[ilverify] Using ilverify with --include-file, --exclude-file or --ignore-error-file gives a System.NullReferenceException

[Haarmees]

Description

When using any of the "file" options (--include-file, --exclude-file or --ignore-error-file) with the ilverify tool a System.NullReferenceException is thrown. I looked into it and this happens because the code tries to get the length on the "non-file" variants of these options:

string[] includePatterns = options.Include;
if (options.IncludeFile != null)
{
    if (options.Include.Length != 0)
        WriteLine("[Warning] --include-file takes precedence over --include");
    includePatterns = File.ReadAllLines(options.IncludeFile.FullName);
}

Here options.Include is null, because the option is not given when running the command.

Reproduction Steps

Run ILVerify with either --include-file, --exclude-file or --ignore-error-file, but not --include, --exclude or --ignore-error. For example:

ilverify .\MyCode.dll --include-file .\include.txt
ilverify .\MyCode.dll --exclude-file .\exclude.txt
ilverify .\MyCode.dll --ignore-error-file .\ignore.txt

Expected behavior

Expected behavior is that the tool gives no System.NullReferenceException and uses the entries in the file.

Actual behavior

Actual behavior is that a System.NullReferenceException is thrown:

Error: System.NullReferenceException: Object reference not set to an instance of an object.
   at ILVerify.Program..ctor(Options options)
   at ILVerify.Program.Run(Options options)

Regression?

No response

Known Workarounds

A workaround is to also define the 'non-file' options, when using a 'file' option. For example:

ilverify .\MyCode.dll --include-file .\include.txt --include DummyInclude
ilverify .\MyCode.dll --exclude-file .\exclude.txt --exclude DummyExclude
ilverify .\MyCode.dll --ignore-error-file .\ignore.txt --ignore-error DummyIgnore

Configuration

Version 6.0.0 of the ilverify tool: https://www.nuget.org/packages/dotnet-ilverify/

Other information

Created PR that should fixe this: #62013

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