checker

func HasAmbiguousAmpersand ¶

func HasAmbiguousAmpersand(val string) bool

HasAmbiguousAmpersand returns true if the argument contains a substring that is an ambiguous ampersand.

An ambiguous ampersand is a U+0026 AMPERSAND character (&) that is
followed by one or more alphanumeric ASCII characters, followed by
a ";" (U+003B) character, where these characters do not match any
of the names given in the named character references section.

It is ambiguous if it looks like a named character reference but is NOT one: "&ambiguous;" is ambiguous, but "&" is not because "&" is a valid reference. See also IsCharacterReferenceName and IsCharacterReference.

fmt.Println(HasAmbiguousAmpersand("this & that"))
fmt.Println(HasAmbiguousAmpersand("this & that"))
fmt.Println(HasAmbiguousAmpersand("nothing here"))
fmt.Println(HasAmbiguousAmpersand("Can &what; be one?"))

Output:

false
false
false
true

func IsCharacterReference ¶

func IsCharacterReference(ref string) bool

IsCharacterReference returns true if the argument is a valid character reference. See also IsCharacterReferenceName.

fmt.Println(IsCharacterReference("&"))
fmt.Println(IsCharacterReference("&"))
fmt.Println(IsCharacterReference("amp"))   // Needs & and ;
fmt.Println(IsCharacterReference("&Amp;")) // Case sensitive

Output:

true
true
false
false

func IsCharacterReferenceName ¶

func IsCharacterReferenceName(name string) bool

IsCharacterReferenceName returns true if the argument is a valid character reference name according to this list:

http://www.w3.org/TR/html5/syntax.html#named-character-references

See also IsCharacterReference.

fmt.Println(IsCharacterReferenceName("amp"))
fmt.Println(IsCharacterReferenceName("AMP"))
fmt.Println(IsCharacterReferenceName("Amp")) // Names are case sensitive.
fmt.Println(IsCharacterReferenceName("&"))

Output:

true
true
false
false

func IsHTMLTagName ¶

func IsHTMLTagName(name string) bool

IsHTMLTagName returns true if the argument is a defined HTML5 tag, case insensitive.

Note: In the interest of optimizing for the common case, the argument is assumed to be lowercase or uppercase. If `name` is mixed case, this function may return a false negative. Use IsHTMLTagNameSafe for a version that won't return a false negative.

fmt.Println(IsHTMLTagName("strong"))
fmt.Println(IsHTMLTagName("tuesday"))

Output:

true
false

func IsHTMLTagNameSafe ¶

func IsHTMLTagNameSafe(name string) bool

IsHTMLTagNameSafe returns true if the argument is a defined HTML5 tag. Unlike IsHTMLTagName, this version downcases the argument first to prevent mixed- case false negatives.

func IsValidAttributeName ¶

func IsValidAttributeName(name string) bool

IsValidAttributeName returns true if the argument is a HTML5-valid attribute name, as defined here: http://www.w3.org/TR/html5/syntax.html#attributes-0

Attribute names must consist of one or more characters other than the
space characters, U+0000 NULL, U+0022 QUOTATION MARK ("), U+0027
APOSTROPHE ('), ">" (U+003E), "/" (U+002F), and "=" (U+003D) characters,
the control characters, and any characters that are not defined by
Unicode.

This is merely a syntax check. This function makes no judgments about the semantic validity of the argument.

fmt.Println(IsValidAttributeName("example"))
fmt.Println(IsValidAttributeName("not valid"))

Output:

true
false

func IsValidAttributeValue ¶

func IsValidAttributeValue(val string) bool

IsValidAttributeValue returns true if the argument is a valid attribute value, with the caveat that additional rules apply to unquoted, single- quoted, and double-quoted attribute values.

Attribute values are a mixture of text and character references,
except with the additional restriction that the text cannot contain
an ambiguous ampersand.

Definition: http://www.w3.org/TR/html5/syntax.html#attributes-0

Note: It is almost certainly a bad idea to call this function directly. Use one of IsValidAttributeValueUnquoted, IsValidAttributeValueSingleQuoted, or IsValidAttributeValueDoubleQuoted instead.

func IsValidAttributeValueDoubleQuoted ¶

func IsValidAttributeValueDoubleQuoted(val string) bool

IsValidAttributeValueDoubleQuoted return true if the argument is a valid double-quoted attribute value. Note, the argument must not contain the double quotes.

the attribute value, which, in addition to the requirements given above
for attribute values, must not contain any literal """ (U+0022)
characters

From http://www.w3.org/TR/html5/syntax.html#attributes-0

fmt.Println(IsValidAttributeValueDoubleQuoted("yes"))
fmt.Println(IsValidAttributeValueDoubleQuoted(`"no"`))

Output:

true
false

func IsValidAttributeValueSingleQuoted ¶

func IsValidAttributeValueSingleQuoted(val string) bool

IsValidAttributeValueSingleQuoted return true if the argument is a valid single-quoted attribute value. Note, the argument must not contain the single quotes.

the attribute value, which, in addition to the requirements given above
for attribute values, must not contain any literal "'" (U+0027)
characters

From http://www.w3.org/TR/html5/syntax.html#attributes-0

fmt.Println(IsValidAttributeValueSingleQuoted("yes"))
fmt.Println(IsValidAttributeValueSingleQuoted("'no'"))

Output:

true
false

func IsValidAttributeValueUnquoted ¶

func IsValidAttributeValueUnquoted(val string) bool

IsValidAttributeValueUnquoted return true if the argument is a valid unquoted attribute value. For example, "email" in <input type=email>.

The attribute name, followed by zero or more space characters, followed
by a single U+003D EQUALS SIGN character, followed by zero or more space
characters, followed by the attribute value, which, in addition to the
requirements given above for attribute values, must not contain any
literal space characters, any U+0022 QUOTATION MARK characters ("),
U+0027 APOSTROPHE characters ('), "=" (U+003D) characters, "<" (U+003C)
characters, ">" (U+003E) characters, or "`" (U+0060) characters, and
must not be the empty string

From http://www.w3.org/TR/html5/syntax.html#attributes-0

func IsValidCss3IdValue ¶

func IsValidCss3IdValue(val string) bool

IsValidCss3IdValue returns true if the argument is a valid CSS 3 ID value.

From http://www.w3.org/TR/css3-selectors/#id-selectors

An ID selector contains a "number sign" (U+0023, #) immediately followed
by the ID value, which must be an CSS identifiers.

See also IsValidCss3Identifier.

func IsValidCss3Identifier ¶

func IsValidCss3Identifier(val string) bool

IsValidCss3Identifier returns true if the argument is a valid CSS3 identifier. Identifiers include element names, and the selector part of ID and class names.

Prohibited characters can be included using escaped values, and this function takes escaped values into account.

From http://www.w3.org/TR/CSS21/syndata.html#value-def-identifier

In CSS, identifiers ... can contain only:

- the characters [a-zA-Z0-9] and
- ISO 10646 characters U+00A0 and higher, plus
- the hyphen (-) and
- the underscore (_);
- they cannot start with a digit, two hyphens, or a hyphen followed by a
  digit.

Also, special characters can be escaped:

Any character (except a hexadecimal digit, linefeed, carriage return, or
form feed) can be escaped with a backslash to remove its special meaning.

or

Third, backslash escapes allow authors to refer to characters they cannot
easily put in a document. In this case, the backslash is followed by at
most six hexadecimal digits (0..9A..F), which stand for the ISO 10646
([ISO10646]) character with that number, which must not be zero.

BUG(dr): IsValidCss3Identifier uses the CSS 2.1 spec, which the CSS 3 spec links to when it refers "identifiers". Is this the most up-to-date?

fmt.Println(IsValidCss3Identifier("hullo"))

Output:

true

func IsValidHTMLTagName ¶

func IsValidHTMLTagName(name string) bool

IsValidHTMLTagName returns true if the argument *can be* a valid HTML 5 tag name.

Tags contain a tag name, giving the element's name. HTML elements all
have names that only use alphanumeric ASCII characters. In the HTML
syntax, tag names, even those for foreign elements, may be written with
any mix of lower- and uppercase letters that, when converted to all-
lowercase, matches the element's tag name; tag names are case-
insensitive.

This function checks the structural syntax of the argument (i.e. alphanumeric ASCII characters). It does not check if the argument is a pre-defined HTML5 tag name. Use IsHTMLTagName to see if it is a pre-defined name.

func IsValidHtml4IdValue ¶

func IsValidHtml4IdValue(val string) bool

IsValidHtml4IdValue returns true if the argument is a valid HTML 4 ID attribute value.

Note: HTML 4 is more strict than HTML 5.

Note: HTML 4 ID values are strict enough that a valid ID value will be valid also for a quoted or unquoted attribute value.

Note: This function only checks the syntax. Additional restrictions on ID values, such as global uniqueness, also apply.

From http://www.w3.org/TR/html401/types.html#type-name

ID and NAME tokens must begin with a letter ([A-Za-z]) and may be
followed by any number of letters, digits ([0-9]), hyphens ("-"),
underscores ("_"), colons (":"), and periods (".").

fmt.Println(IsValidHtml4IdValue("introduction"))
fmt.Println(IsValidHtml4IdValue("last remarks"))

Output:

true
false

func IsValidHtml5IdValue ¶

func IsValidHtml5IdValue(val string) bool

IsValidHtml5IdValue returns true if the argument is a valid HTML 5 ID value.

Note: This is much more permissive than HTML 4 ID values and CSS3 ID values, so don't get too wacky.

Note: Additional restrictions of HTML attribute values apply.

From http://dev.w3.org/html5/markup/global-attributes.html#common.attrs.id

Any string, with the following restrictions:
 - must be at least one character long
 - must not contain any space characters

fmt.Println(IsValidHtml5IdValue("introduction"))
fmt.Println(IsValidHtml5IdValue("last remarks"))

Output:

true
false