How can I detect in m4 template whether define/variable is empty while it also can contain commas? It's passed through m4 arguments, so it can contain any value.
Problem is that when I write the ifelse condition without putting the variable inside quotes, it works, but when the var contains commas, it breaks the template. If I put it inside quotes, empty string won't get detected.
Example #1:
File template.m4:
ifelse(`_VAR_', `', `empty; "_VAR_"', `non-empty; "_VAR_"')
Results:
$ m4 -D _VAR_=text template.m4
non-empty; "text"
$ m4 -D _VAR_="a, a, INJECTED" template.m4
non-empty; "a, a, INJECTED"
These are ok.
$ m4 -D _VAR_= template.m4
non-empty; ""
$ m4 -D _VAR_="" template.m4
non-empty; ""
Problem, expected: empty; "" (in both cases).
Example #2:
File template.m4:
ifelse(_VAR_, `', `empty; "_VAR_"', `non-empty; "_VAR_"')
Results:
$ m4 -D _VAR_=test template.m4
non-empty; "test"
$ m4 -D _VAR_= template.m4
empty; ""
$ m4 -D _VAR_="" template.m4
empty; ""
These are ok.
$ m4 -D _VAR_="a, a, INJECTED" template.m4
INJECTED
Wasn't handled correctly, expected: non-empty; "a, a, INJECTED"
My environment
I think the following will be your desire:
ifelse(defn(`_VAR_'),`',`empty',`non empty: _VAR_')