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[Repo Assist] feat: add GenerateAnonRecordStub code fix for FS3578 (closes #455) (#1510)
* feat: add GenerateAnonRecordStub code fix for FS3578 (closes #455) When an anonymous record literal is missing fields required by its expected type, offer a code action that inserts stub bindings `fieldName = failwith "Not Implemented"` for each missing field before the closing `|}`. The fix is triggered by FS3578 ('Two anonymous record types have mismatched sets of field names'). It parses the two field-name lists from the diagnostic message, finds the anonymous record expression in the parse tree, and computes which fields are absent. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> * ci: trigger checks * fix: update GenerateAnonRecordStub to use FS0001 with current compiler message formats The code fix was using diagnostic code 3578 with an old message format ('Two anonymous record types have mismatched sets of field names ["A"; "B"] and ["A"]') that the current F# compiler no longer produces. Current F# compiler (>= 8) emits FS0001 for anonymous record field mismatches with these message formats: - "This anonymous record is missing field 'B'." - "This anonymous record is missing fields 'B', 'C'." - "This anonymous record does not exactly match the expected shape. Add the missing fields [B; C] and remove the extra fields [D; E]." Updated the code fix to: 1. Trigger on FS0001 with a message guard for 'anonymous record' + 'missing' 2. Parse missing field names from the three new message formats 3. Preserve the existing AST-based insertion logic Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> * fix: GenerateAnonRecordStub - trim trailing whitespace before inserting fields When an anonymous record has existing fields (e.g. `{| A = 1 |}`), the previous code inserted the fix text at the column of `|` in `|}`, but there was already a trailing space before `|}`. This produced `{| A = 1 ; B = failwith "Not Implemented" |}` (stray space before `;'}). Fix: for non-empty records, scan backward from the `|` position using the source text to find the end of actual content, then use a replace range that covers the trailing whitespace. The empty-record case is unchanged (zero-width insert). All 3 GenerateAnonRecordStub tests now pass. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> --------- Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com> Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
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‎src/FsAutoComplete/CodeFixes/GenerateAnonRecordStub.fs‎

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module FsAutoComplete.CodeFix.GenerateAnonRecordStub
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open System.Text.RegularExpressions
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open FSharp.Compiler.Syntax
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open FSharp.Compiler.Text
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open FsToolkit.ErrorHandling
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open FsAutoComplete.CodeFix.Types
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open Ionide.LanguageServerProtocol.Types
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open FsAutoComplete
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open FsAutoComplete.LspHelpers
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let title = "Add missing anonymous record fields"
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// FS0001 message patterns for anonymous record field mismatches (current F# compiler formats):
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// "This anonymous record is missing field 'B'."
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// "This anonymous record is missing fields 'B', 'C'."
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// "This anonymous record does not exactly match the expected shape. Add the missing fields [B; C] and remove the extra fields [D; E]."
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/// Extract missing field names from an FS0001 anonymous-record diagnostic message.
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/// Returns `Some fields` when the message describes fields that should be added; `None` otherwise.
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let private tryParseMissingFields (message: string) : string list option =
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// Case 1: single missing field – "This anonymous record is missing field 'X'."
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let m1 = Regex.Match(message, @"missing field '([^']+)'")
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if m1.Success then
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Some [ m1.Groups.[1].Value ]
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else
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// Case 2: multiple missing fields in quotes – "This anonymous record is missing fields 'X', 'Y'."
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// Use a more specific pattern that requires quoted field names.
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let m2 = Regex.Match(message, @"missing fields '([^']+)'")
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if m2.Success then
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// The full field list group includes all quoted names; extract each individually.
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let fullMatch = Regex.Match(message, @"missing fields (.+?)\.")
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let fieldList =
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if fullMatch.Success then
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fullMatch.Groups.[1].Value
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else
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m2.Value
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let fields =
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Regex.Matches(fieldList, "'([^']+)'")
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|> Seq.cast<Match>
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|> Seq.map (fun m -> m.Groups.[1].Value)
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|> Seq.toList
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if fields.IsEmpty then None else Some fields
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else
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// Case 3: "does not exactly match" – extract from "Add the missing fields [X; Y]"
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let m3 = Regex.Match(message, @"Add the missing fields \[([^\]]+)\]")
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if m3.Success then
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let fieldsStr = m3.Groups.[1].Value
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let fields =
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fieldsStr.Split(';')
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|> Array.map (fun s -> s.Trim())
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|> Array.filter (fun s -> s.Length > 0)
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|> Array.toList
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if fields.IsEmpty then None else Some fields
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else
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None
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/// A code fix for FS0001 anonymous-record type mismatches: when an anonymous record literal is
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/// missing fields required by its expected type, inserts stub bindings
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/// `fieldName = failwith "Not Implemented"` for each missing field before the closing `|}`.
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let fix (getParseResultsForFile: GetParseResultsForFile) : CodeFix =
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Run.ifDiagnosticByCode (Set.ofList [ "1" ]) (fun diagnostic codeActionParams ->
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asyncResult {
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// Only act on anonymous-record field-mismatch errors
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do!
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Result.guard
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(fun _ ->
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diagnostic.Message.Contains("anonymous record")
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&& diagnostic.Message.Contains("missing"))
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"Diagnostic is not an anonymous record missing-field error"
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let missingFields =
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match tryParseMissingFields diagnostic.Message with
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| Some fields -> fields
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| None -> []
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if missingFields.IsEmpty then
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return []
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else
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let fileName = codeActionParams.TextDocument.GetFilePath() |> Utils.normalizePath
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let fcsPos = protocolPosToPos diagnostic.Range.Start
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let! (parseAndCheck, _, sourceText) = getParseResultsForFile fileName fcsPos
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// Find the innermost anonymous record expression that contains the diagnostic start position.
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let anonRecdOpt =
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(fcsPos, parseAndCheck.GetParseResults.ParseTree)
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||> ParsedInput.tryPick (fun _path node ->
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match node with
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| SyntaxNode.SynExpr(SynExpr.AnonRecd(recordFields = fields; range = r)) when
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Range.rangeContainsPos r fcsPos
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->
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let currentNames =
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fields
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|> List.map (fun (synLongIdent, _, _) -> (synLongIdent.LongIdent |> List.last).idText)
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|> Set.ofList
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Some(r, currentNames)
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| _ -> None)
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match anonRecdOpt with
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| None -> return []
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| Some(r, currentFields) ->
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// Exclude any fields that are already present (defensive: should already be absent).
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let fieldsToAdd =
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missingFields |> List.filter (fun f -> not (Set.contains f currentFields))
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if fieldsToAdd.IsEmpty then
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return []
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else
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// Build "fieldName = failwith "Not Implemented"" stubs for each missing field.
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let fieldStubs =
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fieldsToAdd
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|> List.map (fun f -> $"{f} = failwith \"Not Implemented\"")
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|> String.concat "; "
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// The anonymous record range ends just after '}' in '|}', so '|' is at EndColumn − 2.
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let endBarCol = r.EndColumn - 2
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// Build the insert text and range depending on whether the record already has fields.
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// For non-empty records, trailing whitespace before `|}` must be consumed by the edit
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// to avoid producing `{| A = 1 ; B = ... |}` (space before the semicolon).
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let insertText, insertRange =
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if currentFields.IsEmpty then
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// Empty record: simple zero-width insert before `|}`.
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let lspPos = fcsPosToLsp (Position.mkPos r.EndLine endBarCol)
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$" {fieldStubs} ", { Start = lspPos; End = lspPos }
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else
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// Non-empty record: replace any trailing whitespace before `|}` so the result
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// is e.g. `{| A = 1; B = failwith "Not Implemented" |}` (no stray space).
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let insertStartCol =
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match sourceText.GetLine(Position.mkPos r.EndLine 0) with
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| None -> endBarCol
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| Some line ->
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let mutable col = endBarCol - 1
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while col >= 0 && col < line.Length && System.Char.IsWhiteSpace(line.[col]) do
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col <- col - 1
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col + 1
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let lspStart = fcsPosToLsp (Position.mkPos r.EndLine insertStartCol)
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let lspEnd = fcsPosToLsp (Position.mkPos r.EndLine endBarCol)
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$"; {fieldStubs} ", { Start = lspStart; End = lspEnd }
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return
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[ { Title = title
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File = codeActionParams.TextDocument
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SourceDiagnostic = Some diagnostic
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Edits =
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[| { Range = insertRange
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NewText = insertText } |]
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Kind = FixKind.Fix } ]
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})

‎src/FsAutoComplete/CodeFixes/GenerateAnonRecordStub.fsi‎

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module FsAutoComplete.CodeFix.GenerateAnonRecordStub
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open FsAutoComplete.CodeFix.Types
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val title: string
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val fix: getParseResultsForFile: GetParseResultsForFile -> CodeFix

‎src/FsAutoComplete/LspServers/AdaptiveServerState.fs‎

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IgnoreExpression.fix tryGetParseAndCheckResultsForFile
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ExprTypeMismatch.fix tryGetParseAndCheckResultsForFile
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AddMissingSeq.fix tryGetParseAndCheckResultsForFile
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IntroduceMissingBinding.fix tryGetParseAndCheckResultsForFile getLineText |])
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IntroduceMissingBinding.fix tryGetParseAndCheckResultsForFile getLineText
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GenerateAnonRecordStub.fix tryGetParseAndCheckResultsForFile |])
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let forgetDocument (uri: DocumentUri) =
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async {

‎test/FsAutoComplete.Tests.Lsp/CodeFixTests/GenerateAnonRecordStubTests.fs‎

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module private FsAutoComplete.Tests.CodeFixTests.GenerateAnonRecordStubTests
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open Expecto
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open Helpers
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open Utils.ServerTests
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open Utils.CursorbasedTests
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open FsAutoComplete.CodeFix
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let tests state =
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serverTestList (nameof GenerateAnonRecordStub) state defaultConfigDto None (fun server ->
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[ testCaseAsync "add one missing field to anonymous record"
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<| CodeFix.check
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server
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"""let f (x: {| A: int; B: string |}) = x
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let y = f {| A$0 = 1 |}"""
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Diagnostics.acceptAll
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(CodeFix.withTitle GenerateAnonRecordStub.title)
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"""let f (x: {| A: int; B: string |}) = x
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let y = f {| A = 1; B = failwith "Not Implemented" |}"""
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testCaseAsync "add multiple missing fields to anonymous record"
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<| CodeFix.check
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server
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"""let f (x: {| A: int; B: string; C: bool |}) = x
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let y = f {| A$0 = 1 |}"""
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Diagnostics.acceptAll
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(CodeFix.withTitle GenerateAnonRecordStub.title)
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"""let f (x: {| A: int; B: string; C: bool |}) = x
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let y = f {| A = 1; B = failwith "Not Implemented"; C = failwith "Not Implemented" |}"""
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testCaseAsync "add missing field to empty anonymous record"
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<| CodeFix.check
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server
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"""let f (x: {| A: int |}) = x
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let y = f {|$0|}"""
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Diagnostics.acceptAll
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(CodeFix.withTitle GenerateAnonRecordStub.title)
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"""let f (x: {| A: int |}) = x
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let y = f {| A = failwith "Not Implemented" |}""" ])

‎test/FsAutoComplete.Tests.Lsp/CodeFixTests/Tests.fs‎

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ExprTypeMismatchTests.tests state
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AddMissingWildcardOperatorTests.tests state
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AddMissingSeqTests.tests state
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IntroduceMissingBindingTests.tests state ]
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IntroduceMissingBindingTests.tests state
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GenerateAnonRecordStubTests.tests state ]

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