forked from Team-Ortix/golang-wasm
feat: Add reflection to create JS value from Go value
parent
f3864a59ca
commit
ad5b341b1e
GPG Key ID:
7E9A74B1B07A7558
@ -0,0 +1,105 @@
|
||||
package wasm
|
||||
|
||||
import (
|
||||
"errors"
|
||||
"reflect"
|
||||
"syscall/js"
|
||||
)
|
||||
|
||||
// ErrInvalidArgumentType is returned when a generated Go function wrapper receives invalid argument types from JS.
|
||||
var ErrInvalidArgumentType = errors.New("invalid argument passed into Go function")
|
||||
|
||||
var errorType = reflect.TypeOf((*error)(nil)).Elem()
|
||||
|
||||
type goThrowable struct {
|
||||
Result js.Value `wasm:"result"`
|
||||
Error js.Value `wasm:"error"`
|
||||
}
|
||||
|
||||
func toJSFunc(x reflect.Value) js.Value {
|
||||
funcType := x.Type()
|
||||
var hasError bool
|
||||
if funcType.NumOut() != 0 {
|
||||
hasError = funcType.Out(funcType.NumOut()-1) == errorType
|
||||
}
|
||||
|
||||
return js.FuncOf(func(this js.Value, args []js.Value) interface{} {
|
||||
in, err := conformJSValueToType(funcType, this, args)
|
||||
if err != nil {
|
||||
return ToJSValue(goThrowable{
|
||||
Error: NewError(err),
|
||||
})
|
||||
}
|
||||
|
||||
out := x.Call(in)
|
||||
|
||||
if !hasError {
|
||||
return ToJSValue(goThrowable{
|
||||
Result: returnValue(out),
|
||||
})
|
||||
}
|
||||
|
||||
lastParam := out[len(out)-1]
|
||||
if !lastParam.IsNil() {
|
||||
return ToJSValue(goThrowable{
|
||||
Error: NewError(lastParam.Interface().(error)),
|
||||
})
|
||||
}
|
||||
return ToJSValue(goThrowable{
|
||||
Result: returnValue(out[:len(out)-1]),
|
||||
})
|
||||
}).JSValue()
|
||||
}
|
||||
|
||||
var jsValueType = reflect.TypeOf(js.Value{})
|
||||
|
||||
func conformJSValueToType(funcType reflect.Type, this js.Value, values []js.Value) ([]reflect.Value, error) {
|
||||
if funcType.NumIn() == 0 {
|
||||
if len(values) != 0 {
|
||||
return nil, ErrInvalidArgumentType
|
||||
}
|
||||
return []reflect.Value{}, nil
|
||||
}
|
||||
|
||||
if funcType.In(0) == jsValueType {
|
||||
values = append([]js.Value{this}, values...)
|
||||
}
|
||||
|
||||
if funcType.IsVariadic() && funcType.NumIn()-1 > len(values) {
|
||||
return nil, ErrInvalidArgumentType
|
||||
}
|
||||
|
||||
if !funcType.IsVariadic() && funcType.NumIn() != len(values) {
|
||||
return nil, ErrInvalidArgumentType
|
||||
}
|
||||
|
||||
in := make([]reflect.Value, 0, len(values))
|
||||
for i, v := range values {
|
||||
paramType := funcType.In(i)
|
||||
x := reflect.Zero(paramType).Interface()
|
||||
err := FromJSValue(v, &x)
|
||||
if err != nil {
|
||||
return nil, err
|
||||
}
|
||||
|
||||
in = append(in, reflect.ValueOf(x))
|
||||
}
|
||||
|
||||
return in, nil
|
||||
}
|
||||
|
||||
func returnValue(x []reflect.Value) js.Value {
|
||||
switch len(x) {
|
||||
case 0:
|
||||
return js.Undefined()
|
||||
case 1:
|
||||
return ToJSValue(x[0].Interface())
|
||||
}
|
||||
|
||||
xInterface := make([]interface{}, 0, len(x))
|
||||
for _, v := range x {
|
||||
xInterface = append(xInterface, v.Interface())
|
||||
}
|
||||
|
||||
return ToJSValue(xInterface)
|
||||
}
|
||||
@ -0,0 +1,11 @@
|
||||
package wasm
|
||||
|
||||
import (
|
||||
"fmt"
|
||||
"syscall/js"
|
||||
)
|
||||
|
||||
func FromJSValue(x js.Value, out interface{}) error {
|
||||
// TODO
|
||||
return fmt.Errorf("unimplemented")
|
||||
}
|
||||
@ -0,0 +1,161 @@
|
||||
package wasm
|
||||
|
||||
import (
|
||||
"fmt"
|
||||
"reflect"
|
||||
"syscall/js"
|
||||
"unsafe"
|
||||
)
|
||||
|
||||
// ToJSValue converts a given Go value into its equivalent JS form.
|
||||
//
|
||||
// One special case is that complex numbers (complex64 and complex128) are converted into objects with a real and imag
|
||||
// property holding a number each.
|
||||
//
|
||||
// A function is converted into a JS function where the function returns an error if the provided arguments do not conform
|
||||
// to the Go equivalent but otherwise calls the Go function.
|
||||
//
|
||||
// The "this" argument of a function is always passed to the Go function if its first parameter is of type js.Value.
|
||||
// Otherwise, it is simply ignored.
|
||||
//
|
||||
// If the last return value of a function is an error, it will be thrown in JS if it's non-nil.
|
||||
// If the function returns multiple non-error values, it is converted to an array when returning to JS.
|
||||
//
|
||||
// It panics when a channel or a map with keys other than string and integers are passed in.
|
||||
func ToJSValue(x interface{}) js.Value {
|
||||
if x == nil {
|
||||
return js.Null()
|
||||
}
|
||||
|
||||
// Fast path for basic types that do not require reflection.
|
||||
switch x := x.(type) {
|
||||
case js.Value:
|
||||
return x
|
||||
case js.Wrapper:
|
||||
return x.JSValue()
|
||||
case bool, int, int8, int16, int32, int64, uint, uint8, uint16, uint32, uint64, uintptr,
|
||||
unsafe.Pointer, float32, float64, string:
|
||||
return js.ValueOf(x)
|
||||
case complex64:
|
||||
return js.ValueOf(map[string]interface{}{
|
||||
"real": real(x),
|
||||
"imag": imag(x),
|
||||
})
|
||||
case complex128:
|
||||
return js.ValueOf(map[string]interface{}{
|
||||
"real": real(x),
|
||||
"imag": imag(x),
|
||||
})
|
||||
}
|
||||
|
||||
value := reflect.ValueOf(x)
|
||||
|
||||
if value.Kind() == reflect.Ptr {
|
||||
value = reflect.Indirect(value)
|
||||
if !value.IsValid() {
|
||||
return js.Undefined()
|
||||
}
|
||||
}
|
||||
|
||||
switch value.Kind() {
|
||||
case reflect.Array, reflect.Slice:
|
||||
return toJSArray(value)
|
||||
case reflect.Func:
|
||||
return toJSFunc(value)
|
||||
case reflect.Map:
|
||||
return mapToJSObject(value)
|
||||
case reflect.Struct:
|
||||
return structToJSObject(value)
|
||||
default:
|
||||
panic(fmt.Sprintf("cannot convert %T to a JS value", x))
|
||||
}
|
||||
}
|
||||
|
||||
func toJSArray(x reflect.Value) js.Value {
|
||||
arrayConstructor, err := Global().Get("Array")
|
||||
if err != nil {
|
||||
panic("Array constructor not found")
|
||||
}
|
||||
|
||||
array := arrayConstructor.New()
|
||||
for i := 0; i < x.Len(); i++ {
|
||||
array.SetIndex(i, ToJSValue(x.Index(i).Interface()))
|
||||
}
|
||||
|
||||
return array
|
||||
}
|
||||
|
||||
func mapToJSObject(x reflect.Value) js.Value {
|
||||
objectConstructor, err := Global().Get("Object")
|
||||
if err != nil {
|
||||
panic("Object constructor not found")
|
||||
}
|
||||
|
||||
obj := objectConstructor.New()
|
||||
iter := x.MapRange()
|
||||
for {
|
||||
if !iter.Next() {
|
||||
break
|
||||
}
|
||||
|
||||
key := iter.Key()
|
||||
value := iter.Value().Interface()
|
||||
switch key := key.Interface().(type) {
|
||||
case int:
|
||||
obj.SetIndex(key, ToJSValue(value))
|
||||
case int8:
|
||||
obj.SetIndex(int(key), ToJSValue(value))
|
||||
case int16:
|
||||
obj.SetIndex(int(key), ToJSValue(value))
|
||||
case int32:
|
||||
obj.SetIndex(int(key), ToJSValue(value))
|
||||
case int64:
|
||||
obj.SetIndex(int(key), ToJSValue(value))
|
||||
case uint:
|
||||
obj.SetIndex(int(key), ToJSValue(value))
|
||||
case uint8:
|
||||
obj.SetIndex(int(key), ToJSValue(value))
|
||||
case uint16:
|
||||
obj.SetIndex(int(key), ToJSValue(value))
|
||||
case uint32:
|
||||
obj.SetIndex(int(key), ToJSValue(value))
|
||||
case uint64:
|
||||
obj.SetIndex(int(key), ToJSValue(value))
|
||||
case uintptr:
|
||||
obj.SetIndex(int(key), ToJSValue(value))
|
||||
case string:
|
||||
obj.Set(key, ToJSValue(value))
|
||||
default:
|
||||
panic(fmt.Sprintf("cannot convert %T into a JS value as its key is not a string or an integer",
|
||||
x.Interface()))
|
||||
}
|
||||
}
|
||||
|
||||
return obj
|
||||
}
|
||||
|
||||
func structToJSObject(x reflect.Value) js.Value {
|
||||
objectConstructor, err := Global().Get("Object")
|
||||
if err != nil {
|
||||
panic("Object constructor not found")
|
||||
}
|
||||
|
||||
obj := objectConstructor.New()
|
||||
|
||||
structType := x.Type()
|
||||
for i := 0; i < structType.NumField(); i++ {
|
||||
field := structType.Field(i)
|
||||
if field.PkgPath != "" {
|
||||
continue
|
||||
}
|
||||
|
||||
name := field.Name
|
||||
if tagName, ok := field.Tag.Lookup("wasm"); ok {
|
||||
name = tagName
|
||||
}
|
||||
|
||||
obj.Set(name, ToJSValue(x.Field(i).Interface()))
|
||||
}
|
||||
|
||||
return obj
|
||||
}
|
||||
@ -0,0 +1,32 @@
|
||||
package wasm
|
||||
|
||||
// Magic values to communicate with the JS library.
|
||||
const (
|
||||
globalIdent = "__go_wasm__"
|
||||
readyHint = "__ready__"
|
||||
)
|
||||
|
||||
var bridge Object
|
||||
|
||||
func init() {
|
||||
bridgeJS, err := Global().Get(globalIdent)
|
||||
if err != nil {
|
||||
panic("JS wrapper " + globalIdent + " not found")
|
||||
}
|
||||
|
||||
bridge, err = NewObject(bridgeJS)
|
||||
if err != nil {
|
||||
panic("JS wrapper " + globalIdent + " is not an object")
|
||||
}
|
||||
}
|
||||
|
||||
// Ready notifies the JS bridge that the WASM is ready.
|
||||
// It should be called when every value and function is exposed.
|
||||
func Ready() {
|
||||
Expose(readyHint, true)
|
||||
}
|
||||
|
||||
// Expose exposes a copy of the provided value in JS.
|
||||
func Expose(property string, x interface{}) {
|
||||
bridge.Set(property, x)
|
||||
}
|
||||
Loading…
Reference in New Issue