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refactor(ra_syntax.validation): removed code duplication from validate_literal() #2834

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Jan 14, 2020
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refactor(ra_syntax.validation): removed code duplication from validate_literal() #2834

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61 changes: 26 additions & 35 deletions crates/ra_syntax/src/validation.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -111,55 +111,46 @@ pub(crate) fn validate(root: &SyntaxNode) -> Vec<SyntaxError> {
errors
}

// FIXME: kill duplication
fn validate_literal(literal: ast::Literal, acc: &mut Vec<SyntaxError>) {
fn unquote(text: &str, prefix_len: usize, end_delimiter: char) -> Option<&str> {
text.rfind(end_delimiter).and_then(|end| text.get(prefix_len..end))
}
Comment on lines +115 to +117
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It might be nice to pull this one out of the function, so it's ready for re-use when we get to #540 at some point :)

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@Veetaha Veetaha Jan 14, 2020 •
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@matklad, @kiljacken I have one concern about this function. Why is it so that we do a linear search for the quote character backwards in the token text string but make a constant offset from its beginning instead?
I guess we should either do a constant offset from the begging and the end of the string or search for a quote character from both ends of the string but not the mixed approach...

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I'd have to check the lexer source to be sure, bit using a constant offset, for everything that's not a raw string (due to the hash matching) should be good

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@kiljacken I do think that constant offset from both ends should be viable too.
Though, I'd like to write tests for this.
Yes, raw strings should have a separate unquote_raw_string() logic.

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I've checked the supposition that the offset from the end of the string is constant.
If fact it is not (maybe it is a bug, I am not sure).
But there is one test that fails when I put a debug assertion to check the precondition about that, which is this one:
https://github.com/rust-analyzer/rust-analyzer/blob/master/crates/ra_assists/src/assists/raw_string.rs#L245

That partial string actually becomes a STRING token where there is only one starting qoute and no ending one

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@matklad maybe you could clarify on whether this behaviour is intended?

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@Veetaha it's true that string literals are not guaranteed to be syntactically valid. The code should not panic for any string, but it doesn't have to report errors if the string itself is not a valid string literal.

This is because we intentionally make the parser and the lexer robust and capable of parsing completely invalid code, so something like r##" might be parsed as a raw string literal.


let token = literal.token();
let text = token.text().as_str();

let mut push_err = |prefix_len, (off, err): (usize, unescape::EscapeError)| {
let off = token.text_range().start() + TextUnit::from_usize(off + prefix_len);
acc.push(SyntaxError::new(err.into(), off));
};
Comment on lines +122 to +125
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Not really a big fan of this, but see my comments below for a possible solution.


match token.kind() {
BYTE => {
if let Some(end) = text.rfind('\'') {
if let Some(without_quotes) = text.get(2..end) {
if let Err((off, err)) = unescape::unescape_byte(without_quotes) {
let off = token.text_range().start() + TextUnit::from_usize(off + 2);
acc.push(SyntaxError::new(err.into(), off))
}
}
if let Some(Err(e)) = unquote(text, 2, '\'').map(unescape::unescape_byte) {
push_err(2, e);
}
Comment on lines +129 to 131
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@kiljacken kiljacken Jan 14, 2020 •
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This is quite good already, but would it make sense to pull it out into a seperate function:

fn validate_char(token: &SyntaxToken, prefix_len: usize, end_delimiter: char, acc: &mut Vec<SyntaxError>) -> {
    let text = token.text().as_str();
    if let Some(Err(e)) = unquote(text, 2, '\'').map(unescape::unescape_byte) {
        let off = token.text_range().start() + TextUnit::from_usize(off + prefix_len);
        acc.push(SyntaxError::new(err.into(), off));
    }
}

and then the match case just becomes:

BYTE => validate_char(&token, 2, '\'', acc),

This would avoid the the push_err lambda, and it would play nicely with #540.

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Yeah, only one addition, unescape::unescape_byte() should also be forwarded as a callback function to validate_char() this way the function will become generic and will have 5 parameters. If you are okay with that, tho?

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Right, hadn't noticed they used different functions, but that makes sense :) This might require a type parameter for the function, are you comfortable with that or do you need a hint?

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Yes, I am comfortable with that, just wanted our approval)

}
CHAR => {
if let Some(end) = text.rfind('\'') {
if let Some(without_quotes) = text.get(1..end) {
if let Err((off, err)) = unescape::unescape_char(without_quotes) {
let off = token.text_range().start() + TextUnit::from_usize(off + 1);
acc.push(SyntaxError::new(err.into(), off))
}
}
if let Some(Err(e)) = unquote(text, 1, '\'').map(unescape::unescape_char) {
push_err(1, e);
}
}
BYTE_STRING => {
if let Some(end) = text.rfind('\"') {
if let Some(without_quotes) = text.get(2..end) {
unescape::unescape_byte_str(without_quotes, &mut |range, char| {
if let Err(err) = char {
let off = range.start;
let off = token.text_range().start() + TextUnit::from_usize(off + 2);
acc.push(SyntaxError::new(err.into(), off))
}
})
}
if let Some(without_quotes) = unquote(text, 2, '"') {
unescape::unescape_byte_str(without_quotes, &mut |range, char| {
if let Err(err) = char {
push_err(2, (range.start, err));
}
})
Comment on lines +139 to +144
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We could do the same here as described for char, e.g. pull into a separate function. I think that would be nice :)

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@Veetaha Veetaha Jan 14, 2020 •
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I've stumbled upon a language limitation here.
Since here we would have a second level higher order function
something like

fn validate_byte_or_char_str_literal(..., impl FnOnce(&str, impl FnMut(...))) {}

Notice the nested impl FnMut(...)

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@Veetaha Veetaha Jan 15, 2020 •
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It would be quite a hack to do it with a dynamic dispatch here.
unescape::unescape_str(&str, impl FnMut(Range<usize>, Result<u8, EscapeError>))
This function expects the second argument (callback) to be Sized.
This means we would end up with the following hack:

fn validate_str_or_byte_str_literal<T>(
    token: &SyntaxToken,
    prefix_len: usize,
    suffix_len: usize,
    acc: &mut Vec<SyntaxError>,
    unescape_fn: impl FnOnce(&str, &mut dyn FnMut(Range<usize>, Result<T, unescape::EscapeError>)),
) {
    let text = token.text().as_str();
    if let Some(without_quotes) = unquote(text, prefix_len, suffix_len) {
        unescape_fn(without_quotes, &mut |range, char| {
            if let Err(err) = char {
                let off = token.text_range().start() + TextUnit::from_usize(range.start + prefix_len);
                acc.push(SyntaxError::new(err.into(), off));
            }
        });
    }
}


validate_str_or_byte_str_literal(
    &token,
    2,
    1,
    acc,
    // we need to explicitly wrap this into two lambdas because cb is `&mut dyn FnMut(...)`
    |s, cb| unescape::unescape_byte_str(s, &mut |range, byte| cb(range, byte)),
);

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I've been unable make the above function reasonable, e.g. less lines of code than what it replaces, so lets just keep it at de-duplicating char and byte for now.

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@Veetaha Veetaha Jan 15, 2020 •
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Same opinion here 😏

}
}
STRING => {
if let Some(end) = text.rfind('\"') {
if let Some(without_quotes) = text.get(1..end) {
unescape::unescape_str(without_quotes, &mut |range, char| {
if let Err(err) = char {
let off = range.start;
let off = token.text_range().start() + TextUnit::from_usize(off + 1);
acc.push(SyntaxError::new(err.into(), off))
}
})
}
if let Some(without_quotes) = unquote(text, 1, '"') {
unescape::unescape_str(without_quotes, &mut |range, char| {
if let Err(err) = char {
push_err(1, (range.start, err));
}
})
}
}
_ => (),
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