feat: improve stint parsing (#22)

- change empty string value to none when optional
- handle null, "null", JNull, seq[stint], seq[?string]

serde/json/deserializer.nim

@@ -16,6 +16,7 @@ import ./errors
 import ./stdjson
 import ./pragmas
 import ./types
+import ./helpers
 
 export parser
 export chronicles except toJson
@@ -124,25 +125,35 @@ proc fromJson*[T: distinct](_: type T, json: JsonNode): ?!T =
   success T(?T.distinctBase.fromJson(json))
 
 proc fromJson*(T: typedesc[StUint or StInt], json: JsonNode): ?!T =
-  expectJsonKind(T, JString, json)
+  expectJsonKind(T, {JString, JInt, JNull}, json)
-  let jsonStr = json.getStr
+
-  let prefix =
+  case json.kind
-    if jsonStr.len >= 2:
+  of JNull: # return 0, optional values are handled up the call stack
-      jsonStr[0 .. 1].toLowerAscii
+    return catch parse("0", T)
+  of JInt:
+    return catch parse($json, T)
+  else: # JString (only other kind allowed)
+    if json.isNullString:
+      return catch parse("0", T)
+
+    let jsonStr = json.getStr
+    let prefix =
+      if jsonStr.len >= 2:
+        jsonStr[0 .. 1].toLowerAscii
+      else:
+        jsonStr
+    case prefix
+    of "0x":
+      catch parse(jsonStr, T, 16)
+    of "0o":
+      catch parse(jsonStr, T, 8)
+    of "0b":
+      catch parse(jsonStr, T, 2)
     else:
-      jsonStr
+      catch parse(jsonStr, T)
-  case prefix
-  of "0x":
-    catch parse(jsonStr, T, 16)
-  of "0o":
-    catch parse(jsonStr, T, 8)
-  of "0b":
-    catch parse(jsonStr, T, 2)
-  else:
-    catch parse(jsonStr, T)
 
 proc fromJson*[T](_: type Option[T], json: JsonNode): ?!Option[T] =
-  if json.isNil or json.kind == JNull:
+  if json.isNil or json.kind == JNull or json.isEmptyString or json.isNullString:
     return success(none T)
   without val =? T.fromJson(json), error:
     return failure(error)

serde/json/helpers.nim

@@ -0,0 +1,7 @@
+import std/json
+
+func isEmptyString*(json: JsonNode): bool =
+  return json.kind == JString and json.getStr == ""
+
+func isNullString*(json: JsonNode): bool =
+  return json.kind == JString and json.getStr == "null"

tests/json/deserialize/objects.nim

@@ -3,6 +3,7 @@ import pkg/serde
 import pkg/questionable
 import pkg/questionable/results
 import pkg/stew/byteutils
+import pkg/stint
 
 suite "json - deserialize objects":
   test "can deserialize json objects":
@@ -165,3 +166,44 @@ suite "json - deserialize objects from string":
           }"""
 
     check !(Option[MyObj].fromJson(myObjJson)) == expected
+
+  test "deserializes object with UInt256 from string":
+    type MyObj = object
+      mystring: string
+      myu256: UInt256
+
+    let expected = MyObj(mystring: "abc", myu256: 1.u256)
+    let myObjJson =
+      """{
+            "mystring": "abc",
+            "myu256": 1
+          }"""
+
+    check !MyObj.fromJson(myObjJson) == expected
+
+  test "deserializes object with stringified UInt256 from string":
+    type MyObj = object
+      mystring: string
+      myu256: UInt256
+
+    let expected = MyObj(mystring: "abc", myu256: 1.u256)
+    let myObjJson =
+      """{
+            "mystring": "abc",
+            "myu256": "1"
+          }"""
+
+    check !MyObj.fromJson(myObjJson) == expected
+
+  test "deserializes object with ?UInt256 from string":
+    type MyObj = object
+      mystring: string
+      myu256: ?UInt256
+
+    let expected = MyObj(mystring: "abc", myu256: UInt256.none)
+    let myObjJson =
+      """{
+            "mystring": "abc",
+          }"""
+
+    check !MyObj.fromJson(myObjJson) == expected

tests/json/deserialize/stint.nim

@@ -13,12 +13,52 @@ suite "json - deserialize stint":
   test "deserializes UInt256 from an empty string":
     check !UInt256.fromJson("") == 0.u256
 
+  test "deserializes UInt256 from null string":
+    check !UInt256.fromJson("null") == 0.u256
+
+  test "deserializes UInt256 from JNull":
+    check !UInt256.fromJson(newJNull()) == 0.u256
+
   test "deserializes ?UInt256 from an empty JString":
     let json = newJString("")
-    check !Option[UInt256].fromJson(json) == 0.u256.some
+    check !Option[UInt256].fromJson(json) == UInt256.none
 
   test "deserializes ?UInt256 from an empty string":
-    check !Option[UInt256].fromJson("") == 0.u256.some
+    check !Option[UInt256].fromJson("") == UInt256.none
+
+  test "deserializes ?UInt256 from null string":
+    check !Option[UInt256].fromJson("null") == UInt256.none
+
+  test "deserializes ?UInt256 from JNull":
+    check !Option[UInt256].fromJson(newJNull()) == UInt256.none
+
+  test "deserializes seq[UInt256] from string":
+    check seq[UInt256].fromJson("[1,2,3]") == success @[1.u256, 2.u256, 3.u256]
+
+  test "deserializes seq[UInt256] from string with empty string item":
+    check seq[UInt256].fromJson("[1,2,\"\"]") == success @[1.u256, 2.u256, 0.u256]
+
+  test "deserializes seq[UInt256] from string with null item":
+    check seq[UInt256].fromJson("[1,2,null]") == success @[1.u256, 2.u256, 0.u256]
+
+  test "deserializes seq[UInt256] from string with null string item":
+    check seq[UInt256].fromJson("[1,2,\"null\"]") == success @[1.u256, 2.u256, 0.u256]
+
+  test "deserializes seq[?UInt256] from string":
+    check seq[?UInt256].fromJson("[1,2,3]") ==
+      success @[1.u256.some, 2.u256.some, 3.u256.some]
+
+  test "deserializes seq[?UInt256] from string with empty string item":
+    check seq[?UInt256].fromJson("[1,2,\"\"]") ==
+      success @[1.u256.some, 2.u256.some, UInt256.none]
+
+  test "deserializes seq[?UInt256] from string with null item":
+    check seq[?UInt256].fromJson("[1,2,null]") ==
+      success @[1.u256.some, 2.u256.some, UInt256.none]
+
+  test "deserializes seq[?UInt256] from string with null string item":
+    check seq[?UInt256].fromJson("[1,2,\"null\"]") ==
+      success @[1.u256.some, 2.u256.some, UInt256.none]
 
   test "deserializes UInt256 from JString with no prefix":
     let json = newJString("1")