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fstring.rs
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237 lines (214 loc) · 6.91 KB
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use std::iter;
use std::mem;
use std::str;
use lalrpop_util::ParseError as LalrpopError;
use crate::ast::{ConversionFlag, StringGroup};
use crate::lexer::{LexicalError, LexicalErrorType, Location, Tok};
use crate::parser::parse_expression;
use self::FStringError::*;
use self::StringGroup::*;
// TODO: consolidate these with ParseError
#[derive(Debug, PartialEq)]
pub enum FStringError {
UnclosedLbrace,
UnopenedRbrace,
InvalidExpression,
InvalidConversionFlag,
EmptyExpression,
MismatchedDelimiter,
}
impl From<FStringError> for LalrpopError<Location, Tok, LexicalError> {
fn from(_err: FStringError) -> Self {
lalrpop_util::ParseError::User {
error: LexicalError {
error: LexicalErrorType::StringError,
location: Default::default(),
},
}
}
}
struct FStringParser<'a> {
chars: iter::Peekable<str::Chars<'a>>,
}
impl<'a> FStringParser<'a> {
fn new(source: &'a str) -> Self {
Self {
chars: source.chars().peekable(),
}
}
fn parse_formatted_value(&mut self) -> Result<StringGroup, FStringError> {
let mut expression = String::new();
let mut spec = String::new();
let mut delims = Vec::new();
let mut conversion = None;
while let Some(ch) = self.chars.next() {
match ch {
'!' if delims.is_empty() => {
conversion = Some(match self.chars.next() {
Some('s') => ConversionFlag::Str,
Some('a') => ConversionFlag::Ascii,
Some('r') => ConversionFlag::Repr,
Some(_) => {
return Err(InvalidConversionFlag);
}
None => {
break;
}
})
}
':' if delims.is_empty() => {
while let Some(&next) = self.chars.peek() {
if next != '}' {
spec.push(next);
self.chars.next();
} else {
break;
}
}
}
'(' | '{' | '[' => {
expression.push(ch);
delims.push(ch);
}
')' => {
if delims.pop() != Some('(') {
return Err(MismatchedDelimiter);
}
expression.push(ch);
}
']' => {
if delims.pop() != Some('[') {
return Err(MismatchedDelimiter);
}
expression.push(ch);
}
'}' if !delims.is_empty() => {
if delims.pop() != Some('{') {
return Err(MismatchedDelimiter);
}
expression.push(ch);
}
'}' => {
if expression.is_empty() {
return Err(EmptyExpression);
}
return Ok(FormattedValue {
value: Box::new(
parse_expression(expression.trim()).map_err(|_| InvalidExpression)?,
),
conversion,
spec,
});
}
'"' | '\'' => {
expression.push(ch);
while let Some(next) = self.chars.next() {
expression.push(next);
if next == ch {
break;
}
}
}
_ => {
expression.push(ch);
}
}
}
Err(UnclosedLbrace)
}
fn parse(mut self) -> Result<StringGroup, FStringError> {
let mut content = String::new();
let mut values = vec![];
while let Some(ch) = self.chars.next() {
match ch {
'{' => {
if let Some('{') = self.chars.peek() {
self.chars.next();
content.push('{');
} else {
if !content.is_empty() {
values.push(Constant {
value: mem::replace(&mut content, String::new()),
});
}
values.push(self.parse_formatted_value()?);
}
}
'}' => {
if let Some('}') = self.chars.peek() {
self.chars.next();
content.push('}');
} else {
return Err(UnopenedRbrace);
}
}
_ => {
content.push(ch);
}
}
}
if !content.is_empty() {
values.push(Constant { value: content })
}
Ok(match values.len() {
0 => Constant {
value: String::new(),
},
1 => values.into_iter().next().unwrap(),
_ => Joined { values },
})
}
}
pub fn parse_fstring(source: &str) -> Result<StringGroup, FStringError> {
FStringParser::new(source).parse()
}
#[cfg(test)]
mod tests {
use crate::ast;
use super::*;
fn mk_ident(name: &str) -> ast::Expression {
ast::Expression::Identifier {
name: name.to_owned(),
}
}
#[test]
fn test_parse_fstring() {
let source = String::from("{a}{ b }{{foo}}");
let parse_ast = parse_fstring(&source).unwrap();
assert_eq!(
parse_ast,
Joined {
values: vec![
FormattedValue {
value: Box::new(mk_ident("a")),
conversion: None,
spec: String::new(),
},
FormattedValue {
value: Box::new(mk_ident("b")),
conversion: None,
spec: String::new(),
},
Constant {
value: "{foo}".to_owned()
}
]
}
);
}
#[test]
fn test_parse_empty_fstring() {
assert_eq!(
parse_fstring(""),
Ok(Constant {
value: String::new(),
}),
);
}
#[test]
fn test_parse_invalid_fstring() {
assert_eq!(parse_fstring("{"), Err(UnclosedLbrace));
assert_eq!(parse_fstring("}"), Err(UnopenedRbrace));
assert_eq!(parse_fstring("{class}"), Err(InvalidExpression));
}
}