fix: encoding negative integers should keep their sign

[core][javascript][python][newtonsoft]

Fix #187

packages/Thoth.Json.Core/Encode.fs

@@ -91,36 +91,37 @@ module Encode =
     let inline sbyte (value: sbyte) =
         { new IEncodable with
             member _.Encode(helpers) =
-                helpers.encodeIntegralNumber (uint32 value)
+                helpers.encodeSignedIntegralNumber (int32 value)
         }
 
     let inline byte (value: byte) =
         { new IEncodable with
             member _.Encode(helpers) =
-                helpers.encodeIntegralNumber (uint32 value)
+                helpers.encodeUnsignedIntegralNumber (uint32 value)
         }
 
     let inline int16 (value: int16) =
         { new IEncodable with
             member _.Encode(helpers) =
-                helpers.encodeIntegralNumber (uint32 value)
+                helpers.encodeSignedIntegralNumber (int32 value)
         }
 
     let inline uint16 (value: uint16) =
         { new IEncodable with
             member _.Encode(helpers) =
-                helpers.encodeIntegralNumber (uint32 value)
+                helpers.encodeUnsignedIntegralNumber (uint32 value)
         }
 
     let inline int (value: int) =
         { new IEncodable with
             member _.Encode(helpers) =
-                helpers.encodeIntegralNumber (uint32 value)
+                helpers.encodeSignedIntegralNumber value
         }
 
     let inline uint32 (value: uint32) =
         { new IEncodable with
-            member _.Encode(helpers) = helpers.encodeIntegralNumber (value)
+            member _.Encode(helpers) =
+                helpers.encodeUnsignedIntegralNumber value
         }
 
     let inline int64 (value: int64) =

packages/Thoth.Json.Core/Types.fs

@@ -30,8 +30,11 @@ type IEncoderHelpers<'JsonValue> =
     abstract encodeArray: 'JsonValue array -> 'JsonValue
     abstract encodeList: 'JsonValue list -> 'JsonValue
     abstract encodeSeq: 'JsonValue seq -> 'JsonValue
-    abstract encodeIntegralNumber: uint32 -> 'JsonValue
-
+    // See https://github.com/thoth-org/Thoth.Json/issues/187 for more information
+    // about why we make a distinction between signed and unsigned integral numbers
+    // when encoding them.
+    abstract encodeSignedIntegralNumber: int32 -> 'JsonValue
+    abstract encodeUnsignedIntegralNumber: uint32 -> 'JsonValue
 
 type ErrorReason<'JsonValue> =
     | BadPrimitive of string * 'JsonValue
@@ -75,7 +78,6 @@ type Json =
 
 type IEncodable =
     abstract member Encode<'JsonValue> :
-        helpers: IEncoderHelpers<'JsonValue> ->
-            'JsonValue
+        helpers: IEncoderHelpers<'JsonValue> -> 'JsonValue
 
 type Encoder<'T> = 'T -> IEncodable

packages/Thoth.Json.JavaScript/Encode.fs

@@ -24,7 +24,8 @@ module Encode =
             member _.encodeList values = JS.Constructors.Array.from values
             member _.encodeSeq values = JS.Constructors.Array.from values
 
-            member _.encodeIntegralNumber value = box value
+            member _.encodeSignedIntegralNumber value = box value
+            member _.encodeUnsignedIntegralNumber value = box value
         }
 
     let toString (space: int) (value: IEncodable) : string =

packages/Thoth.Json.Newtonsoft/Encode.fs

@@ -30,7 +30,9 @@ module Encode =
             member _.encodeList values = JArray(values)
             member _.encodeSeq values = JArray(values)
 
-            member _.encodeIntegralNumber(value: uint32) =
+            member _.encodeSignedIntegralNumber(value: int32) = JValue(value)
+
+            member _.encodeUnsignedIntegralNumber(value: uint32) =
                 // We need to force the cast to uint64 here, otherwise
                 // Newtonsoft resolve the constructor to JValue(decimal)
                 // when we actually want to output a number without decimals

packages/Thoth.Json.Python/Encode.fs

@@ -28,7 +28,8 @@ module Encode =
             member this.encodeSeq values =
                 values |> Seq.toArray |> this.encodeArray
 
-            member _.encodeIntegralNumber value = box value
+            member _.encodeSignedIntegralNumber value = box value
+            member _.encodeUnsignedIntegralNumber value = box value
         }
 
     let toString (space: int) (value: IEncodable) : string =

tests/Thoth.Json.Tests/Encoders.fs

@@ -95,6 +95,12 @@ let tests (runner: TestRunner<_, _>) =
                         let actual = Encode.int 1 |> runner.Encode.toString 0
                         runner.equal actual expected
 
+                    runner.testCase "negative int keeps the sign"
+                    <| fun _ ->
+                        let expected = "-1"
+                        let actual = Encode.int -1 |> runner.Encode.toString 0
+                        runner.equal actual expected
+
                     runner.testCase "a float works"
                     <| fun _ ->
                         let expected = "1.2"
@@ -305,6 +311,15 @@ let tests (runner: TestRunner<_, _>) =
 
                         runner.equal actual expected
 
+                    runner.testCase "negative sbyte keeps the sign"
+                    <| fun _ ->
+                        let expected = "-99"
+
+                        let actual =
+                            -99y |> Encode.sbyte |> runner.Encode.toString 0
+
+                        runner.equal actual expected
+
                     runner.testCase "an int16 works"
                     <| fun _ ->
                         let expected = "99"
@@ -314,6 +329,15 @@ let tests (runner: TestRunner<_, _>) =
 
                         runner.equal actual expected
 
+                    runner.testCase "negative int16 keeps the sign"
+                    <| fun _ ->
+                        let expected = "-99"
+
+                        let actual =
+                            -99s |> Encode.int16 |> runner.Encode.toString 0
+
+                        runner.equal actual expected
+
                     runner.testCase "an uint16 works"
                     <| fun _ ->
                         let expected = "99"