About attributes

A few months ago I wrote about how I envisioned dealing with module and member attributes in the 2.1 cycle:

Annotation/Attributes: fixing these inspection, and the quick-fix that synchronizes annotations with module attributes and vice-versa, will finally expose VB module and member attributes to VBA code panes, using Rubberduck’s annotation syntax.

The idea was to use “magic comments” to annotate a module or a procedure with, for example, this:

'@Description("Does something.")
Public Sub DoSomething()
End Sub

And then since we know there’s a DescriptionAnnotation here for DoSomething, and we also know that there’s no VB_Description attribute for that member because of how we parse VBA code… then we’d issue an inspection result saying “annotations and attributes aren’t synchronized”, and you’d run a quickfix and there you have it, a comment that inserts invisible code.

And, it “works”. But there’s a showstopper here: the VBE itself.

You see the code that’s in the editor is not all the code that’s actually in that file: the VBE is hiding the attributes. So the line positions we get from the VBIDE API aren’t the line positions we’d get from reading the complete code… and this complicates things… rather massively.

We have one parse pass on the exported code to pick up these attributes. Then one parser pass on the in-editor code to build our knowledge of the code as the user sees it.

So we have two ModuleRewriter, each working independently on their own version of the same code. And when the code pane rewriter… rewrites, we run into an annoying VBE quirk I [annoyingly] had already experienced before:

I think that’s a VBE quirk – editing the signature of the method, whether manually or with Rubberduck, tends to obliterate the VB_Attributes (and the shortcut key is a VB_Attribute). — ThunderFrame

We need a “code pane pass” to avoid mangling the code with offset line positions, because the VBE is hiding the attributes.

What’s so important about these attributes anyway? Why bother?

Our resolver needs the critical metadata that’s hidden there. Without them, knowing the actual scope of a declaration is impossible. Nowhere else can we pick up a hint about a VB_PredeclaredId attribute, or VB_Exposed. Besides, Rubberduck knowing about VB_Description attributes has very interesting implications, UX-wise. Even better once we handle line breaks:


The Solution

Of course there’s a solution. We’ve been chatting about this solution for a long time now. There won’t be subclassed code panes. The VBE is literally fighting with everything it’s got, to keep its scrollbars in place and visible – it’s a better idea to pick one’s battles and drop that idea. So instead we’re going to abuse docked toolwindows and put our entire UI in a single such toolwindow – and that includes the current toolwindows/panels, …as well as the code panes client area.

Once we have our very own code pane user control, what happens in it is under our complete supervision, and we’re free to intervene at any point in the process of code being modified, in any conceivable way.

So the idea would be to bring the attributes themselves into the code panes (optionally hidden), and shave off an entire parser pass just like that. This pretty much makes the whole annotation+inspection+quickfix combo rather useless.

So instead of pursuing a lost cause, I’ve decided to drop my work on getting attributes to synchronize with annotations, and get on with the other 2.1 cycle targets: the attributes problem will just solve itself when we get there.

In the meantime I’d recommend to disable the MissingAnnotation and MissingAttribute inspections. Not that the inspections themselves are harmful, but the SynchronizeModuleAttributes quickfix is: that quickfix is being decommissioned.

There is no worksheet.

Your VBA project is embedded in an Excel workbook. It references the VBA standard library; it references the library that exposes the host application’s (i.e. in this case, Excel’s) object model; it includes global-scope objects of types that are declared in these libraries – like Sheet1 (an Excel.Worksheet instance) and ThisWorkbook (an Excel.Workbook instance). These free, global-scope objects are right here to take and run with.

You’re free to use them, wisely.

True, they’re global – they can be accessed from anywhere in the code.
They can… and that doesn’t mean they should.

And if you’re willing to do whatever it takes to abstract away the host application’s object model in your “business logic”, then you can isolate your logic from the worksheet boilerplate and write pretty much the same code you’d be writing in, say, VB.NET… or any other object-oriented language for that matter.


Abstracting Worksheets

There is no worksheet. There is data. Data going in, data going out: data is all it is. When the data is coming from a database, many programmers immediately say “I know! Let’s implement a repository pattern!“, or otherwise come up with various ways to abstract away the data-handling boilerplate. If you think of worksheets as data, then it’s not any different, really.

So we shall treat worksheets as such: data. What do we need to do with this data?

Some tried to make worksheets Implements interfaces, and ran into issues (here too, and oh another). I completely agree with this post, which basically boils down to don’t.

Whatever you do, don’t make worksheets implement an interface.

Wrap them instead. Make a proxy class implement the interface you need, and then make sure everything that needs anything on a worksheet, accesses it through an interface, say IWorkbookData.FooSheet, where FooSheet is a property that returns a FooSheetProxy instance, exposed as an IFooSheet.


The only thing that ever needs to use a FooSheet directly, is a FooSheetProxy.

I don’t know about you, but I don’t like diagrams. So how about some real-world code instead?

Say you have an order form workbook, that you distribute to your sales reps and that come back filled with customer order details. Now imagine you need a macro that reads the form contents and imports it into your ERP system.

You could write a macro that reads the customer account number in cell O8, the order date in cell J6, the delivery and cancel dates in cells J8 and J10, and loops through rows 33 to 73 to pull the model codes from column F, and the per-size quantities in columns V through AQ… and it would work.

…Until it doesn’t anymore, because an order came back without a customer account number because it’s a new customer and the data validation wouldn’t let them enter an account that didn’t exist at the time you issued the order form. Or you had to shift all the sized units columns to the right because someone asked if it was possible to enter arbitrary notes at line item level. Or a new category needed to be added and now you have two size scales atop your sized units columns, and you can’t just grab the size codes from row 31 anymore. In other words, it works, until someone else uses (or sees) it and the requirements change.

Sounds familiar?

If you’ve written a script-like god-procedure that starts at the top and finishes with a MsgBox "Completed!" call at the bottom, (because that’s all VBA is good for, right?), then you’re going to modify your code, increase the cyclomatic complexity with new cases and conditions, and rinse and repeat. Been there, done that.

Not anymore.

Name things.

Abstraction is key. Your code doesn’t really care about what’s in cell O8. Your code needs to know about a customer account number. So you name that range Header_AccountNumber, proceed to name all the things, and before you know it you’re looking at Header_OrderDate, Header_DeliveryDate and Header_CancelDate, and then Details_DetailArea and Details_SizedUnits named ranges, you’ve ajusted your code to use them instead of hard-coding cell references, and that’s already a tremendous improvement: now the code isn’t going to break every time something needs to move around.

But you’re still looking at a god-like procedure that does everything, and the only way to test it is to run it: the more complex things are, the less possible it is to cover everything and guarantee that the code behaves as intended in every single corner case. So you download Rubberduck and think “I’m going to write a bunch of unit tests”, and there you are, writing “unit tests” that interact with the real worksheet, firing worksheet events at every change, calculating totals and whatnot: they’re automated tests, but they’re not unit tests. You simply can’t write unit tests against a god-like macro procedure that knows everything and does everything. Abstraction level needs to go further up.

The [Order Form] worksheet has a code-behind module. Here’s mine:

Option Explicit

Yup. That’s absolutely all of it. Your princess is in another castle. A “proxy” class implements an interface that the rest of the code uses. The interface exposes everything we’re going to need – something like this:

Option Explicit

Public Property Get AccountNumber() As String
End Property

Public Property Get OrderNumber() As String
End Property


Public Function CreateOrderHeaderEntity() As ISageEntity
End Function

Public Function CreateOrderDetailEntities() As VBA.Collection
End Function

Public Sub Lockdown(Optional ByVal locked As Boolean = True)
End Sub

Then there’s a proxy class that implements this interface; the AccountNumber property implementation might look like this:

Private Property Get IOrderSheet_AccountNumber() As String
    Dim value As Variant
    value = OrderSheet.Range("Header_Account").value
    If Not IsError(value) Then IOrderSheet_AccountNumber = value
End Property

And then the CreateOrderHeaderEntity creates and returns an object that your “import into ERP system” macro will consume, using the named ranges defined on OrderSheet. Now instead of depending directly on OrderSheet, your macro depends on this OrderSheetProxy class, and you can even refactor the macro into its own class and make it work against an IOrderSheet instead.

What gives? Well, now that you have code that works off an IOrderSheet interface, you can write some OrderSheetTestProxy implementation that doesn’t even know or care about the actual OrderSheet worksheet, and just like that, you can write unit tests that don’t use any worksheet at all, and still be able to automatically test the entire set of functionliaties!

Of course this isn’t the full picture, but it gives an idea. A recent order form project of mine currently contains 86 class modules, 3 standard modules, 11 user forms, and 25 worksheets (total worksheet code-behind procedures: 0) – not counting anything test-related – and using this pattern (combined with MVP), the code is extremely clear and surprisingly simple; most macros look more or less like this:

Public Sub AddCustomerAccount()
    Dim proxy As IWorkbookData
    Set proxy = New WorkbookProxy
    If Not proxy.SettingsSheet.EnableAddCustomerAccounts Then
        MsgBox MSG_FeatureDisabled, vbExclamation
        Exit Sub
    End If

    With New AccountsPresenter
        .Present proxy
    End With
End Sub

Without abstraction, this project would be a huge unscalable copy-pasta mess, impossible to extend or maintain, let alone debug.

See, there is no worksheet!