Hacktoberfest 2019 & Rubberduck

For the 3rd year in 2019, Rubberduck celebrated open-source with Digital Ocean’s (6th) Hacktoberfest event. This year’s was our busiest ever, with ~50 pull requests created, 11 new forks and 24 new stars in the past month; 67 issues were closed since October 1st, by 11 authors – including 4 first-time contributors!

This means… quite a lot was accomplished. Recap.

Parser & Resolver Tweaks

I’m always impressed with these, because such tweaks always enhance Rubberduck’s understanding of VBA code, so every such enhancement means better and more accurate inspections and overall functionality. This time, attention was given to Debug.Print and other statements that support a particular “output list” syntax, which would previously break the parser and fail to resolve identifier references in such expressions. Debug is no longer being treated as a “fake class”; rather, we’re now treating it as a more accurate “fake module”. VBA is special-casing Print methods in a way that forces us to parse it differently than a standard member call, and if you look carefully at how it’s syntax-highlighted, you’ll notice Debug.Print is really treated as a keyword, which is rather awkward. Print statements will now correctly parse and process their output list arguments.

It was also brought to our attention that under some regional settings OS configurations, exported forms could format decimal numbers in form properties with a comma for a decimal separator, and this tripped the parser since decimal literals are expected to be US-formatted! This was also fixed.

Default members and let-coercion behavior received significant attention too, and now bang notation (! operators) correctly resolve… and Rubberduck is now able to expand this notation (and other implicit default member calls) into explicit, early-bound code that preserves compiler validation and prevents the various problems associated with inadvertent late binding. Implicit procedure calls are now being identified, suspicious Let assignments are now being flagged, and jagged arrays now resolve correctly, too.

The broken resolution of Enum members has been corrected, and Next i will now correctly resolve the reference to i.

Inspection & Refactoring Fixes

An oversight in the implementation of the “Parameter can be ByVal” inspection was causing false positives with Enum types – a rather trivial fix. Much less trivial, the handling of @Ignore and @IgnoreModule annotations across all inspections was refactored and centralized, making it much harder to implement an inspection that doesn’t heed these annotations. Bugs were fixed in EncapsulatePublicField, UntypedFunction, and EmptyMethod inspections.

Name validation (e.g. when renaming an identifier) was refined and consolidated, and will now be more consistent and less prone to falsely claim name clashes.

UI & UX Enhancements

Autocompletion features will now be enabled by default for a new installation (note that the updated default will not affect an upgrade install). The caption of the “Ok” button of the settings dialog was changed to “Save & Close”, and the Extract Interface refactoring can now be invoked from the Code Explorer context menu. Inspection grouping was improved, every search box can now be cleared with the ESC key, and a long-standing issue with undocked toolwindows has been fixed: toolwindows made undockable can now easily be made dockable again.

The version check feature was updated, too: the wording of the notification message now includes the currently-running version number, and a new setting can now enable notifications for every pre-release build in-between. This update was made possible with the deployment of important changes to the project’s website: previously, the /Build/Version/stable URL would return the version of the Rubberduck build that was running on the web server – now, we hit the GitHub REST API and grab all releases: that’s how the home page can display this table with the breakdown of download stats; it’s how the /Build/Version endpoints know what version number to return, and how the /Inspections content is now generated directly from XML-doc comments in the source code. Note that caching/timing issues may cause the feature to announce a version number, and the actual latest build is actually more recent than that.


Our AppVeyor builds now generate a SHA256 hash for installer builds, that we issue as an asset that can be downloaded separately from the installer itself. Downloadable assets also include the .xml file that the website uses to generate the /Inspections content; because this content needs to follow certain specific conventions, a suite of Roslyn analyzers was implemented to inspect the XML documentation in the source code, and fail the build if a new inspection couldn’t properly show up on the website.

The PermissiveAssertClass is now leveraging Variant conversion in its IEqualityComparer<object> implementation, making Assert.AreEqual behave exactly as you would expect VBA to work. The settings dialog lets you select which IAssertClass implementation to use for new test modules.

Rubberduck’s own test suite is now up to well over 7,100 unit tests, and there are many refactoring opportunities, and a long-time contributor proposed to introduce an InspectionTestsBase abstract class, enhance our MockVbeBuilder, and boil writing test cases for inspections down to a one-liner, in two pull requests that netted a significant and welcome cut in our test code (diffs were +426/-1,759 and +1,431/-5,262, respectively), making a good payment on some technical debt.

Coming Up

With Hacktoberfest behind us, we’re getting ready to release v2.5.0 in November; translation rounds have begun, so now is a very good time to submit a pull request to add a new supported language, or to help complete other translations.

Rubberduck is currently built with Visual Studio 2017; there’s a draft pull request that changes the AppVeyor build environment to use Visual Studio 2019 and the newest SDK – the current and new build processes aren’t compatible: once that pull request is merged, Rubberduck will build correctly with Visual Studio 2019, and will start failing in VS 2017. The plan is to proceed with this IDE upgrade as v2.5.0 is released later this month.

Here’s to a successful Hacktoberfest, thanks to everyone that participated!