fn is_write_patch_constrained_to_writable_paths()

in codex-rs/core/src/safety.rs [115:191]

• 64 lines of code
• 11 McCabe index (conditional complexity)

fn is_write_patch_constrained_to_writable_paths(
    changes: &HashMap<PathBuf, ApplyPatchFileChange>,
    writable_roots: &[PathBuf],
) -> bool {
    // Early‑exit if there are no declared writable roots.
    if writable_roots.is_empty() {
        return false;
    }

    // Normalize a path by removing `.` and resolving `..` without touching the
    // filesystem (works even if the file does not exist).
    fn normalize(path: &Path) -> Option<PathBuf> {
        let mut out = PathBuf::new();
        for comp in path.components() {
            match comp {
                Component::ParentDir => {
                    out.pop();
                }
                Component::CurDir => { /* skip */ }
                other => out.push(other.as_os_str()),
            }
        }
        Some(out)
    }

    // Determine whether `path` is inside **any** writable root. Both `path`
    // and roots are converted to absolute, normalized forms before the
    // prefix check.
    let is_path_writable = |p: &PathBuf| {
        let cwd = match std::env::current_dir() {
            Ok(cwd) => cwd,
            Err(_) => return false,
        };

        let abs = if p.is_absolute() {
            p.clone()
        } else {
            cwd.join(p)
        };
        let abs = match normalize(&abs) {
            Some(v) => v,
            None => return false,
        };

        writable_roots.iter().any(|root| {
            let root_abs = if root.is_absolute() {
                root.clone()
            } else {
                normalize(&cwd.join(root)).unwrap_or_else(|| cwd.join(root))
            };

            abs.starts_with(&root_abs)
        })
    };

    for (path, change) in changes {
        match change {
            ApplyPatchFileChange::Add { .. } | ApplyPatchFileChange::Delete => {
                if !is_path_writable(path) {
                    return false;
                }
            }
            ApplyPatchFileChange::Update { move_path, .. } => {
                if !is_path_writable(path) {
                    return false;
                }
                if let Some(dest) = move_path {
                    if !is_path_writable(dest) {
                        return false;
                    }
                }
            }
        }
    }

    true
}