Rudder

When we use an optionnal fields in Technique, there are two differents behaviour that are confusing :

1. if there is only one value for this field, and it is empty, the generated value is a "null" (nothing)
2. if there are several values for this fields, all the empty values are replaced by "" (empty string)

This lead to unexpected behaviour, as both are clearly different

We should clarify this behaviour, surely by having one "optional" field that replaced empty value by "" , and on that is replaced by null and that can't be multivalued

Under is a technical details of what happen on the technique generatin side
Using the same parameters than the files:

• EnforceFileContentExpandVarBug1.png
• EnforceFileContentExpandVarBug2.png

It will lead to a CFEngine promise generated without variable generic_file_content_modification_destination:

debian-5-64:~# grep 'generic_file_content_modification_destination' /var/rudder/cfengine-community/inputs/checkGenericFileContent/3.0/checkGenericFileContent.cf 
            "replacement_dest_defined_$(index)"  expression => isvariable("generic_file_content_modification_destination[$(index)]");
                    edit_line => set_arbitrary_file_content_modify("$(generic_file_content_modification_regexp[$(index)])", "$(generic_file_content_modification_destination[$(index)])"),

Adding a new Directive with the same parameters than the files:

• EnforceFileContentExpandVarBug1.png
• EnforceFileContentExpandVarBug1.png

debian-5-64:~# grep 'generic_file_content_modification_destination' /var/rudder/cfengine-community/inputs/checkGenericFileContent/3.0/checkGenericFileContent.cf 
            "generic_file_content_modification_destination[1]" string => "";
            "generic_file_content_modification_destination[2]" string => "";
            "replacement_dest_defined_$(index)"  expression => isvariable("generic_file_content_modification_destination[$(index)]");
                    edit_line => set_arbitrary_file_content_modify("$(generic_file_content_modification_regexp[$(index)])", "$(generic_file_content_modification_destination[$(index)])"),

It seems that this is linked to the application instead of the Techniques (#2819).