[Repo Assist] feat: add GenerateAnonRecordStub code fix for FS3578 (closes #455)

src/FsAutoComplete/CodeFixes/GenerateAnonRecordStub.fs

@@ -0,0 +1,164 @@
+module FsAutoComplete.CodeFix.GenerateAnonRecordStub
+
+open System.Text.RegularExpressions
+open FSharp.Compiler.Syntax
+open FSharp.Compiler.Text
+open FsToolkit.ErrorHandling
+open FsAutoComplete.CodeFix.Types
+open Ionide.LanguageServerProtocol.Types
+open FsAutoComplete
+open FsAutoComplete.LspHelpers
+
+let title = "Add missing anonymous record fields"
+
+// FS0001 message patterns for anonymous record field mismatches (current F# compiler 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]."
+
+/// Extract missing field names from an FS0001 anonymous-record diagnostic message.
+/// Returns `Some fields` when the message describes fields that should be added; `None` otherwise.
+let private tryParseMissingFields (message: string) : string list option =
+  // Case 1: single missing field – "This anonymous record is missing field 'X'."
+  let m1 = Regex.Match(message, @"missing field '([^']+)'")
+
+  if m1.Success then
+    Some [ m1.Groups.[1].Value ]
+  else
+    // Case 2: multiple missing fields in quotes – "This anonymous record is missing fields 'X', 'Y'."
+    // Use a more specific pattern that requires quoted field names.
+    let m2 = Regex.Match(message, @"missing fields '([^']+)'")
+
+    if m2.Success then
+      // The full field list group includes all quoted names; extract each individually.
+      let fullMatch = Regex.Match(message, @"missing fields (.+?)\.")
+
+      let fieldList =
+        if fullMatch.Success then
+          fullMatch.Groups.[1].Value
+        else
+          m2.Value
+
+      let fields =
+        Regex.Matches(fieldList, "'([^']+)'")
+        |> Seq.cast<Match>
+        |> Seq.map (fun m -> m.Groups.[1].Value)
+        |> Seq.toList
+
+      if fields.IsEmpty then None else Some fields
+    else
+      // Case 3: "does not exactly match" – extract from "Add the missing fields [X; Y]"
+      let m3 = Regex.Match(message, @"Add the missing fields \[([^\]]+)\]")
+
+      if m3.Success then
+        let fieldsStr = m3.Groups.[1].Value
+
+        let fields =
+          fieldsStr.Split(';')
+          |> Array.map (fun s -> s.Trim())
+          |> Array.filter (fun s -> s.Length > 0)
+          |> Array.toList
+
+        if fields.IsEmpty then None else Some fields
+      else
+        None
+
+/// A code fix for FS0001 anonymous-record type mismatches: when an anonymous record literal is
+/// missing fields required by its expected type, inserts stub bindings
+/// `fieldName = failwith "Not Implemented"` for each missing field before the closing `|}`.
+let fix (getParseResultsForFile: GetParseResultsForFile) : CodeFix =
+  Run.ifDiagnosticByCode (Set.ofList [ "1" ]) (fun diagnostic codeActionParams ->
+    asyncResult {
+      // Only act on anonymous-record field-mismatch errors
+      do!
+        Result.guard
+          (fun _ ->
+            diagnostic.Message.Contains("anonymous record")
+            && diagnostic.Message.Contains("missing"))
+          "Diagnostic is not an anonymous record missing-field error"
+
+      let missingFields =
+        match tryParseMissingFields diagnostic.Message with
+        | Some fields -> fields
+        | None -> []
+
+      if missingFields.IsEmpty then
+        return []
+      else
+
+        let fileName = codeActionParams.TextDocument.GetFilePath() |> Utils.normalizePath
+        let fcsPos = protocolPosToPos diagnostic.Range.Start
+        let! (parseAndCheck, _, sourceText) = getParseResultsForFile fileName fcsPos
+
+        // Find the innermost anonymous record expression that contains the diagnostic start position.
+        let anonRecdOpt =
+          (fcsPos, parseAndCheck.GetParseResults.ParseTree)
+          ||> ParsedInput.tryPick (fun _path node ->
+            match node with
+            | SyntaxNode.SynExpr(SynExpr.AnonRecd(recordFields = fields; range = r)) when
+              Range.rangeContainsPos r fcsPos
+              ->
+              let currentNames =
+                fields
+                |> List.map (fun (synLongIdent, _, _) -> (synLongIdent.LongIdent |> List.last).idText)
+                |> Set.ofList
+
+              Some(r, currentNames)
+            | _ -> None)
+
+        match anonRecdOpt with
+        | None -> return []
+        | Some(r, currentFields) ->
+
+          // Exclude any fields that are already present (defensive: should already be absent).
+          let fieldsToAdd =
+            missingFields |> List.filter (fun f -> not (Set.contains f currentFields))
+
+          if fieldsToAdd.IsEmpty then
+            return []
+          else
+
+            // Build "fieldName = failwith "Not Implemented"" stubs for each missing field.
+            let fieldStubs =
+              fieldsToAdd
+              |> List.map (fun f -> $"{f} = failwith \"Not Implemented\"")
+              |> String.concat "; "
+
+            // The anonymous record range ends just after '}' in '|}', so '|' is at EndColumn − 2.
+            let endBarCol = r.EndColumn - 2
+
+            // Build the insert text and range depending on whether the record already has fields.
+            // For non-empty records, trailing whitespace before `|}` must be consumed by the edit
+            // to avoid producing `{| A = 1 ; B = ... |}` (space before the semicolon).
+            let insertText, insertRange =
+              if currentFields.IsEmpty then
+                // Empty record: simple zero-width insert before `|}`.
+                let lspPos = fcsPosToLsp (Position.mkPos r.EndLine endBarCol)
+                $" {fieldStubs} ", { Start = lspPos; End = lspPos }
+              else
+                // Non-empty record: replace any trailing whitespace before `|}` so the result
+                // is e.g. `{| A = 1; B = failwith "Not Implemented" |}` (no stray space).
+                let insertStartCol =
+                  match sourceText.GetLine(Position.mkPos r.EndLine 0) with
+                  | None -> endBarCol
+                  | Some line ->
+                    let mutable col = endBarCol - 1
+
+                    while col >= 0 && col < line.Length && System.Char.IsWhiteSpace(line.[col]) do
+                      col <- col - 1
+
+                    col + 1
+
+                let lspStart = fcsPosToLsp (Position.mkPos r.EndLine insertStartCol)
+                let lspEnd = fcsPosToLsp (Position.mkPos r.EndLine endBarCol)
+                $"; {fieldStubs} ", { Start = lspStart; End = lspEnd }
+
+            return
+              [ { Title = title
+                  File = codeActionParams.TextDocument
+                  SourceDiagnostic = Some diagnostic
+                  Edits =
+                    [| { Range = insertRange
+                         NewText = insertText } |]
+                  Kind = FixKind.Fix } ]
+    })

src/FsAutoComplete/CodeFixes/GenerateAnonRecordStub.fsi

@@ -0,0 +1,6 @@
+module FsAutoComplete.CodeFix.GenerateAnonRecordStub
+
+open FsAutoComplete.CodeFix.Types
+
+val title: string
+val fix: getParseResultsForFile: GetParseResultsForFile -> CodeFix

src/FsAutoComplete/LspServers/AdaptiveServerState.fs

@@ -2388,7 +2388,8 @@ type AdaptiveState
          IgnoreExpression.fix tryGetParseAndCheckResultsForFile
          ExprTypeMismatch.fix tryGetParseAndCheckResultsForFile
          AddMissingSeq.fix tryGetParseAndCheckResultsForFile
-         IntroduceMissingBinding.fix tryGetParseAndCheckResultsForFile getLineText |])
+         IntroduceMissingBinding.fix tryGetParseAndCheckResultsForFile getLineText
+         GenerateAnonRecordStub.fix tryGetParseAndCheckResultsForFile |])
 
   let forgetDocument (uri: DocumentUri) =
     async {

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

@@ -0,0 +1,39 @@
+module private FsAutoComplete.Tests.CodeFixTests.GenerateAnonRecordStubTests
+
+open Expecto
+open Helpers
+open Utils.ServerTests
+open Utils.CursorbasedTests
+open FsAutoComplete.CodeFix
+
+let tests state =
+  serverTestList (nameof GenerateAnonRecordStub) state defaultConfigDto None (fun server ->
+    [ testCaseAsync "add one missing field to anonymous record"
+      <| CodeFix.check
+        server
+        """let f (x: {| A: int; B: string |}) = x
+let y = f {| A$0 = 1 |}"""
+        Diagnostics.acceptAll
+        (CodeFix.withTitle GenerateAnonRecordStub.title)
+        """let f (x: {| A: int; B: string |}) = x
+let y = f {| A = 1; B = failwith "Not Implemented" |}"""
+
+      testCaseAsync "add multiple missing fields to anonymous record"
+      <| CodeFix.check
+        server
+        """let f (x: {| A: int; B: string; C: bool |}) = x
+let y = f {| A$0 = 1 |}"""
+        Diagnostics.acceptAll
+        (CodeFix.withTitle GenerateAnonRecordStub.title)
+        """let f (x: {| A: int; B: string; C: bool |}) = x
+let y = f {| A = 1; B = failwith "Not Implemented"; C = failwith "Not Implemented" |}"""
+
+      testCaseAsync "add missing field to empty anonymous record"
+      <| CodeFix.check
+        server
+        """let f (x: {| A: int |}) = x
+let y = f {|$0|}"""
+        Diagnostics.acceptAll
+        (CodeFix.withTitle GenerateAnonRecordStub.title)
+        """let f (x: {| A: int |}) = x
+let y = f {| A = failwith "Not Implemented" |}""" ])

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

@@ -3735,4 +3735,5 @@ let tests textFactory state =
       ExprTypeMismatchTests.tests state
       AddMissingWildcardOperatorTests.tests state
       AddMissingSeqTests.tests state
-      IntroduceMissingBindingTests.tests state ]
+      IntroduceMissingBindingTests.tests state
+      GenerateAnonRecordStubTests.tests state ]