227 lines
6.8 KiB
Go
227 lines
6.8 KiB
Go
// Copyright 2011 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package template
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import (
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"reflect"
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"sync"
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"text/template/parse"
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)
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// common holds the information shared by related templates.
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type common struct {
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tmpl map[string]*Template // Map from name to defined templates.
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option option
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// We use two maps, one for parsing and one for execution.
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// This separation makes the API cleaner since it doesn't
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// expose reflection to the client.
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muFuncs sync.RWMutex // protects parseFuncs and execFuncs
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parseFuncs FuncMap
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execFuncs map[string]reflect.Value
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}
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// Template is the representation of a parsed template. The *parse.Tree
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// field is exported only for use by html/template and should be treated
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// as unexported by all other clients.
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type Template struct {
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name string
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*parse.Tree
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*common
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leftDelim string
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rightDelim string
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}
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// New allocates a new, undefined template with the given name.
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func New(name string) *Template {
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t := &Template{
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name: name,
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}
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t.init()
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return t
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}
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// Name returns the name of the template.
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func (t *Template) Name() string {
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return t.name
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}
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// New allocates a new, undefined template associated with the given one and with the same
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// delimiters. The association, which is transitive, allows one template to
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// invoke another with a {{template}} action.
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func (t *Template) New(name string) *Template {
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t.init()
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nt := &Template{
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name: name,
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common: t.common,
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leftDelim: t.leftDelim,
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rightDelim: t.rightDelim,
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}
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return nt
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}
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// init guarantees that t has a valid common structure.
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func (t *Template) init() {
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if t.common == nil {
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c := new(common)
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c.tmpl = make(map[string]*Template)
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c.parseFuncs = make(FuncMap)
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c.execFuncs = make(map[string]reflect.Value)
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t.common = c
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}
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}
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// Clone returns a duplicate of the template, including all associated
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// templates. The actual representation is not copied, but the name space of
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// associated templates is, so further calls to Parse in the copy will add
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// templates to the copy but not to the original. Clone can be used to prepare
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// common templates and use them with variant definitions for other templates
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// by adding the variants after the clone is made.
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func (t *Template) Clone() (*Template, error) {
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nt := t.copy(nil)
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nt.init()
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if t.common == nil {
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return nt, nil
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}
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for k, v := range t.tmpl {
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if k == t.name {
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nt.tmpl[t.name] = nt
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continue
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}
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// The associated templates share nt's common structure.
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tmpl := v.copy(nt.common)
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nt.tmpl[k] = tmpl
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}
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t.muFuncs.RLock()
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defer t.muFuncs.RUnlock()
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for k, v := range t.parseFuncs {
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nt.parseFuncs[k] = v
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}
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for k, v := range t.execFuncs {
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nt.execFuncs[k] = v
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}
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return nt, nil
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}
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// copy returns a shallow copy of t, with common set to the argument.
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func (t *Template) copy(c *common) *Template {
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nt := New(t.name)
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nt.Tree = t.Tree
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nt.common = c
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nt.leftDelim = t.leftDelim
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nt.rightDelim = t.rightDelim
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return nt
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}
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// AddParseTree adds parse tree for template with given name and associates it with t.
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// If the template does not already exist, it will create a new one.
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// If the template does exist, it will be replaced.
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func (t *Template) AddParseTree(name string, tree *parse.Tree) (*Template, error) {
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t.init()
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// If the name is the name of this template, overwrite this template.
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nt := t
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if name != t.name {
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nt = t.New(name)
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}
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// Even if nt == t, we need to install it in the common.tmpl map.
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if replace, err := t.associate(nt, tree); err != nil {
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return nil, err
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} else if replace || nt.Tree == nil {
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nt.Tree = tree
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}
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return nt, nil
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}
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// Templates returns a slice of defined templates associated with t.
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func (t *Template) Templates() []*Template {
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if t.common == nil {
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return nil
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}
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// Return a slice so we don't expose the map.
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m := make([]*Template, 0, len(t.tmpl))
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for _, v := range t.tmpl {
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m = append(m, v)
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}
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return m
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}
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// Delims sets the action delimiters to the specified strings, to be used in
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// subsequent calls to Parse, ParseFiles, or ParseGlob. Nested template
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// definitions will inherit the settings. An empty delimiter stands for the
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// corresponding default: {{ or }}.
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// The return value is the template, so calls can be chained.
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func (t *Template) Delims(left, right string) *Template {
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t.init()
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t.leftDelim = left
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t.rightDelim = right
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return t
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}
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// Funcs adds the elements of the argument map to the template's function map.
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// It must be called before the template is parsed.
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// It panics if a value in the map is not a function with appropriate return
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// type or if the name cannot be used syntactically as a function in a template.
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// It is legal to overwrite elements of the map. The return value is the template,
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// so calls can be chained.
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func (t *Template) Funcs(funcMap FuncMap) *Template {
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t.init()
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t.muFuncs.Lock()
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defer t.muFuncs.Unlock()
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addValueFuncs(t.execFuncs, funcMap)
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addFuncs(t.parseFuncs, funcMap)
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return t
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}
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// Lookup returns the template with the given name that is associated with t.
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// It returns nil if there is no such template or the template has no definition.
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func (t *Template) Lookup(name string) *Template {
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if t.common == nil {
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return nil
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}
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return t.tmpl[name]
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}
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// Parse parses text as a template body for t.
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// Named template definitions ({{define ...}} or {{block ...}} statements) in text
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// define additional templates associated with t and are removed from the
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// definition of t itself.
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//
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// Templates can be redefined in successive calls to Parse.
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// A template definition with a body containing only white space and comments
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// is considered empty and will not replace an existing template's body.
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// This allows using Parse to add new named template definitions without
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// overwriting the main template body.
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func (t *Template) Parse(text string) (*Template, error) {
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t.init()
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t.muFuncs.RLock()
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trees, err := parse.Parse(t.name, text, t.leftDelim, t.rightDelim, t.parseFuncs, builtins)
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t.muFuncs.RUnlock()
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if err != nil {
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return nil, err
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}
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// Add the newly parsed trees, including the one for t, into our common structure.
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for name, tree := range trees {
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if _, err := t.AddParseTree(name, tree); err != nil {
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return nil, err
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}
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}
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return t, nil
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}
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// associate installs the new template into the group of templates associated
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// with t. The two are already known to share the common structure.
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// The boolean return value reports whether to store this tree as t.Tree.
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func (t *Template) associate(new *Template, tree *parse.Tree) (bool, error) {
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if new.common != t.common {
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panic("internal error: associate not common")
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}
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if old := t.tmpl[new.name]; old != nil && parse.IsEmptyTree(tree.Root) && old.Tree != nil {
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// If a template by that name exists,
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// don't replace it with an empty template.
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return false, nil
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}
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t.tmpl[new.name] = new
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return true, nil
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}
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