Make type lenses plugin configurable

[berberman]

This PR is rebased on #1471, so we could close #1471 in favour of this (if it looks good).

Closes #1477
Closes #1468
Closes #622

Demo

output.mp4

Previously, we set Opt_WarnMissingSignatures and Opt_WarnMissingPatternSynonymSignatures for each module to produce hidden diagnostics and generate code lenses. By contrast, types of global bindings are derived from results of typecheck, instead of parsing diagnostic messages.

There are four working modes introduced in generic plugin config:

• Enabled Always -- always displays type lenses of global bindings, no matter what GHC flags are set by users
• Exported -- similar to Enabled, but only shows for exported global bindings
• Diagnostics -- follows error messages produced by GHC, users can control the display of code lenses by setting GHC flags in this mode
  * Disabled -- fully disabled

For local bindings, corrsponding type lenses show only when Opt_WarnMissingLocalSignatures is set and works in Always mode.

[jneira]

Wow, impressive work, many thanks

There would be a generic config option to enable or disable code lenses for the plugin, if ghcide plugins honour the generic configuration (and they should be imo, see #1321)

Add such a generic configuration maybe is out of the scope of this pr but maybe we should design the options taking in account the plugin will have enable/disable at some point.
You alway will be able to disable it setting diagnostics and disable all ghc warnings about missing type definitions in the meanwhile, no?

So the options could be

• Always-- always displays type lenses of global bindings, no matter what GHC flags are set by users
• Exported -- similar to Enabled, but only shows for exported global bindings
• Diagnostics -- follows error messages produced by GHC, users can control the display of code lenses by setting GHC flags in this mode

[jneira]

You alway will be able to disable it setting diagnostics and disable all ghc warnings about missing type definitions in the meanwhile, no?

What about some test negating the ghc warnings, to check no type lens is emitted?

[berberman]

So the options could be

• Always-- always displays type lenses of global bindings, no matter what GHC flags are set by users
• Exported -- similar to Enabled, but only shows for exported global bindings
• Diagnostics -- follows error messages produced by GHC, users can control the display of code lenses by setting GHC flags in this mode

Yeah, that makes sense.

What about some test negating the ghc warnings, to check no type lens is emitted?

Agree, we need update tests to run against each mode.

[isovector]

There appears to be a space in the config string in the video. Is that intentional? Necessary?

[berberman]

@isovector Ah, good catch. It's not intentional, but works coincidentally because of the Read instance.

[jneira]

great work, tests looks great too

[jneira]

3 issues closed in a row, amazing 👏