overleaf/services/web/frontend/js/features/source-editor/lezer-bibtex/bibtex.grammar

@top Bibliography {
  (Declaration | StringDeclaration)*
}

@tokens {
  whiteSpace { @whitespace+ }
  Identifier { $[a-zA-Z:_0-9-]+ }
  StringName { $[a-zA-Z:_] $[a-zA-Z:_0-9-]* }
  FieldName {$[a-zA-Z-_0-9]+}
  LiteralString {
    '"' (!["] | "\\" _)* '"'?
  }
  EntryTypeName { $[a-zA-Z]+ }
  Number { @digit+ }
  StringKeyword {"@"$[Ss]$[Tt]$[Rr]$[Ii]$[Nn]$[Gg]}
  "{"[closedBy="}"]
  "}"[openedBy="{"]
  "@" "\"" "," "#" "@string"
  Comment { "%" ![\n]* }
}

// FIXME: Technically skipping comments is wrong here. They can only appear
//        alone on a line, but I'm not sure how to express that easily in Lezer
@skip {whiteSpace | Comment}

StringDeclaration {
  StringKeyword "{"
      Field<StringName>*
  "}"
}

Declaration {
  EntryName { "@" EntryTypeName }  "{"
      Identifier
      
      fieldEntry { 
        (","  Field<FieldName> )
      }*
      ("," )?
  "}"
}

Field<Name> {
  Name  "="  Expression
}

Expression {
  BracedString |
  Number | 
  StringConcatenation
}

@local tokens {
  OpenBracedContents[closedBy="}", @name="{"] {"{"}
  CloseBracedContents[openedBy="{", @name="}"] {"}"}
  @else nonClosingBracedContents
}

@skip {}{
  BracedStringContents {
  (
      nonClosingBracedContents |
      nestedBracedString {
        OpenBracedContents
        BracedStringContents
        CloseBracedContents
      }
    )*
}
  BracedString {
    "{" BracedStringContents CloseBracedContents
  }  
}

@precedence { concatenation @left }

StringConcatenation {
  StringConcatenation !concatenation "#" StringConcatenation |
  LiteralString |
  StringName
}

@external propSource highlighting from "./highlight.mjs"