Move flatErrors tests from fsharpqa (#15251)

* temp

* tests

* flaterrors

* update tests

src/Compiler/Interactive/fsi.fs

@@ -4689,7 +4689,7 @@ type FsiEvaluationSession
         let errs = diagnosticsLogger.GetDiagnostics()
 
         let errorInfos =
-            DiagnosticHelpers.CreateDiagnostics(errorOptions, true, scriptFile, errs, true)
+            DiagnosticHelpers.CreateDiagnostics(errorOptions, true, scriptFile, errs, true, tcConfigB.flatErrors)
 
         let userRes =
             match res with

src/Compiler/Service/FSharpCheckerResults.fs

@@ -2207,7 +2207,8 @@ module internal ParseAndCheckFile =
             mainInputFileName,
             diagnosticsOptions: FSharpDiagnosticOptions,
             sourceText: ISourceText,
-            suggestNamesForErrors: bool
+            suggestNamesForErrors: bool,
+            flatErrors: bool
         ) =
         let mutable options = diagnosticsOptions
         let diagnosticsCollector = ResizeArray<_>()
@@ -2218,7 +2219,16 @@ module internal ParseAndCheckFile =
 
         let collectOne severity diagnostic =
             for diagnostic in
-                DiagnosticHelpers.ReportDiagnostic(options, false, mainInputFileName, fileInfo, diagnostic, severity, suggestNamesForErrors) do
+                DiagnosticHelpers.ReportDiagnostic(
+                    options,
+                    false,
+                    mainInputFileName,
+                    fileInfo,
+                    diagnostic,
+                    severity,
+                    suggestNamesForErrors,
+                    flatErrors
+                ) do
                 diagnosticsCollector.Add diagnostic
 
                 if severity = FSharpDiagnosticSeverity.Error then
@@ -2327,7 +2337,7 @@ module internal ParseAndCheckFile =
 
         usingLexbufForParsing (createLexbuf options.LangVersionText sourceText, fileName) (fun lexbuf ->
             let errHandler =
-                DiagnosticsHandler(false, fileName, options.DiagnosticOptions, sourceText, suggestNamesForErrors)
+                DiagnosticsHandler(false, fileName, options.DiagnosticOptions, sourceText, suggestNamesForErrors, false)
 
             let lexfun = createLexerFunction fileName options lexbuf errHandler
 
@@ -2421,6 +2431,7 @@ module internal ParseAndCheckFile =
             options: FSharpParsingOptions,
             userOpName: string,
             suggestNamesForErrors: bool,
+            flatErrors: bool,
             identCapture: bool
         ) =
         Trace.TraceInformation("FCS: {0}.{1} ({2})", userOpName, "parseFile", fileName)
@@ -2429,7 +2440,7 @@ module internal ParseAndCheckFile =
             Activity.start "ParseAndCheckFile.parseFile" [| Activity.Tags.fileName, fileName |]
 
         let errHandler =
-            DiagnosticsHandler(true, fileName, options.DiagnosticOptions, sourceText, suggestNamesForErrors)
+            DiagnosticsHandler(true, fileName, options.DiagnosticOptions, sourceText, suggestNamesForErrors, flatErrors)
 
         use _ = UseDiagnosticsLogger errHandler.DiagnosticsLogger
 
@@ -2596,7 +2607,14 @@ module internal ParseAndCheckFile =
 
             // Initialize the error handler
             let errHandler =
-                DiagnosticsHandler(true, mainInputFileName, tcConfig.diagnosticsOptions, sourceText, suggestNamesForErrors)
+                DiagnosticsHandler(
+                    true,
+                    mainInputFileName,
+                    tcConfig.diagnosticsOptions,
+                    sourceText,
+                    suggestNamesForErrors,
+                    tcConfig.flatErrors
+                )
 
             use _ = UseDiagnosticsLogger errHandler.DiagnosticsLogger
 
@@ -3260,6 +3278,7 @@ type FsiInteractiveChecker(legacyReferenceResolver, tcConfig: TcConfig, tcGlobal
                     parsingOptions,
                     userOpName,
                     suggestNamesForErrors,
+                    tcConfig.flatErrors,
                     tcConfig.captureIdentifiersWhenParsing
                 )
 

src/Compiler/Service/FSharpCheckerResults.fsi

@@ -537,6 +537,7 @@ module internal ParseAndCheckFile =
         options: FSharpParsingOptions *
         userOpName: string *
         suggestNamesForErrors: bool *
+        flatErrors: bool *
         identCapture: bool ->
             FSharpDiagnostic[] * ParsedInput * bool
 

src/Compiler/Service/IncrementalBuild.fs

@@ -1599,16 +1599,18 @@ type IncrementalBuilder(initialState: IncrementalBuilderInitialState, state: Inc
          }
 
         let diagnostics =
-            match builderOpt with
-            | Some builder ->
-                let diagnosticsOptions = builder.TcConfig.diagnosticsOptions
-                let diagnosticsLogger = CompilationDiagnosticLogger("IncrementalBuilderCreation", diagnosticsOptions)
-                delayedLogger.CommitDelayedDiagnostics diagnosticsLogger
-                diagnosticsLogger.GetDiagnostics()
-            | _ ->
-                Array.ofList delayedLogger.Diagnostics
+            let diagnostics, flatErrors =
+                match builderOpt with
+                | Some builder ->
+                    let diagnosticsOptions = builder.TcConfig.diagnosticsOptions
+                    let diagnosticsLogger = CompilationDiagnosticLogger("IncrementalBuilderCreation", diagnosticsOptions)
+                    delayedLogger.CommitDelayedDiagnostics diagnosticsLogger
+                    diagnosticsLogger.GetDiagnostics(), builder.TcConfig.flatErrors
+                | _ ->
+                    Array.ofList delayedLogger.Diagnostics, false
+            diagnostics
             |> Array.map (fun (diagnostic, severity) ->
-                FSharpDiagnostic.CreateFromException(diagnostic, severity, range.Zero, suggestNamesForErrors))
+                FSharpDiagnostic.CreateFromException(diagnostic, severity, range.Zero, suggestNamesForErrors, flatErrors))
 
         return builderOpt, diagnostics
       }

src/Compiler/Service/ServiceAssemblyContent.fs

@@ -247,7 +247,7 @@ module AssemblyContent =
         // are not triggered (see "if not entity.IsProvided") and the other data accessed is immutable or computed safely 
         // on-demand.  However a more compete review may be warranted.
 
-        use _ignoreAllDiagnostics = new DiagnosticsScope()  
+        use _ignoreAllDiagnostics = new DiagnosticsScope(false)  
 
         signature.TryGetEntities()
         |> Seq.collect (traverseEntity contentType Parent.Empty)
@@ -265,7 +265,7 @@ module AssemblyContent =
         // concurrently with other threads.  On an initial review this is not a problem since type provider computations
         // are not triggered (see "if not entity.IsProvided") and the other data accessed is immutable or computed safely 
         // on-demand.  However a more compete review may be warranted.
-        use _ignoreAllDiagnostics = new DiagnosticsScope()  
+        use _ignoreAllDiagnostics = new DiagnosticsScope(false)
 
 #if !NO_TYPEPROVIDERS 
         match assemblies |> List.filter (fun x -> not x.IsProviderGenerated), fileName with

src/Compiler/Service/ServiceParsedInputOps.fs

@@ -2012,7 +2012,7 @@ module ParsedInput =
         // We ignore all diagnostics during this operation
         //
         // Based on an initial review, no diagnostics should be generated.  However the code should be checked more closely.
-        use _ignoreAllDiagnostics = new DiagnosticsScope()
+        use _ignoreAllDiagnostics = new DiagnosticsScope(false)
 
         let mutable result = None
         let mutable ns = None
@@ -2175,7 +2175,7 @@ module ParsedInput =
             // We ignore all diagnostics during this operation
             //
             // Based on an initial review, no diagnostics should be generated.  However the code should be checked more closely.
-            use _ignoreAllDiagnostics = new DiagnosticsScope()
+            use _ignoreAllDiagnostics = new DiagnosticsScope(false)
 
             match res with
             | None -> [||]

src/Compiler/Service/service.fs

@@ -99,14 +99,14 @@ module Helpers =
         | _ -> false
 
 module CompileHelpers =
-    let mkCompilationDiagnosticsHandlers () =
+    let mkCompilationDiagnosticsHandlers (flatErrors) =
         let diagnostics = ResizeArray<_>()
 
         let diagnosticsLogger =
             { new DiagnosticsLogger("CompileAPI") with
 
                 member _.DiagnosticSink(diag, isError) =
-                    diagnostics.Add(FSharpDiagnostic.CreateFromException(diag, isError, range0, true)) // Suggest names for errors
+                    diagnostics.Add(FSharpDiagnostic.CreateFromException(diag, isError, range0, true, flatErrors)) // Suggest names for errors
 
                 member _.ErrorCount =
                     diagnostics
@@ -137,7 +137,8 @@ module CompileHelpers =
     /// Compile using the given flags.  Source files names are resolved via the FileSystem API. The output file must be given by a -o flag.
     let compileFromArgs (ctok, argv: string[], legacyReferenceResolver, tcImportsCapture, dynamicAssemblyCreator) =
 
-        let diagnostics, diagnosticsLogger, loggerProvider = mkCompilationDiagnosticsHandlers ()
+        let diagnostics, diagnosticsLogger, loggerProvider =
+            mkCompilationDiagnosticsHandlers (argv |> Array.contains "--flaterrors")
 
         let result =
             tryCompile diagnosticsLogger (fun exiter ->
@@ -487,7 +488,7 @@ type BackgroundCompiler
                 checkFileInProjectCache.Set(ltok, key, res)
                 res)
 
-    member _.ParseFile(fileName: string, sourceText: ISourceText, options: FSharpParsingOptions, cache: bool, userOpName: string) =
+    member _.ParseFile(fileName: string, sourceText: ISourceText, options: FSharpParsingOptions, cache: bool, flatErrors: bool, userOpName: string) =
         async {
             use _ =
                 Activity.start
@@ -507,14 +508,22 @@ type BackgroundCompiler
                     Interlocked.Increment(&actualParseFileCount) |> ignore
 
                     let parseDiagnostics, parseTree, anyErrors =
-                        ParseAndCheckFile.parseFile (sourceText, fileName, options, userOpName, suggestNamesForErrors, captureIdentifiersWhenParsing)
+                        ParseAndCheckFile.parseFile (
+                            sourceText,
+                            fileName,
+                            options,
+                            userOpName,
+                            suggestNamesForErrors,
+                            flatErrors,
+                            captureIdentifiersWhenParsing
+                        )
 
                     let res = FSharpParseFileResults(parseDiagnostics, parseTree, anyErrors, options.SourceFiles)
                     parseCacheLock.AcquireLock(fun ltok -> parseFileCache.Set(ltok, (fileName, hash, options), res))
                     return res
             else
                 let parseDiagnostics, parseTree, anyErrors =
-                    ParseAndCheckFile.parseFile (sourceText, fileName, options, userOpName, false, captureIdentifiersWhenParsing)
+                    ParseAndCheckFile.parseFile (sourceText, fileName, options, userOpName, false, flatErrors, captureIdentifiersWhenParsing)
 
                 return FSharpParseFileResults(parseDiagnostics, parseTree, anyErrors, options.SourceFiles)
         }
@@ -537,7 +546,14 @@ type BackgroundCompiler
                 let parseTree, _, _, parseDiagnostics = builder.GetParseResultsForFile fileName
 
                 let parseDiagnostics =
-                    DiagnosticHelpers.CreateDiagnostics(builder.TcConfig.diagnosticsOptions, false, fileName, parseDiagnostics, suggestNamesForErrors)
+                    DiagnosticHelpers.CreateDiagnostics(
+                        builder.TcConfig.diagnosticsOptions,
+                        false,
+                        fileName,
+                        parseDiagnostics,
+                        suggestNamesForErrors,
+                        builder.TcConfig.flatErrors
+                    )
 
                 let diagnostics = [| yield! creationDiags; yield! parseDiagnostics |]
 
@@ -767,6 +783,7 @@ type BackgroundCompiler
                             parsingOptions,
                             userOpName,
                             suggestNamesForErrors,
+                            builder.TcConfig.flatErrors,
                             captureIdentifiersWhenParsing
                         )
 
@@ -835,12 +852,26 @@ type BackgroundCompiler
                 let diagnosticsOptions = builder.TcConfig.diagnosticsOptions
 
                 let parseDiagnostics =
-                    DiagnosticHelpers.CreateDiagnostics(diagnosticsOptions, false, fileName, parseDiagnostics, suggestNamesForErrors)
+                    DiagnosticHelpers.CreateDiagnostics(
+                        diagnosticsOptions,
+                        false,
+                        fileName,
+                        parseDiagnostics,
+                        suggestNamesForErrors,
+                        builder.TcConfig.flatErrors
+                    )
 
                 let parseDiagnostics = [| yield! creationDiags; yield! parseDiagnostics |]
 
                 let tcDiagnostics =
-                    DiagnosticHelpers.CreateDiagnostics(diagnosticsOptions, false, fileName, tcDiagnostics, suggestNamesForErrors)
+                    DiagnosticHelpers.CreateDiagnostics(
+                        diagnosticsOptions,
+                        false,
+                        fileName,
+                        tcDiagnostics,
+                        suggestNamesForErrors,
+                        builder.TcConfig.flatErrors
+                    )
 
                 let tcDiagnostics = [| yield! creationDiags; yield! tcDiagnostics |]
 
@@ -994,7 +1025,14 @@ type BackgroundCompiler
                 let tcDependencyFiles = tcInfo.tcDependencyFiles
 
                 let tcDiagnostics =
-                    DiagnosticHelpers.CreateDiagnostics(diagnosticsOptions, true, fileName, tcDiagnostics, suggestNamesForErrors)
+                    DiagnosticHelpers.CreateDiagnostics(
+                        diagnosticsOptions,
+                        true,
+                        fileName,
+                        tcDiagnostics,
+                        suggestNamesForErrors,
+                        builder.TcConfig.flatErrors
+                    )
 
                 let diagnostics = [| yield! creationDiags; yield! tcDiagnostics |]
 
@@ -1083,8 +1121,6 @@ type BackgroundCompiler
                 [| Activity.Tags.fileName, fileName; Activity.Tags.userOpName, _userOpName |]
 
         cancellable {
-            use diagnostics = new DiagnosticsScope()
-
             // Do we add a reference to FSharp.Compiler.Interactive.Settings by default?
             let useFsiAuxLib = defaultArg useFsiAuxLib true
             let useSdkRefs = defaultArg useSdkRefs true
@@ -1102,6 +1138,8 @@ type BackgroundCompiler
 
             let otherFlags = defaultArg otherFlags extraFlags
 
+            use diagnostics = new DiagnosticsScope(otherFlags |> Array.contains "--flaterrors")
+
             let useSimpleResolution = otherFlags |> Array.exists (fun x -> x = "--simpleresolution")
 
             let loadedTimeStamp = defaultArg loadedTimeStamp DateTime.MaxValue // Not 'now', we don't want to force reloading
@@ -1159,7 +1197,8 @@ type BackgroundCompiler
 
             let diags =
                 loadClosure.LoadClosureRootFileDiagnostics
-                |> List.map (fun (exn, isError) -> FSharpDiagnostic.CreateFromException(exn, isError, range.Zero, false))
+                |> List.map (fun (exn, isError) ->
+                    FSharpDiagnostic.CreateFromException(exn, isError, range.Zero, false, options.OtherOptions |> Array.contains "--flaterrors"))
 
             return options, (diags @ diagnostics.Diagnostics)
         }
@@ -1414,7 +1453,7 @@ type FSharpChecker
     member _.ParseFile(fileName, sourceText, options, ?cache, ?userOpName: string) =
         let cache = defaultArg cache true
         let userOpName = defaultArg userOpName "Unknown"
-        backgroundCompiler.ParseFile(fileName, sourceText, options, cache, userOpName)
+        backgroundCompiler.ParseFile(fileName, sourceText, options, cache, false, userOpName)
 
     member ic.ParseFileInProject(fileName, source: string, options, ?cache: bool, ?userOpName: string) =
         let parsingOptions, _ = ic.GetParsingOptionsFromProjectOptions(options)
@@ -1650,7 +1689,7 @@ type FSharpChecker
     member _.GetParsingOptionsFromCommandLineArgs(sourceFiles, argv, ?isInteractive, ?isEditing) =
         let isEditing = defaultArg isEditing false
         let isInteractive = defaultArg isInteractive false
-        use errorScope = new DiagnosticsScope()
+        use errorScope = new DiagnosticsScope(argv |> List.contains "--flaterrors")
 
         let tcConfigB =
             TcConfigBuilder.CreateNew(