Core(Tests): add FavourNestedFunctions rule

Added FavourNestedFunctions rule and tests for it.

Author: webwarrior-ws

src/FSharpLint.Core/FSharpLint.Core.fsproj

@@ -58,6 +58,7 @@
     <Compile Include="Rules\Conventions\UsedUnderscorePrefixedElements.fs" />
     <Compile Include="Rules\Conventions\FavourNonMutablePropertyInitialization.fs" />
     <Compile Include="Rules\Conventions\EnsureTailCallDiagnosticsInRecursiveFunctions.fs" />
+    <Compile Include="Rules\Conventions\FavourNestedFunctions.fs" />
     <Compile Include="Rules\Conventions\RaiseWithTooManyArguments\RaiseWithTooManyArgumentsHelper.fs" />
     <Compile Include="Rules\Conventions\RaiseWithTooManyArguments\FailwithWithSingleArgument.fs" />
     <Compile Include="Rules\Conventions\RaiseWithTooManyArguments\RaiseWithSingleArgument.fs" />

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

@@ -0,0 +1,19 @@
+module FSharpLint.Rules.FavourNestedFunctions
+
+open System
+open FSharp.Compiler.Syntax
+open FSharpLint.Framework.Ast
+open FSharpLint.Framework.Rules
+open FSharpLint.Framework
+open FSharpLint.Framework.Suggestion
+
+let runner (args: AstNodeRuleParams) =
+    failwith "Not yet implemeted"    
+
+let rule =
+    { Name = "FavourNestedFunctions"
+      Identifier = Identifiers.FavourNestedFunctions
+      RuleConfig =
+        { AstNodeRuleConfig.Runner = runner
+          Cleanup = ignore } }
+    |> AstNodeRule

src/FSharpLint.Core/Rules/Identifiers.fs

@@ -92,3 +92,4 @@ let UnneededRecKeyword = identifier 83
 let FavourNonMutablePropertyInitialization = identifier 84
 let EnsureTailCallDiagnosticsInRecursiveFunctions = identifier 85
 let FavourAsKeyword = identifier 86
+let FavourNestedFunctions = identifier 87

tests/FSharpLint.Core.Tests/FSharpLint.Core.Tests.fsproj

@@ -46,6 +46,7 @@
     <Compile Include="Rules\Conventions\UsedUnderscorePrefixedElements.fs" />
     <Compile Include="Rules\Conventions\FavourNonMutablePropertyInitialization.fs" />
     <Compile Include="Rules\Conventions\EnsureTailCallDiagnosticsInRecursiveFunctions.fs" />
+    <Compile Include="Rules\Conventions\FavourNestedFunctions.fs" />
     <Compile Include="Rules\Conventions\Naming\NamingHelpers.fs" />
     <Compile Include="Rules\Conventions\Naming\InterfaceNames.fs" />
     <Compile Include="Rules\Conventions\Naming\ExceptionNames.fs" />

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

@@ -0,0 +1,76 @@
+module FSharpLint.Core.Tests.Rules.Conventions.FavourNestedFunctions
+
+open NUnit.Framework
+open FSharpLint.Rules
+open FSharpLint.Core.Tests
+
+[<TestFixture>]
+type TestFavourNestedFunctions() =
+    inherit TestAstNodeRuleBase.TestAstNodeRuleBase(FavourNestedFunctions.rule)
+
+    [<Test>]
+    member this.``Top level functions that are not used in another function should not give an error`` () =
+        this.Parse """
+let Foo () =
+    ()
+
+let Bar () =
+    ()
+"""
+        
+        this.AssertNoWarnings()
+
+    [<Test>]
+    member this.``Top level private functions that are not used in another function should not give an error`` () =
+        this.Parse """
+let private Foo () =
+    ()
+
+let Bar () =
+    ()
+"""
+        
+        this.AssertNoWarnings()
+
+    [<Test>]
+    member this.``Top level private function that is used in single function should give an error`` () =
+        this.Parse """
+let private Foo () =
+    ()
+
+let Bar () =
+    Foo()
+    ()
+"""
+        
+        Assert.IsTrue this.ErrorsExist
+
+    [<Test>]
+    member this.``Nested functions should not give an error`` () =
+        this.Parse """
+let Bar () =
+    let Foo() =
+        ()
+
+    Foo()
+    ()
+"""
+        
+        this.AssertNoWarnings()
+
+    [<Test>]
+    member this.``Private function that is used in more than one function should not give an error`` () =
+        this.Parse """
+let private Foo () =
+    ()
+
+let Bar () =
+    Foo()
+    ()
+
+let Baz () =
+    Foo ()
+    ()
+"""
+        
+        this.AssertNoWarnings()