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 inspections flag a number of obsolete code constructs and statements that should not be used in new VB6 or VBA7 projects, and hint about implicit language defaults and various other opportunities.
Warns about Def[Type] statements.
Default severity: Suggestion
These declarative statements make the first letter of identifiers determine the data type.
Flags uses of an empty string literal ("").
Default severity: Warning
Standard library constant 'vbNullString' is more explicit about its intent, and should be preferred to a string literal. While the memory gain is meaningless, an empty string literal still takes up 2 bytes of memory, but 'vbNullString' is a null string pointer, and doesn't.
Warns about host-evaluated square-bracketed expressions.
Default severity: Warning
Host-evaluated expressions should be implementable using the host application's object model. If the expression yields an object, member calls against that object are late-bound.
Locates unqualified Worksheet.Range/Cells/Columns/Rows member calls implicitly referring to ActiveSheet.
Default severity: Warning
Implicit references to the active worksheet (ActiveSheet) rarely mean to be working with *whatever worksheet is currently active*. By explicitly qualifying these member calls with a specific Worksheet object, the assumptions are removed, the code is more robust, and will be less likely to throw run-time error 1004 or produce unexpected results when the active sheet isn't the expected one.
This inspection will only run if the Excel library is referenced.
Locates unqualified Workbook.Worksheets/Sheets/Names member calls that implicitly refer to ActiveWorkbook.
Default severity: Warning
Implicit references to the active workbook rarely mean to be working with *whatever workbook is currently active*. By explicitly qualifying these member calls with a specific Workbook object, the assumptions are removed, the code is more robust, and will be less likely to throw run-time error 1004 or produce unexpected results when the active workbook isn't the expected one.
This inspection will only run if the Excel library is referenced.