The manual says halt_error prints its input with no decoration, not
even a newline, but non-string values such as {"a":"xyz"} were printed
with a trailing newline.
Dump non-string values to JSON and print them the same way as strings,
so {"a":"xyz"} | halt_error(1) now writes exactly {"a":"xyz"} to stderr.
Huang-404-Q
bd56a74562