Console,Core: fix FSharpLint warning

Fixing the warning for NoPartialFunctions rule.

Also to use FSharpx.Collections.Seq.tryHeadTail, we must
install and add FSharpx.Collections to our dependencies:
```
Consider using 'FSharpx.Collections.Seq.tryHeadTail' instead of partial function/method 'Array.tail'.
Error on line 126 starting at column 19
                |> Array.tail
```

Author: Mersho

paket.dependencies

@@ -7,6 +7,7 @@ nuget Argu
 nuget BenchmarkDotNet
 nuget BenchmarkDotNet.Diagnostics.Windows
 nuget FParsec
+nuget FSharpx.Collections
 nuget FSharp.Compiler.Service ~> 41.0.1
 nuget Ionide.ProjInfo.ProjectSystem == 0.61.3
 nuget Ionide.ProjInfo.FCS == 0.61.3
@@ -60,4 +61,4 @@ group Build
   nuget Fake.Core.UserInput
   nuget Fake.IO.FileSystem
   nuget Fake.DotNet.MsBuild
-  nuget Fake.Api.GitHub
+  nuget Fake.Api.GitHub

paket.lock

@@ -59,6 +59,8 @@ NUGET
       FSharp.Core (>= 4.7.2)
       System.Reactive (>= 5.0 < 6.0)
     FSharp.Core (6.0.7)
+    FSharpx.Collections (3.1)
+      FSharp.Core (>= 4.3.4)
     Gee.External.Capstone (2.3)
     Iced (1.20)
     Ionide.ProjInfo (0.61.3)

src/FSharpLint.Console/Output.fs

@@ -24,7 +24,7 @@ type StandardOutput () =
             else
                 errorLine
                 |> Seq.mapi (fun index _ -> if index = range.StartColumn then "^" else " ")
-                |> Seq.reduce (+)
+                |> Seq.fold (+) String.Empty
         getErrorMessage range + Environment.NewLine + errorLine + Environment.NewLine + highlightColumnLine
 
     let writeLine (str:string) (color:ConsoleColor) (writer:IO.TextWriter) =

src/FSharpLint.Console/Program.fs

@@ -86,8 +86,10 @@ let private start (arguments:ParseResults<ToolArgs>) (toolsPath:Ionide.ProjInfo.
     if arguments.Contains ToolArgs.Version then
         let version = 
             Assembly.GetExecutingAssembly().GetCustomAttributes false
-            |> Seq.pick (function | :? AssemblyInformationalVersionAttribute as aiva -> Some aiva.InformationalVersion | _ -> None)
-        sprintf "Current version: %s" version |> output.WriteInfo
+            |> Seq.tryPick (function | :? AssemblyInformationalVersionAttribute as aiva -> Some aiva.InformationalVersion | _ -> None)
+        match version with
+        | Some ver -> sprintf "Current version: %s" ver |> output.WriteInfo
+        | None -> output.WriteInfo "No version information found in assembly attributes."
         ()
 
     let handleError (str:string) =

src/FSharpLint.Core/Application/Configuration.fs

@@ -597,8 +597,16 @@ let loadConfig (configPath:string) =
 /// This function loads and returns this default configuration.
 let defaultConfiguration =
     let assembly = typeof<Rules.Rule>.GetTypeInfo().Assembly
-    let resourceName = Assembly.GetExecutingAssembly().GetManifestResourceNames()
-                       |> Seq.find (fun resourceFile -> resourceFile.EndsWith("fsharplint.json", System.StringComparison.Ordinal))
+    let resourceName =
+        let fsharplintJson =
+            Assembly.GetExecutingAssembly().GetManifestResourceNames()
+            |> Seq.tryFind (fun resourceFile ->
+                resourceFile.EndsWith("fsharplint.json", System.StringComparison.Ordinal))
+
+        match fsharplintJson with
+        | Some value -> value
+        | None -> failwith "Resource file 'fsharplint.json' not found in the assembly."
+
     use stream = assembly.GetManifestResourceStream(resourceName)
     match stream with
     | null -> failwithf "Resource '%s' not found in assembly '%s'" resourceName (assembly.FullName)

src/FSharpLint.Core/Framework/HintParser.fs

@@ -272,10 +272,9 @@ module HintParser =
 
         let private getIdentifierHashCode = function
             | identifier when (List.isEmpty >> not) identifier ->
-                identifier
-                |> Seq.last
-                |> ExpressionUtilities.identAsCompiledOpName
-                |> hash
+                match (Seq.tryLast identifier) with
+                | Some value -> value |> ExpressionUtilities.identAsCompiledOpName |> hash
+                | None -> failwith "There's no last element in identifier."
             | _ -> 0
 
         let rec private getHashCode node =
@@ -497,7 +496,10 @@ module HintParser =
         let private pescapechar: Parser<char, unit> =
             skipChar '\\'
             >>. pischar ['"';'\\';'\'';'n';'t';'b';'r';'a';'f';'v']
-            |>> fun escapeChar -> Map.find escapeChar escapeMap
+            |>> fun escapeChar ->
+                match (Map.tryFind escapeChar escapeMap) with
+                | Some value -> value
+                | None -> failwith "Invalid escape character."
 
         let private pnonescapechars: Parser<char, unit> =
             skipChar '\\'

src/FSharpLint.Core/Framework/Resources.fs

@@ -6,8 +6,14 @@ open System.Resources
 /// Provides a way of getting string values from the framework's resource files (files in src/FSharpLint.Framework/Resources/).
 /// Used to retrieve multi-lingual strings inside of the app.
 type Resources() =
-    static let resourceName = Assembly.GetExecutingAssembly().GetManifestResourceNames()
-                              |> Seq.find (fun resource -> resource.EndsWith("Text.resources", System.StringComparison.Ordinal))
+    static let resourceName =
+        let name =
+            Assembly.GetExecutingAssembly().GetManifestResourceNames()
+            |> Seq.tryFind (fun resource -> resource.EndsWith("Text.resources", System.StringComparison.Ordinal))
+
+        match name with
+        | Some value -> value
+        | None -> failwith "There were no resources found."
 
     static let resourceManager = ResourceManager(resourceName.Replace(".resources", System.String.Empty), typeof<Resources>.GetTypeInfo().Assembly)
 

src/FSharpLint.Core/Framework/Utilities.fs

@@ -29,6 +29,8 @@ module ExpressionUtilities =
     open FSharp.Compiler.Text
     open FSharp.Compiler.CodeAnalysis
 
+    open FSharpx.Collections
+
     let (|Identifier|_|) = function
         | SynExpr.Ident(ident) -> Some([ident], ident.idRange)
         | SynExpr.LongIdent(_, longIdent, _, _) -> Some(longIdent.LongIdent, longIdent.Range)
@@ -121,17 +123,19 @@ module ExpressionUtilities =
     let countPrecedingCommentLines (text:string) (startPos:pos) (endPos:pos) =
         let range = Range.mkRange String.Empty startPos endPos
 
-        let map (precedingText: string) =
+        let processComments (text:string) =
             let lines =
-                precedingText.Split '\n'
-                |> Array.rev
-                |> Array.tail
-            lines
-            |> Array.takeWhile (fun line -> line.TrimStart().StartsWith("//"))
-            |> Array.length
+                text.Split '\n'
+                |> Seq.rev
+            match Seq.tryHeadTail lines with
+            | Some (_, tail) ->
+                tail
+                |> Seq.takeWhile (fun line -> line.TrimStart().StartsWith("//"))
+                |> Seq.length
+            | None -> 0
 
         tryFindTextOfRange range text
-        |> Option.map map
+        |> Option.map processComments
         |> Option.defaultValue 0
 
     let rangeContainsOtherRange (containingRange:Range) (range:Range) =

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

@@ -46,20 +46,31 @@ type private BindingStack(maxComplexity: int) =
         let isChildOfCurrent = if List.isEmpty tier1 then
                                     false
                                 else
-                                    args.GetParents args.NodeIndex |> List.tryFind (fun astNode -> Object.ReferenceEquals(tier1.Head.Node, astNode)) |> Option.isSome
+                                    args.GetParents args.NodeIndex
+                                    |> List.tryFind (fun astNode ->
+                                        match (List.tryHead tier1) with
+                                        | Some head -> Object.ReferenceEquals(head.Node, astNode)
+                                        | None -> false)
+                                    |> Option.isSome
         // if the node is not a child and the stack isn't empty, we're finished with the current head of tier1, so move it from tier1 to tier2
         if not isChildOfCurrent && not (List.isEmpty tier1) then
-            let popped = tier1.Head
-            tier1 <- tier1.Tail
-            if popped.Complexity > maxComplexity then
-                tier2.Add popped |> ignore<bool>
+            let popped = List.tryHead tier1
+            match popped with
+            | Some value ->
+                tier1 <- tier1.Tail
+                if value.Complexity > maxComplexity then
+                    tier2.Add value |> ignore<bool>
+            | None -> ()
         // finally, push the item on to the stack
         tier1 <- bs::tier1
 
     member this.IncrComplexityOfCurrentScope incr =
-        let head = tier1.Head
-        let complexity = head.Complexity + incr
-        tier1 <- {head with Complexity = complexity}::tier1.Tail
+        let head = List.tryHead tier1
+        match head with
+        | Some value ->
+            let complexity = value.Complexity + incr
+            tier1 <- {value with Complexity = complexity}::tier1.Tail
+        | None -> ()
 
     interface IEnumerable<BindingScope> with
         member this.GetEnumerator() =

src/FSharpLint.Core/Rules/Conventions/FunctionReimplementation/CanBeReplacedWithComposition.fs

@@ -10,7 +10,7 @@ open FSharpLint.Framework.ExpressionUtilities
 
 let private validateLambdaCannotBeReplacedWithComposition _ lambda range =
     let canBeReplacedWithFunctionComposition expression =
-        let getLastElement = List.rev >> List.head
+        let getLastElement = List.rev >> List.tryHead
 
         let rec lambdaArgumentIsLastApplicationInFunctionCalls expression (lambdaArgument:Ident) numFunctionCalls =
             let rec appliedValuesAreConstants appliedValues =
@@ -25,12 +25,16 @@ let private validateLambdaCannotBeReplacedWithComposition _ lambda range =
                 | (SynExpr.Ident(_) | SynExpr.LongIdent(_))::appliedValues
                         when appliedValuesAreConstants appliedValues ->
 
-                    match getLastElement appliedValues with
-                    | SynExpr.Ident(lastArgument) when numFunctionCalls > 1 ->
-                        lastArgument.idText = lambdaArgument.idText
-                    | SynExpr.App(_, false, _, _, _) as nextFunction ->
-                        lambdaArgumentIsLastApplicationInFunctionCalls nextFunction lambdaArgument (numFunctionCalls + 1)
-                    | _ -> false
+                    let lastElement = getLastElement appliedValues
+                    match lastElement with
+                    | Some element ->
+                        match element with
+                        | SynExpr.Ident(lastArgument) when numFunctionCalls > 1 ->
+                            lastArgument.idText = lambdaArgument.idText
+                        | SynExpr.App(_, false, _, _, _) as nextFunction ->
+                            lambdaArgumentIsLastApplicationInFunctionCalls nextFunction lambdaArgument (numFunctionCalls + 1)
+                        | _ -> false
+                    | None -> failwith "There's no last element."
                 | _ -> false
             | _ -> false
 

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

@@ -263,7 +263,10 @@ let private isNonStaticInstanceMemberCall (checkFile:FSharpCheckFileResults) nam
                 if not (fullyQualifiedInstanceMember.Contains ".") then
                     failwith "Please use fully qualified name for the instance member"
                 let nameSegments = fullyQualifiedInstanceMember.Split '.'
-                let instanceMemberNameOnly = Array.last nameSegments
+                let instanceMemberNameOnly =
+                    match Array.tryLast nameSegments with
+                    | Some value -> value
+                    | None -> failwith "Instance member name cannot be parsed."
                 let isSourcePropSameAsReplacementProp = List.tryFind (fun sourceInstanceMemberName -> sourceInstanceMemberName = instanceMemberNameOnly) names
                 match isSourcePropSameAsReplacementProp with
                 | Some _ ->

src/FSharpLint.Core/paket.references

@@ -11,3 +11,4 @@ Microsoft.Build.Framework
 Microsoft.Build.Locator
 Microsoft.Build.Utilities.Core
 Microsoft.Build
+FSharpx.Collections