ref: a03c631c420a03f9d90699abdf9be7e4fca0ff61
dir: /tpl/internal/go_templates/texttemplate/hugo_template.go/
// Copyright 2019 The Hugo Authors. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package template
import (
"io"
"reflect"
"github.com/gohugoio/hugo/tpl/internal/go_templates/texttemplate/parse"
)
/*
This files contains the Hugo related addons. All the other files in this
package is auto generated.
*/
// Preparer prepares the template before execution.
type Preparer interface {
Prepare() (*Template, error)
}
// ExecHelper allows some custom eval hooks.
type ExecHelper interface {
GetFunc(name string) (reflect.Value, bool)
GetMapValue(receiver, key reflect.Value) (reflect.Value, bool)
}
// Executer executes a given template.
type Executer interface {
Execute(p Preparer, wr io.Writer, data interface{}) error
}
type executer struct {
helper ExecHelper
}
func NewExecuter(helper ExecHelper) Executer {
return &executer{helper: helper}
}
func (t *executer) Execute(p Preparer, wr io.Writer, data interface{}) error {
tmpl, err := p.Prepare()
if err != nil {
return err
}
value, ok := data.(reflect.Value)
if !ok {
value = reflect.ValueOf(data)
}
state := &state{
helper: t.helper,
tmpl: tmpl,
wr: wr,
vars: []variable{{"$", value}},
}
return tmpl.executeWithState(state, value)
}
// Prepare returns a template ready for execution.
func (t *Template) Prepare() (*Template, error) {
return t, nil
}
func (t *Template) executeWithState(state *state, value reflect.Value) (err error) {
defer errRecover(&err)
if t.Tree == nil || t.Root == nil {
state.errorf("%q is an incomplete or empty template", t.Name())
}
state.walk(value, t.Root)
return
}
// Below are modifed structs etc.
// state represents the state of an execution. It's not part of the
// template so that multiple executions of the same template
// can execute in parallel.
type state struct {
tmpl *Template
helper ExecHelper
wr io.Writer
node parse.Node // current node, for errors
vars []variable // push-down stack of variable values.
depth int // the height of the stack of executing templates.
}
func (s *state) evalFunction(dot reflect.Value, node *parse.IdentifierNode, cmd parse.Node, args []parse.Node, final reflect.Value) reflect.Value {
s.at(node)
name := node.Ident
var function reflect.Value
var ok bool
if s.helper != nil {
function, ok = s.helper.GetFunc(name)
}
if !ok {
function, ok = findFunction(name, s.tmpl)
}
if !ok {
s.errorf("%q is not a defined function", name)
}
return s.evalCall(dot, function, cmd, name, args, final)
}
// evalField evaluates an expression like (.Field) or (.Field arg1 arg2).
// The 'final' argument represents the return value from the preceding
// value of the pipeline, if any.
func (s *state) evalField(dot reflect.Value, fieldName string, node parse.Node, args []parse.Node, final, receiver reflect.Value) reflect.Value {
if !receiver.IsValid() {
if s.tmpl.option.missingKey == mapError { // Treat invalid value as missing map key.
s.errorf("nil data; no entry for key %q", fieldName)
}
return zero
}
typ := receiver.Type()
receiver, isNil := indirect(receiver)
if receiver.Kind() == reflect.Interface && isNil {
// Calling a method on a nil interface can't work. The
// MethodByName method call below would panic.
s.errorf("nil pointer evaluating %s.%s", typ, fieldName)
return zero
}
// Unless it's an interface, need to get to a value of type *T to guarantee
// we see all methods of T and *T.
ptr := receiver
if ptr.Kind() != reflect.Interface && ptr.Kind() != reflect.Ptr && ptr.CanAddr() {
ptr = ptr.Addr()
}
if method := ptr.MethodByName(fieldName); method.IsValid() {
return s.evalCall(dot, method, node, fieldName, args, final)
}
hasArgs := len(args) > 1 || final != missingVal
// It's not a method; must be a field of a struct or an element of a map.
switch receiver.Kind() {
case reflect.Struct:
tField, ok := receiver.Type().FieldByName(fieldName)
if ok {
field := receiver.FieldByIndex(tField.Index)
if tField.PkgPath != "" { // field is unexported
s.errorf("%s is an unexported field of struct type %s", fieldName, typ)
}
// If it's a function, we must call it.
if hasArgs {
s.errorf("%s has arguments but cannot be invoked as function", fieldName)
}
return field
}
case reflect.Map:
// If it's a map, attempt to use the field name as a key.
nameVal := reflect.ValueOf(fieldName)
if nameVal.Type().AssignableTo(receiver.Type().Key()) {
if hasArgs {
s.errorf("%s is not a method but has arguments", fieldName)
}
var result reflect.Value
if s.helper != nil {
result, _ = s.helper.GetMapValue(receiver, nameVal)
} else {
result = receiver.MapIndex(nameVal)
}
if !result.IsValid() {
switch s.tmpl.option.missingKey {
case mapInvalid:
// Just use the invalid value.
case mapZeroValue:
result = reflect.Zero(receiver.Type().Elem())
case mapError:
s.errorf("map has no entry for key %q", fieldName)
}
}
return result
}
case reflect.Ptr:
etyp := receiver.Type().Elem()
if etyp.Kind() == reflect.Struct {
if _, ok := etyp.FieldByName(fieldName); !ok {
// If there's no such field, say "can't evaluate"
// instead of "nil pointer evaluating".
break
}
}
if isNil {
s.errorf("nil pointer evaluating %s.%s", typ, fieldName)
}
}
s.errorf("can't evaluate field %s in type %s", fieldName, typ)
panic("not reached")
}