Whitespace are not skipped when parsing a rule inside a quoted string escape sequence

[natinusala]

Hello,

I'm trying to reproduce the string interpolation syntax from Swift: let message = "Hello \(name)!" using Lexy.

I was able to make it work with a backslash escape rule, with a parenthesized expression inside. It works fine except that whitespace skipping doesn't seem to be enabled back when parsing the expression rule.

I made this minimal reproduction project: https://lexy.foonathan.net/playground/?id=z5er56W1j&mode=trace

This parses fine:

{
    20 + 20
    "test string \(20+20)"
}

But this does not (with spaces around the second +):

{
    20 + 20
    "test string \(20 + 20)"
}

It says "expected )" right after the first 20, before the +.

Why is that? Is there something I need to do to explicitely re-enable whitespace skipping while inside the escape rule? Or is that not something that's expected to work?

[natinusala]

I notice that this issue isn't always present - for example this works:

"\("John") has \(bananas) bananas and \(apples) apples, making a total of \(bananas + apples) fruits"

But this does not:

"'\("I have \(bananas + apples) fruits")' is what I would say if I had \(bananas + apples) fruits"

However this does:

"'\("I have \(bananas+apples) fruits")' is what I would say if I had \(bananas + apples) fruits"

The first + cannot have spaces (probably because it's nested?) but the second can.

[foonathan]

Sorry for the delay. This was in fact a bug in dsl::no_whitespace, it is fixed now, and whitespace should work intuitively.

[natinusala]

No worries! I was able to work around this by manually skipping whitespaces. Thanks for the fix!