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|
//! Functions for string case manipulation, such as detecting the identifier case,
//! and converting it into appropriate form.
#[derive(Debug)]
enum DetectedCase {
LowerCamelCase,
UpperCamelCase,
LowerSnakeCase,
UpperSnakeCase,
Unknown,
}
fn detect_case(ident: &str) -> DetectedCase {
let trimmed_ident = ident.trim_matches('_');
let first_lowercase = trimmed_ident.starts_with(|chr: char| chr.is_ascii_lowercase());
let mut has_lowercase = first_lowercase;
let mut has_uppercase = false;
let mut has_underscore = false;
for chr in trimmed_ident.chars() {
if chr == '_' {
has_underscore = true;
} else if chr.is_ascii_uppercase() {
has_uppercase = true;
} else if chr.is_ascii_lowercase() {
has_lowercase = true;
}
}
if has_uppercase {
if !has_lowercase {
DetectedCase::UpperSnakeCase
} else if !has_underscore {
if first_lowercase {
DetectedCase::LowerCamelCase
} else {
DetectedCase::UpperCamelCase
}
} else {
// It has uppercase, it has lowercase, it has underscore.
// No assumptions here
DetectedCase::Unknown
}
} else {
DetectedCase::LowerSnakeCase
}
}
/// Converts an identifier to an UpperCamelCase form.
/// Returns `None` if the string is already is UpperCamelCase.
pub fn to_camel_case(ident: &str) -> Option<String> {
let detected_case = detect_case(ident);
match detected_case {
DetectedCase::UpperCamelCase => return None,
DetectedCase::LowerCamelCase => {
let mut first_capitalized = false;
let output = ident
.chars()
.map(|chr| {
if !first_capitalized && chr.is_ascii_lowercase() {
first_capitalized = true;
chr.to_ascii_uppercase()
} else {
chr
}
})
.collect();
return Some(output);
}
_ => {}
}
let mut output = String::with_capacity(ident.len());
let mut capital_added = false;
for chr in ident.chars() {
if chr.is_alphabetic() {
if !capital_added {
output.push(chr.to_ascii_uppercase());
capital_added = true;
} else {
output.push(chr.to_ascii_lowercase());
}
} else if chr == '_' {
// Skip this character and make the next one capital.
capital_added = false;
} else {
// Put the characted as-is.
output.push(chr);
}
}
if output == ident {
// While we didn't detect the correct case at the beginning, there
// may be special cases: e.g. `A` is both valid CamelCase and UPPER_SNAKE_CASE.
None
} else {
Some(output)
}
}
/// Converts an identifier to a lower_snake_case form.
/// Returns `None` if the string is already in lower_snake_case.
pub fn to_lower_snake_case(ident: &str) -> Option<String> {
// First, assume that it's UPPER_SNAKE_CASE.
match detect_case(ident) {
DetectedCase::LowerSnakeCase => return None,
DetectedCase::UpperSnakeCase => {
return Some(ident.chars().map(|chr| chr.to_ascii_lowercase()).collect())
}
_ => {}
}
// Otherwise, assume that it's CamelCase.
let lower_snake_case = stdx::to_lower_snake_case(ident);
if lower_snake_case == ident {
// While we didn't detect the correct case at the beginning, there
// may be special cases: e.g. `a` is both valid camelCase and snake_case.
None
} else {
Some(lower_snake_case)
}
}
/// Converts an identifier to an UPPER_SNAKE_CASE form.
/// Returns `None` if the string is already is UPPER_SNAKE_CASE.
pub fn to_upper_snake_case(ident: &str) -> Option<String> {
match detect_case(ident) {
DetectedCase::UpperSnakeCase => return None,
DetectedCase::LowerSnakeCase => {
return Some(ident.chars().map(|chr| chr.to_ascii_uppercase()).collect())
}
_ => {}
}
// Normalize the string from whatever form it's in currently, and then just make it uppercase.
let upper_snake_case = stdx::to_upper_snake_case(ident);
if upper_snake_case == ident {
// While we didn't detect the correct case at the beginning, there
// may be special cases: e.g. `A` is both valid CamelCase and UPPER_SNAKE_CASE.
None
} else {
Some(upper_snake_case)
}
}
#[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![[""]]);
}
#[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![[""]]);
}
#[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![[""]]);
}
}
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