String analyzers

src/FSharp.Analyzers/FSharp.Analyzers.fsproj

@@ -1,4 +1,4 @@
-<Project Sdk="Microsoft.NET.Sdk">
+<Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
     <TargetFramework>net6.0</TargetFramework>
@@ -11,9 +11,10 @@
     <ItemGroup>
         <Compile Include="ASTCollecting.fs"/>
         <Compile Include="TASTCollecting.fs" />
-        <Compile Include="StringAnalyzers.fs"/>
         <Compile Include="JsonSerializerOptionsAnalyzer.fs" />
         <Compile Include="UnionCaseAnalyzer.fs" />
+        <Compile Include="StringAnalyzer.fsi" />
+        <Compile Include="StringAnalyzer.fs" />
     </ItemGroup>
 
   <ItemGroup>

src/FSharp.Analyzers/StringAnalyzer.fs

@@ -0,0 +1,127 @@
+module GR.FSharp.Analyzers.StringAnalyzer
+
+open FSharp.Analyzers.SDK
+open FSharp.Compiler.Symbols
+open FSharp.Compiler.Text
+open GR.FSharp.Analyzers.TASTCollecting
+
+[<Literal>]
+let StringEndsWithCode = "GRA-STRING-001"
+
+[<Literal>]
+let StringStartsWithCode = "GRA-STRING-002"
+
+[<Literal>]
+let StringIndexOfCode = "GRA-STRING-003"
+
+let (|StringExpr|_|) (e : FSharpExpr) =
+    if e.Type.ErasedType.BasicQualifiedName = "System.String" then
+        Some ()
+    else
+        None
+
+let (|IntExpr|_|) (e : FSharpExpr) =
+    if e.Type.ErasedType.BasicQualifiedName = "System.Int32" then
+        Some ()
+    else
+        None
+
+let invalidStringFunctionUseAnalyzer
+    functionName
+    code
+    message
+    severity
+    (typedTree : FSharpImplementationFileContents)
+    (typedArgumentPredicate : FSharpExpr list -> bool)
+    =
+    let invocations = ResizeArray<range> ()
+
+    let handler : Handler =
+        Handler.CallHandler (fun (m : range) (mfv : FSharpMemberOrFunctionOrValue) (args : FSharpExpr list) ->
+            if
+                mfv.Assembly.SimpleName = "System.Runtime"
+                && mfv.FullName = $"System.String.{functionName}"
+                && typedArgumentPredicate args
+            then
+                invocations.Add m
+        )
+
+    for decl in typedTree.Declarations do
+        visitDeclaration handler decl
+
+    invocations
+    |> Seq.map (fun mFunctionName ->
+        {
+            Type = $"String.{functionName} analyzer"
+            Message = message
+            Code = code
+            Severity = severity
+            Range = mFunctionName
+            Fixes = []
+        }
+    )
+    |> Seq.toList
+
+[<CliAnalyzer "String.EndsWith Analyzer">]
+let endsWithAnalyzer (ctx : CliContext) : Async<Message list> =
+    async {
+        match ctx.TypedTree with
+        | None -> return List.empty
+        | Some typedTree ->
+
+        return
+            invalidStringFunctionUseAnalyzer
+                "EndsWith"
+                StringEndsWithCode
+                "The usage of String.EndsWith with a single string argument is discouraged. Signal your intention explicitly by calling an overload."
+                Warning
+                typedTree
+                (fun (args : FSharpExpr list) ->
+                    match args with
+                    | [ StringExpr ] -> true
+                    | _ -> false
+                )
+    }
+
+[<CliAnalyzer "String.StartsWith Analyzer">]
+let startsWithAnalyzer (ctx : CliContext) : Async<Message list> =
+    async {
+        match ctx.TypedTree with
+        | None -> return List.empty
+        | Some typedTree ->
+            return
+                invalidStringFunctionUseAnalyzer
+                    "StartsWith"
+                    StringStartsWithCode
+                    "The usage of String.StartsWith with a single string argument is discouraged. Signal your intention explicitly by calling an overload."
+                    Warning
+                    typedTree
+                    (fun (args : FSharpExpr list) ->
+                        match args with
+                        | [ StringExpr ] -> true
+                        | _ -> false
+                    )
+    }
+
+[<CliAnalyzer "String.IndexOf Analyzer">]
+let indexOfAnalyzer (ctx : CliContext) : Async<Message list> =
+    async {
+        match ctx.TypedTree with
+        | None -> return List.empty
+        | Some typedTree ->
+
+        return
+            invalidStringFunctionUseAnalyzer
+                "IndexOf"
+                StringIndexOfCode
+                "The usage of String.IndexOf with a single string argument is discouraged. Signal your intention explicitly by calling an overload."
+                Warning
+                typedTree
+                (fun args ->
+                    match args with
+                    | [ StringExpr ]
+                    | [ StringExpr ; IntExpr ]
+                    | [ StringExpr ; IntExpr ; IntExpr ] -> true
+                    | _ -> false
+                )
+    }

src/FSharp.Analyzers/StringAnalyzer.fsi

@@ -0,0 +1,21 @@
+module GR.FSharp.Analyzers.StringAnalyzer
+
+open FSharp.Analyzers.SDK
+
+[<Literal>]
+val StringEndsWithCode : string = "GRA-STRING-001"
+
+[<Literal>]
+val StringStartsWithCode : string = "GRA-STRING-002"
+
+[<Literal>]
+val StringIndexOfCode : string = "GRA-STRING-003"
+
+[<CliAnalyzer "String.EndsWith Analyzer">]
+val endsWithAnalyzer : ctx : CliContext -> Async<Message list>
+
+[<CliAnalyzer "String.StartsWith Analyzer">]
+val startsWithAnalyzer : ctx : CliContext -> Async<Message list>
+
+[<CliAnalyzer "String.IndexOf Analyzer">]
+val indexOfAnalyzer : ctx : CliContext -> Async<Message list>

tests/FSharp.Analyzers.Tests/Testing.fs → tests/FSharp.Analyzers.Tests/Common.fs

@@ -2,6 +2,7 @@
 
 open System
 open System.IO
+open System.Collections
 open System.Threading.Tasks
 open NUnit.Framework
 open FSharp.Analyzers.SDK
@@ -46,12 +47,16 @@ let assertExpected sourceFile messages =
 
 let dataFolder = Path.Combine (__SOURCE_DIRECTORY__, "..", "data")
 
-let constructTestCaseEnumerator (subDataPath : string array) =
-    let testsDirectory = Path.Combine (dataFolder, Path.Combine subDataPath)
-
-    Directory.EnumerateFiles (testsDirectory, "*.fs")
+let constructTestCaseEnumeratorAux (files : string seq) : IEnumerator =
+    files
     |> Seq.map (fun f ->
         let fileName = Path.GetRelativePath (dataFolder, f)
         [| fileName :> obj |]
     )
     |> fun s -> s.GetEnumerator ()
+
+let constructTestCaseEnumerator (subDataPath : string array) =
+    let testsDirectory = Path.Combine (dataFolder, Path.Combine subDataPath)
+
+    Directory.EnumerateFiles (testsDirectory, "*.fs")
+    |> constructTestCaseEnumeratorAux

tests/FSharp.Analyzers.Tests/FSharp.Analyzers.Tests.fsproj

@@ -10,10 +10,10 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <Compile Include="Testing.fs" />
-    <Compile Include="StringAnalyzerTests.fs" />
+    <Compile Include="Common.fs" />
     <Compile Include="JsonSerializerOptionsAnalyzerTests.fs" />
     <Compile Include="UnionCaseAnalyzerTests.fs" />
+    <Compile Include="StringAnalyzerTests.fs" />
   </ItemGroup>
 
   <ItemGroup>