paste/segment.rs
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233
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)
}