status-go/vendor/go.uber.org/fx/extract.go

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// Copyright (c) 2019 Uber Technologies, Inc.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
package fx
import (
"fmt"
"reflect"
"unicode"
"unicode/utf8"
)
var _typeOfIn = reflect.TypeOf(In{})
// Extract fills the given struct with values from the dependency injection
// container on application initialization. The target MUST be a pointer to a
// struct. Only exported fields will be filled.
//
// Deprecated: Use Populate instead.
func Extract(target interface{}) Option {
v := reflect.ValueOf(target)
if t := v.Type(); t.Kind() != reflect.Ptr || t.Elem().Kind() != reflect.Struct {
return Error(fmt.Errorf("Extract expected a pointer to a struct, got a %v", t))
}
v = v.Elem()
t := v.Type()
// We generate a function which accepts a single fx.In struct as an
// argument. This struct contains all exported fields of the target
// struct.
// Fields of the generated fx.In struct.
fields := make([]reflect.StructField, 0, t.NumField()+1)
// Anonymous dig.In field.
fields = append(fields, reflect.StructField{
Name: _typeOfIn.Name(),
Anonymous: true,
Type: _typeOfIn,
})
// List of values in the target struct aligned with the fields of the
// generated struct.
//
// So for example, if the target is,
//
// var target struct {
// Foo io.Reader
// bar []byte
// Baz io.Writer
// }
//
// The generated struct has the shape,
//
// struct {
// fx.In
//
// F0 io.Reader
// F2 io.Writer
// }
//
// And `targets` is,
//
// [
// target.Field(0), // Foo io.Reader
// target.Field(2), // Baz io.Writer
// ]
//
// As we iterate through the fields of the generated struct, we can copy
// the value into the corresponding value in the targets list.
targets := make([]reflect.Value, 0, t.NumField())
for i := 0; i < t.NumField(); i++ {
f := t.Field(i)
// Skip unexported fields.
if f.Anonymous {
// If embedded, StructField.PkgPath is not a reliable indicator of
// whether the field is exported. See
// https://github.com/golang/go/issues/21122
t := f.Type
if t.Kind() == reflect.Ptr {
t = t.Elem()
}
if !isExported(t.Name()) {
continue
}
} else if f.PkgPath != "" {
continue
}
// We don't copy over names or embedded semantics.
fields = append(fields, reflect.StructField{
Name: fmt.Sprintf("F%d", i),
Type: f.Type,
Tag: f.Tag,
})
targets = append(targets, v.Field(i))
}
// Equivalent to,
//
// func(r struct {
// fx.In
//
// F1 Foo
// F2 Bar
// }) {
// target.Foo = r.F1
// target.Bar = r.F2
// }
fn := reflect.MakeFunc(
reflect.FuncOf(
[]reflect.Type{reflect.StructOf(fields)},
nil, /* results */
false, /* variadic */
),
func(args []reflect.Value) []reflect.Value {
result := args[0]
for i := 1; i < result.NumField(); i++ {
targets[i-1].Set(result.Field(i))
}
return nil
},
)
return Invoke(fn.Interface())
}
// isExported reports whether the identifier is exported.
func isExported(id string) bool {
r, _ := utf8.DecodeRuneInString(id)
return unicode.IsUpper(r)
}