pub fn indent(s: &str, prefix: &str) -> String {
let mut result = String::with_capacity(2 * s.len());
let trimmed_prefix = prefix.trim_end();
for (idx, line) in s.split_terminator('\n').enumerate() {
if idx > 0 {
result.push('\n');
}
if line.trim().is_empty() {
result.push_str(trimmed_prefix);
} else {
result.push_str(prefix);
}
result.push_str(line);
}
if s.ends_with('\n') {
result.push('\n');
}
result
}
pub fn dedent(s: &str) -> String {
let mut prefix = "";
let mut lines = s.lines();
for line in &mut lines {
let mut whitespace_idx = line.len();
for (idx, ch) in line.char_indices() {
if !ch.is_whitespace() {
whitespace_idx = idx;
break;
}
}
if whitespace_idx < line.len() {
prefix = &line[..whitespace_idx];
break;
}
}
for line in &mut lines {
let mut whitespace_idx = line.len();
for ((idx, a), b) in line.char_indices().zip(prefix.chars()) {
if a != b {
whitespace_idx = idx;
break;
}
}
if whitespace_idx < line.len() && whitespace_idx < prefix.len() {
prefix = &line[..whitespace_idx];
}
}
let mut result = String::new();
for line in s.lines() {
if line.starts_with(&prefix) && line.chars().any(|c| !c.is_whitespace()) {
let (_, tail) = line.split_at(prefix.len());
result.push_str(tail);
}
result.push('\n');
}
if result.ends_with('\n') && !s.ends_with('\n') {
let new_len = result.len() - 1;
result.truncate(new_len);
}
result
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn indent_empty() {
assert_eq!(indent("\n", " "), "\n");
}
#[test]
#[rustfmt::skip]
fn indent_nonempty() {
let text = [
" foo\n",
"bar\n",
" baz\n",
].join("");
let expected = [
"// foo\n",
"// bar\n",
"// baz\n",
].join("");
assert_eq!(indent(&text, "// "), expected);
}
#[test]
#[rustfmt::skip]
fn indent_empty_line() {
let text = [
" foo",
"bar",
"",
" baz",
].join("\n");
let expected = [
"// foo",
"// bar",
"//",
"// baz",
].join("\n");
assert_eq!(indent(&text, "// "), expected);
}
#[test]
fn dedent_empty() {
assert_eq!(dedent(""), "");
}
#[test]
#[rustfmt::skip]
fn dedent_multi_line() {
let x = [
" foo",
" bar",
" baz",
].join("\n");
let y = [
" foo",
"bar",
" baz"
].join("\n");
assert_eq!(dedent(&x), y);
}
#[test]
#[rustfmt::skip]
fn dedent_empty_line() {
let x = [
" foo",
" bar",
" ",
" baz"
].join("\n");
let y = [
" foo",
"bar",
"",
" baz"
].join("\n");
assert_eq!(dedent(&x), y);
}
#[test]
#[rustfmt::skip]
fn dedent_blank_line() {
let x = [
" foo",
"",
" bar",
" foo",
" bar",
" baz",
].join("\n");
let y = [
"foo",
"",
" bar",
" foo",
" bar",
" baz",
].join("\n");
assert_eq!(dedent(&x), y);
}
#[test]
#[rustfmt::skip]
fn dedent_whitespace_line() {
let x = [
" foo",
" ",
" bar",
" foo",
" bar",
" baz",
].join("\n");
let y = [
"foo",
"",
" bar",
" foo",
" bar",
" baz",
].join("\n");
assert_eq!(dedent(&x), y);
}
#[test]
#[rustfmt::skip]
fn dedent_mixed_whitespace() {
let x = [
"\tfoo",
" bar",
].join("\n");
let y = [
"\tfoo",
" bar",
].join("\n");
assert_eq!(dedent(&x), y);
}
#[test]
#[rustfmt::skip]
fn dedent_tabbed_whitespace() {
let x = [
"\t\tfoo",
"\t\t\tbar",
].join("\n");
let y = [
"foo",
"\tbar",
].join("\n");
assert_eq!(dedent(&x), y);
}
#[test]
#[rustfmt::skip]
fn dedent_mixed_tabbed_whitespace() {
let x = [
"\t \tfoo",
"\t \t\tbar",
].join("\n");
let y = [
"foo",
"\tbar",
].join("\n");
assert_eq!(dedent(&x), y);
}
#[test]
#[rustfmt::skip]
fn dedent_mixed_tabbed_whitespace2() {
let x = [
"\t \tfoo",
"\t \tbar",
].join("\n");
let y = [
"\tfoo",
" \tbar",
].join("\n");
assert_eq!(dedent(&x), y);
}
#[test]
#[rustfmt::skip]
fn dedent_preserve_no_terminating_newline() {
let x = [
" foo",
" bar",
].join("\n");
let y = [
"foo",
" bar",
].join("\n");
assert_eq!(dedent(&x), y);
}
}