Use struct-returning partial active patterns

src/FSharp.Data.GraphQL.Client/ReflectionPatterns.fs

@@ -24,6 +24,13 @@ module ReflectionPatterns =
     let isOption (t : Type) =
         t.IsGenericType && t.GetGenericTypeDefinition() = typedefof<_ option>
 
+    /// <summary>
+    /// Returns <see langword="true"/> when <paramref name="t"/> is an F# <c>voption</c> type.
+    /// </summary>
+    /// <param name="t">Type to inspect.</param>
+    let isValueOption (t : Type) =
+        t.IsGenericType && t.GetGenericTypeDefinition() = typedefof<_ voption>
+
     let isMap (t : Type) =
        t = typeof<Map<string, obj>>
 
@@ -70,49 +77,86 @@ module ReflectionPatterns =
         let (_, none, _) = getOptionCases t
         FSharpValue.MakeUnion(none, [||])
 
+    let private getValueOptionCases (t : Type) =
+        let votype = typedefof<_ voption>.MakeGenericType(t)
+        let cases = FSharpType.GetUnionCases (votype)
+        let valueSome = cases |> Array.find (fun c -> c.Name = "ValueSome")
+        let valueNone = cases |> Array.find (fun c -> c.Name = "ValueNone")
+        (valueSome, valueNone, votype)
+
+    /// <summary>
+    /// Builds a boxed <c>'T voption</c> value: <see langword="null"/> becomes <c>ValueNone</c>, otherwise the value is wrapped as <c>ValueSome</c>.
+    /// </summary>
+    let makeValueOption (t : Type) (value : obj) =
+        let (valueSome, valueNone, _) = getValueOptionCases t
+        if isNull value then
+            FSharpValue.MakeUnion (valueNone, [||])
+        else
+            FSharpValue.MakeUnion (valueSome, [| value |])
+
+    [<return: Struct>]
     let (|Option|_|) t =
-        if isOption t then Some (Option (t.GetGenericArguments().[0]))
-        else None
+        if isOption t then ValueSome (Option (t.GetGenericArguments().[0]))
+        else ValueNone
+
+    /// <summary>
+    /// Matches F# <c>voption</c> types and extracts their generic value type.
+    /// </summary>
+    /// <param name="t">Type to inspect.</param>
+    [<return: Struct>]
+    let (|ValueOption|_|) t =
+        if isValueOption t then ValueSome (ValueOption (t.GetGenericArguments().[0]))
+        else ValueNone
 
     let isType (expected : Type) (t : Type) =
         match t with
         | Option t -> t = expected
+        | ValueOption t -> t = expected
         | _ -> t = expected
 
     let isNumericType (t : Type) =
         numericTypes |> Array.exists (fun expected -> isType expected t)
 
+    [<return: Struct>]
     let (|Array|_|) (t : Type) =
-        if t.IsArray then Some (Array (t.GetElementType()))
-        else None
+        if t.IsArray then ValueSome (Array (t.GetElementType()))
+        else ValueNone
 
+    [<return: Struct>]
     let (|List|_|) (t : Type) =
-        if isList t then Some (List (t.GetGenericArguments().[0]))
-        else None
+        if isList t then ValueSome (List (t.GetGenericArguments().[0]))
+        else ValueNone
 
+    [<return: Struct>]
     let (|Seq|_|) (t : Type) =
-        if isSeq t then Some (Seq (t.GetGenericArguments().[0]))
-        else None
+        if isSeq t then ValueSome (Seq (t.GetGenericArguments().[0]))
+        else ValueNone
 
+    [<return: Struct>]
     let (|EnumerableValue|_|) (x : obj) =
         match x with
-        | :? IEnumerable as x -> Some (EnumerableValue (Seq.cast<obj> x |> Array.ofSeq))
-        | _ -> None
+        | :? IEnumerable as x -> ValueSome (EnumerableValue (Seq.cast<obj> x |> Array.ofSeq))
+        | _ -> ValueNone
 
+    [<return: Struct>]
     let (|OptionValue|_|) (x : obj) =
         let xtype = x.GetType()
+        let tryGetValue optionType =
+            match FSharpValue.GetUnionFields(x, optionType) with
+            | (_, [|value|]) -> ValueSome (OptionValue Some value)
+            | _ -> ValueSome (OptionValue None)
         if isOption xtype
-        then
-            match FSharpValue.GetUnionFields(x, xtype) with
-            | (_, [|value|]) -> Some (OptionValue Some value)
-            | _ -> Some (OptionValue None)
-        else None
+        then tryGetValue xtype
+        elif isValueOption xtype
+        then tryGetValue xtype
+        else ValueNone
 
+    [<return: Struct>]
     let (|EnumValue|_|) (x : obj) =
         let xtype = x.GetType()
         if xtype.IsEnum
-        then Some (x.ToString())
-        else None
+        then ValueSome (x.ToString())
+        else ValueNone
 
     let makeValue (t : Type) (value : obj) =
         let isOption = isOption t

src/FSharp.Data.GraphQL.Client/Serialization.fs

@@ -24,11 +24,13 @@ module Serialization =
     let private downcastNone<'T> t =
         match t with
         | Option t -> downcast (makeOption t null)
+        | ValueOption t -> downcast (makeValueOption t null)
         | _ -> failwith $"Error parsing JSON value: %O{t} is not an option value."
 
     let private downcastType (t : Type) x =
         match t with
         | Option t -> downcast (makeOption t (Convert.ChangeType(x, t)))
+        | ValueOption t -> downcast (makeValueOption t (Convert.ChangeType(x, t)))
         | _ -> downcast (Convert.ChangeType(x, t))
 
     let private isStringType = isType typeof<string>
@@ -37,7 +39,7 @@ module Serialization =
     let private isUriType = isType typeof<Uri>
     let private isGuidType = isType typeof<Guid>
     let private isBooleanType = isType typeof<bool>
-    let private isEnumType = function (Option t | t) when t.IsEnum -> true | _ -> false
+    let private isEnumType = function (Option t | ValueOption t | t) when t.IsEnum -> true | _ -> false
 
     let private downcastString (t : Type) (s : string) =
         match t with
@@ -60,7 +62,7 @@ module Serialization =
             | _ -> failwith $"Error parsing JSON value: %O{t} is a Guid type, but parsing of value \"%s{s}\" failed."
         | t when isEnumType t ->
             match t with
-            | (Option et | et) ->
+            | (Option et | ValueOption et | et) ->
                 try Enum.Parse(et, s) |> downcastType t
                 with _ -> failwith $"Error parsing JSON value: %O{t} is a Enum type, but parsing of value \"%s{s}\" failed."
         | _ -> failwith $"Error parsing JSON value: %O{t} is not a string type."
@@ -92,6 +94,7 @@ module Serialization =
         Tracer.runAndMeasureExecutionTime "Converted Array JsonValue to CLR array" (fun _ ->
             match t with
             | Option t -> getArrayValue t converter items |> makeOption t
+            | ValueOption t -> getArrayValue t converter items |> makeValueOption t
             | Array itype | Seq itype -> items |> Array.map (converter itype) |> castArray itype
             | List itype -> items |> Array.map (converter itype) |> Array.toList |> castList itype
             | _ -> failwith $"Error parsing JSON value: %O{t} is not an array type.")
@@ -121,9 +124,12 @@ module Serialization =
                     |> Array.map (fun (n, t) ->
                         match Map.tryFind n jprops with
                         | Some p -> n, convert t p
-                        | None -> n, makeOption t null)
+                        | None ->
+                            match t with
+                            | ValueOption vt -> n, makeValueOption vt null
+                            | _ -> n, makeOption t null)
                 let rcrd =
-                    let t = match t with Option t -> t | _ -> t
+                    let t = match t with Option t | ValueOption t -> t | _ -> t
                     let vals = vals t
                     if isMap t
                     then Map.ofArray vals |> box

src/FSharp.Data.GraphQL.Client/TextConversions.fs

@@ -16,12 +16,14 @@ open System.Text.RegularExpressions
 module private TextConversionHelpers =
   let asOption = function true, v -> Some v | _ -> None
 
+  [<return: Struct>]
   let (|StringEqualsIgnoreCase|_|) (s1:string) s2 =
     if s1.Equals(s2, StringComparison.OrdinalIgnoreCase)
-      then Some () else None
+      then ValueSome () else ValueNone
 
+  [<return: Struct>]
   let (|OneOfIgnoreCase|_|) set str =
-    if Array.exists (fun s -> StringComparer.OrdinalIgnoreCase.Compare(s, str) = 0) set then Some() else None
+    if Array.exists (fun s -> StringComparer.OrdinalIgnoreCase.Compare(s, str) = 0) set then ValueSome() else ValueNone
 
   let msDateRegex = lazy Regex(@"^/Date\((-?\d+)([-+]\d+)?\)/$", RegexOptions.Compiled)
 

src/FSharp.Data.GraphQL.Server.AspNetCore/GraphQLWebsocketMiddleware.fs

@@ -51,10 +51,11 @@ module internal IncrementalPayloadSplitting =
 
     /// Matches a path ending in a list of indices, such as the path of a batched deferred payload, returning the
     /// path of the batch's own field and the indices of its items.
+    [<return: Struct>]
     let (|BatchPath|_|) (path : obj list) =
         match List.rev path with
-        | (:? (obj list) as indices) :: fieldPathRev -> Some (List.rev fieldPathRev, indices)
-        | _ -> None
+        | (:? (obj list) as indices) :: fieldPathRev -> ValueSome (List.rev fieldPathRev, indices)
+        | _ -> ValueNone
 
     /// Splits a batch's data (an array with one element per index, in the same order) and errors (each carrying the
     /// full path of the item it belongs to, since every error of a batch originates from resolving one specific

src/FSharp.Data.GraphQL.Server/Execution.fs

@@ -412,8 +412,8 @@ and private executeResolvers (inputContext : InputExecutionContextProvider) (ctx
 
     let rec innerListDef = function
         | Nullable (Output innerDef) -> innerListDef innerDef
-        | List (Output innerDef) -> Some innerDef
-        | _ -> None
+        | List (Output innerDef) -> ValueSome innerDef
+        | _ -> ValueNone
 
     let (|HasList|_|) = innerListDef
 

src/FSharp.Data.GraphQL.Server/ObservableExtensions.fs

@@ -65,10 +65,11 @@ module internal Observable =
     /// Distinguishes a linked-token cancellation, typically caused by a resolution failure, from the
     /// subscription itself being disposed.
     /// </remarks>
+    [<return: Struct>]
     let (|CanceledIndependently|_|) (cancellationToken : CancellationToken) (ex : exn) =
         match ex with
-        | :? OperationCanceledException when not cancellationToken.IsCancellationRequested -> Some ()
-        | _ -> None
+        | :? OperationCanceledException when not cancellationToken.IsCancellationRequested -> ValueSome ()
+        | _ -> ValueNone
 
     /// <summary>
     /// Creates a cold observable, which enumerates the asynchronous sequence for every subscription.

src/FSharp.Data.GraphQL.Server/ReflectionHelper.fs

@@ -24,40 +24,46 @@ type internal Methods =
 
 module internal Gen =
 
+    [<return: Struct>]
     let (|List|_|) (t: Type) =
         let typeParam = t.GetGenericArguments().[0]
         let tList = typedefof<_ list>.MakeGenericType [| typeParam |]
-        if t = tList then Some typeParam
-        else None
+        if t = tList then ValueSome typeParam
+        else ValueNone
 
+    [<return: Struct>]
     let (|Array|_|) (t: Type) =
-        if t.IsArray then Some (t.GetGenericArguments().[0])
-        else None
+        if t.IsArray then ValueSome (t.GetGenericArguments().[0])
+        else ValueNone
 
+    [<return: Struct>]
     let (|Set|_|) (t: Type) =
         let typeParam = t.GetGenericArguments().[0]
         let tArray = typedefof<Set<_>>.MakeGenericType [| typeParam |]
-        if t = tArray then Some typeParam
-        else None
+        if t = tArray then ValueSome typeParam
+        else ValueNone
 
     let inline defaultArgOnNull a b = if isNull a |> not then a else b
     let private optionType = typedefof<option<_>>
+    [<return: Struct>]
     let (|Option|_|) (t: Type) =
         if t.IsGenericType && t.GetGenericTypeDefinition() = optionType
-        then Some (t.GetGenericArguments().[0])
-        else None
+        then ValueSome (t.GetGenericArguments().[0])
+        else ValueNone
 
+    [<return: Struct>]
     let (|Enumerable|_|) t =
         if typeof<System.Collections.IEnumerable>.IsAssignableFrom t
         then
             let e = defaultArgOnNull (t.GetInterface("IEnumerable`1")) t
-            Some (e.GetGenericArguments().[0])
-        else None
+            ValueSome (e.GetGenericArguments().[0])
+        else ValueNone
 
+    [<return: Struct>]
     let (|Queryable|_|) t =
         if typeof<IQueryable>.IsAssignableFrom t
-        then Some (Queryable (t.GetInterface("IQueryable`1").GetGenericArguments().[0]))
-        else None
+        then ValueSome (Queryable (t.GetInterface("IQueryable`1").GetGenericArguments().[0]))
+        else ValueNone
 
     let genericType<'t> typeParams = typedefof<'t>.MakeGenericType typeParams
 

src/FSharp.Data.GraphQL.Shared/AsyncVal.fs

@@ -230,10 +230,12 @@ module AsyncExtensions =
     let asyncVal = AsyncValBuilder ()
 
     /// Active pattern used for checking if AsyncVal contains immediate value.
-    let (|Immediate|_|) (x : AsyncVal<'T>) = match x with | Value v -> Some v | _ -> None
+    [<return: Struct>]
+    let (|Immediate|_|) (x : AsyncVal<'T>) = match x with | Value v -> ValueSome v | _ -> ValueNone
 
     /// Active patter used for checking if AsyncVal wraps an Async computation.
-    let (|Async|_|) (x : AsyncVal<'T>) = match x with | Async a -> Some a | _ -> None
+    [<return: Struct>]
+    let (|Async|_|) (x : AsyncVal<'T>) = match x with | Async a -> ValueSome a | _ -> ValueNone
 
     type Microsoft.FSharp.Control.AsyncBuilder with
 

src/FSharp.Data.GraphQL.Shared/Helpers/Reflection.fs

@@ -171,28 +171,31 @@ module Helpers =
 
     let rec internal moduleType = ReflectionHelper.getModuleType <@ moduleType @>
 
-    /// <summary>
-    /// Casts a <see cref="System.Object"/> to a <see cref="option{System.Object}"/>.
-    /// </summary>
-    let optionCast (value: obj) =
-        if isNull value then None
+    let private objectOptionCast (value: obj) =
+        if isNull value then ValueNone
         else
             let t = value.GetType()
             if t.FullName.StartsWith ReflectionHelper.OptionTypeName then
                 let p = t.GetProperty("Value")
-                Some (p.GetValue(value, [||]))
+                ValueSome (p.GetValue(value, [||]))
             elif t.FullName.StartsWith ReflectionHelper.ValueOptionTypeName then
-                if value = Activator.CreateInstance t then None
+                if value = Activator.CreateInstance t then ValueNone
                 else
                     let p = t.GetProperty("Value")
-                    Some (p.GetValue(value, [||]))
-            else None
+                    ValueSome (p.GetValue(value, [||]))
+            else ValueNone
+
+    /// <summary>
+    /// Casts a <see cref="System.Object"/> to a <see cref="option{System.Object}"/>.
+    /// </summary>
+    let optionCast (value: obj) = objectOptionCast value |> ValueOption.toOption
 
     /// <summary>
-    /// Matches a System.Object with an option.
-    /// If the object is an <see cref="Option{T}", returns it as Some, otherwise, return <see cref="None"/>.
+    /// Matches a <see cref="System.Object"/> containing a boxed <see cref="Option{T}"/> or <see cref="ValueOption{T}"/>.
+    /// Returns the wrapped value for <see cref="Some"/> and <see cref="ValueSome"/>, and does not match for <see cref="None"/>, <see cref="ValueNone"/>, or non-option values.
     /// </summary>
-    let (|ObjectOption|_|) = optionCast
+    [<return: Struct>]
+    let (|ObjectOption|_|) (value : obj) = objectOptionCast value
 
     /// <summary>
     /// Lifts a <see cref="System.Object"/> to an <see cref="option{System.Object}"/>, unless it is already an <see cref="option{System.Object}"/>.

src/FSharp.Data.GraphQL.Shared/Output.fs

@@ -23,10 +23,11 @@ type NameValueLookup(keyValues: KeyValuePair<string, obj> []) =
             else i <- i+1
     let getValue key = (kvals |> Array.find (fun kv -> kv.Key = key)).Value
 
+    [<return: Struct>]
     let (|BoxedSeq|_|) (xs : obj) =
         match xs with
-        | (:? System.Collections.IEnumerable as enumerable) -> Some (Seq.cast<obj> enumerable)
-        | _ -> None
+        | (:? System.Collections.IEnumerable as enumerable) -> ValueSome (Seq.cast<obj> enumerable)
+        | _ -> ValueNone
 
     let rec structEq (x: NameValueLookup) (y: NameValueLookup) =
         if Object.ReferenceEquals(x, y) then true

src/FSharp.Data.GraphQL.Shared/SchemaDefinitions.fs

@@ -183,13 +183,14 @@ module SchemaDefinitions =
         | other -> None
 
     /// Check if provided obj value is an Option and extract its wrapped value as object if possible
+    [<return: Struct>]
     let private (|Option|_|) (x : obj) =
-        if isNull x then None
+        if isNull x then ValueNone
         else
             let t = x.GetType().GetTypeInfo()
             if t.IsGenericType && t.GetGenericTypeDefinition() = typedefof<option<_>> then
-                t.GetDeclaredProperty("Value").GetValue(x) |> Some
-            else None
+                t.GetDeclaredProperty("Value").GetValue(x) |> ValueSome
+            else ValueNone
 
     /// Tries to convert any value to string.
     let coerceStringValue (x : obj) : string option =