decoder2: support custom decoders (#25021)

Larsimusrex · web-flow · commit 809e617501ae · 2025-08-02T14:07:29.000+03:00
diff --git a/vlib/math/big/json_decode.v b/vlib/math/big/json_decode.v
@@ -0,0 +1,30 @@
+module big
+
+// from_json_number implements a custom decoder for json2
+pub fn (mut result Integer) from_json_number(raw_number string) ! {
+	mut index := 0
+	mut is_negative := false
+
+	if raw_number[0] == `-` {
+		is_negative = true
+		index++
+	}
+
+	ten := integer_from_int(10)
+
+	for index < raw_number.len {
+		digit := raw_number[index] - `0`
+
+		if digit > 9 { // comma, e and E are all smaller 0 in ASCII so they underflow
+			return error('expected integer but got real number')
+		}
+
+		result = (result * ten) + integer_from_int(int(digit))
+
+		index++
+	}
+
+	if is_negative {
+		result = result * integer_from_int(-1)
+	}
+}
diff --git a/vlib/time/json_decode.c.v b/vlib/time/json_decode.c.v
@@ -0,0 +1,6 @@
+module time
+
+// from_json_string implements a custom decoder for json2
+pub fn (mut t Time) from_json_string(raw_string string) ! {
+	t = parse_rfc3339(raw_string) or { Time{} }
+}
diff --git a/vlib/x/json2/decoder2/custom.v b/vlib/x/json2/decoder2/custom.v
@@ -0,0 +1,50 @@
+module decoder2
+
+// implements decoding json strings, e.g. "hello, \u2164!"
+pub interface StringDecoder {
+mut:
+	// called with raw string (minus apostrophes) e.g. 'hello, \u2164!'
+	from_json_string(raw_string string) !
+}
+
+// implements decoding json numbers, e.g. -1.234e23
+pub interface NumberDecoder {
+mut:
+	// called with raw string of number e.g. '-1.234e23'
+	from_json_number(raw_number string) !
+}
+
+// implements decoding json true/false
+pub interface BooleanDecoder {
+mut:
+	// called with converted bool
+	// already checked so no error needed
+	from_json_boolean(boolean_value bool)
+}
+
+// implements decoding json null
+pub interface NullDecoder {
+mut:
+	// only has one value
+	// already checked so no error needed
+	from_json_null()
+}
+
+// Implement once generic interfaces are more stable
+
+// // implements decoding json arrays, e.g. ["hi", "bye", 0.9, true]
+// // elements are already decoded
+// pub interface ArrayDecoder[T] {
+// mut:
+// 	// called for every element in array e.g. 'hi', 'bye', '0.9', 'true'
+// 	from_json_value(raw_value T)!
+// }
+
+// // implements decoding json object, e.g. {"name": "foo", "name": "bar", "age": 99}
+// // this allows for duplicate/ordered keys to be decoded
+// // elements are already decoded
+// pub interface ObjectDecoder[T] {
+// mut:
+// 	// called for every key-value pair in object (minus apostrophes for keys) e.g. ('name': 'foo'), ('name': 'bar'), ('age': '99')
+// 	from_json_pair(raw_key string, raw_value T)!
+// }
diff --git a/vlib/x/json2/decoder2/decode.v b/vlib/x/json2/decoder2/decode.v
@@ -1,7 +1,6 @@
 module decoder2
 
 import strconv
-import time
 import strings
 
 const null_in_string = 'null'
@@ -533,8 +532,7 @@ fn (mut checker Decoder) check_json_format(val string) ! {
 		}
 		.number {
 			// check if the JSON string is a valid float or integer
-
-			if val[0] == `-` {
+			if val[checker.checker_idx] == `-` {
 				checker.checker_idx++
 			}
 
@@ -786,15 +784,6 @@ fn (mut decoder Decoder) decode_value[T](mut val T) ! {
 	} $else $if T.unaliased_typ is $sumtype {
 		decoder.decode_sumtype(mut val)!
 		return
-	} $else $if T.unaliased_typ is time.Time {
-		time_info := decoder.current_node.value
-
-		if time_info.value_kind == .string_ {
-			string_time := decoder.json.substr_unsafe(time_info.position + 1, time_info.position +
-				time_info.length - 1)
-
-			val = time.parse_rfc3339(string_time) or { time.Time{} }
-		}
 	} $else $if T.unaliased_typ is $map {
 		decoder.decode_map(mut val)!
 		return
@@ -811,6 +800,50 @@ fn (mut decoder Decoder) decode_value[T](mut val T) ! {
 	} $else $if T.unaliased_typ is $struct {
 		struct_info := decoder.current_node.value
 
+		// Custom Decoders
+		$if val is StringDecoder {
+			if struct_info.value_kind == .string_ {
+				val.from_json_string(decoder.json[struct_info.position + 1..struct_info.position +
+					struct_info.length - 1])!
+				if decoder.current_node != unsafe { nil } {
+					decoder.current_node = decoder.current_node.next
+				}
+
+				return
+			}
+		}
+		$if val is NumberDecoder {
+			if struct_info.value_kind == .number {
+				val.from_json_number(decoder.json[struct_info.position..struct_info.position +
+					struct_info.length])!
+				if decoder.current_node != unsafe { nil } {
+					decoder.current_node = decoder.current_node.next
+				}
+
+				return
+			}
+		}
+		$if val is BooleanDecoder {
+			if struct_info.value_kind == .boolean {
+				val.from_json_boolean(decoder.json[struct_info.position] == `t`)
+				if decoder.current_node != unsafe { nil } {
+					decoder.current_node = decoder.current_node.next
+				}
+
+				return
+			}
+		}
+		$if val is NullDecoder {
+			if struct_info.value_kind == .null {
+				val.from_json_null()
+				if decoder.current_node != unsafe { nil } {
+					decoder.current_node = decoder.current_node.next
+				}
+
+				return
+			}
+		}
+
 		// struct field info linked list
 		mut struct_fields_info := LinkedList[StructFieldInfo]{}
 
diff --git a/vlib/x/json2/decoder2/decode_sumtype.v b/vlib/x/json2/decoder2/decode_sumtype.v
@@ -47,6 +47,8 @@ fn (mut decoder Decoder) check_element_type_valid[T](element T, current_node &No
 				return true
 			} $else $if element is time.Time {
 				return true
+			} $else $if element is StringDecoder {
+				return true
 			}
 		}
 		.number {
@@ -56,16 +58,22 @@ fn (mut decoder Decoder) check_element_type_valid[T](element T, current_node &No
 				return true
 			} $else $if element is $enum {
 				return true
+			} $else $if element is NumberDecoder {
+				return true
 			}
 		}
 		.boolean {
 			$if element is bool {
 				return true
+			} $else $if element is BooleanDecoder {
+				return true
 			}
 		}
 		.null {
 			$if element is $option {
 				return true
+			} $else $if element is NullDecoder {
+				return true
 			}
 		}
 		.array {
@@ -221,6 +229,9 @@ fn (mut decoder Decoder) init_sumtype_by_value_kind[T](mut val T, value_info Val
 				} $else $if v.typ is time.Time {
 					val = T(v)
 					return
+				} $else $if v.typ is StringDecoder {
+					val = T(v)
+					return
 				}
 			}
 		}
@@ -235,6 +246,9 @@ fn (mut decoder Decoder) init_sumtype_by_value_kind[T](mut val T, value_info Val
 				} $else $if v.typ is $enum {
 					val = T(v)
 					return
+				} $else $if v.typ is NumberDecoder {
+					val = T(v)
+					return
 				}
 			}
 		}
@@ -243,6 +257,9 @@ fn (mut decoder Decoder) init_sumtype_by_value_kind[T](mut val T, value_info Val
 				$if v.typ is bool {
 					val = T(v)
 					return
+				} $else $if v.typ is BooleanDecoder {
+					val = T(v)
+					return
 				}
 			}
 		}
@@ -251,6 +268,9 @@ fn (mut decoder Decoder) init_sumtype_by_value_kind[T](mut val T, value_info Val
 				$if v.typ is $option {
 					val = T(v)
 					return
+				} $else $if v.typ is NullDecoder {
+					val = T(v)
+					return
 				}
 			}
 		}
diff --git a/vlib/x/json2/decoder2/tests/decode_custom_test.v b/vlib/x/json2/decoder2/tests/decode_custom_test.v
@@ -0,0 +1,89 @@
+import decoder2 as json
+import x.json2
+import math.big
+
+struct MyString implements json.StringDecoder, json.NumberDecoder, json.BooleanDecoder, json.NullDecoder {
+mut:
+	data string
+}
+
+pub fn (mut ms MyString) from_json_string(raw_string string) ! {
+	ms.data = raw_string
+}
+
+pub fn (mut ms MyString) from_json_number(raw_number string) ! {
+	mut first := true
+
+	for digit in raw_number {
+		if first {
+			first = false
+		} else {
+			ms.data += '-'
+		}
+
+		ms.data += match digit {
+			`-` { 'minus' }
+			`.` { 'dot' }
+			`e`, `E` { 'e' }
+			`0` { 'zero' }
+			`1` { 'one' }
+			`2` { 'two' }
+			`3` { 'three' }
+			`4` { 'four' }
+			`5` { 'five' }
+			`6` { 'six' }
+			`7` { 'seven' }
+			`8` { 'eight' }
+			`9` { 'nine' }
+			else { 'none' }
+		}
+	}
+}
+
+pub fn (mut ms MyString) from_json_boolean(boolean_value bool) {
+	ms.data = if boolean_value { 'yes' } else { 'no' }
+}
+
+pub fn (mut ms MyString) from_json_null() {
+	ms.data = 'default value'
+}
+
+struct NoCustom {
+	a int
+	b string
+}
+
+fn test_custom() {
+	assert json.decode[NoCustom]('{"a": 99, "b": "hi"}')! == NoCustom{
+		a: 99
+		b: 'hi'
+	}
+
+	assert json.decode[[]MyString]('["hi", -9.8e7, true, null]')! == [
+		MyString{
+			data: 'hi'
+		},
+		MyString{
+			data: 'minus-nine-dot-eight-e-seven'
+		},
+		MyString{
+			data: 'yes'
+		},
+		MyString{
+			data: 'default value'
+		},
+	]
+}
+
+fn test_null() {
+	assert json.decode[json2.Any]('null]')! == json2.Any(json2.null)
+	assert json.decode[json2.Any]('{"hi": 90, "bye": ["lol", -1, null]}')!.str() == '{"hi":90,"bye":["lol",-1,null]}'
+}
+
+fn test_big() {
+	assert json.decode[big.Integer]('0')!.str() == '0'
+
+	assert json.decode[big.Integer]('12345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890')!.str() == '12345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890'
+
+	assert json.decode[big.Integer]('-12345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890')!.str() == '-12345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890'
+}
diff --git a/vlib/x/json2/types.v b/vlib/x/json2/types.v
@@ -41,6 +41,9 @@ pub struct Null {
 // null is an instance of the Null type, to ease comparisons with it.
 pub const null = Null{}
 
+// from_json_null implements a custom decoder for json2
+pub fn (mut n Null) from_json_null() {}
+
 // ValueKind enumerates the kinds of possible values of the Any sumtype.
 pub enum ValueKind {
 	unknown

Original file line number	Diff line number	Diff line change
`@@ -47,6 +47,8 @@ fn (mut decoder Decoder) check_element_type_valid[T](element T, current_node &No`
`47`	`47`	`return true`
`48`	`48`	`} $else $if element is time.Time {`
`49`	`49`	`return true`
	`50`	`+ } $else $if element is StringDecoder {`
	`51`	`+ return true`
`50`	`52`	`}`
`51`	`53`	`}`
`52`	`54`	`.number {`
`@@ -56,16 +58,22 @@ fn (mut decoder Decoder) check_element_type_valid[T](element T, current_node &No`
`56`	`58`	`return true`
`57`	`59`	`} $else $if element is $enum {`
`58`	`60`	`return true`
	`61`	`+ } $else $if element is NumberDecoder {`
	`62`	`+ return true`
`59`	`63`	`}`
`60`	`64`	`}`
`61`	`65`	`.boolean {`
`62`	`66`	`$if element is bool {`
`63`	`67`	`return true`
	`68`	`+ } $else $if element is BooleanDecoder {`
	`69`	`+ return true`
`64`	`70`	`}`
`65`	`71`	`}`
`66`	`72`	`.null {`
`67`	`73`	`$if element is $option {`
`68`	`74`	`return true`
	`75`	`+ } $else $if element is NullDecoder {`
	`76`	`+ return true`
`69`	`77`	`}`
`70`	`78`	`}`
`71`	`79`	`.array {`
`@@ -221,6 +229,9 @@ fn (mut decoder Decoder) init_sumtype_by_value_kind[T](mut val T, value_info Val`
`221`	`229`	`} $else $if v.typ is time.Time {`
`222`	`230`	`val = T(v)`
`223`	`231`	`return`
	`232`	`+ } $else $if v.typ is StringDecoder {`
	`233`	`+ val = T(v)`
	`234`	`+ return`
`224`	`235`	`}`
`225`	`236`	`}`
`226`	`237`	`}`
`@@ -235,6 +246,9 @@ fn (mut decoder Decoder) init_sumtype_by_value_kind[T](mut val T, value_info Val`
`235`	`246`	`} $else $if v.typ is $enum {`
`236`	`247`	`val = T(v)`
`237`	`248`	`return`
	`249`	`+ } $else $if v.typ is NumberDecoder {`
	`250`	`+ val = T(v)`
	`251`	`+ return`
`238`	`252`	`}`
`239`	`253`	`}`
`240`	`254`	`}`
`@@ -243,6 +257,9 @@ fn (mut decoder Decoder) init_sumtype_by_value_kind[T](mut val T, value_info Val`
`243`	`257`	`$if v.typ is bool {`
`244`	`258`	`val = T(v)`
`245`	`259`	`return`
	`260`	`+ } $else $if v.typ is BooleanDecoder {`
	`261`	`+ val = T(v)`
	`262`	`+ return`
`246`	`263`	`}`
`247`	`264`	`}`
`248`	`265`	`}`
`@@ -251,6 +268,9 @@ fn (mut decoder Decoder) init_sumtype_by_value_kind[T](mut val T, value_info Val`
`251`	`268`	`$if v.typ is $option {`
`252`	`269`	`val = T(v)`
`253`	`270`	`return`
	`271`	`+ } $else $if v.typ is NullDecoder {`
	`272`	`+ val = T(v)`
	`273`	`+ return`
`254`	`274`	`}`
`255`	`275`	`}`
`256`	`276`	`}`