1 files changed, 536 insertions, 0 deletions
diff --git a/src/html/template/template.go b/src/html/template/template.go
new file mode 100644
index 0000000..69312d3
--- /dev/null
+++ b/src/html/template/template.go
@@ -0,0 +1,536 @@
+// 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 (
+	"fmt"
+	"io"
+	"io/fs"
+	"os"
+	"path"
+	"path/filepath"
+	"sync"
+	"text/template"
+	"text/template/parse"
+)
+
+// 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
+}
+
+// escapeOK is a sentinel value used to indicate valid escaping.
+var escapeOK = fmt.Errorf("template escaped correctly")
+
+// 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
+}
+
+// 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
+}
+
+// Option sets options for the template. Options are described by
+// strings, either a simple string or "key=value". There can be at
+// most one equals sign in an option string. If the option string
+// is unrecognized or otherwise invalid, Option panics.
+//
+// Known options:
+//
+// missingkey: Control the behavior during execution if a map is
+// indexed with a key that is not present in the map.
+//	"missingkey=default" or "missingkey=invalid"
+//		The default behavior: Do nothing and continue execution.
+//		If printed, the result of the index operation is the string
+//		"<no value>".
+//	"missingkey=zero"
+//		The operation returns the zero value for the map type's element.
+//	"missingkey=error"
+//		Execution stops immediately with an error.
+//
+func (t *Template) Option(opt ...string) *Template {
+	t.text.Option(opt...)
+	return t
+}
+
+// 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
+}
+
+// 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
+}
+
+// Execute applies a parsed template to the specified data object,
+// writing the output to wr.
+// If an error occurs executing the template or writing its output,
+// execution stops, but partial results may already have been written to
+// the output writer.
+// A template may be executed safely in parallel, although if parallel
+// executions share a Writer the output may be interleaved.
+func (t *Template) Execute(wr io.Writer, data interface{}) error {
+	if err := t.escape(); err != nil {
+		return err
+	}
+	return t.text.Execute(wr, data)
+}
+
+// ExecuteTemplate applies the template associated with t that has the given
+// name to the specified data object and writes the output to wr.
+// If an error occurs executing the template or writing its output,
+// execution stops, but partial results may already have been written to
+// the output writer.
+// A template may be executed safely in parallel, although if parallel
+// executions share a Writer the output may be interleaved.
+func (t *Template) ExecuteTemplate(wr io.Writer, name string, data interface{}) error {
+	tmpl, err := t.lookupAndEscapeTemplate(name)
+	if err != nil {
+		return err
+	}
+	return tmpl.text.Execute(wr, data)
+}
+
+// lookupAndEscapeTemplate guarantees that the template with the given name
+// is escaped, or returns an error if it cannot be. It returns the named
+// template.
+func (t *Template) lookupAndEscapeTemplate(name string) (tmpl *Template, err error) {
+	t.nameSpace.mu.Lock()
+	defer t.nameSpace.mu.Unlock()
+	t.nameSpace.escaped = true
+	tmpl = t.set[name]
+	if tmpl == nil {
+		return nil, fmt.Errorf("html/template: %q is undefined", name)
+	}
+	if tmpl.escapeErr != nil && tmpl.escapeErr != escapeOK {
+		return nil, tmpl.escapeErr
+	}
+	if tmpl.text.Tree == nil || tmpl.text.Root == nil {
+		return nil, fmt.Errorf("html/template: %q is an incomplete template", name)
+	}
+	if t.text.Lookup(name) == nil {
+		panic("html/template internal error: template escaping out of sync")
+	}
+	if tmpl.escapeErr == nil {
+		err = escapeTemplate(tmpl, tmpl.text.Root, name)
+	}
+	return tmpl, err
+}
+
+// DefinedTemplates returns a string listing the defined templates,
+// prefixed by the string "; defined templates are: ". If there are none,
+// it returns the empty string. Used to generate an error message.
+func (t *Template) DefinedTemplates() string {
+	return t.text.DefinedTemplates()
+}
+
+// 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
+}
+
+// AddParseTree creates a new template with the name and parse tree
+// and associates it with t.
+//
+// It returns an error if t or any associated template has already been executed.
+func (t *Template) AddParseTree(name string, tree *parse.Tree) (*Template, error) {
+	if err := t.checkCanParse(); err != nil {
+		return nil, err
+	}
+
+	t.nameSpace.mu.Lock()
+	defer t.nameSpace.mu.Unlock()
+	text, err := t.text.AddParseTree(name, tree)
+	if err != nil {
+		return nil, err
+	}
+	ret := &Template{
+		nil,
+		text,
+		text.Tree,
+		t.nameSpace,
+	}
+	t.set[name] = ret
+	return ret, nil
+}
+
+// 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
+}
+
+// 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
+}
+
+// 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
+}
+
+// Name returns the name of the template.
+func (t *Template) Name() string {
+	return t.text.Name()
+}
+
+// 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]interface{}
+
+// 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
+}
+
+// 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.text.Delims(left, right)
+	return t
+}
+
+// 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]
+}
+
+// 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
+}
+
+// ParseFiles creates a new Template and parses the template definitions from
+// the named files. The returned template's name will have the (base) name and
+// (parsed) contents of the first file. There must be at least one file.
+// If an error occurs, parsing stops and the returned *Template is nil.
+//
+// When parsing multiple files with the same name in different directories,
+// the last one mentioned will be the one that results.
+// For instance, ParseFiles("a/foo", "b/foo") stores "b/foo" as the template
+// named "foo", while "a/foo" is unavailable.
+func ParseFiles(filenames ...string) (*Template, error) {
+	return parseFiles(nil, readFileOS, filenames...)
+}
+
+// ParseFiles parses the named files and associates the resulting templates with
+// t. If an error occurs, parsing stops and the returned template is nil;
+// otherwise it is t. There must be at least one file.
+//
+// When parsing multiple files with the same name in different directories,
+// the last one mentioned will be the one that results.
+//
+// ParseFiles returns an error if t or any associated template has already been executed.
+func (t *Template) ParseFiles(filenames ...string) (*Template, error) {
+	return parseFiles(t, readFileOS, filenames...)
+}
+
+// parseFiles is the helper for the method and function. If the argument
+// template is nil, it is created from the first file.
+func parseFiles(t *Template, readFile func(string) (string, []byte, error), filenames ...string) (*Template, error) {
+	if err := t.checkCanParse(); err != nil {
+		return nil, err
+	}
+
+	if len(filenames) == 0 {
+		// Not really a problem, but be consistent.
+		return nil, fmt.Errorf("html/template: no files named in call to ParseFiles")
+	}
+	for _, filename := range filenames {
+		name, b, err := readFile(filename)
+		if err != nil {
+			return nil, err
+		}
+		s := string(b)
+		// First template becomes return value if not already defined,
+		// and we use that one for subsequent New calls to associate
+		// all the templates together. Also, if this file has the same name
+		// as t, this file becomes the contents of t, so
+		//  t, err := New(name).Funcs(xxx).ParseFiles(name)
+		// works. Otherwise we create a new template associated with t.
+		var tmpl *Template
+		if t == nil {
+			t = New(name)
+		}
+		if name == t.Name() {
+			tmpl = t
+		} else {
+			tmpl = t.New(name)
+		}
+		_, err = tmpl.Parse(s)
+		if err != nil {
+			return nil, err
+		}
+	}
+	return t, nil
+}
+
+// ParseGlob creates a new Template and parses the template definitions from
+// the files identified by the pattern. The files are matched according to the
+// semantics of filepath.Match, and the pattern must match at least one file.
+// The returned template will have the (base) name and (parsed) contents of the
+// first file matched by the pattern. ParseGlob is equivalent to calling
+// ParseFiles with the list of files matched by the pattern.
+//
+// When parsing multiple files with the same name in different directories,
+// the last one mentioned will be the one that results.
+func ParseGlob(pattern string) (*Template, error) {
+	return parseGlob(nil, pattern)
+}
+
+// ParseGlob parses the template definitions in the files identified by the
+// pattern and associates the resulting templates with t. The files are matched
+// according to the semantics of filepath.Match, and the pattern must match at
+// least one file. ParseGlob is equivalent to calling t.ParseFiles with the
+// list of files matched by the pattern.
+//
+// When parsing multiple files with the same name in different directories,
+// the last one mentioned will be the one that results.
+//
+// ParseGlob returns an error if t or any associated template has already been executed.
+func (t *Template) ParseGlob(pattern string) (*Template, error) {
+	return parseGlob(t, pattern)
+}
+
+// parseGlob is the implementation of the function and method ParseGlob.
+func parseGlob(t *Template, pattern string) (*Template, error) {
+	if err := t.checkCanParse(); err != nil {
+		return nil, err
+	}
+	filenames, err := filepath.Glob(pattern)
+	if err != nil {
+		return nil, err
+	}
+	if len(filenames) == 0 {
+		return nil, fmt.Errorf("html/template: pattern matches no files: %#q", pattern)
+	}
+	return parseFiles(t, readFileOS, filenames...)
+}
+
+// IsTrue reports whether the value is 'true', in the sense of not the zero of its type,
+// and whether the value has a meaningful truth value. This is the definition of
+// truth used by if and other such actions.
+func IsTrue(val interface{}) (truth, ok bool) {
+	return template.IsTrue(val)
+}
+
+// ParseFS is like ParseFiles or ParseGlob but reads from the file system fs
+// instead of the host operating system's file system.
+// It accepts a list of glob patterns.
+// (Note that most file names serve as glob patterns matching only themselves.)
+func ParseFS(fs fs.FS, patterns ...string) (*Template, error) {
+	return parseFS(nil, fs, patterns)
+}
+
+// ParseFS is like ParseFiles or ParseGlob but reads from the file system fs
+// instead of the host operating system's file system.
+// It accepts a list of glob patterns.
+// (Note that most file names serve as glob patterns matching only themselves.)
+func (t *Template) ParseFS(fs fs.FS, patterns ...string) (*Template, error) {
+	return parseFS(t, fs, patterns)
+}
+
+func parseFS(t *Template, fsys fs.FS, patterns []string) (*Template, error) {
+	var filenames []string
+	for _, pattern := range patterns {
+		list, err := fs.Glob(fsys, pattern)
+		if err != nil {
+			return nil, err
+		}
+		if len(list) == 0 {
+			return nil, fmt.Errorf("template: pattern matches no files: %#q", pattern)
+		}
+		filenames = append(filenames, list...)
+	}
+	return parseFiles(t, readFileFS(fsys), filenames...)
+}
+
+func readFileOS(file string) (name string, b []byte, err error) {
+	name = filepath.Base(file)
+	b, err = os.ReadFile(file)
+	return
+}
+
+func readFileFS(fsys fs.FS) func(string) (string, []byte, error) {
+	return func(file string) (name string, b []byte, err error) {
+		name = path.Base(file)
+		b, err = fs.ReadFile(fsys, file)
+		return
+	}
+}