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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)
}