How to parse POSITION(A IN B)

[yuchaofan13]

This is for PostgreSQL. I can specify:

class Custom(Dialect):
  class Parser(Parser):
          STRICT_CAST = False
  
          FUNCTIONS = {
              **Parser.FUNCTIONS,
              
              "POSITION": lambda args: exp.StrPosition(
                  this=list_get(args, 1),
                  substr=list_get(args, 0),
              ),
    
          }
      
    
  class Generator(Generator):
    TRANSFORMS = {exp.StrPosition: lambda self, e: f"POSITION({self.sql(e, 'substr')} IN {self.sql(e, 'this')})",

But even without this, the parser is fine with POSITION. The problem is the IN token. Because there are no parentheses around 'B', it doesn't work. I am not sure how to modify parse_in() in parser.py to account for this.

[georgesittas]

I think that there are two options here. You can:

1. Leave parse_in as is and create a custom function parser for POSITION, then add it to FUNCTION_PARSERS.
2. Extend the parse_in by adding another case to check if '(' can be matched. If it can't, just parse a single expression.

There are some examples you can follow if you want to do the first one (see latest commits related to trim, substring).