have never tried to build ghcide with ghc-lib. Ping @cocreature

[alanz]

LGTM

My only concern is that it provides code actions for the whole file, rather than in the context.

I wonder if we shouldn't split this into diagnostics and code actions, much as hlint (in hie) does.

[pepeiborra]

LGTM

My only concern is that it provides code actions for the whole file, rather than in the context.

I wonder if we shouldn't split this into diagnostics and code actions, much as hlint (in hie) does.

The intent is for the code actions to be attached to the relevant lines, not to the whole file. Is that not what you see?

I don't follow your second comment, what diagnostics?

[alanz]

The intent is for the code actions to be attached to the relevant lines, not to the whole file. Is that not what you see?

TBH, I have not run the code, just looked at it. And I see now that the range is converted to a pos and then used as a filter.

I don't follow your second comment, what diagnostics?

The normal process is that a plugin provides diagnostics, which show up as markings in the file and a list of issues to address. When the cursor is placed on a line with a diagnostic, this is returned to the code action provider which can propose fixes.

It seems to me that you will not know that retrie has a rewrite suggestion unless the cursor is on a line with a rewrite in it?

If so, my suggestion is to run retrie in an unconstrained way, on the whole file, and turn the suggestions into diagnostics. This is how we process hlint, it runs to generate diagnostics about possible changes, and if you go to the line you get an action to actually change it.

[pepeiborra]

If so, my suggestion is to run retrie in an unconstrained way, on the whole file, and turn the suggestions into diagnostics. This is how we process hlint, it runs to generate diagnostics about possible changes, and if you go to the line you get an action to actually change it.

Retrie does not generate suggestions. It takes code modding commands as inputs, e.g. "unfold foo" and applies them.

[alanz]

Ok, any reason not to merge then?

[pepeiborra]

Ok, any reason not to merge then?

Merge away, I'll open issues for the future work items and any TODOs left in the code.