Create lightweight forks of text/template and html/template

This commit also removes support for Ace and Amber templates.

Updates #6594

tpl/internal/go_templates/texttemplate/template.go

@@ -0,0 +1,228 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package template
+
+import (
+	"github.com/gohugoio/hugo/tpl/internal/go_templates/texttemplate/parse"
+	"reflect"
+	"sync"
+)
+
+// common holds the information shared by related templates.
+type common struct {
+	tmpl   map[string]*Template // Map from name to defined templates.
+	option option
+	// We use two maps, one for parsing and one for execution.
+	// This separation makes the API cleaner since it doesn't
+	// expose reflection to the client.
+	muFuncs    sync.RWMutex // protects parseFuncs and execFuncs
+	parseFuncs FuncMap
+	execFuncs  map[string]reflect.Value
+}
+
+// Template is the representation of a parsed template. The *parse.Tree
+// field is exported only for use by html/template and should be treated
+// as unexported by all other clients.
+type Template struct {
+	name string
+	*parse.Tree
+	*common
+	leftDelim  string
+	rightDelim string
+}
+
+// New allocates a new, undefined template with the given name.
+func New(name string) *Template {
+	t := &Template{
+		name: name,
+	}
+	t.init()
+	return t
+}
+
+// Name returns the name of the template.
+func (t *Template) Name() string {
+	return t.name
+}
+
+// New allocates a new, undefined 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.
+//
+// Because associated templates share underlying data, template construction
+// cannot be done safely in parallel. Once the templates are constructed, they
+// can be executed in parallel.
+func (t *Template) New(name string) *Template {
+	t.init()
+	nt := &Template{
+		name:       name,
+		common:     t.common,
+		leftDelim:  t.leftDelim,
+		rightDelim: t.rightDelim,
+	}
+	return nt
+}
+
+// init guarantees that t has a valid common structure.
+func (t *Template) init() {
+	if t.common == nil {
+		c := new(common)
+		c.tmpl = make(map[string]*Template)
+		c.parseFuncs = make(FuncMap)
+		c.execFuncs = make(map[string]reflect.Value)
+		t.common = c
+	}
+}
+
+// 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.
+func (t *Template) Clone() (*Template, error) {
+	nt := t.copy(nil)
+	nt.init()
+	if t.common == nil {
+		return nt, nil
+	}
+	for k, v := range t.tmpl {
+		if k == t.name {
+			nt.tmpl[t.name] = nt
+			continue
+		}
+		// The associated templates share nt's common structure.
+		tmpl := v.copy(nt.common)
+		nt.tmpl[k] = tmpl
+	}
+	t.muFuncs.RLock()
+	defer t.muFuncs.RUnlock()
+	for k, v := range t.parseFuncs {
+		nt.parseFuncs[k] = v
+	}
+	for k, v := range t.execFuncs {
+		nt.execFuncs[k] = v
+	}
+	return nt, nil
+}
+
+// copy returns a shallow copy of t, with common set to the argument.
+func (t *Template) copy(c *common) *Template {
+	nt := New(t.name)
+	nt.Tree = t.Tree
+	nt.common = c
+	nt.leftDelim = t.leftDelim
+	nt.rightDelim = t.rightDelim
+	return nt
+}
+
+// AddParseTree adds parse tree for template with given name and associates it with t.
+// If the template does not already exist, it will create a new one.
+// If the template does exist, it will be replaced.
+func (t *Template) AddParseTree(name string, tree *parse.Tree) (*Template, error) {
+	t.init()
+	// If the name is the name of this template, overwrite this template.
+	nt := t
+	if name != t.name {
+		nt = t.New(name)
+	}
+	// Even if nt == t, we need to install it in the common.tmpl map.
+	if t.associate(nt, tree) || nt.Tree == nil {
+		nt.Tree = tree
+	}
+	return nt, nil
+}
+
+// Templates returns a slice of defined templates associated with t.
+func (t *Template) Templates() []*Template {
+	if t.common == nil {
+		return nil
+	}
+	// Return a slice so we don't expose the map.
+	m := make([]*Template, 0, len(t.tmpl))
+	for _, v := range t.tmpl {
+		m = append(m, v)
+	}
+	return m
+}
+
+// Delims sets the action delimiters to the specified strings, to be used in
+// subsequent calls to Parse, ParseFiles, or ParseGlob. Nested template
+// definitions will inherit the settings. An empty delimiter stands for the
+// corresponding default: {{ or }}.
+// The return value is the template, so calls can be chained.
+func (t *Template) Delims(left, right string) *Template {
+	t.init()
+	t.leftDelim = left
+	t.rightDelim = right
+	return t
+}
+
+// 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 or if the name cannot be used syntactically as a function in a template.
+// 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.init()
+	t.muFuncs.Lock()
+	defer t.muFuncs.Unlock()
+	addValueFuncs(t.execFuncs, funcMap)
+	addFuncs(t.parseFuncs, funcMap)
+	return t
+}
+
+// Lookup returns the template with the given name that is associated with t.
+// It returns nil if there is no such template or the template has no definition.
+func (t *Template) Lookup(name string) *Template {
+	if t.common == nil {
+		return nil
+	}
+	return t.tmpl[name]
+}
+
+// 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.
+// 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) {
+	t.init()
+	t.muFuncs.RLock()
+	trees, err := parse.Parse(t.name, text, t.leftDelim, t.rightDelim, t.parseFuncs, builtins)
+	t.muFuncs.RUnlock()
+	if err != nil {
+		return nil, err
+	}
+	// Add the newly parsed trees, including the one for t, into our common structure.
+	for name, tree := range trees {
+		if _, err := t.AddParseTree(name, tree); err != nil {
+			return nil, err
+		}
+	}
+	return t, nil
+}
+
+// associate installs the new template into the group of templates associated
+// with t. The two are already known to share the common structure.
+// The boolean return value reports whether to store this tree as t.Tree.
+func (t *Template) associate(new *Template, tree *parse.Tree) bool {
+	if new.common != t.common {
+		panic("internal error: associate not common")
+	}
+	if old := t.tmpl[new.name]; old != nil && parse.IsEmptyTree(tree.Root) && old.Tree != nil {
+		// If a template by that name exists,
+		// don't replace it with an empty template.
+		return false
+	}
+	t.tmpl[new.name] = new
+	return true
+}