Core: combine hint configs

When combining configs, if both base and overriding configs
have Hints config, combine `add` and `ignore` arrays in
HintConfig objects instead of totally overriding base hint
config by overriding one.

Also actually use `ignore` array to filter out available hints
when flattening config. Before, `ignore` was not used at all.

Fixes #466

Author: webwarrior-ws

src/FSharpLint.Core/Application/Configuration.fs

@@ -428,13 +428,18 @@ with
 
 // </Deprecated>
 
-let private getOrEmptyList hints = Option.defaultValue Array.empty hints
-
 type HintConfig = {
     add:string [] option
     ignore:string [] option
 }
 
+let private flattenHints (config: HintConfig) = 
+    let ignores = 
+        Option.defaultValue Array.empty config.ignore
+        |> Set.ofArray
+    Option.defaultValue Array.empty config.add
+    |> Array.filter (fun hint -> not <| ignores.Contains hint)
+
 type GlobalConfig = {
     numIndentationSpaces:int option
 }
@@ -663,6 +668,17 @@ let loadConfig (configPath:string) =
     File.ReadAllText configPath
     |> parseConfig
 
+let private combineHints (baseConfig: HintConfig) (overridingConfig: HintConfig) =
+    let mergeLists baseList overridingList =
+        match (baseList, overridingList) with
+        | Some baseArray, None -> Some baseArray
+        | Some baseArray, Some overridingArray -> Array.append baseArray overridingArray |> Array.distinct |> Some
+        | None, _ -> overridingList
+    { 
+        add = mergeLists baseConfig.add overridingConfig.add
+        ignore = mergeLists baseConfig.ignore overridingConfig.ignore
+    }
+
 /// Combine two configs into one: all values that are Some in second config override 
 /// corresponding values in first config.
 let combineConfigs (baseConfig: Configuration) (overridingConfig: Configuration) : Configuration =
@@ -678,9 +694,16 @@ let combineConfigs (baseConfig: Configuration) (overridingConfig: Configuration)
                     overridingValue)
             baseFields
             partialConfigFields
-    
-    FSharp.Reflection.FSharpValue.MakeRecord(typeof<Configuration>, resultingRecordFields) 
-        :?> Configuration
+
+    let mergedConfig =
+        FSharp.Reflection.FSharpValue.MakeRecord(typeof<Configuration>, resultingRecordFields) 
+            :?> Configuration
+
+    match (baseConfig.Hints, overridingConfig.Hints) with
+    | Some baseHints, Some overridingHints ->
+        { mergedConfig with Hints = Some(combineHints baseHints overridingHints) }
+    | _ -> 
+        mergedConfig    
 
 /// A default configuration specifying every analyser and rule is included as a resource file in the framework.
 /// This function loads and returns this default configuration.
@@ -771,7 +794,7 @@ let flattenConfig (config:Configuration) =
                 config.typography |> Option.map (fun config -> config.Flatten()) |> Option.toArray |> Array.concat
                 // </Deprecated>
 
-                config.Hints |> Option.map (fun config -> HintMatcher.rule { HintMatcher.Config.HintTrie = parseHints (getOrEmptyList config.add) }) |> Option.toArray
+                config.Hints |> Option.map (fun config -> HintMatcher.rule { HintMatcher.Config.HintTrie = parseHints (flattenHints config) }) |> Option.toArray
             |]
 
     let allRules =