Zsh export ignoring quotes and backslashes - shell

Question

I have a shell script (let's call it produce.sh) which outputs data in the following form, but does not save it to a file:
FOO=value
BAR=value2
ZAP=value3
I'd like to use these values as environment variables in a shell script. I'm currently doing this using the following shell code:
export $(./produce.sh)
This works great, except when the values to the right of the = contain spaces. For instance:
FOO=split value
I've tried two different approaches in produce.sh:
Wrapping the values in quotes (FOO="split value")
Escaping whitespace with backslashes (FOO=split\ value)
Both of these do not work: if I inspect the environment variables, FOO contains "split in the first example and split\ in the second.
How can I get export to handle this correctly?

Answer 1

The f parameter expansion flag in zsh will split an input on newlines, so this should handle input values with whitespace:
export ${(f)"$(./produce.sh)"}
What's happening
The output from produce.sh:
key-value pairs.
each kv pair is on its own line.
key is separated from the value by =.
syntax is shell-like, but not exactly shell syntax, so,
white space and some other characters special to the shell are allowed in the value.
The parts of the substitution:
produce.sh : generates the key-value output, for example: N=V1\nP=V 2\n.
$(...) : command substitution. It is replaced with the output, minus trailing newlines: N=V1\nP=V 2.
"..." : the quotes ensure that the prior result is treated as a single term for the next step.
${(f)...} : expands that single term into multiple scalar values, splitting on newlines due to the (f) flag. The result is effectively 'N=V1' 'P=V 2'.
export : assigns and exports each parameter, acting like export 'N=V1' 'P=V 2'.
Another option
The substitution below adds some other cryptic zsh-isms to create an associative array. This avoids adding arbitrary variables to the consuming shell's
environment:
% ./s2.sh
A=A
B=
C=C C
% typeset -A vals=("${(#s:=:)${(f)"$(./s2.sh)"}}")
% print ${vals[A]}
A
% print ${vals[C]}
C C
A minor tradeoff - this will not work if the value contains an equals, e.g.
D=D=D.

Answer 2

FOO=split value
Does not set a variable to a value containing a space. It temporarily sets FOO to split and runs the command value in an environment where FOO has been set. The overall effect is similar to
(export FOO=split; value)
You can experiment with this by doing a
FOO=split printenv
which will run printenv and show in its output the value of FOO.
To set a variable to a value containing space, you need to escape the space, for instance with
FOO=split\ value
or by using quotes.
For processing this file, you could use eval:
eval export $(./produce.sh)
Of course you should this only if you have full control over what produce.sh is writing to stdout (i.e. don't let any tainted data sneak in), because eval is a potential security hole.
Alternatively, you could modify produce.sh to already produce the export prefix in front of each line, and then do just a
eval $(./produce.sh)