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template.go
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template.go
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package template
import (
"fmt"
template "github.com/sunwei/hugo-playground/tpl/internal/go_templates/texttemplate"
"github.com/sunwei/hugo-playground/tpl/internal/go_templates/texttemplate/parse"
"sync"
)
// FuncMap is the type of the map defining the mapping from names to
// functions. Each function must have either a single return value, or two
// return values of which the second has type error. In that case, if the
// second (error) argument evaluates to non-nil during execution, execution
// terminates and Execute returns that error. FuncMap has the same base type
// as FuncMap in "text/template", copied here so clients need not import
// "text/template".
type FuncMap map[string]any
// Template is a specialized Template from "text/template" that produces a safe
// HTML document fragment.
type Template struct {
// Sticky error if escaping fails, or escapeOK if succeeded.
escapeErr error
// We could embed the text/template field, but it's safer not to because
// we need to keep our version of the name space and the underlying
// template's in sync.
text *template.Template
// The underlying template's parse tree, updated to be HTML-safe.
Tree *parse.Tree
*nameSpace // common to all associated templates
}
// Name returns the name of the template.
func (t *Template) Name() string {
return t.text.Name()
}
// nameSpace is the data structure shared by all templates in an association.
type nameSpace struct {
mu sync.Mutex
set map[string]*Template
escaped bool
esc escaper
}
// escapeOK is a sentinel value used to indicate valid escaping.
var escapeOK = fmt.Errorf("template escaped correctly")
// escape escapes all associated templates.
func (t *Template) escape() error {
t.nameSpace.mu.Lock()
defer t.nameSpace.mu.Unlock()
t.nameSpace.escaped = true
if t.escapeErr == nil {
if t.Tree == nil {
return fmt.Errorf("template: %q is an incomplete or empty template", t.Name())
}
if err := escapeTemplate(t, t.text.Root, t.Name()); err != nil {
return err
}
} else if t.escapeErr != escapeOK {
return t.escapeErr
}
return nil
}
// Lookup returns the template with the given name that is associated with t,
// or nil if there is no such template.
func (t *Template) Lookup(name string) *Template {
t.nameSpace.mu.Lock()
defer t.nameSpace.mu.Unlock()
return t.set[name]
}
// New allocates a new HTML template associated with the given one
// and with the same delimiters. The association, which is transitive,
// allows one template to invoke another with a {{template}} action.
//
// If a template with the given name already exists, the new HTML template
// will replace it. The existing template will be reset and disassociated with
// t.
func (t *Template) New(name string) *Template {
t.nameSpace.mu.Lock()
defer t.nameSpace.mu.Unlock()
return t.new(name)
}
// new is the implementation of New, without the lock.
func (t *Template) new(name string) *Template {
tmpl := &Template{
nil,
t.text.New(name),
nil,
t.nameSpace,
}
if existing, ok := tmpl.set[name]; ok {
emptyTmpl := New(existing.Name())
*existing = *emptyTmpl
}
tmpl.set[name] = tmpl
return tmpl
}
// New allocates a new HTML template with the given name.
func New(name string) *Template {
ns := &nameSpace{set: make(map[string]*Template)}
ns.esc = makeEscaper(ns)
tmpl := &Template{
nil,
template.New(name),
nil,
ns,
}
tmpl.set[name] = tmpl
return tmpl
}
// Parse parses text as a template body for t.
// Named template definitions ({{define ...}} or {{block ...}} statements) in text
// define additional templates associated with t and are removed from the
// definition of t itself.
//
// Templates can be redefined in successive calls to Parse,
// before the first use of Execute on t or any associated template.
// A template definition with a body containing only white space and comments
// is considered empty and will not replace an existing template's body.
// This allows using Parse to add new named template definitions without
// overwriting the main template body.
func (t *Template) Parse(text string) (*Template, error) {
if err := t.checkCanParse(); err != nil {
return nil, err
}
ret, err := t.text.Parse(text)
if err != nil {
return nil, err
}
// In general, all the named templates might have changed underfoot.
// Regardless, some new ones may have been defined.
// The template.Template set has been updated; update ours.
t.nameSpace.mu.Lock()
defer t.nameSpace.mu.Unlock()
for _, v := range ret.Templates() {
name := v.Name()
tmpl := t.set[name]
if tmpl == nil {
tmpl = t.new(name)
}
tmpl.text = v
tmpl.Tree = v.Tree
}
return t, nil
}
// checkCanParse checks whether it is OK to parse templates.
// If not, it returns an error.
func (t *Template) checkCanParse() error {
if t == nil {
return nil
}
t.nameSpace.mu.Lock()
defer t.nameSpace.mu.Unlock()
if t.nameSpace.escaped {
return fmt.Errorf("html/template: cannot Parse after Execute")
}
return nil
}
// Must is a helper that wraps a call to a function returning (*Template, error)
// and panics if the error is non-nil. It is intended for use in variable initializations
// such as
// var t = template.Must(template.New("name").Parse("html"))
func Must(t *Template, err error) *Template {
if err != nil {
panic(err)
}
return t
}
// Clone returns a duplicate of the template, including all associated
// templates. The actual representation is not copied, but the name space of
// associated templates is, so further calls to Parse in the copy will add
// templates to the copy but not to the original. Clone can be used to prepare
// common templates and use them with variant definitions for other templates
// by adding the variants after the clone is made.
//
// It returns an error if t has already been executed.
func (t *Template) Clone() (*Template, error) {
t.nameSpace.mu.Lock()
defer t.nameSpace.mu.Unlock()
if t.escapeErr != nil {
return nil, fmt.Errorf("html/template: cannot Clone %q after it has executed", t.Name())
}
textClone, err := t.text.Clone()
if err != nil {
return nil, err
}
ns := &nameSpace{set: make(map[string]*Template)}
ns.esc = makeEscaper(ns)
ret := &Template{
nil,
textClone,
textClone.Tree,
ns,
}
ret.set[ret.Name()] = ret
for _, x := range textClone.Templates() {
name := x.Name()
src := t.set[name]
if src == nil || src.escapeErr != nil {
return nil, fmt.Errorf("html/template: cannot Clone %q after it has executed", t.Name())
}
x.Tree = x.Tree.Copy()
ret.set[name] = &Template{
nil,
x,
x.Tree,
ret.nameSpace,
}
}
// Return the template associated with the name of this template.
return ret.set[ret.Name()], nil
}
// Templates returns a slice of the templates associated with t, including t
// itself.
func (t *Template) Templates() []*Template {
ns := t.nameSpace
ns.mu.Lock()
defer ns.mu.Unlock()
// Return a slice so we don't expose the map.
m := make([]*Template, 0, len(ns.set))
for _, v := range ns.set {
m = append(m, v)
}
return m
}
// Funcs adds the elements of the argument map to the template's function map.
// It must be called before the template is parsed.
// It panics if a value in the map is not a function with appropriate return
// type. However, it is legal to overwrite elements of the map. The return
// value is the template, so calls can be chained.
func (t *Template) Funcs(funcMap FuncMap) *Template {
t.text.Funcs(template.FuncMap(funcMap))
return t
}