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#![cfg_attr(nightly, feature(proc_macro_span))]
use proc_macro2::{Span, TokenStream, TokenTree};
use quote::{quote, quote_spanned, ToTokens};
#[cfg(feature = "interactive")]
use syn::Block;
use syn::{parse, AttrStyle, Ident, ItemFn, Pat, Path, Stmt};
mod colours;
mod format;
#[proc_macro_attribute]
pub fn code_tour(
_attributes: proc_macro::TokenStream,
input: proc_macro::TokenStream,
) -> proc_macro::TokenStream {
if let Ok(mut function) = parse::<ItemFn>(input.clone()) {
let block_statements = &function.block.stmts;
let mut statements = Vec::with_capacity(block_statements.len());
for statement in block_statements.into_iter() {
// That's a `let` binding.
if let Stmt::Local(local) = statement {
// Extract the local pattern.
if let Pat::Ident(local_pat) = &local.pat {
// There is attributes, which are normally `///`
// (outer doc) or `/** */` (outer block) comments
// before the `let` binding.
if !local.attrs.is_empty() {
// Write `println!("{}", ident_comment)`.
{
let formatted_comment = local
.attrs
.iter()
.filter_map(|attribute| match (attribute.style, &attribute.path) {
(
AttrStyle::Outer,
Path {
leading_colon: None,
segments,
},
) if !segments.is_empty()
&& segments[0].ident
== Ident::new("doc", Span::call_site()) =>
{
if let Some(TokenTree::Literal(literal)) =
attribute.tokens.clone().into_iter().nth(1)
{
let literal_string =
literal.to_string().replace("\\\'", "'");
Some(format!(
"▍{:<80}",
&literal_string[1..literal_string.len() - 1]
))
} else {
None
}
}
_ => None,
})
.map(colours::comment)
.collect::<Vec<String>>()
.join("\n ");
let empty_line = colours::comment(format!("▍{:<80}", " "));
let formatted_comment = format!(
"\n {empty}\n {comment}\n {empty}\n",
empty = empty_line,
comment = formatted_comment
);
statements.push(println(quote!("{}", #formatted_comment)));
}
let mut local_without_attrs = local.clone();
local_without_attrs.attrs = vec![];
// Write `println!("{}", stringify!(<local>))`.
{
let statement =
colours::statement(format::rust_code(&local_without_attrs));
statements.push(println(quote!(" {}\n", #statement)));
}
// Write the original statement, without the documentation.
{
statements.push(Stmt::Local(local_without_attrs));
}
// Write `println!("{:?}", <ident>)`.
{
statements.push(println({
let ident = &local_pat.ident;
quote!(
" ◀︎ {}\n\n",
format!("{:#?}", #ident).replace("\n", "\n ▐ ")
)
}));
}
// Insert “Press Enter to continue…”
#[cfg(feature = "interactive")]
{
let stream = quote!({
{
use std::io::BufRead;
let mut line = String::new();
let stdin = ::std::io::stdin();
println!(
"\n(Press Enter to continue, otherwise Ctrl-C to exit).\n\n"
);
stdin
.lock()
.read_line(&mut line)
.expect("Failed to read a line from the user.");
}
});
let block = parse::<Block>(stream.into()).unwrap();
for statement in block.stmts {
statements.push(statement);
}
}
continue;
}
}
}
statements.push(statement.clone());
}
function.block.stmts = statements;
quote!(#function).to_token_stream().into()
} else {
let span = TokenStream::from(input).into_iter().nth(0).unwrap().span();
quote_spanned!(span => compile_error!("`code_tour` works on functions only")).into()
}
}
fn println(tokens: TokenStream) -> Stmt {
let stream = quote!(if ::std::env::var("CODE_TOUR_QUIET").is_err() {
println!(#tokens);
});
let semi = parse::<Stmt>(stream.into()).unwrap();
semi
}