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extern crate proc_macro; use std::iter; use proc_macro::{Group, Span, TokenStream, TokenTree}; #[doc(hidden)] #[proc_macro] pub fn __cmd(macro_arg: TokenStream) -> TokenStream { try_cmd(macro_arg).unwrap_or_else(|msg| parse_ts(&format!("compile_error!({:?})", msg))) } type Result<T> = std::result::Result<T, String>; fn try_cmd(macro_arg: TokenStream) -> Result<TokenStream> { let (cmd, literal) = { let mut iter = macro_arg.into_iter(); let cmd = iter.next().unwrap(); let literal = iter.next().unwrap(); assert!(iter.next().is_none()); (cmd, literal) }; let literal_text = literal.to_string(); if !(matches!(literal, TokenTree::Literal(_)) && literal_text.starts_with('"')) { return Err("expected a plain string literal".to_string()); } let mut args = shell_lex(literal_text.as_str(), literal.span()); let mut res = TokenStream::new(); { let (_joined_to_prev, splat, program) = args.next().ok_or_else(|| "command can't be empty".to_string())??; if splat { return Err("can't splat program name".to_string()); } res.extend(Some(cmd)); res.extend(parse_ts("::new")); res.extend(program); } let mut prev_spat = false; for arg in args { let (joined_to_prev, splat, arg) = arg?; if prev_spat && joined_to_prev { return Err(format!( "can't combine splat with concatenation, add spaces around `{{{}...}}`", trim_decorations(&res.into_iter().last().unwrap().to_string()), )); } prev_spat = splat; let method = match (joined_to_prev, splat) { (false, false) => ".arg", (false, true) => ".args", (true, false) => ".__extend_arg", (true, true) => { return Err(format!( "can't combine splat with concatenation, add spaces around `{{{}...}}`", trim_decorations(&arg.to_string()), )) } }; res.extend(parse_ts(method)); res.extend(arg); } Ok(res) } fn trim_decorations(s: &str) -> &str { &s[1..s.len() - 1] } fn shell_lex( cmd: &str, call_site: Span, ) -> impl Iterator<Item = Result<(bool, bool, TokenStream)>> + '_ { tokenize(cmd).map(move |token| { let token = token?; let mut splat = false; let ts = match token.kind { TokenKind::Word => parse_ts(&format!("(\"{}\")", token.text)), TokenKind::String => parse_ts(&format!("(\"{}\")", trim_decorations(token.text))), TokenKind::Interpolation { splat: s } => { splat = s; let text = trim_decorations(token.text); let text = &text[..text.len() - (if splat { "...".len() } else { 0 })]; if !(text.chars().all(|c| c.is_ascii_alphanumeric() || c == '_')) { return Err(format!( "can only interpolate simple variables, got this expression instead: `{}`", text )); } let ts = if splat { format!("({})", text) } else { format!("(&({}))", text) }; respan(parse_ts(&ts), call_site) } }; Ok((token.joined_to_prev, splat, ts)) }) } fn tokenize(cmd: &str) -> impl Iterator<Item = Result<Token<'_>>> + '_ { let mut cmd = cmd.trim_matches('"'); iter::from_fn(move || { let old_len = cmd.len(); cmd = cmd.trim_start(); let joined_to_prev = old_len == cmd.len(); if cmd.is_empty() { return None; } let (len, kind) = match next_token(cmd) { Ok(it) => it, Err(err) => { cmd = ""; return Some(Err(err)); } }; let token = Token { joined_to_prev, text: &cmd[..len], kind }; cmd = &cmd[len..]; Some(Ok(token)) }) } #[derive(Debug)] struct Token<'a> { joined_to_prev: bool, text: &'a str, kind: TokenKind, } #[derive(Debug)] enum TokenKind { Word, String, Interpolation { splat: bool }, } fn next_token(s: &str) -> Result<(usize, TokenKind)> { if s.starts_with('{') { let len = s.find('}').ok_or_else(|| "unclosed `{` in command".to_string())? + 1; let splat = s[..len].ends_with("...}"); return Ok((len, TokenKind::Interpolation { splat })); } if s.starts_with('\'') { let len = s[1..].find('\'').ok_or_else(|| "unclosed `'` in command".to_string())? + 2; return Ok((len, TokenKind::String)); } let len = s.find(|it: char| it.is_ascii_whitespace() || it == '\'' || it == '{').unwrap_or(s.len()); Ok((len, TokenKind::Word)) } fn respan(ts: TokenStream, span: Span) -> TokenStream { let mut res = TokenStream::new(); for tt in ts { let tt = match tt { TokenTree::Ident(mut ident) => { ident.set_span(ident.span().resolved_at(span).located_at(span)); TokenTree::Ident(ident) } TokenTree::Group(group) => { TokenTree::Group(Group::new(group.delimiter(), respan(group.stream(), span))) } _ => tt, }; res.extend(Some(tt)) } res } fn parse_ts(s: &str) -> TokenStream { s.parse().unwrap() }