Home page example doesn't work as described

[eugenesvk]

upd: the website Editor should try to pick the semantically top-level rule instead of the first in an alphabetically sorted order, or if it's not possible, at least do this for the example from the homepage

Or maybe the easier option is to just document that the user needs to select the general rule manually

Describe the bug

I was trying out the example from the home page and instead of getting the error mentioned there got a working - alpha: "a"

To Reproduce

1. add the grammar from the home page

alpha = { 'a'..'z' | 'A'..'Z' }
digit = { '0'..'9' }

ident = { (alpha | digit)+ }

ident_list = _{ !digit ~ ident ~ (" " ~ ident)+ }
          // ^
          // ident_list rule is silent (produces no tokens or error reports)

2. paste ab *

Expected behavior

Get the error message

thread 'main' panicked at ' --> 1:1
  |
1 | ab *
  |    ^---
  |
  = expected ident', src/main.rs:12

Actual behavior

Happy parsing outcome - alpha: "a"

Additional context

[tomtau]

@eugenesvk you may need to use the "ident_list" rule (instead of "alpha") -- i.e. select it in the web editor or use Rule::ident_list in your parser Rust code... then you should see the expected behavior.

[eugenesvk]

Oh, I see, so it just doesn't select the most general rule by default, but defaults to the alphabetic sorting

I'm not sure it's possible to generically determine what the top-level rule is, but I think at least for the homepage example the preselection should do the right thing

[tomtau]

Yeah, it's not possible to tell which rule is the top-level one, but perhaps the homepage editor could be pre-filled with that example. @nathanielknight wdyt?

[HoloTheDrunk]

Oh, I see, so it just doesn't select the most general rule by default, but defaults to the alphabetic sorting

Fairly certain it's actually just the one that's at the top, not the first in alphabetical order

[nathanielknight]

@eugenesvk Thanks for the report; I'm sure you're not the only person who's been caught out by this UX issue.

I think adding this as a default example (perhaps with an explanatory comment) would be an improvement.