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Make 'where' template function accepts dot chaining key argument #752

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Make 'where' template function accepts dot chaining key argument #752

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13 changes: 13 additions & 0 deletions docs/content/templates/functions.md
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Original file line number Diff line number Diff line change
Expand Up @@ -66,6 +66,19 @@ e.g.
{{ .Content}}
{{ end }}

It can be used with dot chaining second argument to refer a nested element of a value.

e.g.

// Front matter on some pages
+++
series: golang
+++

{{ range where .Site.Recent "Params.series" "golang" }}
{{ .Content}}
{{ end }}

*where and first can be stacked*

e.g.
Expand Down
149 changes: 104 additions & 45 deletions tpl/template.go
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Expand Up @@ -289,6 +289,19 @@ func In(l interface{}, v interface{}) bool {
return false
}

// indirect is taken from 'text/template/exec.go'
func indirect(v reflect.Value) (rv reflect.Value, isNil bool) {
for ; v.Kind() == reflect.Ptr || v.Kind() == reflect.Interface; v = v.Elem() {
if v.IsNil() {
return v, true
}
if v.Kind() == reflect.Interface && v.NumMethod() > 0 {
break
}
}
return v, false
}

// First is exposed to templates, to iterate over the first N items in a
// rangeable list.
func First(limit interface{}, seq interface{}) (interface{}, error) {
Expand Down Expand Up @@ -326,76 +339,122 @@ func First(limit interface{}, seq interface{}) (interface{}, error) {
return seqv.Slice(0, limitv).Interface(), nil
}

func Where(seq, key, match interface{}) (interface{}, error) {
var (
zero reflect.Value
errorType = reflect.TypeOf((*error)(nil)).Elem()
)

func evaluateSubElem(obj reflect.Value, elemName string) (reflect.Value, error) {
if !obj.IsValid() {
return zero, errors.New("can't evaluate an invalid value")
}
typ := obj.Type()
obj, isNil := indirect(obj)

// first, check whether obj has a method. In this case, obj is
// an interface, a struct or its pointer. If obj is a struct,
// to check all T and *T method, use obj pointer type Value
objPtr := obj
if objPtr.Kind() != reflect.Interface && objPtr.CanAddr() {
objPtr = objPtr.Addr()
}
mt, ok := objPtr.Type().MethodByName(elemName)
if ok {
if mt.PkgPath != "" {
return zero, fmt.Errorf("%s is an unexported method of type %s", elemName, typ)
}
// struct pointer has one receiver argument and interface doesn't have an argument
if mt.Type.NumIn() > 1 || mt.Type.NumOut() == 0 || mt.Type.NumOut() > 2 {
return zero, fmt.Errorf("%s is a method of type %s but doesn't satisfy requirements", elemName, typ)
}
if mt.Type.NumOut() == 1 && mt.Type.Out(0).Implements(errorType) {
return zero, fmt.Errorf("%s is a method of type %s but doesn't satisfy requirements", elemName, typ)
}
if mt.Type.NumOut() == 2 && !mt.Type.Out(1).Implements(errorType) {
return zero, fmt.Errorf("%s is a method of type %s but doesn't satisfy requirements", elemName, typ)
}
res := objPtr.Method(mt.Index).Call([]reflect.Value{})
if len(res) == 2 && !res[1].IsNil() {
return zero, fmt.Errorf("error at calling a method %s of type %s: %s", elemName, typ, res[1].Interface().(error))
}
return res[0], nil
}

// elemName isn't a method so next start to check whether it is
// a struct field or a map value. In both cases, it mustn't be
// a nil value
if isNil {
return zero, fmt.Errorf("can't evaluate a nil pointer of type %s by a struct field or map key name %s", typ, elemName)
}
switch obj.Kind() {
case reflect.Struct:
ft, ok := obj.Type().FieldByName(elemName)
if ok {
if ft.PkgPath != "" {
return zero, fmt.Errorf("%s is an unexported field of struct type %s", elemName, typ)
}
return obj.FieldByIndex(ft.Index), nil
}
return zero, fmt.Errorf("%s isn't a field of struct type %s", elemName, typ)
case reflect.Map:
kv := reflect.ValueOf(elemName)
if kv.Type().AssignableTo(obj.Type().Key()) {
return obj.MapIndex(kv), nil
}
return zero, fmt.Errorf("%s isn't a key of map type %s", elemName, typ)
}
return zero, fmt.Errorf("%s is neither a struct field, a method nor a map element of type %s", elemName, typ)
}

func Where(seq, key, match interface{}) (r interface{}, err error) {
seqv := reflect.ValueOf(seq)
kv := reflect.ValueOf(key)
mv := reflect.ValueOf(match)

// this is better than my first pass; ripped from text/template/exec.go indirect():
for ; seqv.Kind() == reflect.Ptr || seqv.Kind() == reflect.Interface; seqv = seqv.Elem() {
if seqv.IsNil() {
return nil, errors.New("can't iterate over a nil value")
}
if seqv.Kind() == reflect.Interface && seqv.NumMethod() > 0 {
break
}
seqv, isNil := indirect(seqv)
if isNil {
return nil, errors.New("can't iterate over a nil value of type " + reflect.ValueOf(seq).Type().String())
}

var path []string
if kv.Kind() == reflect.String {
path = strings.Split(strings.Trim(kv.String(), "."), ".")
}

switch seqv.Kind() {
case reflect.Array, reflect.Slice:
r := reflect.MakeSlice(seqv.Type(), 0, 0)
rv := reflect.MakeSlice(seqv.Type(), 0, 0)
for i := 0; i < seqv.Len(); i++ {
var vvv reflect.Value
vv := seqv.Index(i)
switch vv.Kind() {
case reflect.Map:
if kv.Type() == vv.Type().Key() && vv.MapIndex(kv).IsValid() {
vvv = vv.MapIndex(kv)
}
case reflect.Struct:
if kv.Kind() == reflect.String {
method := vv.MethodByName(kv.String())
if method.IsValid() && method.Type().NumIn() == 0 && method.Type().NumOut() > 0 {
vvv = method.Call(nil)[0]
} else if vv.FieldByName(kv.String()).IsValid() {
vvv = vv.FieldByName(kv.String())
rvv := seqv.Index(i)
if kv.Kind() == reflect.String {
vvv = rvv
for _, elemName := range path {
vvv, err = evaluateSubElem(vvv, elemName)
if err != nil {
return nil, err
}
}
case reflect.Ptr:
if !vv.IsNil() {
ev := vv.Elem()
switch ev.Kind() {
case reflect.Map:
if kv.Type() == ev.Type().Key() && ev.MapIndex(kv).IsValid() {
vvv = ev.MapIndex(kv)
}
case reflect.Struct:
if kv.Kind() == reflect.String {
method := vv.MethodByName(kv.String())
if method.IsValid() && method.Type().NumIn() == 0 && method.Type().NumOut() > 0 {
vvv = method.Call(nil)[0]
} else if ev.FieldByName(kv.String()).IsValid() {
vvv = ev.FieldByName(kv.String())
}
}
}
} else {
vv, _ := indirect(rvv)
if vv.Kind() == reflect.Map && kv.Type().AssignableTo(vv.Type().Key()) {
vvv = vv.MapIndex(kv)
}
}

if vvv.IsValid() && mv.Type() == vvv.Type() {
switch mv.Kind() {
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
if mv.Int() == vvv.Int() {
r = reflect.Append(r, vv)
rv = reflect.Append(rv, rvv)
}
case reflect.String:
if mv.String() == vvv.String() {
r = reflect.Append(r, vv)
rv = reflect.Append(rv, rvv)
}
}
}
}
return r.Interface(), nil
return rv.Interface(), nil
default:
return nil, errors.New("can't iterate over " + reflect.ValueOf(seq).Type().String())
}
Expand Down
119 changes: 109 additions & 10 deletions tpl/template_test.go
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Original file line number Diff line number Diff line change
@@ -1,6 +1,8 @@
package tpl

import (
"errors"
"fmt"
"html/template"
"reflect"
"testing"
Expand Down Expand Up @@ -305,15 +307,96 @@ func (x TstX) TstRv() string {
return "r" + x.B
}

func (x TstX) unexportedMethod() string {
return x.unexported
}

func (x TstX) MethodWithArg(s string) string {
return s
}

func (x TstX) MethodReturnNothing() {}

func (x TstX) MethodReturnErrorOnly() error {
return errors.New("something error occured")
}

func (x TstX) MethodReturnTwoValues() (string, string) {
return "foo", "bar"
}

func (x TstX) MethodReturnValueWithError() (string, error) {
return "", errors.New("something error occured")
}

func (x TstX) String() string {
return fmt.Sprintf("A: %s, B: %s", x.A, x.B)
}

type TstX struct {
A, B string
unexported string
}

func TestEvaluateSubElem(t *testing.T) {
tstx := TstX{A: "foo", B: "bar"}
var inner struct {
S fmt.Stringer
}
inner.S = tstx
interfaceValue := reflect.ValueOf(&inner).Elem().Field(0)

for i, this := range []struct {
value reflect.Value
key string
expect interface{}
}{
{reflect.ValueOf(tstx), "A", "foo"},
{reflect.ValueOf(&tstx), "TstRp", "rfoo"},
{reflect.ValueOf(tstx), "TstRv", "rbar"},
//{reflect.ValueOf(map[int]string{1: "foo", 2: "bar"}), 1, "foo"},
{reflect.ValueOf(map[string]string{"key1": "foo", "key2": "bar"}), "key1", "foo"},
{interfaceValue, "String", "A: foo, B: bar"},
{reflect.Value{}, "foo", false},
//{reflect.ValueOf(map[int]string{1: "foo", 2: "bar"}), 1.2, false},
{reflect.ValueOf(tstx), "unexported", false},
{reflect.ValueOf(tstx), "unexportedMethod", false},
{reflect.ValueOf(tstx), "MethodWithArg", false},
{reflect.ValueOf(tstx), "MethodReturnNothing", false},
{reflect.ValueOf(tstx), "MethodReturnErrorOnly", false},
{reflect.ValueOf(tstx), "MethodReturnTwoValues", false},
{reflect.ValueOf(tstx), "MethodReturnValueWithError", false},
{reflect.ValueOf((*TstX)(nil)), "A", false},
{reflect.ValueOf(tstx), "C", false},
{reflect.ValueOf(map[int]string{1: "foo", 2: "bar"}), "1", false},
{reflect.ValueOf([]string{"foo", "bar"}), "1", false},
} {
result, err := evaluateSubElem(this.value, this.key)
if b, ok := this.expect.(bool); ok && !b {
if err == nil {
t.Errorf("[%d] evaluateSubElem didn't return an expected error", i)
}
} else {
if err != nil {
t.Errorf("[%d] failed: %s", i, err)
continue
}
if result.Kind() != reflect.String || result.String() != this.expect {
t.Errorf("[%d] evaluateSubElem with %v got %v but expected %v", i, this.key, result, this.expect)
}
}
}
}

func TestWhere(t *testing.T) {
// TODO(spf): Put these page tests back in
//page1 := &Page{contentType: "v", Source: Source{File: *source.NewFile("/x/y/z/source.md")}}
//page2 := &Page{contentType: "w", Source: Source{File: *source.NewFile("/y/z/a/source.md")}}

type Mid struct {
Tst TstX
}

for i, this := range []struct {
sequence interface{}
key interface{}
Expand All @@ -322,21 +405,37 @@ func TestWhere(t *testing.T) {
}{
{[]map[int]string{{1: "a", 2: "m"}, {1: "c", 2: "d"}, {1: "e", 3: "m"}}, 2, "m", []map[int]string{{1: "a", 2: "m"}}},
{[]map[string]int{{"a": 1, "b": 2}, {"a": 3, "b": 4}, {"a": 5, "x": 4}}, "b", 4, []map[string]int{{"a": 3, "b": 4}}},
{[]TstX{{"a", "b"}, {"c", "d"}, {"e", "f"}}, "B", "f", []TstX{{"e", "f"}}},
{[]TstX{{A: "a", B: "b"}, {A: "c", B: "d"}, {A: "e", B: "f"}}, "B", "f", []TstX{{A: "e", B: "f"}}},
{[]*map[int]string{&map[int]string{1: "a", 2: "m"}, &map[int]string{1: "c", 2: "d"}, &map[int]string{1: "e", 3: "m"}}, 2, "m", []*map[int]string{&map[int]string{1: "a", 2: "m"}}},
{[]*TstX{&TstX{"a", "b"}, &TstX{"c", "d"}, &TstX{"e", "f"}}, "B", "f", []*TstX{&TstX{"e", "f"}}},
{[]*TstX{&TstX{"a", "b"}, &TstX{"c", "d"}, &TstX{"e", "c"}}, "TstRp", "rc", []*TstX{&TstX{"c", "d"}}},
{[]TstX{TstX{"a", "b"}, TstX{"c", "d"}, TstX{"e", "c"}}, "TstRv", "rc", []TstX{TstX{"e", "c"}}},
{[]*TstX{&TstX{A: "a", B: "b"}, &TstX{A: "c", B: "d"}, &TstX{A: "e", B: "f"}}, "B", "f", []*TstX{&TstX{A: "e", B: "f"}}},
{[]*TstX{&TstX{A: "a", B: "b"}, &TstX{A: "c", B: "d"}, &TstX{A: "e", B: "c"}}, "TstRp", "rc", []*TstX{&TstX{A: "c", B: "d"}}},
{[]TstX{TstX{A: "a", B: "b"}, TstX{A: "c", B: "d"}, TstX{A: "e", B: "c"}}, "TstRv", "rc", []TstX{TstX{A: "e", B: "c"}}},
{[]map[string]TstX{{"foo": TstX{A: "a", B: "b"}}, {"foo": TstX{A: "c", B: "d"}}, {"foo": TstX{A: "e", B: "f"}}}, "foo.B", "d", []map[string]TstX{{"foo": TstX{A: "c", B: "d"}}}},
{[]map[string]TstX{{"foo": TstX{A: "a", B: "b"}}, {"foo": TstX{A: "c", B: "d"}}, {"foo": TstX{A: "e", B: "f"}}}, ".foo.B", "d", []map[string]TstX{{"foo": TstX{A: "c", B: "d"}}}},
{[]map[string]TstX{{"foo": TstX{A: "a", B: "b"}}, {"foo": TstX{A: "c", B: "d"}}, {"foo": TstX{A: "e", B: "f"}}}, "foo.TstRv", "rd", []map[string]TstX{{"foo": TstX{A: "c", B: "d"}}}},
{[]map[string]*TstX{{"foo": &TstX{A: "a", B: "b"}}, {"foo": &TstX{A: "c", B: "d"}}, {"foo": &TstX{A: "e", B: "f"}}}, "foo.TstRp", "rc", []map[string]*TstX{{"foo": &TstX{A: "c", B: "d"}}}},
{[]map[string]Mid{{"foo": Mid{Tst: TstX{A: "a", B: "b"}}}, {"foo": Mid{Tst: TstX{A: "c", B: "d"}}}, {"foo": Mid{Tst: TstX{A: "e", B: "f"}}}}, "foo.Tst.B", "d", []map[string]Mid{{"foo": Mid{Tst: TstX{A: "c", B: "d"}}}}},
{[]map[string]Mid{{"foo": Mid{Tst: TstX{A: "a", B: "b"}}}, {"foo": Mid{Tst: TstX{A: "c", B: "d"}}}, {"foo": Mid{Tst: TstX{A: "e", B: "f"}}}}, "foo.Tst.TstRv", "rd", []map[string]Mid{{"foo": Mid{Tst: TstX{A: "c", B: "d"}}}}},
{[]map[string]*Mid{{"foo": &Mid{Tst: TstX{A: "a", B: "b"}}}, {"foo": &Mid{Tst: TstX{A: "c", B: "d"}}}, {"foo": &Mid{Tst: TstX{A: "e", B: "f"}}}}, "foo.Tst.TstRp", "rc", []map[string]*Mid{{"foo": &Mid{Tst: TstX{A: "c", B: "d"}}}}},
{(*[]TstX)(nil), "A", "a", false},
{TstX{A: "a", B: "b"}, "A", "a", false},
{[]map[string]*TstX{{"foo": nil}}, "foo.B", "d", false},
//{[]*Page{page1, page2}, "Type", "v", []*Page{page1}},
//{[]*Page{page1, page2}, "Section", "y", []*Page{page2}},
} {
results, err := Where(this.sequence, this.key, this.match)
if err != nil {
t.Errorf("[%d] failed: %s", i, err)
continue
}
if !reflect.DeepEqual(results, this.expect) {
t.Errorf("[%d] Where clause matching %v with %v, got %v but expected %v", i, this.key, this.match, results, this.expect)
if b, ok := this.expect.(bool); ok && !b {
if err == nil {
t.Errorf("[%d] Where didn't return an expected error", i)
}
} else {
if err != nil {
t.Errorf("[%d] failed: %s", i, err)
continue
}
if !reflect.DeepEqual(results, this.expect) {
t.Errorf("[%d] Where clause matching %v with %v, got %v but expected %v", i, this.key, this.match, results, this.expect)
}
}
}
}
Expand Down