Vars not set when sourcing w/ abs path, set -a

[Van Klaveren, Brian N.]

Configuration Information [Automatically generated, do not change]:
Machine: x86_64
OS: linux-gnu
Compiler: gcc
Compilation CFLAGS: -g -O2 -fdebug-prefix-map=/build/bash-2bxm7h/bash-5.0=. 
-fstack-protector-strong -Wformat -Werror=format-security -Wall 
-Wno-parentheses -Wno-format-security
uname output: Linux 339aad08626d 5.10.25-linuxkit #1 SMP Tue Mar 23 09:27:39 
UTC 2021 x86_64 GNU/Linux
Machine Type: x86_64-pc-linux-gnu

Bash Version: 5.0
Patch Level: 3
Release Status: release

Description:
Sourcing a script with `set -a` at the end fails and an absolute path fails to 
set variables
the first time it is executed. 

Repeat-By:
I ran this in a debian docker container to reduce as many variables as possible.

$ docker run -it --rm debian:latest
root@339aad08626d:/# adduser --disabled-password -gecos "" bash-test
Adding user `bash-test' ...
Adding new group `bash-test' (1000) ...
Adding new user `bash-test' (1000) with group `bash-test' ...
Creating home directory `/home/bash-test' ...
Copying files from `/etc/skel' ...
root@339aad08626d:/# su -l bash-test
bash-test@339aad08626d:~$ echo -e '#!/bin/bash\nFOO=bar\nset -a\nenv | grep 
FOO' > sourceme
bash-test@339aad08626d:~$ . /home/bash-test/sourceme
bash-test@339aad08626d:~$ . /home/bash-test/sourceme
FOO=bar

It reproduces in centos:7 container as well. I did not see it in ancient macOS 
bash.

[root@227f958499c1 /]# adduser bash-test 
[root@227f958499c1 /]# su -l bash-test
[bash-test@227f958499c1 ~]$ echo -e '#!/bin/bash\nFOO=bar\nFOO=bar2\nset 
-a\nenv | grep FOO' > sourceme
[bash-test@227f958499c1 ~]$ cat sourceme
#!/bin/bash
FOO=bar
FOO=bar2
set -a
env | grep FOO
[bash-test@227f958499c1 ~]$ . /home/bash-test/sourceme
[bash-test@227f958499c1 ~]$ . /home/bash-test/sourceme
FOO=bar2

It is the same for explicitly using "source":

[root@2ff7740a55e9 /]# adduser bash-test
[root@2ff7740a55e9 /]# su -l bash-test
[bash-test@2ff7740a55e9 ~]$ echo -e '#!/bin/bash\nFOO=bar\nFOO=bar2\nset 
-a\nenv | grep FOO' > sourceme
[bash-test@2ff7740a55e9 ~]$ 
[bash-test@2ff7740a55e9 ~]$ cat sourceme
#!/bin/bash
FOO=bar
FOO=bar2
set -a
env | grep FOO
[bash-test@2ff7740a55e9 ~]$ cat sourceme
#!/bin/bash
FOO=bar
FOO=bar2
set -a
env | grep FOO
[bash-test@2ff7740a55e9 ~]$ source /home/bash-test/sourceme
[bash-test@2ff7740a55e9 ~]$ source /home/bash-test/sourceme
FOO=bar2