The empty_stack() function collects the names of empty values. Its primary job is identifying headers without values. However, it can also check on variables.

empty_stack() without arguments scans all the headers for values and creates a stack of the names of any that are empty. You can provide any number of arguments to empty_stack() to narrow its search down to just those values, both headers and variables.

    $file.csv[*][
        push("empties", empty_stack())
        last() -> var_table("empties")
    ]

This csvpath creates an empties variable that is a stack of stacks. Each item in the empties stack represents the empty headers in a line. The result might look like:

┌───────────────────────────┐ │ empties │ ├───────────────────────────┤ │ ['firstname', 'lastname'] │ ├───────────────────────────┤ │ ['firstname'] │ ├───────────────────────────┤ │ ['lastname'] │ ├───────────────────────────┤ │ [] │ └───────────────────────────┘