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31a8bb8c07
This commit consolidates the reflective collections handling in `.Scratch` vs the `tpl` package so they use the same code paths.
This commit also adds support for a corner case where a typed slice is appended to a nil or empty `[]interface{}`.
Fixes #5275
84 lines
2.2 KiB
Go
84 lines
2.2 KiB
Go
// Copyright 2018 The Hugo Authors. All rights reserved.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package collections
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import (
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"fmt"
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"reflect"
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)
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// Append appends from to a slice to and returns the resulting slice.
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// If lenght of from is one and the only element is a slice of same type as to,
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// it will be appended.
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func Append(to interface{}, from ...interface{}) (interface{}, error) {
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tov, toIsNil := indirect(reflect.ValueOf(to))
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toIsNil = toIsNil || to == nil
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var tot reflect.Type
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if !toIsNil {
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if tov.Kind() != reflect.Slice {
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return nil, fmt.Errorf("expected a slice, got %T", to)
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}
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tot = tov.Type().Elem()
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toIsNil = tov.Len() == 0
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if len(from) == 1 {
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fromv := reflect.ValueOf(from[0])
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if fromv.Kind() == reflect.Slice {
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if toIsNil {
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// If we get nil []string, we just return the []string
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return from[0], nil
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}
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fromt := reflect.TypeOf(from[0]).Elem()
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// If we get []string []string, we append the from slice to to
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if tot == fromt {
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return reflect.AppendSlice(tov, fromv).Interface(), nil
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}
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}
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}
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}
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if toIsNil {
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return Slice(from...), nil
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}
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for _, f := range from {
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fv := reflect.ValueOf(f)
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if tot != fv.Type() {
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return nil, fmt.Errorf("append element type mismatch: expected %v, got %v", tot, fv.Type())
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}
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tov = reflect.Append(tov, fv)
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}
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return tov.Interface(), nil
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}
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// indirect is borrowed from the Go stdlib: 'text/template/exec.go'
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// TODO(bep) consolidate
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func indirect(v reflect.Value) (rv reflect.Value, isNil bool) {
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for ; v.Kind() == reflect.Ptr || v.Kind() == reflect.Interface; v = v.Elem() {
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if v.IsNil() {
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return v, true
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}
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if v.Kind() == reflect.Interface && v.NumMethod() > 0 {
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break
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}
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}
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return v, false
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}
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