Documenting the new generic config for plugins

[jneira]

• We should add in https://github.com/haskell/haskell-language-server#configuring-haskell-language-server how to use the new generic configuration that you can use to disable features (code action, code lensaes, etc) per plugin, added with Introduce generic config for plugins #691 (which closed Regularise the config for plugins #513)
• Even if it is not fully integrated with vscode (see Support new hls generic plugin configuration vscode-haskell#336) you can use it writing a .vscode/settings.json with the desired configuration (and other editors lets you do it too)
• We suggested use it in several issues: HLS crashes with "The Haskell (<proj>) server crashed 5 times in the last 3 minutes. The server will not be restarted." #1342, How to disable fold/unfold suggestions? #510, Option to disable import lens plugin #426...
• It can be used to diagnose bugs and crashes with no or little info in the log, as you can disable all plugins and features to check what is causing the bug: HLS crashes with "The Haskell (<proj>) server crashed 5 times in the last 3 minutes. The server will not be restarted." #1342 (and workaround them disabling the offending feature)
• the full configuration would be:

{
    "haskell": {
        "plugin" : {
            "importLens" : {
                "globalOn" : false,
                "codeActionsOn" : false,
                "codeLensOn" : false,
                "diagnosticsOn" :false,
                "hoverOn" :false,
                "symbolsOn"  :false,
                "formattingOn" :false,
                "completionOn" :false,
                "renameOn" :false,
                "config": {}
            },
            "hlint" : {
                "globalOn" : false,
                 "codeActionsOn" : false,
                "codeLensOn" : false,
                "diagnosticsOn" :false,
                "hoverOn" :false,
                "symbolsOn"  :false,
                "formattingOn" :false,
                "completionOn" :false,
                "renameOn" :false,
                "config": {}
            },
            "eval" : {
                "globalOn" : false,
                "codeActionsOn" : false,
                "codeLensOn" : false,
                "diagnosticsOn" :false,
                "hoverOn" :false,
                "symbolsOn"  :false,
                "formattingOn" :false,
                "completionOn" :false,
                "renameOn" :false,
                "config": {}
            },
            "moduleName" : {
                "globalOn" : false,
                 "codeActionsOn" : false,
                "codeLensOn" : false,
                "diagnosticsOn" :false,
                "hoverOn" :false,
                "symbolsOn"  :false,
                "formattingOn" :false,
                "completionOn" :false,
                "renameOn" :false,
                "config": {}
            },
            "splice" : {
                "globalOn" : false,
                 "codeActionsOn" : false,
                "codeLensOn" : false,
                "diagnosticsOn" :false,
                "hoverOn" :false,
                "symbolsOn"  :false,
                "formattingOn" :false,
                "completionOn" :false,
                "renameOn" :false,
                "config": {}
            },
            "haddockComments" : {
                "globalOn" : false,
                 "codeActionsOn" : false,
                "codeLensOn" : false,
                "diagnosticsOn" :false,
                "hoverOn" :false,
                "symbolsOn"  :false,
                "formattingOn" :false,
                "completionOn" :false,
                "renameOn" :false,
                "config": {}
            },
            "class" : {
                "globalOn" : false,
                 "codeActionsOn" : false,
                "codeLensOn" : false,
                "diagnosticsOn" :false,
                "hoverOn" :false,
                "symbolsOn"  :false,
                "formattingOn" :false,
                "completionOn" :false,
                "renameOn" :false,
                "config": {}
            },
            "retrie" : {
                "globalOn" : false,
                 "codeActionsOn" : false,
                "codeLensOn" : false,
                "diagnosticsOn" :false,
                "hoverOn" :false,
                "symbolsOn"  :false,
                "formattingOn" :false,
                "completionOn" :false,
                "renameOn" :false,
                "config": {}
            },
            "tactic" : {
                "globalOn" : false,
                 "codeActionsOn" : false,
                "codeLensOn" : false,
                "diagnosticsOn" :false,
                "hoverOn" :false,
                "symbolsOn"  :false,
                "formattingOn" :false,
                "completionOn" :false,
                "renameOn" :false,
                "config": { 
                      "features": "not exposed?",
                      "max_use_ctor_actions": "Int"
                 }
            },
            "pragmas" : {
                "globalOn" : false,
                 "codeActionsOn" : false,
                "codeLensOn" : false,
                "diagnosticsOn" :false,
                "hoverOn" :false,
                "symbolsOn"  :false,
                "formattingOn" :false,
                "completionOn" :false,
                "renameOn" :false,
                "config": {}
            },
            "ghcide-hover-and-symbols" : {
                "globalOn" : false,
                 "codeActionsOn" : false,
                "codeLensOn" : false,
                "diagnosticsOn" :false,
                "hoverOn" :false,
                "symbolsOn"  :false,
                "formattingOn" :false,
                "completionOn" :false,
                "renameOn" :false,
                "config": {}
            },
            "ghcide-code-actions" : {
                "globalOn" : false,
                 "codeActionsOn" : false,
                "codeLensOn" : false,
                "diagnosticsOn" :false,
                "hoverOn" :false,
                "symbolsOn"  :false,
                "formattingOn" :false,
                "completionOn" :false,
                "renameOn" :false,
                "config": {}
            },
            "ghcide-completions" : {
                "globalOn" : false,
                 "codeActionsOn" : false,
                "codeLensOn" : false,
                "diagnosticsOn" :false,
                "hoverOn" :false,
                "symbolsOn"  :false,
                "formattingOn" :false,
                "completionOn" :false,
                "renameOn" :false,
                "config": {}
            },
            "ghcide-type-lenses" : {
                "globalOn" : false,
                 "codeActionsOn" : false,
                "codeLensOn" : false,
                "diagnosticsOn" :false,
                "hoverOn" :false,
                "symbolsOn"  :false,
                "formattingOn" :false,
                "completionOn" :false,
                "renameOn" :false,
                "config": {
                    "mode": "Always | Exported | Diagnostics"
                }
            }
        }
    }
}

• Not all plugins provide all features so we should cut down them
• We should mention that existing configuration is deprecated cause is already covered by the generic one (hlintOn)
• I think tactic plugin already have a dedicated configuration under config (@isovector)

[jneira]

• ghcide plugins already honours the generic configuration (ghcide plugins don't honour generic plugin configuration #1321), so it should be added

[jneira]

• full configuration updated
• but not all plugins has all capacities so it would be nice to remove non useful info, to make it more compact and focused
• the tactic specific config should be added

[jneira]

• configuration completed with wingman and ghcide-type-lenses specific configuration
• i guess we dont want expose wingman features to the user in any way? what would be a concise description of max_use_ctor_actions? (@isovector)

[berberman]

The value of ghcide-type-lenses' mode is case insensitive

[isovector]

@jneira

max_use_ctor_actions lets you set the maximum number of Use constructor <x> code actions that can appear. For types like Maybe (2 ctors) it's fine to just show them all, but for HsExpr (~30), that's only going to overwhelm the user, so we don't show them.

max_use_ctor_actions is the cutoff between "OK" and "too many".

I think it's ok to expose features, but maybe with an unhelpful description "Features to enable in the plugin"

[jneira]

• This would be the configuration including only the actual capacities of each plugin. In plugins with only one of them globalOn is enough to control it.
• Formatters could be included here but there are an option to choose what formatter is using and being able to disable only can cause users disabling the formatter chosen.

{
    "haskell": {
        "plugin" : {
            "importLens" : {
                "globalOn" : false,
                "codeActionsOn" : false,
                "codeLensOn" : false
            },
            "hlint" : {
                "globalOn" : false,
                "codeActionsOn" : false,
                "diagnosticsOn" :false
            },
            "eval" : {
                "globalOn" : false,
                "codeLensOn" : false
            },
            "moduleName" : {
                "globalOn" : false,
                "codeLensOn" : false
            },
            "splice" : {
                "globalOn" : false,
                "codeActionsOn" : false
            },
            "haddockComments" : {
                "globalOn" : false,
                "codeActionsOn" : false
            },
            "class" : {
                "globalOn" : false,
                "codeActionsOn" : false
            },
            "retrie" : {
                "globalOn" : false,
                "codeActionsOn" : false
            },
            "tactic" : {
                "globalOn" : false,
                "codeActionsOn" : false,
                "config": { 
                      "features": "not exposed?",
                      "max_use_ctor_actions": "Int"
                 }
            },
            "pragmas" : {
                "globalOn" : false,
                "codeActionsOn" : false,
                "completionOn" : false
            },
            "ghcide-hover-and-symbols" : {
                "globalOn" : false,
                "hoverOn" :false,
                "symbolsOn"  :false
            },
            "ghcide-code-actions" : {
                "globalOn" : false,
                "codeActionsOn" : false
            },
            "ghcide-completions" : {
                "globalOn" : false,
                "completionOn" :false
            },
            "ghcide-type-lenses" : {
                "globalOn" : false,
                "codeLensOn" : false,
                "config": {
                    "mode": "always | exported | diagnostics"
                }
            }
        }
    }
}