Rules

The abstract base of all rules is stylist.rule.Rule. Classes derived from this implement an stylist.rule.Rule.examine() method which is passed a stylist.source.SourceText object. This allows the source to be treated as a plain text file.

Rules relating to Fortran source may be found in the stylist.fortran module. An abstract stylist.fortran.FortranRule is provided which requires an stylist.fortran.FortranRule.examine_fortran() method which is passed a stylist.source.FortranSource object. Thus the rule may examine the Fortran parse tree.

Writing a New Text Rule

Just sub-class stylist.rule.Rule and implement the stylist.rule.Rule.examine() method. Use the stylist.source.SourceText.get_text() method on the passed stylist.source.SourceText object to obtain the text of the source file.

The “trailing white space” rule gives an example of using RegEx on the source text. Meanwhile the “Fortran characterset” rule shows a more elaborate text rule which implements a state-machine to test validity.

Writing a Fortran Rule

An abstract stylist.rule.FortranRule is provided, any new rule should inherit from this and implement the stlist.rule.FortranRule.examine_fortran() method. Use the stylist.source.FortranSource.get_tree() method to obtain an fparser2 parse tree.

The stylist.source.FortranSource class also provides some methods for traversing the parse tree. It is expected that this functionality will eventually become available through fparser2 and so will be removed from stylist.

Documenting the Rule

Don’t forget to add your new rule to the user documentation. This is a slightly clunky process involving adding some boilerplate to documentation/source/user-manual/rule-list.rst.