Dynamically define cfengine class functions

[basvandervlies]

I have asked this question in the newsgroup, maybe I missed the answer!

I want to use the cfengine class functions dynamically. I will try to explain it, eg:

"class_set" expression => isdir("/etc"); 

But in the example above the isdir("/etc") is a variable defined in a json file

"class_set" expression => $(def.class_func)

also tried:

reports:
  "It works"
      if => or( $def.class_func );

Is this possible?

[olehermanse]

@basvandervlies

The only way I can think of is to render a policy file, from a template, with the correct function call(s).

We could consider adding another function:

"class_set" expression => call_function("isdir", "/etc");

What do you think about that idea?

[basvandervlies]

@olehermanse and when a function has multuiple args? eg: classmatch(regex, tag1, tag2, ...)
I was more just pass the fucntion string to the call_function, eg:

• "class_set" expression => call_function('isdir("/etc")');

Or is the above syntax problematic?

[olehermanse]

@basvandervlies It could be done, but it does introduce more complexity, as you have to parse CFEngine syntax inside that string. Parsing is always difficult and adds complexity, i.e.:

"class_set" expression => call_function('isdir()');
"class_set" expression => call_function('isdir("")');
"class_set" expression => call_function('isdir(blah)');
"class_set" expression => call_function('isdir("blah")');
"class_set" expression => call_function('isdir(`blah`)');
"class_set" expression => call_function('isdir(${myvar})');
"class_set" expression => call_function('isdir("${myvar}")');
"class_set" expression => call_function('is${funcname}()');
"class_set" expression => call_function('string_replace(isdir("/etc"), "any", "yes"');

It also adds a lot of quoting inside of quoted strings, have to be careful with alternating types of quots or escape sequences.

etc.

[olehermanse]

@basvanderlies I would make call_function take n arguments, where the last n-1 of them are sent to the called function.