wasm_bindgen_shared/
identifier.rs

1use alloc::string::String;
2
3/// Returns whether a character is a valid JS identifier start character.
4///
5/// This is only ever-so-slightly different from `XID_Start` in a few edge
6/// cases, so we handle those edge cases manually and delegate everything else
7/// to `unicode-ident`.
8fn is_id_start(c: char) -> bool {
9    match c {
10        '\u{037A}' | '\u{0E33}' | '\u{0EB3}' | '\u{309B}' | '\u{309C}' | '\u{FC5E}'
11        | '\u{FC5F}' | '\u{FC60}' | '\u{FC61}' | '\u{FC62}' | '\u{FC63}' | '\u{FDFA}'
12        | '\u{FDFB}' | '\u{FE70}' | '\u{FE72}' | '\u{FE74}' | '\u{FE76}' | '\u{FE78}'
13        | '\u{FE7A}' | '\u{FE7C}' | '\u{FE7E}' | '\u{FF9E}' | '\u{FF9F}' => true,
14        '$' | '_' => true,
15        _ => unicode_ident::is_xid_start(c),
16    }
17}
18
19/// Returns whether a character is a valid JS identifier continue character.
20///
21/// This is only ever-so-slightly different from `XID_Continue` in a few edge
22/// cases, so we handle those edge cases manually and delegate everything else
23/// to `unicode-ident`.
24fn is_id_continue(c: char) -> bool {
25    match c {
26        '\u{037A}' | '\u{309B}' | '\u{309C}' | '\u{FC5E}' | '\u{FC5F}' | '\u{FC60}'
27        | '\u{FC61}' | '\u{FC62}' | '\u{FC63}' | '\u{FDFA}' | '\u{FDFB}' | '\u{FE70}'
28        | '\u{FE72}' | '\u{FE74}' | '\u{FE76}' | '\u{FE78}' | '\u{FE7A}' | '\u{FE7C}'
29        | '\u{FE7E}' => true,
30        '$' | '\u{200C}' | '\u{200D}' => true,
31        _ => unicode_ident::is_xid_continue(c),
32    }
33}
34
35fn maybe_valid_chars(name: &str) -> impl Iterator<Item = Option<char>> + '_ {
36    let mut chars = name.chars();
37    // Always emit at least one `None` item - that way `is_valid_ident` can fail without
38    // a separate check for empty strings, and `to_valid_ident` will always produce at least
39    // one underscore.
40    core::iter::once(chars.next().filter(|&c| is_id_start(c))).chain(chars.map(|c| {
41        if is_id_continue(c) {
42            Some(c)
43        } else {
44            None
45        }
46    }))
47}
48
49/// Javascript keywords.
50///
51/// Note that some of these keywords are only reserved in strict mode. Since we
52/// generate strict mode JS code, we treat all of these as reserved.
53///
54/// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Lexical_grammar#reserved_words
55const JS_KEYWORDS: [&str; 47] = [
56    "arguments",
57    "break",
58    "case",
59    "catch",
60    "class",
61    "const",
62    "continue",
63    "debugger",
64    "default",
65    "delete",
66    "do",
67    "else",
68    "enum",
69    "eval",
70    "export",
71    "extends",
72    "false",
73    "finally",
74    "for",
75    "function",
76    "if",
77    "implements",
78    "import",
79    "in",
80    "instanceof",
81    "interface",
82    "let",
83    "new",
84    "null",
85    "package",
86    "private",
87    "protected",
88    "public",
89    "return",
90    "static",
91    "super",
92    "switch",
93    "this",
94    "throw",
95    "true",
96    "try",
97    "typeof",
98    "var",
99    "void",
100    "while",
101    "with",
102    "yield",
103];
104
105/// Javascript keywords that behave like values in that they can be called like
106/// functions or have properties accessed on them.
107///
108/// Naturally, this list is a subset of `JS_KEYWORDS`.
109const VALUE_LIKE_JS_KEYWORDS: [&str; 7] = [
110    "eval",   // eval is a function-like keyword, so e.g. `eval(...)` is valid
111    "false",  // false resolves to a boolean value, so e.g. `false.toString()` is valid
112    "import", // import.meta and import()
113    "new",    // new.target
114    "super", // super can be used for a function call (`super(...)`) or property lookup (`super.prop`)
115    "this",  // this obviously can be used as a value
116    "true",  // true resolves to a boolean value, so e.g. `false.toString()` is valid
117];
118
119/// Returns whether the given string is a JS keyword.
120pub fn is_js_keyword(keyword: &str) -> bool {
121    JS_KEYWORDS.contains(&keyword)
122}
123/// Returns whether the given string is a JS keyword that does NOT behave like
124/// a value.
125///
126/// Value-like keywords can be called like functions or have properties
127/// accessed, which makes it possible to use them in imports. In general,
128/// imports should use this function to check for reserved keywords.
129pub fn is_non_value_js_keyword(keyword: &str) -> bool {
130    JS_KEYWORDS.contains(&keyword) && !VALUE_LIKE_JS_KEYWORDS.contains(&keyword)
131}
132
133/// Returns whether a string is a valid JavaScript identifier.
134/// Defined at https://tc39.es/ecma262/#prod-IdentifierName.
135pub fn is_valid_ident(name: &str) -> bool {
136    maybe_valid_chars(name).all(|opt| opt.is_some())
137}
138
139/// Converts a string to a valid JavaScript identifier by replacing invalid
140/// characters with underscores.
141pub fn to_valid_ident(name: &str) -> String {
142    let result: String = maybe_valid_chars(name)
143        .map(|opt| opt.unwrap_or('_'))
144        .collect();
145
146    if is_js_keyword(&result) || is_non_value_js_keyword(&result) {
147        alloc::format!("_{result}")
148    } else {
149        result
150    }
151}
wasm_bindgen_shared/identifier.rs

wasm_bindgen_shared/
identifier.rs
