Merge PR #787 from webwarrior-ws/interpolated-strings

Add InterpolatedStringWithNoSubstitution rule.

Author: knocte

docs/content/how-tos/rule-configuration.md

@@ -127,3 +127,4 @@ The following rules can be specified for linting.
 - [FavourNonMutablePropertyInitialization (FL0084)](rules/FL0084.html)
 - [EnsureTailCallDiagnosticsInRecursiveFunctions (FL0085)](rules/FL0085.html)
 - [FavourAsKeyword (FL0086)](rules/FL0086.html)
+- [InterpolatedStringWithNoSubstitution (FL0087)](rules/FL0087.html)

docs/content/how-tos/rules/FL0087.md

@@ -0,0 +1,33 @@
+---
+title: FL0087
+category: how-to
+hide_menu: true
+---
+
+# InterpolatedStringWithNoSubstitution (FL0087)
+
+*Introduced in `0.26.8`*
+
+## Cause
+
+Interpolated string (with `$` prefix, such as `$"foo"`) is used without embedded F# expression (e.g. `$"{foo}"` where foo is some value).
+
+Or string formatting function such as `sprintf` or `failwithf` is used without interpolation.
+
+## Rationale
+
+Usage of interpolated string without embedded F# expression(s) may indicate that the expression was intended to be used but wasn't used by mistake.
+
+## How To Fix
+
+Use regular string or embed F# expression using curly braces (`{}`).
+
+Use `failwith` instead of `failwithf` if no formatting/interpolation is needed.
+
+## Rule Settings
+
+    {
+        "interpolatedStringWithNoSubstitution": {
+            "enabled": true
+        }
+    }

src/FSharpLint.Console/Program.fs

@@ -169,7 +169,7 @@ let private start (arguments:ParseResults<ToolArgs>) (toolsPath:Ionide.ProjInfo.
                 | FileType.Source -> Lint.lintSource lintParams target
                 | FileType.Solution -> Lint.lintSolution lintParams target toolsPath
                 | FileType.Wildcard ->
-                    output.WriteInfo $"Wildcard detected, but not recommended. Using a project (slnx/sln/fsproj) can detect more issues."
+                    output.WriteInfo "Wildcard detected, but not recommended. Using a project (slnx/sln/fsproj) can detect more issues."
                     let files = expandWildcard target
                     if List.isEmpty files then
                         output.WriteInfo $"No files matching pattern '%s{target}' were found."

src/FSharpLint.Core/Application/Configuration.fs

@@ -473,7 +473,8 @@ type Configuration =
       NoPartialFunctions:RuleConfig<NoPartialFunctions.Config> option
       SuggestUseAutoProperty:EnabledConfig option
       EnsureTailCallDiagnosticsInRecursiveFunctions:EnabledConfig option
-      FavourAsKeyword:EnabledConfig option }
+      FavourAsKeyword:EnabledConfig option 
+      InterpolatedStringWithNoSubstitution:EnabledConfig option }
 with
     static member Zero = {
         Global = None
@@ -568,6 +569,7 @@ with
         SuggestUseAutoProperty = None
         EnsureTailCallDiagnosticsInRecursiveFunctions = None
         FavourAsKeyword = None
+        InterpolatedStringWithNoSubstitution = None
     }
 
 // fsharplint:enable RecordFieldNames
@@ -763,6 +765,7 @@ let flattenConfig (config:Configuration) =
                 config.SuggestUseAutoProperty |> Option.bind (constructRuleIfEnabled SuggestUseAutoProperty.rule)
                 config.EnsureTailCallDiagnosticsInRecursiveFunctions |> Option.bind (constructRuleIfEnabled EnsureTailCallDiagnosticsInRecursiveFunctions.rule)
                 config.FavourAsKeyword |> Option.bind (constructRuleIfEnabled FavourAsKeyword.rule)
+                config.InterpolatedStringWithNoSubstitution |> Option.bind (constructRuleIfEnabled InterpolatedStringWithNoSubstitution.rule)
             |]
 
     findDeprecation config deprecatedAllRules allRules

src/FSharpLint.Core/FSharpLint.Core.fsproj

@@ -31,6 +31,7 @@
     <Compile Include="Framework\Suppression.fs" />
     <!-- Rules -->
     <Compile Include="Rules\Identifiers.fs" />
+    <Compile Include="Rules\Smells\InterpolatedStringWithNoSubstitution.fs" />
     <Compile Include="Rules\Formatting\TupleFormatting\TupleFormattingHelper.fs" />
     <Compile Include="Rules\Formatting\TupleFormatting\TupleCommaSpacing.fs" />
     <Compile Include="Rules\Formatting\TupleFormatting\TupleIndentation.fs" />

src/FSharpLint.Core/Rules/Identifiers.fs

@@ -91,3 +91,4 @@ let UnneededRecKeyword = identifier 83
 let FavourNonMutablePropertyInitialization = identifier 84
 let EnsureTailCallDiagnosticsInRecursiveFunctions = identifier 85
 let FavourAsKeyword = identifier 86
+let InterpolatedStringWithNoSubstitution = identifier 87

src/FSharpLint.Core/Rules/Smells/InterpolatedStringWithNoSubstitution.fs

@@ -0,0 +1,54 @@
+module FSharpLint.Rules.InterpolatedStringWithNoSubstitution
+
+open System
+open FSharpLint.Framework
+open FSharpLint.Framework.Suggestion
+open FSharp.Compiler.Syntax
+open FSharpLint.Framework.Ast
+open FSharpLint.Framework.Rules
+
+let private makeWarning range =
+    {
+        Range = range
+        Message = Resources.GetString "InterpolatedStringWithNoSubstitution"
+        SuggestedFix = None
+        TypeChecks = List.Empty
+    }
+
+let checkInterpolatedString (contents: List<SynInterpolatedStringPart>) range =
+    if contents |> List.exists (fun part -> part.IsFillExpr) then
+        Array.empty
+    else
+        Array.singleton (makeWarning range)
+
+let stringFormattingFunctionNames = [ "sprintf"; "failwithf" ]
+
+// https://learn.microsoft.com/en-us/dotnet/fsharp/language-reference/plaintext-formatting#format-specifiers-for-printf
+let formatSpecifierRegex = Text.RegularExpressions.Regex(@"($|[^\%])\%[^\s\%]")
+
+let checkFormattingFunctionApplication (formatString: string) range =
+    if formatSpecifierRegex.IsMatch formatString then
+        Array.empty
+    else
+        Array.singleton (makeWarning range)
+            
+let runner (args: AstNodeRuleParams) =
+    match args.AstNode with
+    | AstNode.Expression(SynExpr.InterpolatedString(contents, _synStringKind, range)) ->
+        checkInterpolatedString contents range
+    | AstNode.Expression(SynExpr.App(_, false, SynExpr.Ident(ident), SynExpr.Const(SynConst.String(text, _, _stringRange),_), range))
+        when stringFormattingFunctionNames |> List.contains ident.idText ->
+        checkFormattingFunctionApplication text range
+    | _ -> Array.empty
+
+let rule =
+    AstNodeRule
+        {
+            Name = "InterpolatedStringWithNoSubstitution"
+            Identifier = Identifiers.InterpolatedStringWithNoSubstitution
+            RuleConfig =
+                {
+                    AstNodeRuleConfig.Runner = runner
+                    Cleanup = ignore
+                }
+        }

src/FSharpLint.Core/Text.resx

@@ -381,4 +381,7 @@
   <data name="RulesFavourAsKeyword" xml:space="preserve">
     <value>Prefer using the 'as' pattern to match a constant and bind it to a variable.</value>
   </data>
+  <data name="InterpolatedStringWithNoSubstitution" xml:space="preserve">
+    <value>Do not use interpolated string syntax (with $ prefix) or formatting functions (sprintf, failwithf) when not really performing any interpolation.</value>
+  </data>
 </root>

src/FSharpLint.Core/fsharplint.json

@@ -333,6 +333,7 @@
     },
     "ensureTailCallDiagnosticsInRecursiveFunctions": { "enabled": true },
     "favourAsKeyword": { "enabled": true },
+    "interpolatedStringWithNoSubstitution": { "enabled": true },
     "hints": {
         "add": [
             "not (a =  b) ===> a <> b",

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

@@ -14,6 +14,7 @@
     <Compile Include="Rules\TestIndentationRule.fs" />
     <Compile Include="Rules\TestNoTabCharactersRule.fs" />
     <Compile Include="Rules\TestLineRule.fs" />
+    <Compile Include="Rules\Smells\InterpolatedStringWithNoSubstitution.fs" />
     <Compile Include="Rules\Formatting\TupleFormatting\TupleParentheses.fs" />
     <Compile Include="Rules\Formatting\TupleFormatting\TupleCommaSpacing.fs" />
     <Compile Include="Rules\Formatting\TupleFormatting\TupleIndentation.fs" />