Only first line of a function’s output gets passed through pipe

When you pipe the output of a multi-line function (in a shell script), only the first line’s output goes into the pipe, and the rest goes direct to stdout. This is the second issue I had pointed out in #859. The difference between quoted and unquoted versions of the variable I pointed out earlier was a red herring because echoing an unquoted multi-line variable is supposed to replace the newlines with spaces when being displayed.

Reproduction script:

~~~sh
#! /bin/sh

foo() {
printf "baa "
printf "caa "
printf "daa "
}

foo | tr 'a' 'z'
printf "\n"
~~~

Expected output:

~~~
bzz czz dzz
~~~

a-Shell output:

~~~
caa daa bzz
~~~