Static code analysis can find hundreds of opportunities in VBA code.
Rubberduck builds its own internal representation of the code, and then proceeds to analyze it. Each individual inspection can easily be disabled, or configured to issue inspection results at different severity levels ranging from Hint to Error.
Use the Inspection Results toolwindow to review Rubberduck’s findings, search, filter, regroup results by inspection, location, type, or severity. Each inspection result comes with a detailed description of what’s being flagged and why, so you can make an enlightened decision.
Unless configured otherwise, Rubberduck automatically runs inspections after the a parser/resolver cycle completes (regardless of whether the inspection results toolwindow is displayed or not).
For the best experience, it would be recommended to first try Rubberduck with an empty project, add a new module, and write, say, a loop that counts 1 to 10 and outputs to the debug pane - then to parse that and review the inspection results; carefully review the inspection settings, and consider disabling the inspections that irreconcilably clash with your preferences: use meaningful names alone can easily produce hundreds upon hundreds of results if you’re not that much into using vowels, or if you, say, prefix all your variable names; these inspections can be re-enabled anytime you’re ready!
These features will be announced as \"new\" when they are merged into the [master] branch. Until then, they are only available in pre-release builds.
Identifies Functions or Properties referenced by the TruePart(second argument) or FalsePart(third argument) of the IIf built-in function.
Default severity: Warning
All arguments of any function/procedure call are always evaluated before the function is invoked so that their respective values can be passed as parameters. Even so, the IIf Function's behavior is sometimes mis-interpreted to expect that ONLY the 'TruePart' or ONLY the 'FalsePart' expression will be evaluated based on the result of the first argument expression. Consequently, the IIf Function can be a source of unanticipated side-effects and errors if the user does not account for the fact that both the TruePart and FalsePart arguments are always evaluated.
Flags MSForms controls being accessed from outside the UserForm that contains them.
Default severity: Hint
MSForms exposes UserForm controls as public fields; accessing these fields outside the UserForm class breaks encapsulation and couples the application logic with specific form controls rather than the data they hold. For a more object-oriented approach and code that can be unit-tested, consider encapsulating the desired values into their own 'model' class, making event handlers in the form manipulate these 'model' properties, then have the code that displayed the form query this encapsulated state as needed.
Identifies Property assigment references where Set or Let Property Members do not exist.
Default severity: Warning
In general, the VBE editor catches this type of error and will not compile. However, there are a few scenarios where the error is overlooked by the compiler and an error is generated at runtime. To avoid the runtime error scenarios, the inspection flags all assignment references of a read-only property.
This inspection warns about references to the default instance of a class, inside that class.
Default severity: Warning
While a stateful default instance might be intentional, when it isn't it's easily a source of bugs. Use the Me qualifier to explicitly refer to the current instance and eliminate any ambiguity. Global state accidentally stored in a class' default instance is not shared by all other instances of that class.