Scripting Refactoring — Overthrowing the GUI (part 3)

This post was imported from blogger, to see the original, likely better-formatted post see kalebpederson.blogspot.com.

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I’ve already mentioned why it might be useful to perform refactorings in bulk. Perhaps we’ve decided we followed a poor naming convention, or perhaps we’ve moved some classes into their own namespace, so part of the class name is redundant and can be removed.

Another point of textual element identification is to remove the necessity of the GUI. Take, for example, Emacs and Vim. Both are very capable editors and and lack (to the best of my knowledge) complete and capable refactoring support. But, if an element can be identified in text, either through line and column information, or through an element reference, the editors like Vim, Emacs, and Textmate could have macros written for them that call out to a command line refactoring engine.

Two Syntaxes for Scripting Refactoring

Each refactoring could look like a function call as in the following:

rename(OldNamespace::OldClass, NewNamespace::NewClass);

In the above case, the rename refactoring takes in two different ElementReference parameters. In order to perform many rename refactorings, we’d end up with a list of the above:

rename(OldNamespace::FirstClass, NewNamespace::FirstClass);
rename(OldClass, NewClass);
rename(OldClass::oldMethod, OldClass::newMethod);
rename(globalFunction, newGlobalFunction);
//...

Although the above is unreadable, it seemed a little repetitive, so I went with a block structure that allowed the refactoring to be specified once, with a list of parameter sequences:

rename {
// support named parameters
// and type restriction after name specifier
oldName = SomeNamespace{namespace}::/(.*)ElementName/,
newName = SomeNamespace::\1Node;

// type restriction within regular expression
/SomeClass{class}::get(.*)Node/,
SomeClass::\1Node;

::memset, ::customMemSet;
}

The block syntax above isn’t as repetitive as the first example. To help the case where an editor would invoke the refactoring, line and column information could be used to identify elements as well.

Conclusion

Although the above is a new syntax, it’s built on many different syntaxes that are common to languages. It uses a block syntax for overall structure. Named parameters are supported in many different dynamic languages. It supports regular expressions for matching and backreferences for substitutions. It also has C++ and Java style comments and uses the sometimes-despised semicolon as a terminator.

Yeah, some people aren’t going to like the syntax and may avoid it like the plague. But, arguably, there are some very good reasons to to make refactorings scriptable to the average programmer, among which are the easy interface it would provide to editors and the ability to doing certain refactorings in bulk.

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