Environment: Ubuntu 20.04, uutils main branch (git commit 1e8e16b), GNU coreutils v8.30

Steps to reproduce:

printf "a\nb\n" | tsort

What happens now: uutils tsort terminates with an error message:

tsort: -: input contains an odd number of tokens

What I expected to happen: GNU tsort treats the pair (a, b) as an edge in the graph:

a
b

Notes: I think this is an instance where the GNU documentation could have been clearer. info tsort says, "‘tsort’ reads its input as pairs of strings, separated by blanks, indicating a partial ordering." I think the "separated by blanks" means "any whitespace".