▹ Example
▹ Example (Autoescaping)
▹ Example (Escape)
func HTMLEscape(w io.Writer, b []byte)
HTMLEscape writes to w the escaped HTML equivalent of the plain text data b.
func HTMLEscapeString(s string) string
HTMLEscapeString returns the escaped HTML equivalent of the plain text data s.
func HTMLEscaper(args ...interface{}) string
HTMLEscaper returns the escaped HTML equivalent of the textual representation of its arguments.
func IsTrue(val interface{}) (truth, ok bool)
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 JSEscape(w io.Writer, b []byte)
JSEscape writes to w the escaped JavaScript equivalent of the plain text data b.
func JSEscapeString(s string) string
JSEscapeString returns the escaped JavaScript equivalent of the plain text data s.
func JSEscaper(args ...interface{}) string
JSEscaper returns the escaped JavaScript equivalent of the textual representation of its arguments.
func URLQueryEscaper(args ...interface{}) string
URLQueryEscaper returns the escaped value of the textual representation of its arguments in a form suitable for embedding in a URL query.
CSS encapsulates known safe content that matches any of:
1. The CSS3 stylesheet production, such as `p { color: purple }`.
2. The CSS3 rule production, such as `a[href=~"https:"].foo#bar`.
3. CSS3 declaration productions, such as `color: red; margin: 2px`.
4. The CSS3 value production, such as `rgba(0, 0, 255, 127)`.
See http://www.w3.org/TR/css3-syntax/#parsing and https://web.archive.org/web/20090211114933/http://w3.org/TR/css3-syntax#style
Use of this type presents a security risk: the encapsulated content should come from a trusted source, as it will be included verbatim in the template output.
type CSS string
Error describes a problem encountered during template Escaping.
type Error struct {
// ErrorCode describes the kind of error.
ErrorCode ErrorCode
// Node is the node that caused the problem, if known.
// If not nil, it overrides Name and Line.
Node parse.Node
// Name is the name of the template in which the error was encountered.
Name string
// Line is the line number of the error in the template source or 0.
Line int
// Description is a human-readable description of the problem.
Description string
}
func (e *Error) Error() string
ErrorCode is a code for a kind of error.
type ErrorCode int
We define codes for each error that manifests while escaping templates, but escaped templates may also fail at runtime.
Output: "ZgotmplZ" Example:
<img src="{{.X}}">
where {{.X}} evaluates to `javascript:...`
Discussion:
"ZgotmplZ" is a special value that indicates that unsafe content reached a CSS or URL context at runtime. The output of the example will be <img src="#ZgotmplZ"> If the data comes from a trusted source, use content types to exempt it from filtering: URL(`javascript:...`).
const (
// OK indicates the lack of an error.
OK ErrorCode = iota
// ErrAmbigContext: "... appears in an ambiguous context within a URL"
// Example:
// <a href="
// {{if .C}}
// /path/
// {{else}}
// /search?q=
// {{end}}
// {{.X}}
// ">
// Discussion:
// {{.X}} is in an ambiguous URL context since, depending on {{.C}},
// it may be either a URL suffix or a query parameter.
// Moving {{.X}} into the condition removes the ambiguity:
// <a href="{{if .C}}/path/{{.X}}{{else}}/search?q={{.X}}">
ErrAmbigContext
// ErrBadHTML: "expected space, attr name, or end of tag, but got ...",
// "... in unquoted attr", "... in attribute name"
// Example:
// <a href = /search?q=foo>
// <href=foo>
// <form na<e=...>
// <option selected<
// Discussion:
// This is often due to a typo in an HTML element, but some runes
// are banned in tag names, attribute names, and unquoted attribute
// values because they can tickle parser ambiguities.
// Quoting all attributes is the best policy.
ErrBadHTML
// ErrBranchEnd: "{{if}} branches end in different contexts"
// Example:
// {{if .C}}<a href="{{end}}{{.X}}
// Discussion:
// Package html/template statically examines each path through an
// {{if}}, {{range}}, or {{with}} to escape any following pipelines.
// The example is ambiguous since {{.X}} might be an HTML text node,
// or a URL prefix in an HTML attribute. The context of {{.X}} is
// used to figure out how to escape it, but that context depends on
// the run-time value of {{.C}} which is not statically known.
//
// The problem is usually something like missing quotes or angle
// brackets, or can be avoided by refactoring to put the two contexts
// into different branches of an if, range or with. If the problem
// is in a {{range}} over a collection that should never be empty,
// adding a dummy {{else}} can help.
ErrBranchEnd
// ErrEndContext: "... ends in a non-text context: ..."
// Examples:
// <div
// <div title="no close quote>
// <script>f()
// Discussion:
// Executed templates should produce a DocumentFragment of HTML.
// Templates that end without closing tags will trigger this error.
// Templates that should not be used in an HTML context or that
// produce incomplete Fragments should not be executed directly.
//
// {{define "main"}} <script>{{template "helper"}}</script> {{end}}
// {{define "helper"}} document.write(' <div title=" ') {{end}}
//
// "helper" does not produce a valid document fragment, so should
// not be Executed directly.
ErrEndContext
// ErrNoSuchTemplate: "no such template ..."
// Examples:
// {{define "main"}}<div {{template "attrs"}}>{{end}}
// {{define "attrs"}}href="{{.URL}}"{{end}}
// Discussion:
// Package html/template looks through template calls to compute the
// context.
// Here the {{.URL}} in "attrs" must be treated as a URL when called
// from "main", but you will get this error if "attrs" is not defined
// when "main" is parsed.
ErrNoSuchTemplate
// ErrOutputContext: "cannot compute output context for template ..."
// Examples:
// {{define "t"}}{{if .T}}{{template "t" .T}}{{end}}{{.H}}",{{end}}
// Discussion:
// A recursive template does not end in the same context in which it
// starts, and a reliable output context cannot be computed.
// Look for typos in the named template.
// If the template should not be called in the named start context,
// look for calls to that template in unexpected contexts.
// Maybe refactor recursive templates to not be recursive.
ErrOutputContext
// ErrPartialCharset: "unfinished JS regexp charset in ..."
// Example:
// <script>var pattern = /foo[{{.Chars}}]/</script>
// Discussion:
// Package html/template does not support interpolation into regular
// expression literal character sets.
ErrPartialCharset
// ErrPartialEscape: "unfinished escape sequence in ..."
// Example:
// <script>alert("\{{.X}}")</script>
// Discussion:
// Package html/template does not support actions following a
// backslash.
// This is usually an error and there are better solutions; for
// example
// <script>alert("{{.X}}")</script>
// should work, and if {{.X}} is a partial escape sequence such as
// "xA0", mark the whole sequence as safe content: JSStr(`\xA0`)
ErrPartialEscape
// ErrRangeLoopReentry: "on range loop re-entry: ..."
// Example:
// <script>var x = [{{range .}}'{{.}},{{end}}]</script>
// Discussion:
// If an iteration through a range would cause it to end in a
// different context than an earlier pass, there is no single context.
// In the example, there is missing a quote, so it is not clear
// whether {{.}} is meant to be inside a JS string or in a JS value
// context. The second iteration would produce something like
//
// <script>var x = ['firstValue,'secondValue]</script>
ErrRangeLoopReentry
// ErrSlashAmbig: '/' could start a division or regexp.
// Example:
// <script>
// {{if .C}}var x = 1{{end}}
// /-{{.N}}/i.test(x) ? doThis : doThat();
// </script>
// Discussion:
// The example above could produce `var x = 1/-2/i.test(s)...`
// in which the first '/' is a mathematical division operator or it
// could produce `/-2/i.test(s)` in which the first '/' starts a
// regexp literal.
// Look for missing semicolons inside branches, and maybe add
// parentheses to make it clear which interpretation you intend.
ErrSlashAmbig
)
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{}
HTML encapsulates a known safe HTML document fragment. It should not be used for HTML from a third-party, or HTML with unclosed tags or comments. The outputs of a sound HTML sanitizer and a template escaped by this package are fine for use with HTML.
Use of this type presents a security risk: the encapsulated content should come from a trusted source, as it will be included verbatim in the template output.
type HTML string
HTMLAttr encapsulates an HTML attribute from a trusted source, for example, ` dir="ltr"`.
Use of this type presents a security risk: the encapsulated content should come from a trusted source, as it will be included verbatim in the template output.
type HTMLAttr string
JS encapsulates a known safe EcmaScript5 Expression, for example, `(x + y * z())`. Template authors are responsible for ensuring that typed expressions do not break the intended precedence and that there is no statement/expression ambiguity as when passing an expression like "{ foo: bar() }\n['foo']()", which is both a valid Expression and a valid Program with a very different meaning.
Use of this type presents a security risk: the encapsulated content should come from a trusted source, as it will be included verbatim in the template output.
Using JS to include valid but untrusted JSON is not safe. A safe alternative is to parse the JSON with json.Unmarshal and then pass the resultant object into the template, where it will be converted to sanitized JSON when presented in a JavaScript context.
type JS string
JSStr encapsulates a sequence of characters meant to be embedded between quotes in a JavaScript expression. The string must match a series of StringCharacters:
StringCharacter :: SourceCharacter but not `\` or LineTerminator
| EscapeSequence
Note that LineContinuations are not allowed. JSStr("foo\\nbar") is fine, but JSStr("foo\\\nbar") is not.
Use of this type presents a security risk: the encapsulated content should come from a trusted source, as it will be included verbatim in the template output.
type JSStr string
Template is a specialized Template from "text/template" that produces a safe HTML document fragment.
type Template struct {
// The underlying template's parse tree, updated to be HTML-safe.
Tree *parse.Tree
// contains filtered or unexported fields
}
▹ Example (Block)
▹ Example (Glob)
▹ Example (Helpers)
▹ Example (Parsefiles)
func Must(t *Template, err error) *Template
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 New(name string) *Template
New allocates a new HTML template with the given name.
func ParseFiles(filenames ...string) (*Template, error)
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 ParseGlob(pattern string) (*Template, error)
ParseGlob creates a new Template and parses the template definitions from the files identified by the pattern, which 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 (t *Template) AddParseTree(name string, tree *parse.Tree) (*Template, error)
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) Clone() (*Template, error)
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) DefinedTemplates() string
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) Delims(left, right string) *Template
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) Execute(wr io.Writer, data interface{}) error
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.
func (t *Template) ExecuteTemplate(wr io.Writer, name string, data interface{}) error
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.
func (t *Template) Funcs(funcMap FuncMap) *Template
Funcs adds the elements of the argument map to the template's function map. 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) Lookup(name string) *Template
Lookup returns the template with the given name that is associated with t, or nil if there is no such template.
func (t *Template) Name() string
Name returns the name of the template.
func (t *Template) New(name string) *Template
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.
func (t *Template) Option(opt ...string) *Template
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) Parse(text string) (*Template, error)
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) ParseFiles(filenames ...string) (*Template, error)
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) ParseGlob(pattern string) (*Template, error)
ParseGlob parses the template definitions in the files identified by the pattern and associates the resulting templates with t. The pattern is processed by filepath.Glob and 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) Templates() []*Template
Templates returns a slice of the templates associated with t, including t itself.
URL encapsulates a known safe URL or URL substring (see RFC 3986). A URL like `javascript:checkThatFormNotEditedBeforeLeavingPage()` from a trusted source should go in the page, but by default dynamic `javascript:` URLs are filtered out since they are a frequently exploited injection vector.
Use of this type presents a security risk: the encapsulated content should come from a trusted source, as it will be included verbatim in the template output.
type URL string