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//! Functions for string case manipulation, such as detecting the identifier case,
//! and converting it into appropriate form.
// Code that was taken from rustc was taken at commit 89fdb30,
// from file /compiler/rustc_lint/src/nonstandard_style.rs
/// Converts an identifier to an UpperCamelCase form.
/// Returns `None` if the string is already in UpperCamelCase.
pub(crate) fn to_camel_case(ident: &str) -> Option<String> {
if is_camel_case(ident) {
return None;
}
// Taken from rustc.
let ret = ident
.trim_matches('_')
.split('_')
.filter(|component| !component.is_empty())
.map(|component| {
let mut camel_cased_component = String::with_capacity(component.len());
let mut new_word = true;
let mut prev_is_lower_case = true;
for c in component.chars() {
// Preserve the case if an uppercase letter follows a lowercase letter, so that
// `camelCase` is converted to `CamelCase`.
if prev_is_lower_case && c.is_uppercase() {
new_word = true;
}
if new_word {
camel_cased_component.extend(c.to_uppercase());
} else {
camel_cased_component.extend(c.to_lowercase());
}
prev_is_lower_case = c.is_lowercase();
new_word = false;
}
camel_cased_component
})
.fold((String::new(), None), |(acc, prev): (_, Option<String>), next| {
// separate two components with an underscore if their boundary cannot
// be distinguished using an uppercase/lowercase case distinction
let join = prev
.and_then(|prev| {
let f = next.chars().next()?;
let l = prev.chars().last()?;
Some(!char_has_case(l) && !char_has_case(f))
})
.unwrap_or(false);
(acc + if join { "_" } else { "" } + &next, Some(next))
})
.0;
Some(ret)
}
/// Converts an identifier to a lower_snake_case form.
/// Returns `None` if the string is already in lower_snake_case.
pub(crate) fn to_lower_snake_case(ident: &str) -> Option<String> {
if is_lower_snake_case(ident) {
return None;
} else if is_upper_snake_case(ident) {
return Some(ident.to_lowercase());
}
Some(stdx::to_lower_snake_case(ident))
}
/// Converts an identifier to an UPPER_SNAKE_CASE form.
/// Returns `None` if the string is already is UPPER_SNAKE_CASE.
pub(crate) fn to_upper_snake_case(ident: &str) -> Option<String> {
if is_upper_snake_case(ident) {
return None;
} else if is_lower_snake_case(ident) {
return Some(ident.to_uppercase());
}
Some(stdx::to_upper_snake_case(ident))
}
// Taken from rustc.
// Modified by replacing the use of unstable feature `array_windows`.
fn is_camel_case(name: &str) -> bool {
let name = name.trim_matches('_');
if name.is_empty() {
return true;
}
let mut fst = None;
// start with a non-lowercase letter rather than non-uppercase
// ones (some scripts don't have a concept of upper/lowercase)
name.chars().next().map_or(true, |c| !c.is_lowercase())
&& !name.contains("__")
&& !name.chars().any(|snd| {
let ret = match fst {
None => false,
Some(fst) => char_has_case(fst) && snd == '_' || char_has_case(snd) && fst == '_',
};
fst = Some(snd);
ret
})
}
fn is_lower_snake_case(ident: &str) -> bool {
is_snake_case(ident, char::is_uppercase)
}
fn is_upper_snake_case(ident: &str) -> bool {
is_snake_case(ident, char::is_lowercase)
}
// Taken from rustc.
// Modified to allow checking for both upper and lower snake case.
fn is_snake_case<F: Fn(char) -> bool>(ident: &str, wrong_case: F) -> bool {
if ident.is_empty() {
return true;
}
let ident = ident.trim_matches('_');
let mut allow_underscore = true;
ident.chars().all(|c| {
allow_underscore = match c {
'_' if !allow_underscore => return false,
'_' => false,
// It would be more obvious to check for the correct case,
// but some characters do not have a case.
c if !wrong_case(c) => true,
_ => return false,
};
true
})
}
// Taken from rustc.
fn char_has_case(c: char) -> bool {
c.is_lowercase() || c.is_uppercase()
}
#[cfg(test)]
mod tests {
use super::*;
use expect_test::{expect, Expect};
fn check<F: Fn(&str) -> Option<String>>(fun: F, input: &str, expect: Expect) {
// `None` is translated to empty string, meaning that there is nothing to fix.
let output = fun(input).unwrap_or_default();
expect.assert_eq(&output);
}
#[test]
fn test_to_lower_snake_case() {
check(to_lower_snake_case, "lower_snake_case", expect![[""]]);
check(to_lower_snake_case, "UPPER_SNAKE_CASE", expect![["upper_snake_case"]]);
check(to_lower_snake_case, "Weird_Case", expect![["weird_case"]]);
check(to_lower_snake_case, "CamelCase", expect![["camel_case"]]);
check(to_lower_snake_case, "lowerCamelCase", expect![["lower_camel_case"]]);
check(to_lower_snake_case, "a", expect![[""]]);
check(to_lower_snake_case, "abc", expect![[""]]);
check(to_lower_snake_case, "foo__bar", expect![["foo_bar"]]);
check(to_lower_snake_case, "Δ", expect!["δ"]);
}
#[test]
fn test_to_camel_case() {
check(to_camel_case, "CamelCase", expect![[""]]);
check(to_camel_case, "CamelCase_", expect![[""]]);
check(to_camel_case, "_CamelCase", expect![[""]]);
check(to_camel_case, "lowerCamelCase", expect![["LowerCamelCase"]]);
check(to_camel_case, "lower_snake_case", expect![["LowerSnakeCase"]]);
check(to_camel_case, "UPPER_SNAKE_CASE", expect![["UpperSnakeCase"]]);
check(to_camel_case, "Weird_Case", expect![["WeirdCase"]]);
check(to_camel_case, "name", expect![["Name"]]);
check(to_camel_case, "A", expect![[""]]);
check(to_camel_case, "AABB", expect![[""]]);
// Taken from rustc: /compiler/rustc_lint/src/nonstandard_style/tests.rs
check(to_camel_case, "X86_64", expect![[""]]);
check(to_camel_case, "x86__64", expect![["X86_64"]]);
check(to_camel_case, "Abc_123", expect![["Abc123"]]);
check(to_camel_case, "A1_b2_c3", expect![["A1B2C3"]]);
}
#[test]
fn test_to_upper_snake_case() {
check(to_upper_snake_case, "UPPER_SNAKE_CASE", expect![[""]]);
check(to_upper_snake_case, "lower_snake_case", expect![["LOWER_SNAKE_CASE"]]);
check(to_upper_snake_case, "Weird_Case", expect![["WEIRD_CASE"]]);
check(to_upper_snake_case, "CamelCase", expect![["CAMEL_CASE"]]);
check(to_upper_snake_case, "lowerCamelCase", expect![["LOWER_CAMEL_CASE"]]);
check(to_upper_snake_case, "A", expect![[""]]);
check(to_upper_snake_case, "ABC", expect![[""]]);
check(to_upper_snake_case, "X86_64", expect![[""]]);
check(to_upper_snake_case, "FOO_BAr", expect![["FOO_BAR"]]);
check(to_upper_snake_case, "FOO__BAR", expect![["FOO_BAR"]]);
check(to_upper_snake_case, "ß", expect!["SS"]);
}
}
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