My old rule does not work anymore with the latest version of arara

Question

I have a rule which worked with the previous version of arara:

!config
# Open the every <filename>.<format> that can be opened
# The default for <filename> is the current file.
# The default for <format> is pdf. 
#
# Sample usage: 
# - if myfile.tex is the current file, all these open myfile.pdf
# % arara: showfile
# % arara: showfile: {format: pdf}
# % arara: showfile: {filename: myfile, format: pdf}
# and both these open myfile.log:
# % arara: showfile: {format: log}
# % arara: showfile: {filename: myfile, format: log}
#
identifier: showfile
name: Display
commands: 
- name: Show file
  command: >
    @{
      prefix = isWindows( [ 'cmd', '/c', 'start' ], [ 'xdg-open' ] );
      view = getBasename(reference) + '.' + format;
      return getCommand(prefix, view);
    }
arguments:
- identifier: format
  flag: >
    @{
        return parameters.format;
    }
  default: pdf

Now, if I try it with prova.tex:

% arara: pdflatex 
% arara: showfile 
% arara: showfile: {format: log}
\documentclass{article}

\begin{document}

My rule does not work anymore

\end{document}

I get the error:

Impossible to find the file "prova.[pdf]"

Answer 1

Version 6.0 introduced a (breaking) change in how arguments values (either default or provided) are passed to the command logic. The rationale behind this change is because we have plans for a safer and easier rule format in the future, and having a proper, explicit type scheme would be very welcome.

You can refer to our CHANGELOG for a complete list of features and fixes in the version 6 series, as well as reading about them in our lovely blog post. :)

Long story short, argument values are handled now as a list of string values, so format, as in

% arara: showfile: { format: pdf }

will be translated as

Variable	Type (version 5)	Type (version 6)	Value (version 5)	Value (version 6)
format	String	List of strings	"pdf"	[ "pdf" ]

We need to update the way this value is handled in the command logic (note: I opted for the .concat method, but using + as in the original rule works exactly the same):

view = getBasename(reference).concat('.').concat(format[0]);

Explanation: we get the first value in the format list (index count starts at zero) and concatenate it as suffix for the view variable, which holds a string value, so

Variable	Value	Type
format	[ "pdf" ]	List of strings
view	"mydoc.pdf"	String

Finally, we change this line from

view = getBasename(reference) + '.' + format;

to

view = getBasename(reference).concat('.').concat(format[0]);

which should do the trick.

The complete and updated showfile.yaml rule:

!config
identifier: showfile
name: Display
commands: 
- name: Show file
  command: >
    @{
      prefix = isWindows( [ 'cmd', '/c', 'start' ], [ 'xdg-open' ] );
      view = getBasename(reference).concat('.').concat(format[0]);
      return getCommand(prefix, view);
    }
arguments:
- identifier: format
  flag: >
    @{
        return parameters.format;
    }
  default: pdf

Hope it helps!