github.com/graemephi/kahugo@v0.62.3-0.20211121071557-d78c0423784d/tpl/collections/apply.go (about)

     1  // Copyright 2017 The Hugo Authors. All rights reserved.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  // http://www.apache.org/licenses/LICENSE-2.0
     7  //
     8  // Unless required by applicable law or agreed to in writing, software
     9  // distributed under the License is distributed on an "AS IS" BASIS,
    10  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    11  // See the License for the specific language governing permissions and
    12  // limitations under the License.
    13  
    14  package collections
    15  
    16  import (
    17  	"errors"
    18  	"fmt"
    19  	"reflect"
    20  	"strings"
    21  
    22  	"github.com/gohugoio/hugo/tpl"
    23  )
    24  
    25  // Apply takes a map, array, or slice and returns a new slice with the function fname applied over it.
    26  func (ns *Namespace) Apply(seq interface{}, fname string, args ...interface{}) (interface{}, error) {
    27  	if seq == nil {
    28  		return make([]interface{}, 0), nil
    29  	}
    30  
    31  	if fname == "apply" {
    32  		return nil, errors.New("can't apply myself (no turtles allowed)")
    33  	}
    34  
    35  	seqv := reflect.ValueOf(seq)
    36  	seqv, isNil := indirect(seqv)
    37  	if isNil {
    38  		return nil, errors.New("can't iterate over a nil value")
    39  	}
    40  
    41  	fnv, found := ns.lookupFunc(fname)
    42  	if !found {
    43  		return nil, errors.New("can't find function " + fname)
    44  	}
    45  
    46  	// fnv := reflect.ValueOf(fn)
    47  
    48  	switch seqv.Kind() {
    49  	case reflect.Array, reflect.Slice:
    50  		r := make([]interface{}, seqv.Len())
    51  		for i := 0; i < seqv.Len(); i++ {
    52  			vv := seqv.Index(i)
    53  
    54  			vvv, err := applyFnToThis(fnv, vv, args...)
    55  			if err != nil {
    56  				return nil, err
    57  			}
    58  
    59  			r[i] = vvv.Interface()
    60  		}
    61  
    62  		return r, nil
    63  	default:
    64  		return nil, fmt.Errorf("can't apply over %v", seq)
    65  	}
    66  }
    67  
    68  func applyFnToThis(fn, this reflect.Value, args ...interface{}) (reflect.Value, error) {
    69  	n := make([]reflect.Value, len(args))
    70  	for i, arg := range args {
    71  		if arg == "." {
    72  			n[i] = this
    73  		} else {
    74  			n[i] = reflect.ValueOf(arg)
    75  		}
    76  	}
    77  
    78  	num := fn.Type().NumIn()
    79  
    80  	if fn.Type().IsVariadic() {
    81  		num--
    82  	}
    83  
    84  	// TODO(bep) see #1098 - also see template_tests.go
    85  	/*if len(args) < num {
    86  		return reflect.ValueOf(nil), errors.New("Too few arguments")
    87  	} else if len(args) > num {
    88  		return reflect.ValueOf(nil), errors.New("Too many arguments")
    89  	}*/
    90  
    91  	for i := 0; i < num; i++ {
    92  		// AssignableTo reports whether xt is assignable to type targ.
    93  		if xt, targ := n[i].Type(), fn.Type().In(i); !xt.AssignableTo(targ) {
    94  			return reflect.ValueOf(nil), errors.New("called apply using " + xt.String() + " as type " + targ.String())
    95  		}
    96  	}
    97  
    98  	res := fn.Call(n)
    99  
   100  	if len(res) == 1 || res[1].IsNil() {
   101  		return res[0], nil
   102  	}
   103  	return reflect.ValueOf(nil), res[1].Interface().(error)
   104  }
   105  
   106  func (ns *Namespace) lookupFunc(fname string) (reflect.Value, bool) {
   107  	if !strings.ContainsRune(fname, '.') {
   108  		templ := ns.deps.Tmpl().(tpl.TemplateFuncGetter)
   109  		return templ.GetFunc(fname)
   110  	}
   111  
   112  	ss := strings.SplitN(fname, ".", 2)
   113  
   114  	// namespace
   115  	nv, found := ns.lookupFunc(ss[0])
   116  	if !found {
   117  		return reflect.Value{}, false
   118  	}
   119  
   120  	// method
   121  	m := nv.MethodByName(ss[1])
   122  	// if reflect.DeepEqual(m, reflect.Value{}) {
   123  	if m.Kind() == reflect.Invalid {
   124  		return reflect.Value{}, false
   125  	}
   126  	return m, true
   127  }
   128  
   129  // indirect is borrowed from the Go stdlib: 'text/template/exec.go'
   130  func indirect(v reflect.Value) (rv reflect.Value, isNil bool) {
   131  	for ; v.Kind() == reflect.Ptr || v.Kind() == reflect.Interface; v = v.Elem() {
   132  		if v.IsNil() {
   133  			return v, true
   134  		}
   135  		if v.Kind() == reflect.Interface && v.NumMethod() > 0 {
   136  			break
   137  		}
   138  	}
   139  	return v, false
   140  }
   141  
   142  func indirectInterface(v reflect.Value) (rv reflect.Value, isNil bool) {
   143  	for ; v.Kind() == reflect.Interface; v = v.Elem() {
   144  		if v.IsNil() {
   145  			return v, true
   146  		}
   147  		if v.Kind() == reflect.Interface && v.NumMethod() > 0 {
   148  			break
   149  		}
   150  	}
   151  	return v, false
   152  }