Refuses an unquoted pipe inside a list, set, or map

All 3 scenarios hold

These rules cover how one line divides into fields. They apply before the parser reads a field as a value.

Each Row below is parsed as the only data row under a one-column header. Fields shows the captured field list, printed back out. Fields is text rather than a list column because a list cannot hold a null element: writing [a, , c] is itself a parse error. A null field is what several of these rules are about.

Brackets and braces do not protect a pipe. Only quotes do.

The pipe splits the row inside the collection and leaves an unbalanced fragment. The parser therefore names the whole row, not the pipe. To keep a pipe inside a collection, quote the element: ['a | b'].