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#[cfg(feature = "colours")]
use ansi_term::{Colour, Style};
use proc_macro2::{Span, TokenStream, TokenTree};
use quote::{quote, quote_spanned, ToTokens};
use std::iter::FromIterator;
use syn::{
parse, punctuated::Punctuated, token, AttrStyle, Expr, ExprMacro, Ident, ItemFn, Macro,
MacroDelimiter, Pat, Path, PathArguments, PathSegment, Stmt,
};
#[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(format_comment)
.collect::<Vec<String>>()
.join("\n ");
let empty_line = format_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 =
format_statement(quote!(#local_without_attrs).to_string());
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 ▐ ")
)
}));
}
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 {
Stmt::Semi(
Expr::Macro(ExprMacro {
attrs: vec![],
mac: Macro {
path: Path {
leading_colon: None,
segments: Punctuated::from_iter(
vec![PathSegment {
ident: Ident::new("println", Span::call_site()),
arguments: PathArguments::None,
}]
.into_iter(),
),
},
bang_token: token::Bang {
spans: [Span::call_site()],
},
delimiter: MacroDelimiter::Paren(token::Paren {
span: Span::call_site(),
}),
tokens,
},
}),
token::Semi {
spans: [Span::call_site()],
},
)
}
fn format_comment(comment: String) -> String {
#[cfg(feature = "colours")]
{
Style::new()
.fg(Colour::Fixed(253))
.on(Colour::Fixed(238))
.paint(comment)
.to_string()
}
#[cfg(not(feature = "colours"))]
{
comment
}
}
fn format_statement(statement: String) -> String {
#[cfg(feature = "colours")]
{
Style::new()
.fg(Colour::Fixed(228))
.paint(format!("▶︎ {}", statement))
.to_string()
}
#[cfg(not(feature = "colours"))]
{
statement
}
}