Add ability to except random numbers about bogus

[bchavez]

Hi @acnicholls-kroll, this is a bit of a tricky request;

The reason Bogus doesn't support this out of the box is that this scenario can present a few problems:

• First, "keeping an exclusion list" in memory potentially leads to multiple invocations of the random generator. That is, multiple invocations of the random generator "for another value" in a single method call can make deterministic sequences hard to debug in large complex generations or object graphs.
• Second, we open up a potential big O(runtime) scaling problem when the exclusion list starts to grow. What matching algorithm do we use to scan for values? binary search? or quick array scan? Additionally, as the exclusion list grows, we slow down (and performance problems like this are hard to diagnose).
• Lastly, what happens when we accidentally run NumberWithExclusion(1, 3, except: listOfExclusions); we get stuck an infinite loop when listOfExclusions = [1,2,3]. It seems obvious right now, but when except: is a dynamically generated/derived exclusion list because of database removals, we start leading the developer down a bad path of potentially getting their code in a stuck state.

For example, to create a custom extension method for the Randomizer instance:

void Main()
{
   var faker = new Faker();
   var result = faker.Random.NumberWithExclusion(1,4, except: [1, 2, 3]);
   result.Dump();
}

public static class MyBogusExtensions
{
   public static int NumberWithExclusion(this Randomizer random, int min, int max, int[] except)
   {
      int result = 0;
      do
      {
         result = random.Number(min, max);
      }
      while( except.Contains(result) );
      
      return result;
   }
}

Notice, we need to re-generate the random.Number() when the generated value is in exclusion. And this kind of code inside Bogus makes it extremely difficult to debug a deterministic sequence because we could potentially pull more values from the seeded sequence rather than just one time.

So in summary, I try to avoid adding "try again" code in Bogus because it makes deterministic debugging more difficult.

But nothing prevents you from adding the extension method above to your code base.

I'll keep it in mind for future enhancement (if I continue to get more requests like this), but for now, I'll try to avoid adding code like this to the main codebase.

[acnicholls-kroll]

many thanks for the detailed response. Will look at adding this extension to our code where we need it.