x.json2: add ability to decode arrays

[ttytm]

Fixes #21150

Adds the ability to decode arrays, as currently it is an empty block:

• Current master
  

  v/vlib/x/json2/decoder.v

  Lines 251 to 252 in 5da1fcc

  	} $else $if field.is_array {
  	} $else $if field.is_struct {

The feature is integrated in a simple enough manner that it should create little interference with #21039 . It might even help with a TODO there.

[Delta456]

Isn't there a more efficient way to do this? It feels too lengthy to me.

[ttytm]

I hope there is one but didn't found one yet. Unfortunately there is mess with accessing the comptime type of the array. Had to integrate a similar approach in toml as last option back then :/.

It is now used for arrays and maps there:

v/vlib/toml/toml.v

Lines 59 to 87 in c086bee

	} $else $if field.is_array {
	arr := value.array()
	match typeof(typ.$(field.name)).name {
	'[]string' { typ.$(field.name) = arr.as_strings() }
	'[]int' { typ.$(field.name) = arr.map(it.int()) }
	'[]i64' { typ.$(field.name) = arr.map(it.i64()) }
	'[]u64' { typ.$(field.name) = arr.map(it.u64()) }
	'[]f32' { typ.$(field.name) = arr.map(it.f32()) }
	'[]f64' { typ.$(field.name) = arr.map(it.f64()) }
	'[]bool' { typ.$(field.name) = arr.map(it.bool()) }
	'[]toml.DateTime' { typ.$(field.name) = arr.map(it.datetime()) }
	'[]toml.Date' { typ.$(field.name) = arr.map(it.date()) }
	'[]toml.Time' { typ.$(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()
	})
	}

If that's whats available atm, I hope there will be better ways soon.

[Delta456]

I hope there is one but didn't found one yet. Unfortunately there is mess with accessing the comptime type of the array. Had to integrate a similar approach in toml back then as last option :/. There it is now used for arrays and maps.

v/vlib/toml/toml.v

Lines 59 to 87 in c086bee

	} $else $if field.is_array {
	arr := value.array()
	match typeof(typ.$(field.name)).name {
	'[]string' { typ.$(field.name) = arr.as_strings() }
	'[]int' { typ.$(field.name) = arr.map(it.int()) }
	'[]i64' { typ.$(field.name) = arr.map(it.i64()) }
	'[]u64' { typ.$(field.name) = arr.map(it.u64()) }
	'[]f32' { typ.$(field.name) = arr.map(it.f32()) }
	'[]f64' { typ.$(field.name) = arr.map(it.f64()) }
	'[]bool' { typ.$(field.name) = arr.map(it.bool()) }
	'[]toml.DateTime' { typ.$(field.name) = arr.map(it.datetime()) }
	'[]toml.Date' { typ.$(field.name) = arr.map(it.date()) }
	'[]toml.Time' { typ.$(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()
	})
	}

If there is none, I hope there will be one soon.

I think we need to support checking the array in a much more functional way.

[enghitalo]

Very good initiative!! But I think this will cause a lot of headaches. In the end, the biggest problem today would be finding a good solution to decode Sumtypes (This will probably have to be done more "manually/handled" by the user, calling some method...). After that, array decodes became much simpler.

[enghitalo]

I can't wait to have fun again with the new json2 decode. I hope that within the next few months I will have time to finish this project.

[ttytm]

Very good initiative!! But I think this will cause a lot of headaches. In the end, the biggest problem today would be finding a good solution to decode Sumtypes (This will probably have to be done more "manually/handled" by the user, calling some method...). After that, array decodes became much simpler.

The change just adds array decoding for the types that the current decoder is handling. This might be better then getting empty arrays. Sumtypes might be in their own scope then.

[spytheman]

Excellent work.

[spytheman]

@enghitalo JSON does not have sumtypes. JSON does have arrays.

-> For the completion of x.json2, first class support for arrays is much more important.