toml: add decoding for struct fields of type map[string]T (#19447)

vlib/toml/tests/encode_and_decode_test.v

@@ -7,14 +7,15 @@ enum JobTitle {
 }
 
 struct Pet {
-	name      string
-	nicknames []string
-	age       u64
-	income    int
-	height    f32
-	has_furr  bool
-	title     JobTitle
-	address   Address
+	name           string
+	nicknames      []string
+	age            u64
+	income         int
+	height         f32
+	has_furr       bool
+	title          JobTitle
+	address        Address
+	meal_frequency map[string]int
 	// *¹ Currently it is only possible to decode a single nested struct generically.
 	// As soon as we decode another nested struct (e.g. within this struct, like `contact` below)
 	// or only one nested struct within another struct, it results in wrong values or errors.
@@ -58,7 +59,10 @@ struct Arrs {
 fn test_encode_and_decode() {
 	// *¹
 	// p := Pet{'Mr. Scratchy McEvilPaws', ['Freddy', 'Fred', 'Charles'], 8, -1, 0.8, true, .manager, Address{'1428 Elm Street', 'Springwood'}, Contact{'123-456-7890'}}
-	p := Pet{'Mr. Scratchy McEvilPaws', ['Freddy', 'Fred', 'Charles'], 8, -1, 0.8, true, .manager, Address{'1428 Elm Street', 'Springwood'}}
+	p := Pet{'Mr. Scratchy McEvilPaws', ['Freddy', 'Fred', 'Charles'], 8, -1, 0.8, true, .manager, Address{'1428 Elm Street', 'Springwood'}, {
+		'bones':  2
+		'kibble': 5
+	}}
 	s := 'name = "Mr. Scratchy McEvilPaws"
 nicknames = [
   "Freddy",
@@ -70,7 +74,8 @@ income = -1
 height = 0.8
 has_furr = true
 title = 2
-address = { street = "1428 Elm Street", city = "Springwood" }'
+address = { street = "1428 Elm Street", city = "Springwood" }
+meal_frequency = { bones = 2, kibble = 5 }'
 	// contact = { phone = "123-456-7890" }' // *¹
 
 	assert toml.encode[Pet](p) == s

vlib/toml/toml.v

@@ -7,6 +7,7 @@ import toml.ast
 import toml.input
 import toml.scanner
 import toml.parser
+import maps
 
 // Null is used in sumtype checks as a "default" value when nothing else is possible.
 pub struct Null {
@@ -70,6 +71,63 @@ fn decode_struct[T](doc Any, mut typ T) {
 				'[]toml.Time' { typ.$(field.name) = arr.map(it.time()) }
 				else {}
 			}
+		} $else $if field.is_map {
+			mut mmap := value.as_map()
+			match typeof(typ.$(field.name)).name {
+				'map[string]string' {
+					typ.$(field.name) = mmap.as_strings()
+				}
+				// Should be cleaned up to use the more modern lambda syntax
+				// |k, v| k, v.int()
+				// Unfortunately lambdas have issues with multiple return at the time of writing
+				'map[string]int' {
+					typ.$(field.name) = maps.to_map[string, Any, string, int](mmap, fn (k string, v Any) (string, int) {
+						return k, v.int()
+					})
+				}
+				'map[string]i64' {
+					typ.$(field.name) = maps.to_map[string, Any, string, i64](mmap, fn (k string, v Any) (string, i64) {
+						return k, v.i64()
+					})
+				}
+				'map[string]u64' {
+					typ.$(field.name) = maps.to_map[string, Any, string, u64](mmap, fn (k string, v Any) (string, u64) {
+						return k, v.u64()
+					})
+				}
+				'map[string]f32' {
+					typ.$(field.name) = maps.to_map[string, Any, string, f32](mmap, fn (k string, v Any) (string, f32) {
+						return k, v.f32()
+					})
+				}
+				'map[string]f64' {
+					typ.$(field.name) = maps.to_map[string, Any, string, f64](mmap, fn (k string, v Any) (string, f64) {
+						return k, v.f64()
+					})
+				}
+				'map[string]bool' {
+					typ.$(field.name) = maps.to_map[string, Any, string, bool](mmap, fn (k string, v Any) (string, bool) {
+						return k, v.bool()
+					})
+				}
+				'map[string]toml.DateTime' {
+					typ.$(field.name) = maps.to_map[string, Any, string, DateTime](mmap,
+						fn (k string, v Any) (string, DateTime) {
+						return k, v.datetime()
+					})
+				}
+				'map[string]toml.Date' {
+					typ.$(field.name) = maps.to_map[string, Any, string, Date](mmap, fn (k string, v Any) (string, Date) {
+						return k, v.date()
+					})
+				}
+				'map[string]toml.Time' {
+					typ.$(field.name) = maps.to_map[string, Any, string, Time](mmap, fn (k string, v Any) (string, Time) {
+						return k, v.time()
+					})
+				}
+				else {}
+			}
 		} $else $if field.is_struct {
 			mut s := typ.$(field.name)
 			decode_struct(value, mut s)