nushell/crates/nu-cli/src/shell/completer.rs

use crate::completion::{self, Suggestion};
use crate::context;

pub(crate) struct NuCompleter {}

impl NuCompleter {}

impl NuCompleter {
    pub fn complete(
        &self,
        line: &str,
        pos: usize,
        context: &completion::Context,
    ) -> (usize, Vec<Suggestion>) {
        use crate::completion::engine::LocationType;

        let nu_context: &context::Context = context.as_ref();
        let lite_block = match nu_parser::lite_parse(line, 0) {
            Ok(block) => Some(block),
            Err(result) => result.partial,
        };

        let location = lite_block
            .map(|block| nu_parser::classify_block(&block, &nu_context.registry))
            .and_then(|block| {
                crate::completion::engine::completion_location(line, &block.block, pos)
            });

        if let Some(location) = location {
            let partial = location.span.slice(line);

            let suggestions = match location.item {
                LocationType::Command => {
                    let command_completer = crate::completion::command::Completer {};
                    command_completer.complete(context, partial)
                }

                LocationType::Flag(cmd) => {
                    let flag_completer = crate::completion::flag::Completer {};
                    flag_completer.complete(context, cmd, partial)
                }

                LocationType::Argument(_cmd, _arg_name) => {
                    // TODO use cmd and arg_name to narrow things down further
                    let path_completer = crate::completion::path::Completer::new();
                    path_completer.complete(context, partial)
                }

                LocationType::Variable => Vec::new(),
            }
            .into_iter()
            .map(requote)
            .collect();

            (location.span.start(), suggestions)
        } else {
            (pos, Vec::new())
        }
    }
}

fn requote(item: Suggestion) -> Suggestion {
    let unescaped = rustyline::completion::unescape(&item.replacement, Some('\\'));
    if unescaped != item.replacement {
        Suggestion {
            display: item.display,
            replacement: format!("\"{}\"", unescaped),
        }
    } else {
        item
    }
}