core(checkSourceLengthRule): Fix issues with multiple block comments

src/FSharpLint.Core/AssemblyInfo.fs

@@ -3,5 +3,6 @@ module FSharpLint.Core.AssemblyInfo
 open System.Runtime.CompilerServices
 
 [<assembly: InternalsVisibleToAttribute("FSharpLint.Benchmarks")>]
+[<assembly: InternalsVisibleToAttribute("FSharpLint.Core.Tests")>]
 
 ()

src/FSharpLint.Core/Rules/Conventions/SourceLength/SourceLengthHelper.fs

@@ -1,6 +1,7 @@
 module FSharpLint.Rules.Helper.SourceLength
 
 open System
+open System.Text
 open System.Text.RegularExpressions
 open FSharpLint.Framework
 open FSharpLint.Framework.Suggestion
@@ -34,31 +35,38 @@ let rec private getTopLevelBalancedPairs (toProcess: List<MultilineCommentMarker
         | [ beginIndex ] -> (beginIndex, index) :: getTopLevelBalancedPairs tail List.Empty
         | _::restOfStack -> getTopLevelBalancedPairs tail restOfStack
 
+let internal stripMultilineComments (source: string) =
+    let markers = 
+        multilineCommentMarkerRegex.Matches source
+        |> Seq.map (fun markerMatch -> 
+            let index = markerMatch.Index
+            if source.[index] = '(' then
+                Begin index
+            else
+                End index)
+        |> Seq.sortBy (function | Begin index -> index | End index -> index)
+        |> Seq.toList
+
+    // Process block comment removal
+    // - If no comments, return input as is
+    // - If one comment, just remove it directly
+    // - If several comments, remove them all starting from the last, as removing them from the front changes the offsets of later ones
+    match getTopLevelBalancedPairs markers List.Empty with
+    | [] -> source
+    | [ (startIndex, endIndex) ] -> source.Remove(startIndex, (endIndex + multilineCommentMarkerRegexCaptureGroupLength) - startIndex )
+    | pairs ->
+
+        (pairs, StringBuilder(source))
+        ||> List.foldBack
+            (fun (startIndex, endIndex)(currSource: StringBuilder)  ->
+                currSource.Remove(startIndex, (endIndex + multilineCommentMarkerRegexCaptureGroupLength) - startIndex))
+        |> _.ToString()
+
 let checkSourceLengthRule (config:Config) range fileContents errorName (skipRanges: array<Range>) =
     let error name lineCount actual =
         let errorFormatString = Resources.GetString("RulesSourceLengthError")
         String.Format(errorFormatString, name, lineCount, actual)
 
-    let stripMultilineComments (source: string) =
-        let markers = 
-            multilineCommentMarkerRegex.Matches source
-            |> Seq.map (fun markerMatch -> 
-                let index = markerMatch.Index
-                if source.[index] = '(' then
-                    Begin index
-                else
-                    End index)
-            |> Seq.sortBy (function | Begin index -> index | End index -> index)
-            |> Seq.toList
-
-        getTopLevelBalancedPairs markers List.Empty
-        |> List.fold
-            (fun (currSource: string) (startIndex, endIndex) ->
-                let left = currSource.AsSpan(0, startIndex) 
-                let right = currSource.AsSpan(endIndex + multilineCommentMarkerRegexCaptureGroupLength)
-                String.Concat(left, right))
-            source
-
     match tryFindTextOfRange range fileContents with
     | Some(sourceCode) -> 
         let sourceCode =

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

@@ -75,6 +75,23 @@ let dog x =
     ()""")
         Assert.IsFalse this.ErrorsExist
 
+    [<Test>]
+    member this.FunctionTooManyLinesWithMultiLineCommentAtEnd() =
+        this.Parse($"""
+module Program
+
+let dog x =
+    (*
+    Foo
+    Bar
+    *)
+    %s{generateNewLines (FunctionLength - 4) 4}
+    (*
+    Baz
+    *)
+    ()""")
+        Assert.IsFalse this.ErrorsExist
+
     [<Test>]
     member this.FunctionTooManyLinesWithNestsedMultiLineComment() =
         this.Parse($"""
@@ -354,7 +371,20 @@ let UnionLength = 500
 [<TestFixture>]
 type TestMaxLinesInUnion() =
     inherit TestAstNodeRuleBase.TestAstNodeRuleBase(MaxLinesInUnion.rule { Config.MaxLines = UnionLength })
-    // TODO: Add tests.
+
+    // Test a Union type with an acceptable number of lines, with inline block comments
+    // This cased used to trip the exception described in https://github.com/fsprojects/FSharpLint/issues/869
+    //   but should be fixed now.
+    [<Test>]
+    member this.UnionNotTooManyLines() =
+        this.Parse """
+/// Represents a single group of bindings in a class with an implicit constructor
+type IncrClassBindingGroup = 
+    | IncrClassBindingGroup of Tast.Binding list * (*isStatic:*) bool* (*recursive:*) bool
+    | IncrClassDo of Expr * (*isStatic:*) bool     
+"""
+
+        Assert.IsFalse(this.ErrorExistsAt(4, 5))
 
 [<Literal>]
 let RecordLength = 500
@@ -414,3 +444,75 @@ module Program
 let foo = ""
 exception SomeException of string""")
         Assert.IsFalse(this.ErrorExistsAt(2, 0))
+
+// Tests for 'stripMultilineComments' 
+// ref https://github.com/fsprojects/FSharpLint/issues/869
+[<TestFixture>]
+type TestStripMultilineComments() =
+
+    [<Test>]
+    member this.RemoveCommentFromStart() =
+        let input = """
+let dog x =
+    (*
+    Foo
+    Bar
+    *)
+    printf System.String.Empty
+    ()"""
+
+        let expected = """
+let dog x =
+
+    printf System.String.Empty
+    ()"""
+
+        let actual = FSharpLint.Rules.Helper.SourceLength.stripMultilineComments input
+        Assert.AreEqual(expected, actual)
+
+    [<Test>]
+    member this.RemoveCommentFromEnd() =
+        let input = """
+let dog x =
+    printf System.String.Empty
+    (*
+    Baz
+    *)
+    ()"""
+
+        let expected = """
+let dog x =
+    printf System.String.Empty
+
+    ()"""
+
+        let actual = FSharpLint.Rules.Helper.SourceLength.stripMultilineComments input
+        Assert.AreEqual(expected, actual)
+
+    [<Test>]
+    member this.RemoveMultipleComments() =
+        let input = """
+let dog x =
+    (*
+    Foo (* baz *)
+    let (*) = id
+    Bar
+    *)
+    let (*) a b = a + b
+    printf System.String.Empty
+    (*
+    Baz
+    *)
+    ()"""
+
+        let expected = """
+let dog x =
+
+    let (*) a b = a + b
+    printf System.String.Empty
+
+    ()"""
+
+        let actual = FSharpLint.Rules.Helper.SourceLength.stripMultilineComments input
+        Assert.AreEqual(expected, actual)
+