Is this a bug or not? String concatenation of backtick command substitution generating extra argument splits

[unphased]

This code:

echo 'TESTING!' 'abc'$(pwd)"def"
echo 'TESTING2!' 'abc'`pwd`"def"
echo 'TESTING3!' 'abc'"$(pwd)""def"
echo 'TESTING4!' 'abc'"`pwd`""def"

Parses out to (this is a copy of TSPlayground output):

command [96, 0] - [96, 32]
  name: command_name [96, 0] - [96, 4]
    word [96, 0] - [96, 4]
  argument: raw_string [96, 5] - [96, 15]
  argument: concatenation [96, 16] - [96, 32]
    raw_string [96, 16] - [96, 21]
    command_substitution [96, 21] - [96, 27]
      command [96, 23] - [96, 26]
        name: command_name [96, 23] - [96, 26]
          word [96, 23] - [96, 26]
    string [96, 27] - [96, 32]
      string_content [96, 28] - [96, 31]
command [97, 0] - [97, 32]
  name: command_name [97, 0] - [97, 4]
    word [97, 0] - [97, 4]
  argument: raw_string [97, 5] - [97, 16]
  argument: raw_string [97, 17] - [97, 22]
  argument: concatenation [97, 22] - [97, 32]
    command_substitution [97, 22] - [97, 27]
      command [97, 23] - [97, 26]
        name: command_name [97, 23] - [97, 26]
          word [97, 23] - [97, 26]
    string [97, 27] - [97, 32]
      string_content [97, 28] - [97, 31]
command [98, 0] - [98, 34]
  name: command_name [98, 0] - [98, 4]
    word [98, 0] - [98, 4]
  argument: raw_string [98, 5] - [98, 15]
  argument: concatenation [98, 16] - [98, 34]
    raw_string [98, 16] - [98, 21]
    string [98, 21] - [98, 29]
      command_substitution [98, 22] - [98, 28]
        command [98, 24] - [98, 27]
          name: command_name [98, 24] - [98, 27]
            word [98, 24] - [98, 27]
    string [98, 29] - [98, 34]
      string_content [98, 30] - [98, 33]
command [99, 0] - [99, 34]
  name: command_name [99, 0] - [99, 4]
    word [99, 0] - [99, 4]
  argument: raw_string [99, 5] - [99, 16]
  argument: concatenation [99, 17] - [99, 34]
    raw_string [99, 17] - [99, 22]
    string [99, 22] - [99, 29]
      command_substitution [99, 23] - [99, 28]
        command [99, 24] - [99, 27]
          name: command_name [99, 24] - [99, 27]
            word [99, 24] - [99, 27]
    string [99, 29] - [99, 34]
      string_content [99, 30] - [99, 33]

I think it's clear that the whole "abc$(pwd)def" string should be a SINGLE argument in all cases. It is not working properly to generate it as a single argument (as a "concatenation" node) in the second case where backticks are used (without double quotes) to generate the command substitution. Note it is the only one that treesitter is parsing out to three arguments instead of the expected two.

---

I use this bash script to confirm the argument parsing that bash performs:

#!/bin/bash
 
ITERATION=1
while (( "$#" )); do 
  echo '$'"${ITERATION}: ${1}"
  shift
  (( ITERATION ++ ))
done

When replacing the echos with argshow above the output is as expected

$1: TESTING!
$2: abc/Users/sludef
$1: TESTING2!
$2: abc/Users/sludef
$1: TESTING3!
$2: abc/Users/sludef
$1: TESTING4!
$2: abc/Users/sludef

---

I was considering doing something in my tool built on top of tree-sitter to auto-enumerate arguments and this is one wrinkle that would make it potentially incorrect. 😀