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use proc_macro2::{Delimiter, Group, Spacing, TokenStream, TokenTree};
/// Formats RDL source into canonical indented form.
pub fn format(input: &str) -> String {
let stream: TokenStream = input.parse().unwrap_or_default();
let tokens: Vec<TokenTree> = stream.into_iter().collect();
let mut output = String::new();
format_seq(&tokens, &mut output, 0, false);
output
}
fn format_seq(tokens: &[TokenTree], output: &mut String, indent: usize, inline: bool) {
let mut i = 0;
let mut angle_depth: usize = 0;
while i < tokens.len() {
// Detect outer attribute: `#` followed by a `[...]` group.
if let TokenTree::Punct(p) = &tokens[i]
&& p.as_char() == '#'
&& let Some(TokenTree::Group(g)) = tokens.get(i + 1)
&& g.delimiter() == Delimiter::Bracket
{
// An attribute that immediately follows `->` is a return-type
// attribute and must stay inline (e.g. `-> #[Const] *const u8`).
// An attribute that immediately follows `: ` is in type position
// (e.g. an inline nested `field: #[packed(1)] struct { .. }`) and
// likewise stays inline.
let after_arrow = output.ends_with("-> ");
let after_colon = output.ends_with(": ");
let treat_inline = inline || after_arrow || after_colon;
if !treat_inline && at_line_start(output) {
push_indent(output, indent);
}
format_attribute(g, output);
if treat_inline {
output.push(' ');
} else {
output.push('\n');
}
i += 2;
continue;
}
if !inline && at_line_start(output) {
push_indent(output, indent);
}
match &tokens[i] {
TokenTree::Ident(id) => {
output.push_str(&id.to_string());
output.push(' ');
}
TokenTree::Literal(lit) => {
output.push_str(&lit.to_string());
output.push(' ');
}
TokenTree::Punct(p) => match (p.as_char(), p.spacing()) {
(':', Spacing::Joint) => {
trim_space(output);
output.push_str("::");
i += 1; // skip the second `:`
}
(':', _) => {
trim_space(output);
output.push_str(": ");
}
(',', _) => {
trim_space(output);
output.push(',');
if inline || angle_depth > 0 {
output.push(' ');
} else {
output.push('\n');
}
}
(';', _) => {
trim_space(output);
output.push(';');
if inline {
output.push(' ');
} else {
output.push('\n');
}
}
// Single member-access dot: trim the preceding space.
// Joint dots are part of `...` (variadic) and must not trim
// the preceding space so that `, ...` formats correctly.
('.', Spacing::Alone) => {
trim_space(output);
output.push('.');
}
('.', _) => output.push('.'),
// `->` return-type arrow
('-', Spacing::Joint) => {
output.push_str("-> ");
i += 1; // skip the `>`
}
('-', _) => output.push('-'),
('*', _) => output.push('*'),
('&', _) => output.push('&'),
('+', _) => {
trim_space(output);
output.push_str(" + ");
}
('=', _) => {
trim_space(output);
output.push_str(" = ");
}
('|', _) => {
trim_space(output);
output.push_str(" | ");
}
('<', _) => {
trim_space(output);
output.push('<');
angle_depth = angle_depth.saturating_add(1);
}
('>', _) => {
trim_space(output);
output.push('>');
angle_depth = angle_depth.saturating_sub(1);
}
_ => output.push(p.as_char()),
},
TokenTree::Group(g) => match g.delimiter() {
Delimiter::Brace => {
let inner: Vec<TokenTree> = g.stream().into_iter().collect();
if inner.is_empty() {
output.push_str("{}\n");
} else {
if !output.ends_with(' ') {
output.push(' ');
}
output.push_str("{\n");
format_seq(&inner, output, indent + 1, false);
push_indent(output, indent);
output.push('}');
if matches!(tokens.get(i + 1), Some(TokenTree::Punct(p)) if p.as_char() == ',')
{
output.push_str(",\n");
i += 1; // skip the `,`
} else {
output.push('\n');
}
}
}
Delimiter::Parenthesis => {
trim_space(output);
output.push('(');
let inner: Vec<TokenTree> = g.stream().into_iter().collect();
format_seq(&inner, output, indent, true);
trim_space(output);
output.push_str(") ");
}
Delimiter::Bracket => {
output.push('[');
let inner: Vec<TokenTree> = g.stream().into_iter().collect();
format_seq(&inner, output, indent, true);
trim_space(output);
output.push(']');
}
_ => {}
},
}
i += 1;
}
}
fn format_attribute(g: &Group, output: &mut String) {
output.push_str("#[");
let inner: Vec<TokenTree> = g.stream().into_iter().collect();
if matches!(&inner[..], [TokenTree::Ident(ident)] if ident == "r#in") {
output.push_str("in]");
return;
}
format_seq(&inner, output, 0, true);
trim_space(output);
output.push(']');
}
fn at_line_start(output: &str) -> bool {
output.ends_with('\n') || output.is_empty()
}
fn push_indent(output: &mut String, level: usize) {
for _ in 0..level {
output.push_str(" ");
}
}
fn trim_space(output: &mut String) {
if output.ends_with(' ') {
output.pop();
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn input_direction_uses_rdl_spelling() {
assert_eq!(format("#[r#in]"), "#[in]\n");
}
}