Function clean_doc

crates/codegen/src/compile.rs:10428–10458

Strips leading whitespace from a docstring. `inspect.cleandoc` is a good reference, but has a few incompatibilities. = _PyCompile_CleanDoc

(doc: &str)

/// `inspect.cleandoc` is a good reference, but has a few incompatibilities.
// = _PyCompile_CleanDoc
fn clean_doc(doc: &str) -> String {
    let doc = expandtabs(doc, 8);
    // First pass: find minimum indentation of non-blank lines AFTER the first line.
    // A "blank line" is one containing only spaces (or empty).
    let margin = doc
        .split('\n')
        .skip(1) // skip first line
        .filter(|line| line.chars().any(|c| c != ' ')) // non-blank lines only
        .map(|line| line.chars().take_while(|c| *c == ' ').count())
        .min()
        .unwrap_or(0);

    let mut cleaned = String::with_capacity(doc.len());
    // Strip all leading spaces from the first line
    if let Some(first_line) = doc.split('\n').next() {
        let trimmed = first_line.trim_start();
        // Early exit: no leading spaces on first line AND margin == 0
        if trimmed.len() == first_line.len() && margin == 0 {
            return doc.to_owned();
        }
        cleaned.push_str(trimmed);
    }
    // Subsequent lines: skip up to `margin` leading spaces
    for line in doc.split('\n').skip(1) {
        cleaned.push('\n');
        let skip = line.chars().take(margin).take_while(|c| *c == ' ').count();
        cleaned.push_str(&line[skip..]);
    }

    cleaned
}

// copied from rustpython_common::str, so we don't have to depend on it just for this function
fn expandtabs(input: &str, tab_size: usize) -> String {