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/// Returns a substring of `s` starting at `line` and `column`. At most `max_chars` are returned.
pub(crate) fn excerpt(s: &str, line: usize, column: usize, max_chars: usize) -> String {
s.lines() // omits the newlines
.skip(line - 1)
.map(|line| {
line.chars().chain(std::iter::once('\n')) // adds the newlines again
})
.flatten()
.skip(column - 1)
.take(max_chars)
.collect()
}
#[test]
fn excerpt_returns_string_starting_from_line_and_column() {
assert_eq!(
"ne 2\nline 3\n",
excerpt("line 1\nline 2\nline 3\n", 2, 3, 80)
);
assert_eq!("n", excerpt("line 1\nline 2\nline 3\n", 2, 3, 1));
}
#[test]
fn excerpt_returns_string_starting_from_line_and_column_but_limits_output() {
let expected = "ne 2\nli";
let result = excerpt("line 1\nline 2\nline 3\n", 2, 3, 7);
assert_eq!(expected, result);
}
#[test]
fn excerpt_counts_newline_as_one_char_from_beginning() {
let expected = "\n\n\n";
let result = excerpt("\n\n\n\n", 1, 1, 3);
assert_eq!(expected, result);
}
#[test]
fn excerpt_counts_newline_as_one_char_in_between_lines() {
let expected = "\n\n";
let result = excerpt("\n\n\n\n", 2, 1, 2);
assert_eq!(expected, result);
}
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