Why is StyleCop SA1305 not respecting the allowed prefixes list in VS2010 (or MSBuild)?

Question

I just upgraded a project from 2008 to 2010 Beta 2 and StyleCop is now reporting SA1305 (Hungarian notation) warnings on variable names with the prefix 'is'. 'Is' is definitely in the list of allowed prefixes.

Is this a known issue? Has anyone else run across this problem? The code was definitely compiling without any warnings in 2008.

Update: It turns out that this can work as expected in Visual Studio, but then fail through MSBuild. See the answer below for why.

Answer 1

You can manually add the "is" exception to Settings.StyleCop:

<Analyzers>    
  <Analyzer AnalyzerId="Microsoft.StyleCop.CSharp.NamingRules">
    <AnalyzerSettings>
      <CollectionProperty Name="Hungarian">
        <Value>is</Value>
      </CollectionProperty>
    </AnalyzerSettings>
  </Analyzer>
</Analyzers>

Answer 2

I ran across a similar issue now when building with msbuild vs on a developer box. It turns out that the default Settings.StyleCop (C:\Program Files (x86)\MSBuild\Microsoft\StyleCop\v4.4) that is installed actually contains a bunch of values you will need to duplicate in your own file if either:

• you are not installing StyleCop on the "other" (build) machine

or

• you have "do not merge with any other settings files" enabled

Specifically - the StyleCop Settings Editor picks up the Hungarian notation excludes from the other file automatically, regardless of what the "Settings Files" tab says.