Prevent IDE crash in case of file duplicate in fsproj (#14496)

* Prevent IDE crash in case of file duplicate in fsproj

- Prevent IDE error in the first place
- Report diagnostics in case of fsc.exe build
- Report warning in case of service build
- Fix bug in componenttest framework for .fsi compilation

src/Compiler/Driver/CompilerOptions.fs

@@ -2304,6 +2304,23 @@ let GetCoreFsiCompilerOptions (tcConfigB: TcConfigBuilder) =
         )
     ]
 
+let CheckAndReportSourceFileDuplicates (sourceFiles: ResizeArray<string>) =
+    let visited = Dictionary.newWithSize (sourceFiles.Count * 2)
+    let count = sourceFiles.Count
+
+    [
+        for i = 0 to (count - 1) do
+            let source = sourceFiles[i]
+
+            match visited.TryGetValue source with
+            | true, duplicatePosition ->
+
+                warning (Error(FSComp.SR.buildDuplicateFile (source, i + 1, count, duplicatePosition + 1, count), range0))
+            | false, _ ->
+                visited.Add(source, i)
+                yield source
+    ]
+
 let ApplyCommandLineArgs (tcConfigB: TcConfigBuilder, sourceFiles: string list, argv) =
     try
         let sourceFilesAcc = ResizeArray sourceFiles
@@ -2313,7 +2330,7 @@ let ApplyCommandLineArgs (tcConfigB: TcConfigBuilder, sourceFiles: string list,
                 sourceFilesAcc.Add name
 
         ParseCompilerOptions(collect, GetCoreServiceCompilerOptions tcConfigB, argv)
-        ResizeArray.toList sourceFilesAcc
+        sourceFilesAcc |> CheckAndReportSourceFileDuplicates
     with e ->
         errorRecovery e range0
         sourceFiles

src/Compiler/Driver/CompilerOptions.fsi

@@ -66,6 +66,8 @@ val GetCoreFsiCompilerOptions: TcConfigBuilder -> CompilerOptionBlock list
 
 val GetCoreServiceCompilerOptions: TcConfigBuilder -> CompilerOptionBlock list
 
+val CheckAndReportSourceFileDuplicates: ResizeArray<string> -> string list
+
 /// Apply args to TcConfigBuilder and return new list of source files
 val ApplyCommandLineArgs: tcConfigB: TcConfigBuilder * sourceFiles: string list * argv: string list -> string list
 

src/Compiler/Driver/fsc.fs

@@ -536,6 +536,7 @@ let main1
         // Rather than start processing, just collect names, then process them.
         try
             let files = ProcessCommandLineFlags(tcConfigB, lcidFromCodePage, argv)
+            let files = CheckAndReportSourceFileDuplicates(ResizeArray.ofList files)
             AdjustForScriptCompile(tcConfigB, files, lexResourceManager, dependencyProvider)
         with e ->
             errorRecovery e rangeStartup

src/Compiler/FSComp.txt

@@ -1663,4 +1663,5 @@ reprStateMachineInvalidForm,"The state machine has an unexpected form"
 3548,matchNotAllowedForUnionCaseWithNoData,"Pattern discard is not allowed for union case that takes no data."
 3549,tcSynTypeOrInvalidInDeclaration,"SynType.Or is not permitted in this declaration"
 3550,chkDuplicatedMethodParameter,"Duplicate parameter. The parameter '%s' has been used more that once in this method."
+3551,buildDuplicateFile,"The source file '%s' (at position %d/%d) already appeared in the compilation list (at position %d/%d). Please verify that it is included only once in the project file."
 featureEscapeBracesInFormattableString,"Escapes curly braces before calling FormattableStringFactory.Create when interpolated string literal is typed as FormattableString"
\ No newline at end of file

src/Compiler/xlf/FSComp.txt.cs.xlf

@@ -7,6 +7,11 @@
         <target state="new">All elements of an array must be implicitly convertible to the type of the first element, which here is a tuple of length {0} of type\n    {1}    \nThis element is a tuple of length {2} of type\n    {3}    \n</target>
         <note />
       </trans-unit>
+      <trans-unit id="buildDuplicateFile">
+        <source>The source file '{0}' (at position {1}/{2}) already appeared in the compilation list (at position {3}/{4}). Please verify that it is included only once in the project file.</source>
+        <target state="new">The source file '{0}' (at position {1}/{2}) already appeared in the compilation list (at position {3}/{4}). Please verify that it is included only once in the project file.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="buildInvalidSourceFileExtensionML">
         <source>The file extension of '{0}' is not recognized. Source files must have extension .fs, .fsi, .fsx or .fsscript. To enable the deprecated use of .ml or .mli extensions, use '--langversion:5.0' and '--mlcompatibility'.</source>
         <target state="translated">Soubor {0} má nerozpoznanou příponu. Zdrojové soubory musí mít příponu .fs, .fsi, .fsx nebo .fsscript. Pokud chcete povolit použití zastaralých přípon .ml nebo .mli, použijte parametry --langversion:5.0 a --mlcompatibility.</target>

src/Compiler/xlf/FSComp.txt.de.xlf

@@ -7,6 +7,11 @@
         <target state="new">All elements of an array must be implicitly convertible to the type of the first element, which here is a tuple of length {0} of type\n    {1}    \nThis element is a tuple of length {2} of type\n    {3}    \n</target>
         <note />
       </trans-unit>
+      <trans-unit id="buildDuplicateFile">
+        <source>The source file '{0}' (at position {1}/{2}) already appeared in the compilation list (at position {3}/{4}). Please verify that it is included only once in the project file.</source>
+        <target state="new">The source file '{0}' (at position {1}/{2}) already appeared in the compilation list (at position {3}/{4}). Please verify that it is included only once in the project file.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="buildInvalidSourceFileExtensionML">
         <source>The file extension of '{0}' is not recognized. Source files must have extension .fs, .fsi, .fsx or .fsscript. To enable the deprecated use of .ml or .mli extensions, use '--langversion:5.0' and '--mlcompatibility'.</source>
         <target state="translated">Die Dateierweiterung von „{0}“ wurde nicht erkannt. Quelldateien müssen die Erweiterung .fs, .fsi, .fsx oder .fsscript haben. Um die veraltete Verwendung der Erweiterungen .ml oder .mli zu aktivieren, verwenden Sie „--langversion:5.0“ und „--mlcompatibility“.</target>

src/Compiler/xlf/FSComp.txt.es.xlf

@@ -7,6 +7,11 @@
         <target state="new">All elements of an array must be implicitly convertible to the type of the first element, which here is a tuple of length {0} of type\n    {1}    \nThis element is a tuple of length {2} of type\n    {3}    \n</target>
         <note />
       </trans-unit>
+      <trans-unit id="buildDuplicateFile">
+        <source>The source file '{0}' (at position {1}/{2}) already appeared in the compilation list (at position {3}/{4}). Please verify that it is included only once in the project file.</source>
+        <target state="new">The source file '{0}' (at position {1}/{2}) already appeared in the compilation list (at position {3}/{4}). Please verify that it is included only once in the project file.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="buildInvalidSourceFileExtensionML">
         <source>The file extension of '{0}' is not recognized. Source files must have extension .fs, .fsi, .fsx or .fsscript. To enable the deprecated use of .ml or .mli extensions, use '--langversion:5.0' and '--mlcompatibility'.</source>
         <target state="translated">No se reconoce la extensión de archivo de '{0}'. Los archivos de código fuente deben tener las extensiones .fs, .fsi, .fsx o .fsscript. Para habilitar el uso en desuso de las extensiones .ml o .mli, use '--langversion:5.0' y '--mlcompatibility'.</target>

src/Compiler/xlf/FSComp.txt.fr.xlf

@@ -7,6 +7,11 @@
         <target state="new">All elements of an array must be implicitly convertible to the type of the first element, which here is a tuple of length {0} of type\n    {1}    \nThis element is a tuple of length {2} of type\n    {3}    \n</target>
         <note />
       </trans-unit>
+      <trans-unit id="buildDuplicateFile">
+        <source>The source file '{0}' (at position {1}/{2}) already appeared in the compilation list (at position {3}/{4}). Please verify that it is included only once in the project file.</source>
+        <target state="new">The source file '{0}' (at position {1}/{2}) already appeared in the compilation list (at position {3}/{4}). Please verify that it is included only once in the project file.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="buildInvalidSourceFileExtensionML">
         <source>The file extension of '{0}' is not recognized. Source files must have extension .fs, .fsi, .fsx or .fsscript. To enable the deprecated use of .ml or .mli extensions, use '--langversion:5.0' and '--mlcompatibility'.</source>
         <target state="translated">L’extension de fichier « {0} » n’est pas reconnue. Les fichiers sources doivent avoir l’extension. FS,. FSI,. FSX ou. fsscript. Pour activer l’utilisation déconseillée des extensions. ml ou. MLI, utilisez'--langversion : 5.0 'et'--mlcompatibility'.</target>

src/Compiler/xlf/FSComp.txt.it.xlf

@@ -7,6 +7,11 @@
         <target state="new">All elements of an array must be implicitly convertible to the type of the first element, which here is a tuple of length {0} of type\n    {1}    \nThis element is a tuple of length {2} of type\n    {3}    \n</target>
         <note />
       </trans-unit>
+      <trans-unit id="buildDuplicateFile">
+        <source>The source file '{0}' (at position {1}/{2}) already appeared in the compilation list (at position {3}/{4}). Please verify that it is included only once in the project file.</source>
+        <target state="new">The source file '{0}' (at position {1}/{2}) already appeared in the compilation list (at position {3}/{4}). Please verify that it is included only once in the project file.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="buildInvalidSourceFileExtensionML">
         <source>The file extension of '{0}' is not recognized. Source files must have extension .fs, .fsi, .fsx or .fsscript. To enable the deprecated use of .ml or .mli extensions, use '--langversion:5.0' and '--mlcompatibility'.</source>
         <target state="translated">L'estensione di file di '{0}' non è riconosciuta. I file di origine devono avere estensione fs, fsi, fsx o fsscript. Per abilitare l'uso deprecato delle estensioni ml o mli, usare '--langversion:5.0' e '--mlcompatibility'.</target>

src/Compiler/xlf/FSComp.txt.ja.xlf

@@ -7,6 +7,11 @@
         <target state="new">All elements of an array must be implicitly convertible to the type of the first element, which here is a tuple of length {0} of type\n    {1}    \nThis element is a tuple of length {2} of type\n    {3}    \n</target>
         <note />
       </trans-unit>
+      <trans-unit id="buildDuplicateFile">
+        <source>The source file '{0}' (at position {1}/{2}) already appeared in the compilation list (at position {3}/{4}). Please verify that it is included only once in the project file.</source>
+        <target state="new">The source file '{0}' (at position {1}/{2}) already appeared in the compilation list (at position {3}/{4}). Please verify that it is included only once in the project file.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="buildInvalidSourceFileExtensionML">
         <source>The file extension of '{0}' is not recognized. Source files must have extension .fs, .fsi, .fsx or .fsscript. To enable the deprecated use of .ml or .mli extensions, use '--langversion:5.0' and '--mlcompatibility'.</source>
         <target state="translated">'{0}' のファイル拡張子を認識できません。ソース ファイル拡張子は .fs、.fsi、.fsx、または .fsscript にする必要があります。非推奨の拡張子 .ml または .mli の使用を有効にするには、'--langversion:5.0' および '--mlcompatibility' を使用してください。</target>

src/Compiler/xlf/FSComp.txt.ko.xlf

@@ -7,6 +7,11 @@
         <target state="new">All elements of an array must be implicitly convertible to the type of the first element, which here is a tuple of length {0} of type\n    {1}    \nThis element is a tuple of length {2} of type\n    {3}    \n</target>
         <note />
       </trans-unit>
+      <trans-unit id="buildDuplicateFile">
+        <source>The source file '{0}' (at position {1}/{2}) already appeared in the compilation list (at position {3}/{4}). Please verify that it is included only once in the project file.</source>
+        <target state="new">The source file '{0}' (at position {1}/{2}) already appeared in the compilation list (at position {3}/{4}). Please verify that it is included only once in the project file.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="buildInvalidSourceFileExtensionML">
         <source>The file extension of '{0}' is not recognized. Source files must have extension .fs, .fsi, .fsx or .fsscript. To enable the deprecated use of .ml or .mli extensions, use '--langversion:5.0' and '--mlcompatibility'.</source>
         <target state="translated">'{0}'의 파일 확장자가 인식되지 않습니다. 원본 파일의 확장자는 .fs, .fsi, .fsx 또는 .fsscript여야 합니다. 더 이상 사용되지 않는 .ml 또는 .mli 확장자를 사용하려면 '--langversion:5.0' 및 '--mlcompatibility'를 사용하세요.</target>

src/Compiler/xlf/FSComp.txt.pl.xlf

@@ -7,6 +7,11 @@
         <target state="new">All elements of an array must be implicitly convertible to the type of the first element, which here is a tuple of length {0} of type\n    {1}    \nThis element is a tuple of length {2} of type\n    {3}    \n</target>
         <note />
       </trans-unit>
+      <trans-unit id="buildDuplicateFile">
+        <source>The source file '{0}' (at position {1}/{2}) already appeared in the compilation list (at position {3}/{4}). Please verify that it is included only once in the project file.</source>
+        <target state="new">The source file '{0}' (at position {1}/{2}) already appeared in the compilation list (at position {3}/{4}). Please verify that it is included only once in the project file.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="buildInvalidSourceFileExtensionML">
         <source>The file extension of '{0}' is not recognized. Source files must have extension .fs, .fsi, .fsx or .fsscript. To enable the deprecated use of .ml or .mli extensions, use '--langversion:5.0' and '--mlcompatibility'.</source>
         <target state="translated">Rozszerzenie pliku "{0}" nie zostało rozpoznane. Pliki źródłowe muszą mieć rozszerzenie .fs, .fsi, .fsx lub .fsscript. Aby włączyć przestarzałe używanie rozszerzeń. ml lub .mli, użyj polecenia "--langversion: 5.0" i "--mlcompatibility".</target>

src/Compiler/xlf/FSComp.txt.pt-BR.xlf

@@ -7,6 +7,11 @@
         <target state="new">All elements of an array must be implicitly convertible to the type of the first element, which here is a tuple of length {0} of type\n    {1}    \nThis element is a tuple of length {2} of type\n    {3}    \n</target>
         <note />
       </trans-unit>
+      <trans-unit id="buildDuplicateFile">
+        <source>The source file '{0}' (at position {1}/{2}) already appeared in the compilation list (at position {3}/{4}). Please verify that it is included only once in the project file.</source>
+        <target state="new">The source file '{0}' (at position {1}/{2}) already appeared in the compilation list (at position {3}/{4}). Please verify that it is included only once in the project file.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="buildInvalidSourceFileExtensionML">
         <source>The file extension of '{0}' is not recognized. Source files must have extension .fs, .fsi, .fsx or .fsscript. To enable the deprecated use of .ml or .mli extensions, use '--langversion:5.0' and '--mlcompatibility'.</source>
         <target state="translated">A extensão do arquivo '{0}' não foi reconhecida. Os arquivos de origem devem ter a extensão .fs, .fsi, .fsx ou .fsscript. Para ativar o uso preterido das extensões .ml ou .mli, use '--langversion:5.0' e '--mlcompatibility'.</target>

src/Compiler/xlf/FSComp.txt.ru.xlf

@@ -7,6 +7,11 @@
         <target state="new">All elements of an array must be implicitly convertible to the type of the first element, which here is a tuple of length {0} of type\n    {1}    \nThis element is a tuple of length {2} of type\n    {3}    \n</target>
         <note />
       </trans-unit>
+      <trans-unit id="buildDuplicateFile">
+        <source>The source file '{0}' (at position {1}/{2}) already appeared in the compilation list (at position {3}/{4}). Please verify that it is included only once in the project file.</source>
+        <target state="new">The source file '{0}' (at position {1}/{2}) already appeared in the compilation list (at position {3}/{4}). Please verify that it is included only once in the project file.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="buildInvalidSourceFileExtensionML">
         <source>The file extension of '{0}' is not recognized. Source files must have extension .fs, .fsi, .fsx or .fsscript. To enable the deprecated use of .ml or .mli extensions, use '--langversion:5.0' and '--mlcompatibility'.</source>
         <target state="translated">Расширение файла "{0}" не распознано. Исходные файлы должны иметь расширения FS, FSI, FSX или FSSCRIPT. Чтобы включить использование нерекомендуемых расширений ML или MLI, примените команду "--langversion:5.0" и "--mlcompatibility".</target>

src/Compiler/xlf/FSComp.txt.tr.xlf

@@ -7,6 +7,11 @@
         <target state="new">All elements of an array must be implicitly convertible to the type of the first element, which here is a tuple of length {0} of type\n    {1}    \nThis element is a tuple of length {2} of type\n    {3}    \n</target>
         <note />
       </trans-unit>
+      <trans-unit id="buildDuplicateFile">
+        <source>The source file '{0}' (at position {1}/{2}) already appeared in the compilation list (at position {3}/{4}). Please verify that it is included only once in the project file.</source>
+        <target state="new">The source file '{0}' (at position {1}/{2}) already appeared in the compilation list (at position {3}/{4}). Please verify that it is included only once in the project file.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="buildInvalidSourceFileExtensionML">
         <source>The file extension of '{0}' is not recognized. Source files must have extension .fs, .fsi, .fsx or .fsscript. To enable the deprecated use of .ml or .mli extensions, use '--langversion:5.0' and '--mlcompatibility'.</source>
         <target state="translated">'{0}' kaynak dosyasının dosya uzantısı tanınmadı. Kaynak dosyaların uzantısı .fs, .fsi, .fsx veya .fsscript olmalıdır. Kullanım dışı .ml veya .mli uzantılarını etkinleştirmek için '--langversion:5.0' ve '--mlcompatibility' kullanın.</target>

src/Compiler/xlf/FSComp.txt.zh-Hans.xlf

@@ -7,6 +7,11 @@
         <target state="new">All elements of an array must be implicitly convertible to the type of the first element, which here is a tuple of length {0} of type\n    {1}    \nThis element is a tuple of length {2} of type\n    {3}    \n</target>
         <note />
       </trans-unit>
+      <trans-unit id="buildDuplicateFile">
+        <source>The source file '{0}' (at position {1}/{2}) already appeared in the compilation list (at position {3}/{4}). Please verify that it is included only once in the project file.</source>
+        <target state="new">The source file '{0}' (at position {1}/{2}) already appeared in the compilation list (at position {3}/{4}). Please verify that it is included only once in the project file.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="buildInvalidSourceFileExtensionML">
         <source>The file extension of '{0}' is not recognized. Source files must have extension .fs, .fsi, .fsx or .fsscript. To enable the deprecated use of .ml or .mli extensions, use '--langversion:5.0' and '--mlcompatibility'.</source>
         <target state="translated">无法识别“{0}”的文件扩展名。源文件必须具有扩展名 .fs、.fsi、.fsx 或 .fsscript。要启用已弃用的 .ml 或 .mli 扩展名，请使用 “--langversion:5.0” 和 “--mlcompatibility”。</target>

src/Compiler/xlf/FSComp.txt.zh-Hant.xlf

@@ -7,6 +7,11 @@
         <target state="new">All elements of an array must be implicitly convertible to the type of the first element, which here is a tuple of length {0} of type\n    {1}    \nThis element is a tuple of length {2} of type\n    {3}    \n</target>
         <note />
       </trans-unit>
+      <trans-unit id="buildDuplicateFile">
+        <source>The source file '{0}' (at position {1}/{2}) already appeared in the compilation list (at position {3}/{4}). Please verify that it is included only once in the project file.</source>
+        <target state="new">The source file '{0}' (at position {1}/{2}) already appeared in the compilation list (at position {3}/{4}). Please verify that it is included only once in the project file.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="buildInvalidSourceFileExtensionML">
         <source>The file extension of '{0}' is not recognized. Source files must have extension .fs, .fsi, .fsx or .fsscript. To enable the deprecated use of .ml or .mli extensions, use '--langversion:5.0' and '--mlcompatibility'.</source>
         <target state="translated">無法辨識 '{0}' 的副檔名。來源檔案的副檔名必須是 fsi、.fsx 或 .fsscript。若要啟用已被取代的 .ml 或 .mli 副檔名，請使用 '--langversion:5.0' and '--mlcompatibility'。</target>

tests/FSharp.Compiler.ComponentTests/CompilerOptions/fsc/sourceFiles.fs

+// Copyright (c) Microsoft Corporation.  All Rights Reserved.  See License.txt in the project root for license information.
+
+module FSharp.Compiler.ComponentTests.CompilerOptions.FscSourceFilesArguments
+
+open Xunit
+open FSharp.Test
+open FSharp.Test.Compiler
+
+
+[<Fact>]
+let ``Reports duplicate sources via warning``() =
+    let file = SourceCodeFileKind.Fs({FileName="test.fs"; SourceText=Some """printfn "Hello" """ })
+ 
+    fsFromString file
+    |> FS
+    |> asExe
+    |> withAdditionalSourceFile file
+    |> compile
+    |> withWarningCodes [3551]
+    |> withErrorCodes []
\ No newline at end of file

tests/FSharp.Compiler.ComponentTests/EmittedIL/Structure/UnionTypeWithSignature02.fs

@@ -2,7 +2,7 @@
 // Regression test for FSHARP1.0:4040
 // "Signature files do not prevent compiler-generated public constructors from leaking out of discriminated unions"
 // Note that the corresponsing .fsi file is NOT missing the "| C of int" part of the DU
-namespace N
+module N
 
 type T = | C of int
 

tests/FSharp.Compiler.ComponentTests/FSharp.Compiler.ComponentTests.fsproj

@@ -199,6 +199,7 @@
     <Compile Include="CompilerOptions\fsc\reference.fs" />
     <Compile Include="CompilerOptions\fsc\reflectionfree.fs" />
     <Compile Include="CompilerOptions\fsc\refonlyrefout.fs" />
+	<Compile Include="CompilerOptions\fsc\sourceFiles.fs" />
     <Compile Include="Debugger\PortablePdbs.fs" />
     <Compile Include="Diagnostics\async.fs" />
     <Compile Include="Diagnostics\General.fs" />

tests/FSharp.Compiler.ComponentTests/FSharpChecker/CommonWorkflows.fs

@@ -89,3 +89,13 @@ let ``Changes in a referenced project`` () =
         saveFile "Library"
         checkFile "Last" expectSignatureChanged
     }
+
+[<Fact>]
+let ``Language service works if the same file is listed twice`` () = 
+    let file = sourceFile "First" []
+    let project =  SyntheticProject.Create(file)
+    project.Workflow {       
+        checkFile "First" expectOk
+        addFileAbove "First" file
+        checkFile "First" (expectSingleWarningAndNoErrors "Please verify that it is included only once in the project file.")
+    }
\ No newline at end of file

tests/FSharp.Test.Utilities/Compiler.fs

@@ -193,7 +193,7 @@ module rec Compiler =
     // Load the source file from the path
     let loadSourceFromFile path = getSource(TestType.Path path)
 
-    let private fsFromString (source: SourceCodeFileKind): FSharpCompilationSource =
+    let fsFromString (source: SourceCodeFileKind): FSharpCompilationSource =
         {
             Source            = source
             AdditionalSources = []
@@ -321,6 +321,7 @@ module rec Compiler =
 
     let asFs (cUnit: CompilationUnit) : CompilationUnit =
         match cUnit with
+        | FS { Source = SourceCodeFileKind.Fsi _} -> cUnit
         | FS src -> FS {src with Source=SourceCodeFileKind.Fs({FileName=src.Source.GetSourceFileName; SourceText=src.Source.GetSourceText})}
         | _ -> failwith "Only F# compilation can be of type Fs."
 

tests/FSharp.Test.Utilities/ProjectGeneration.fs

@@ -222,15 +222,6 @@ module Internal =
         let content = renderSourceFile p f
         writeFileIfChanged fileName content
 
-    let validateFileIdsAreUnique (project: SyntheticProject) =
-        let ids = [ for _, f in project.GetAllFiles() -> f.Id ]
-        let duplicates = ids |> List.groupBy id |> List.filter (fun (_, g) -> g.Length > 1)
-
-        if duplicates.Length > 0 then
-            failwith
-                $"""Source file IDs have to be unique across the project and all referenced projects. Found duplicates: {String.Join(", ", duplicates |> List.map fst)}"""
-
-
 open Internal
 
 
@@ -311,6 +302,21 @@ module ProjectOperations =
         if checkResult.Diagnostics.Length > 0 then
             failwith $"Expected no errors, but there were some: \n%A{checkResult.Diagnostics}"
 
+    let expectSingleWarningAndNoErrors (warningSubString:string) parseAndCheckResults _  = 
+        let checkResult = getTypeCheckResult parseAndCheckResults
+        let errors = checkResult.Diagnostics|> Array.filter (fun d -> d.Severity = FSharpDiagnosticSeverity.Error)
+        if errors.Length > 0 then
+            failwith $"Expected no errors, but there were some: \n%A{errors}"
+
+        let warnings = checkResult.Diagnostics|> Array.filter (fun d -> d.Severity = FSharpDiagnosticSeverity.Warning)
+        match warnings |> Array.tryExactlyOne with
+        | None -> failwith $"Expected 1 warning, but got {warnings.Length} instead: \n%A{warnings}"
+        | Some w -> 
+            if w.Message.Contains warningSubString then
+                ()
+            else 
+                failwith $"Expected 1 warning with substring '{warningSubString}' but got %A{w}"
+
     let expectErrors parseAndCheckResults _ =
         let checkResult = getTypeCheckResult parseAndCheckResults
 
@@ -378,7 +384,6 @@ type WorkflowContext =
 
 let SaveAndCheckProject project checker =
     async {
-        validateFileIdsAreUnique project
 
         do! saveProject project true checker
 

tests/fsharpqa/Source/CompilerOptions/fsc/gccerrors/env.lst

-ReqENU	SOURCE=gccerrors01.fs COMPILE_ONLY=1 SCFLAGS="--gccerrors --nologo gccerrors01.fs >gccerrors01.txt" POSTCMD="\$FSI_PIPE --nologo --quiet --exec ..\\..\\..\\comparer.fsx gccerrors01.txt gccerrors01.bsl"	
+ReqENU	SOURCE=gccerrors01.fs COMPILE_ONLY=1 SCFLAGS="--gccerrors --nologo >gccerrors01.txt" POSTCMD="\$FSI_PIPE --nologo --quiet --exec ..\\..\\..\\comparer.fsx gccerrors01.txt gccerrors01.bsl"	

tests/fsharpqa/Source/test.lst

@@ -10,7 +10,7 @@ CompilerOptions01,NoMT				CompilerOptions\fsc\crossoptimize
 CompilerOptions01,NoMT,Determinism  CompilerOptions\fsc\determinism
 CompilerOptions01,NoMT				CompilerOptions\fsc\dumpAllCommandLineOptions
 CompilerOptions01,NoMT				CompilerOptions\fsc\flaterrors
-CompilerOptions02,NoMT				CompilerOptions\fsc\gccerrors
+CompilerOptions02,NoMT,gcc			CompilerOptions\fsc\gccerrors
 CompilerOptions01,NoMT,help			CompilerOptions\fsc\help
 CompilerOptions01,NoMT				CompilerOptions\fsc\highentropyva
 CompilerOptions01,NoMT				CompilerOptions\fsc\langversion

tests/fsharpqa/run.fsharpqa.test.fsx

@@ -60,4 +60,4 @@ let runPerl arguments =
 
 let testResultDir = Path.Combine(rootFolder, "tests", "TestResults")
 let perlScript = Path.Combine(rootFolder, "tests", "fsharpqa", "testenv", "bin", "runall.pl")
-runPerl [|perlScript; "-resultsroot";testResultDir ;"-ttags:Determinism"|]
\ No newline at end of file
+runPerl [|perlScript; "-resultsroot";testResultDir ;"-ttags:gcc"|]
\ No newline at end of file