From bcc242c17d74fcc96de87727cc96326d244afc1e Mon Sep 17 00:00:00 2001
From: bchavez <bchavez@bitarmory.com>
Date: Wed, 26 Sep 2018 02:15:15 -0700
Subject: [PATCH] #178, #124. Added `nullWeight` parameter to `.OrNull()`
 extension method for weighted generation of null values.

---
 HISTORY.md                                    |  3 ++
 Source/Bogus.Tests/GitHubIssues/Issue178.cs   | 29 +++++++++++++++++++
 .../Bogus/Extensions/ExtensionsForFakerT.cs   | 10 +++++--
 3 files changed, 39 insertions(+), 3 deletions(-)
 create mode 100644 Source/Bogus.Tests/GitHubIssues/Issue178.cs

diff --git a/HISTORY.md b/HISTORY.md
index 6cf50fe3..519f8c1c 100644
--- a/HISTORY.md
+++ b/HISTORY.md
@@ -1,3 +1,6 @@
+## v24.0.1
+* Added `nullWeight` parameter to `.OrNull()` extension method for weighted generation of null values.
+
 ## v24.0.0
 * BREAKING: Deterministic values may have changed. Parity with **faker.js** @ 07f39bd3.
 * `en_ZA` - South Africa (English) locale added.
diff --git a/Source/Bogus.Tests/GitHubIssues/Issue178.cs b/Source/Bogus.Tests/GitHubIssues/Issue178.cs
new file mode 100644
index 00000000..df6f2d65
--- /dev/null
+++ b/Source/Bogus.Tests/GitHubIssues/Issue178.cs
@@ -0,0 +1,29 @@
+using System.Linq;
+using Bogus.Extensions;
+using FluentAssertions;
+using Xunit;
+
+namespace Bogus.Tests.GitHubIssues
+{
+   public class Issue178 : SeededTest
+   {
+      [Fact]
+      public void weighted_null_check()
+      {
+         var f = new Faker();
+         var mostlyNull = Enumerable.Range(1, 100)
+            .Select(n => (int?)n.OrNull(f, 0.9))
+            .Count( n => !n.HasValue);
+
+         mostlyNull.Should().BeGreaterThan(80);
+
+
+         var mostlyNotNull = Enumerable.Range(1, 100)
+            .Select(n => (int?)n.OrNull(f, 0.1))
+            .Count(n => !n.HasValue);
+
+         mostlyNotNull.Should().BeLessThan(20);
+
+      }
+   }
+}
\ No newline at end of file
diff --git a/Source/Bogus/Extensions/ExtensionsForFakerT.cs b/Source/Bogus/Extensions/ExtensionsForFakerT.cs
index b8cfdfe7..f97dd451 100644
--- a/Source/Bogus/Extensions/ExtensionsForFakerT.cs
+++ b/Source/Bogus/Extensions/ExtensionsForFakerT.cs
@@ -1,4 +1,5 @@
-using System.Collections.Generic;
+using System;
+using System.Collections.Generic;
 
 namespace Bogus.Extensions
 {
@@ -26,9 +27,12 @@ public static List<T> GenerateBetween<T>(this Faker<T> faker, int min, int max,
       /// Helpful extension for creating randomly null values for <seealso cref="Faker{T}"/>.RuleFor() rules.
       /// Example: .RuleFor(x=>x.Prop, f=>f.Random.Word().OrNull(f))
       /// </summary>
-      public static object OrNull(this object value, Faker f)
+      /// <param name="f">The Faker facade. This is usually the f from f => lambda.</param>
+      /// <param name="nullWeight">The probability of null occuring. Range [1.0f - 0.0f] (100% and 0%) respectively. For example, if 15% null is desired pass nullWeight = 0.15f.</param>
+      public static object OrNull(this object value, Faker f, double nullWeight = 0.5f)
       {
-         return f.Random.Bool() ? value : null;
+         if (nullWeight > 1 || nullWeight < 0) throw new ArgumentOutOfRangeException(nameof(nullWeight), $".{nameof(OrNull)}() {nameof(nullWeight)} of '{nullWeight}' must be between 1.0f and 0.0f. ");
+         return f.Random.Float() > nullWeight ? value : null;
       }
    }
 }
\ No newline at end of file