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Diffstat (limited to 'third_party/rust/paste/src/segment.rs')
| -rw-r--r-- | third_party/rust/paste/src/segment.rs | 233 |
1 files changed, 233 insertions, 0 deletions
diff --git a/third_party/rust/paste/src/segment.rs b/third_party/rust/paste/src/segment.rs new file mode 100644 index 0000000000..592a047021 --- /dev/null +++ b/third_party/rust/paste/src/segment.rs @@ -0,0 +1,233 @@ +use crate::error::{Error, Result}; +use proc_macro::{token_stream, Delimiter, Ident, Span, TokenTree}; +use std::iter::Peekable; + +pub(crate) enum Segment { + String(LitStr), + Apostrophe(Span), + Env(LitStr), + Modifier(Colon, Ident), +} + +pub(crate) struct LitStr { + pub value: String, + pub span: Span, +} + +pub(crate) struct Colon { + pub span: Span, +} + +pub(crate) fn parse(tokens: &mut Peekable<token_stream::IntoIter>) -> Result<Vec<Segment>> { + let mut segments = Vec::new(); + while match tokens.peek() { + None => false, + Some(TokenTree::Punct(punct)) => punct.as_char() != '>', + Some(_) => true, + } { + match tokens.next().unwrap() { + TokenTree::Ident(ident) => { + let mut fragment = ident.to_string(); + if fragment.starts_with("r#") { + fragment = fragment.split_off(2); + } + if fragment == "env" + && match tokens.peek() { + Some(TokenTree::Punct(punct)) => punct.as_char() == '!', + _ => false, + } + { + let bang = tokens.next().unwrap(); // `!` + let expect_group = tokens.next(); + let parenthesized = match &expect_group { + Some(TokenTree::Group(group)) + if group.delimiter() == Delimiter::Parenthesis => + { + group + } + Some(wrong) => return Err(Error::new(wrong.span(), "expected `(`")), + None => { + return Err(Error::new2( + ident.span(), + bang.span(), + "expected `(` after `env!`", + )); + } + }; + let mut inner = parenthesized.stream().into_iter(); + let lit = match inner.next() { + Some(TokenTree::Literal(lit)) => lit, + Some(wrong) => { + return Err(Error::new(wrong.span(), "expected string literal")) + } + None => { + return Err(Error::new2( + ident.span(), + parenthesized.span(), + "expected string literal as argument to env! macro", + )) + } + }; + let lit_string = lit.to_string(); + if lit_string.starts_with('"') + && lit_string.ends_with('"') + && lit_string.len() >= 2 + { + // TODO: maybe handle escape sequences in the string if + // someone has a use case. + segments.push(Segment::Env(LitStr { + value: lit_string[1..lit_string.len() - 1].to_owned(), + span: lit.span(), + })); + } else { + return Err(Error::new(lit.span(), "expected string literal")); + } + if let Some(unexpected) = inner.next() { + return Err(Error::new( + unexpected.span(), + "unexpected token in env! macro", + )); + } + } else { + segments.push(Segment::String(LitStr { + value: fragment, + span: ident.span(), + })); + } + } + TokenTree::Literal(lit) => { + segments.push(Segment::String(LitStr { + value: lit.to_string(), + span: lit.span(), + })); + } + TokenTree::Punct(punct) => match punct.as_char() { + '_' => segments.push(Segment::String(LitStr { + value: "_".to_owned(), + span: punct.span(), + })), + '\'' => segments.push(Segment::Apostrophe(punct.span())), + ':' => { + let colon_span = punct.span(); + let colon = Colon { span: colon_span }; + let ident = match tokens.next() { + Some(TokenTree::Ident(ident)) => ident, + wrong => { + let span = wrong.as_ref().map_or(colon_span, TokenTree::span); + return Err(Error::new(span, "expected identifier after `:`")); + } + }; + segments.push(Segment::Modifier(colon, ident)); + } + _ => return Err(Error::new(punct.span(), "unexpected punct")), + }, + TokenTree::Group(group) => { + if group.delimiter() == Delimiter::None { + let mut inner = group.stream().into_iter().peekable(); + let nested = parse(&mut inner)?; + if let Some(unexpected) = inner.next() { + return Err(Error::new(unexpected.span(), "unexpected token")); + } + segments.extend(nested); + } else { + return Err(Error::new(group.span(), "unexpected token")); + } + } + } + } + Ok(segments) +} + +pub(crate) fn paste(segments: &[Segment]) -> Result<String> { + let mut evaluated = Vec::new(); + let mut is_lifetime = false; + + for segment in segments { + match segment { + Segment::String(segment) => { + evaluated.push(segment.value.clone()); + } + Segment::Apostrophe(span) => { + if is_lifetime { + return Err(Error::new(*span, "unexpected lifetime")); + } + is_lifetime = true; + } + Segment::Env(var) => { + let resolved = match std::env::var(&var.value) { + Ok(resolved) => resolved, + Err(_) => { + return Err(Error::new( + var.span, + &format!("no such env var: {:?}", var.value), + )); + } + }; + let resolved = resolved.replace('-', "_"); + evaluated.push(resolved); + } + Segment::Modifier(colon, ident) => { + let last = match evaluated.pop() { + Some(last) => last, + None => { + return Err(Error::new2(colon.span, ident.span(), "unexpected modifier")) + } + }; + match ident.to_string().as_str() { + "lower" => { + evaluated.push(last.to_lowercase()); + } + "upper" => { + evaluated.push(last.to_uppercase()); + } + "snake" => { + let mut acc = String::new(); + let mut prev = '_'; + for ch in last.chars() { + if ch.is_uppercase() && prev != '_' { + acc.push('_'); + } + acc.push(ch); + prev = ch; + } + evaluated.push(acc.to_lowercase()); + } + "camel" => { + let mut acc = String::new(); + let mut prev = '_'; + for ch in last.chars() { + if ch != '_' { + if prev == '_' { + for chu in ch.to_uppercase() { + acc.push(chu); + } + } else if prev.is_uppercase() { + for chl in ch.to_lowercase() { + acc.push(chl); + } + } else { + acc.push(ch); + } + } + prev = ch; + } + evaluated.push(acc); + } + _ => { + return Err(Error::new2( + colon.span, + ident.span(), + "unsupported modifier", + )); + } + } + } + } + } + + let mut pasted = evaluated.into_iter().collect::<String>(); + if is_lifetime { + pasted.insert(0, '\''); + } + Ok(pasted) +} |