fix(flags): handle null early_exit values

Author: dustinbyrne

.changeset/pink-items-stick.md

@@ -0,0 +1,5 @@
+---
+"PostHog": patch
+---
+
+Allow local feature flag definitions with a null `early_exit` value.

src/PostHog/Api/LocalEvaluationApiResult.cs

@@ -167,10 +167,11 @@ internal record FeatureFlagFilters
     /// When <c>true</c>, local condition evaluation stops and returns a definitive disabled result
     /// as soon as a condition group's property filters match (or the group has no property filters)
     /// but the rollout percentage excludes the user, instead of falling through to later condition
-    /// groups. Mirrors the server-side Rust evaluation engine. Defaults to <c>false</c> when absent.
+    /// groups. Mirrors the server-side Rust evaluation engine. Defaults to <c>false</c> when absent;
+    /// explicit <c>null</c> values are also treated as <c>false</c> during evaluation.
     /// </summary>
     [JsonPropertyName("early_exit")]
-    public bool EarlyExit { get; init; }
+    public bool? EarlyExit { get; init; } = false;
 
     /// <summary>
     /// Compares this instance to another <see cref="FeatureFlagFilters"/> for equality.

tests/UnitTests/Features/LocalEvaluatorTests.cs

@@ -2744,13 +2744,12 @@ public void EarlyExitReturnsExpectedResult(bool earlyExit, string firstGroupEmai
         Assert.Equal(expected, result.Value);
     }
 
-    [Fact]
-    public void EarlyExitDeserializesFromJsonAndEarlyExits()
+    [Theory]
+    [InlineData("true", false)]
+    [InlineData("null", true)]
+    public void EarlyExitDeserializesFromJson(string earlyExit, bool expected)
     {
-        // Verifies that "early_exit": true round-trips through JSON correctly. A typo in the
-        // [JsonPropertyName] attribute would silently deserialize to false and disable the
-        // feature in production while all object-initializer tests still pass.
-        var json = """
+        var json = $$"""
         {
             "flags": [
                 {
@@ -2760,7 +2759,7 @@ public void EarlyExitDeserializesFromJsonAndEarlyExits()
                     "key": "early-exit",
                     "active": true,
                     "filters": {
-                        "early_exit": true,
+                        "early_exit": {{earlyExit}},
                         "groups": [
                             {
                                 "properties": [
@@ -2785,14 +2784,12 @@ public void EarlyExitDeserializesFromJsonAndEarlyExits()
         var flags = JsonSerializer.Deserialize<LocalEvaluationApiResult>(json, JsonSerializerHelper.Options)!;
         var localEvaluator = new LocalEvaluator(flags);
 
-        // early_exit=true + rollout 0 on first group (OUT_OF_ROLLOUT_BOUND) must short-circuit
-        // and return false, never reaching the second group with rollout 100.
         var result = localEvaluator.EvaluateFeatureFlag(
             key: "early-exit",
             distinctId: "1234",
             personProperties: new Dictionary<string, object?> { ["email"] = "tyrion@example.com" });
 
-        Assert.False(result.Value);
+        Assert.Equal(expected, result.Value);
     }
 
     [Fact]