Editor: Fix Record fields completion in update record with partial field name (#18946)

Author: edgarfgp

docs/release-notes/.FSharp.Compiler.Service/10.0.100.md

@@ -36,6 +36,7 @@
 * Caches: type subsumption cache key perf regression ([Issue #18925](https://github.com/dotnet/fsharp/issues/18925) [PR #18926](https://github.com/dotnet/fsharp/pull/18926))
 * Ensure that line directives are applied to source identifiers (issue [#18908](https://github.com/dotnet/fsharp/issues/18908), PR [#18918](https://github.com/dotnet/fsharp/pull/18918))
 * Fix expected and actual types in ErrorFromAddingTypeEquation message and extended diagnostic data. ([PR #18915](https://github.com/dotnet/fsharp/pull/18915))
+* Editor: Fix Record fields completion in update record with partial field name. ([PR #18946](https://github.com/dotnet/fsharp/pull/18946))
 
 ### Changed
 * Use `errorR` instead of `error` in `CheckDeclarations.fs` when possible. ([PR #18645](https://github.com/dotnet/fsharp/pull/18645))

src/Compiler/Service/ServiceParseTreeWalk.fs

@@ -528,7 +528,17 @@ module SyntaxTraversal =
                         for SynExprRecordField(fieldName = (field, _); expr = e; blockSeparator = sepOpt) in fields do
                             yield
                                 dive (path, copyOpt, Some field) field.Range (fun r ->
-                                    if rangeContainsPos field.Range pos then
+                                    // Treat the caret placed right after the field name (before '=' or a value) as "inside" the field,
+                                    // but only if the field does not yet have a value.
+                                    //
+                                    // Examples (the '$' marks the caret):
+                                    //   { r with Field1$ }
+                                    //   { r with
+                                    //       Field1$
+                                    //   }
+                                    let isCaretAfterFieldNameWithoutValue = (e.IsNone && posEq pos field.Range.End)
+
+                                    if rangeContainsPos field.Range pos || isCaretAfterFieldNameWithoutValue then
                                         visitor.VisitRecordField r
                                     else
                                         None)

tests/FSharp.Compiler.Service.Tests/EditorTests.fs

@@ -1937,6 +1937,15 @@ let hasRecordType (recordTypeName: string) (symbolUses: FSharpSymbolUse list) =
         | _ -> false
     )
     |> fun exists -> Assert.True(exists, $"Record type {recordTypeName} not found.")
+    
+let private assertItemsWithNames contains names (completionInfo: DeclarationListInfo) =
+    let itemNames = completionInfo.Items |> Array.map _.NameInCode |> set
+
+    for name in names do
+        Assert.True(Set.contains name itemNames = contains)
+
+let assertHasItemWithNames names (completionInfo: DeclarationListInfo) =
+    assertItemsWithNames true names completionInfo
 
 [<Fact>]
 let ``Record fields are completed via type name usage`` () =
@@ -2113,34 +2122,63 @@ let rUpdate = { r1 with  }
     hasRecordField "Field1" declarations
     hasRecordField "Field2" declarations
 
-[<Fact(Skip = "Current fails to suggest any record fields")>]
+[<Fact>]
 let ``Record fields are completed in update record with partial field name`` () =
-    let parseResults, checkResults =
-        getParseAndCheckResults """
+    let info = Checker.getCompletionInfo """
 module Module
 
 type R1 =
     { Field1: int; Field2: int }
 
 let r1 = { Field1 = 1; Field2 = 2 }
 
-let rUpdate = { r1 with Fi }
+let rUpdate = { r1 with Fi{caret} }
 """
 
-    let declarations =
-        checkResults.GetDeclarationListSymbols(
-            Some parseResults,
-            9,
-            "let rUpdate = { r1 with Fi }",
-            {
-                EndColumn = 26
-                LastDotPos = None
-                PartialIdent = "Fi"
-                QualifyingIdents = []
-            },
-            fun _ -> List.empty
-        )
-        |> List.concat
+    assertHasItemWithNames ["Field1"; "Field2"] info
 
-    hasRecordField "Field1" declarations
-    hasRecordField "Field2" declarations
+[<Fact>]
+let ``Multiline record fields are completed in update record with partial field name`` () =
+    let info = Checker.getCompletionInfo """
+module Module
+
+type R1 =
+    { Field1: int; Field2: int }
+
+let r1 = { Field1 = 1; Field2 = 2 }
+
+let rUpdate =
+    { r1 with
+        Fi{caret}
+    }
+"""
+
+    assertHasItemWithNames ["Field1"; "Field2"] info
+    
+[<Fact>]
+let ``No record field completion after '=' with missing value in first binding (after =;)`` () =
+    let info = Checker.getCompletionInfo """
+module M
+
+type X =
+   val field1: int
+   val field2: string
+
+let x = new X()
+let _ = { field1 =; {caret} }
+"""
+    assertItemsWithNames false ["field1"; "field2"] info
+
+[<Fact>]
+let ``No record field completion after '=' with missing value in first binding (after =; f)`` () =
+    let info = Checker.getCompletionInfo """
+module M
+
+type X =
+   val field1: int
+   val field2: string
+
+let x = new X()
+let _ = { field1 =; f{caret} }
+"""
+    assertItemsWithNames false ["field1"; "field2"] info