AvoidTooShortNames: fix some false negatives

Also, add unit test for these false negatives.

Author: janus

src/FSharpLint.Core/Rules/Conventions/AvoidTooShortNames.fs

@@ -7,14 +7,17 @@ open FSharpLint.Framework.Rules
 open FSharpLint.Framework
 open FSharpLint.Framework.Suggestion
 
+let private isIdentifierTooShort (identifier: string) =
+    identifier.Length < 2 && not (identifier.StartsWith '_')
+
 let private checkIdentifierPart (identifier:Ident) (idText:string) =
     let formatError errorName =
         String.Format(Resources.GetString errorName, idText)
 
     "RulesAvoidTooShortNamesError" |> formatError |> Array.singleton
 
 let private checkIdentifier (identifier:Ident) (idText:string) =
-    if idText.Length = 1 && not (idText.StartsWith '_') then
+    if isIdentifierTooShort idText then
         checkIdentifierPart identifier idText
         |> Array.map (fun message ->
             { Range = identifier.idRange
@@ -28,7 +31,7 @@ let private getParameterWithBelowMinimumLength (pats: SynPat list): (Ident * str
     let rec loop patArray acc =
         match patArray with
         | SynPat.Named(_, ident, _, _, _)::tail ->
-            if ident.idText.Length = 1 then
+            if isIdentifierTooShort ident.idText then
                 Array.singleton (ident, ident.idText, None) |> Array.append acc |> loop tail 
             else
                 loop tail acc
@@ -43,21 +46,31 @@ let private getIdentifiers (args:AstNodeRuleParams) =
             match identifiers with
             | head::_  ->
                 let result: (Ident * string * (unit -> bool) option) array = getParameterWithBelowMinimumLength names
-                if head.idText.Length = 1 then
+                if isIdentifierTooShort head.idText then
                     Array.append result (Array.singleton (head, head.idText, None))  
                 else 
                     result
             | _ -> Array.empty
-        | SynPat.Named(_, identifier, _, _, _) when identifier.idText.Length = 1 ->
+        | SynPat.Named(_, identifier, _, _, _) when isIdentifierTooShort identifier.idText ->
             (identifier, identifier.idText, None) |> Array.singleton
         | _ -> Array.empty
+    | AstNode.Field(SynField(_, _, Some identifier, _, _, _, _, _)) when isIdentifierTooShort identifier.idText ->
+        (identifier, identifier.idText, None) |> Array.singleton
     | _ -> Array.empty
 
 let runner (args:AstNodeRuleParams) =
-    getIdentifiers args
-    |> Array.collect (fun (identifier, idText, typeCheck) ->
-        let suggestions = checkIdentifier identifier idText
-        suggestions |> Array.map (fun suggestion -> { suggestion with TypeChecks = Option.toList typeCheck }))
+    match args.AstNode with
+    | AstNode.Identifier([identifier], range) when isIdentifierTooShort identifier ->
+        { Range = range
+          Message = Resources.GetString "RulesAvoidTooShortNamesError"
+          SuggestedFix = None
+          TypeChecks = List.empty }
+        |> Array.singleton
+    | _ ->
+        getIdentifiers args
+        |> Array.collect (fun (identifier, idText, typeCheck) ->
+            let suggestions = checkIdentifier identifier idText
+            suggestions |> Array.map (fun suggestion -> { suggestion with TypeChecks = Option.toList typeCheck }))
 
 let rule =
     { Name = "AvoidTooShortNames"

tests/FSharpLint.Core.Tests/Rules/Conventions/AvoidTooShortNames.fs

@@ -67,3 +67,31 @@ let bar baz =
     x """
 
         Assert.IsTrue this.ErrorsExist
+
+    [<Test>]
+    member this.AvoidTooShortNamesShouldProduceError_5() =
+        this.Parse """
+type CellCreatedFast =
+    private
+        {
+            Y: array<byte>
+            DerivativeKeyData: array<byte>
+        }
+ """
+
+        Assert.IsTrue this.ErrorsExist
+
+    [<Test>]
+    member this.AvoidTooShortNamesShouldProduceError_6() =
+        this.Parse """
+type TorStreamCipher(keyBytes: array<byte>, ivOpt: Option<array<byte>>) =
+    member self.Encrypt(data: array<byte>) : array<byte> =
+        let rec innerEncrypt (x: int) (state: array<byte>) =
+            if x >= data.Length then
+                state
+            else
+                Array.empty
+        innerEncrypt 3 keyBytes
+ """
+
+        Assert.IsTrue this.ErrorsExist