find all references – Rubberduck News

This post is the fourth in a series of post that walk you through the various features of the Rubberduck open-source VBE add-in.

Part 1 introduced the navigation features.
Part 2 covered the code inspections.
Part 3 featured the unit testing feature.

Refactorings

At first we were happy to just be able to inspect the code.

Quickly we realized “inspection quick-fixes” could be something else; some of the inspections’ quick-fixes are full-fledged automated refactoring operations. Renaming an identifier – and doing it right – is very different than just Ctrl+H/replace an identifier. Manually removing an uneeded parameter in an existing method breaks all call sites and the code no longer even compiles; Rubberduck sees all call sites, and knows which argument to remove everywhere to keep the code compiling.. and it’s much faster than doing it by hand!

Rubberduck 1.3 had Rename and Extract Method refactorings; v1.4.3 also had Remove Parameters and Reorder Parameters refactorings.

Rubberduck 2.0 introduces a few more.

The context menu commands are enabled depending on context; be it the current parser state, or the current selection.

Rename

That’s a pretty well-named refactoring. It deals with the impacts on the rest of the code base, of renaming pretty much any identifier.

Extract Method

Pretty much completely rewritten, v2.0 Extract Method refactoring is becoming pretty solid. Make a valid selection, and take that selection into its own member, replacing it with a call to the extracted code, all parameters and locals figured out for you.

Extract Interface

VBA supports interface inheritance; Rubberduck makes it easy to pull all public members of a module into a class that the original module then Implements. This is VBA’s own way of coding against abstractions. Unit tests love testing code that’s depending on abstractions, not concrete implementations, because then the tests can provide (“inject”) fake dependencies and test the applicative logic without triggering any unwanted side-effects, like displaying a message box, writing to a file, or to a database.

Implement Interface

Implementing all members of an interface (and all members of an interface must be implemented) can be tedious; Rubberduck automatically creates a stub method for every member of the interface specified in an Implements statement.

Remove/Reorder Parameters

Reworking a member’s signature is always annoying, because then you have to cycle through every single call site and update the argument list; Rubberduck knows where every call site is, and updates all call sites for you.

Move Closer to Usage

Variables should have the smallest possible scope. The “scope too wide” inspection uses this refactoring to move a declaration just above its first usage; it also works to rearrange “walls of declarations” at the top of a huge method you’re trying to cut into more manageable pieces.

Encapsulate Field

Fields are internal data, implementation details; objects shouldn’t expose public fields, but rather, encapsulate them and expose them as properties. Rubberduck turns a field into a property with only as much effort as it takes to name the new property.

Introduce Parameter/Field

Pretty much the antagonist of move closer to usage, this refactoring promotes a local variable to a parameter or a field, or a parameter to a field; if a new parameter is created, call sites will be updated with a “TODO” bogus argument that leaves the code uncompilable until an argument is supplied for the new parameter at all call sites.

More refactorings are planned for 2.1 and future versions, including Inline Method (the inverse of Extract Method), to move the body of a small procedure or function into all its call sites. Ideas for more refactorings and inspections? Suggest a feature!

The wait is over!

I have to say that this release has been… exhausting. Correctly resolving identifier references has proven to be much, much more complicated than I had originally anticipated. VBA has multiple ways of making this hard: with blocks are but one example; user-defined-type fields are but another.

But it’s done. And as far as I could tell, it works.

Why did you tag it as “pre-release” then?

Because resolving identifier references in VBA is hard, and what I released is not without issues; it’s not perfect and still needs some work, but I believe most normal use cases are covered.

For example, this code will blow up with a wonderful StackOverflowException:

Class1

Public Function Foo() As Class2
    Set Foo = New Class2
End Function

Class2

Public Sub Foo()
End Sub

ThisWorkbook

Public Sub DoSomething()
    Dim Foo As New Class1
    With Foo
            .Foo
    End With
End Sub

It compiles, VBA resolves it. And it’s fiendish, and nobody in their right minds would do anything near as ambiguous as that. But it’s legal, and it blows up.

That’s why I tagged it as a “pre-release”: because there are a number of hair-pulling edge cases that just didn’t want to cooperate.

See, finding all references to “foobar” works very well here:

Public Sub DoSomething()
    Dim foobar As New Class1
    With foobar
        With .Foo
            .Bar
        End With
    End With
End Sub

…and finding all references to “Foo” in the below code will not blow up, but the “.Foo” in the 2nd with block resolves as a reference to the local variable “Foo”:

Public Sub DoSomething()
    Dim Foo As New Class1
    With Foo
        With .Foo
            .Bar
        End With
    End With
End Sub

And of course, there are a number of other issues still.

Here’s a non-exhaustive list of relatively minor known issues we’re postponing to 1.31 or other future release – please don’t hesitate to submit a new issue if you find anything that doesn’t work as you’d expect.

There can be only one

Rubberduck doesn’t [yet] handle cross-project references; while all opened VBA projects are parsed and navigatable, they’re all “silos”, as project references aren’t taken into account; this means if project A is referencing project B, and project A contains the only usage of a procedure defined in project B, then that procedure will fire up a code inspection saying the procedure is never used.

It also means “find all references” and “rename” will miss it.

self-referencing Parameters

“Find all references” has been seen listing the declaration of a parameter in its list of references. Not a biggie, but not intended either. There’s no explanation for that one, yet – in fact it’s possible you never even encounter this issue.

Selection Glitches From Code Inspection Results

We know what causes it: the length of the selection is that of the last word/token in the parser context associated with the inspection result. That’s like 80% fixed! Now the other 80% is a little bit tricky…

Performance

Code inspections were meant to get faster. They got more accurate instead. This needs a tune-up. You can speed up inspections by turning off the most expensive ones… although these are often the most useful ones, too.

Function return vAlue not assigned

There has been instances of [hard-to-repro] object-typed property getters that fire up an inspection result, when they shouldn’t. Interestingly this behavior hasn’t been reproduced in smaller projects. This inspection is important because a function (or property getter) that’s not assigned, will not return anything – and that’s more than likely a bug waiting to be discovered.

Parameter can be passed by value

This inspection is meant to indicate that a ByRef parameter is not assigned a value, and could safely be passed ByVal. However if such a parameter is passed to another procedure as a ByRef parameter, Rubberduck should assume that the parameter is assigned. That bit is not yet implemented, so that inspection result should be taken with a grain of salt (like all code inspection results in any static code analysis tool anyway).

This inspection will not fire up a result if the parameter isn’t a primitive type, for performance reason (VBA performance); if performance is critical for your VBA code, passing parameters by reference may yield better results.

Tag: find all references

VBA Rubberducking (Part 4)