feat!: make beforeSend callbacks synchronous

.changeset/v6-major-release.md

@@ -12,6 +12,8 @@
 - **Breaking:** remove `Posthog().getFeatureFlagPayload()` — use `getFeatureFlagResult(key, sendFeatureFlagEvent: false)` and read `payload`
 - **Breaking:** remove the `PostHogSessionReplayConfig.debouncerDelay` setter — use `throttleDelay`
 - **Breaking:** remove `PostHogDataMode.cellular` — use `PostHogDataMode.any`
+- **Breaking:** make `beforeSend` and `logsConfig.beforeSend` callbacks synchronous — load what they need ahead of time instead of using `await`
+- Keep a `reset()`, `identify()` or `optOut()` made right after an un-awaited `capture()`, `screen()` or `captureException()` from applying to that event first, and stop dropping that event on Windows and Linux
 - **Breaking:** remove `toMap()` from the config classes and `PostHogFeatureFlagResult.fromMap()` from the public API
 - **Breaking:** rename `enable()` and `disable()` to `optIn()` and `optOut()` on `PosthogFlutterPlatformInterface`, `PosthogFlutterIO` and `PosthogFlutterWeb`
 - Declare Android `minSdkVersion` 23 to match `posthog-android`

api/posthog_flutter.api.json

@@ -2310,7 +2310,7 @@
                                 "isRequired": false,
                                 "name": "beforeSend",
                                 "relativePath": "lib/src/posthog_config.dart",
-                                "typeName": "List<FutureOr<PostHogEvent?> Function(PostHogEvent)>?"
+                                "typeName": "List<PostHogEvent? Function(PostHogEvent)>?"
                             }
                         ],
                         "relativePath": "lib/src/posthog_config.dart",
@@ -2626,7 +2626,7 @@
                         "isWriteable": true,
                         "name": "beforeSend",
                         "relativePath": "lib/src/posthog_config.dart",
-                        "typeName": "List<FutureOr<PostHogEvent?> Function(PostHogEvent)>"
+                        "typeName": "List<PostHogEvent? Function(PostHogEvent)>"
                     }
                 ],
                 "isDeprecated": false,
@@ -3440,7 +3440,7 @@
                         "isWriteable": true,
                         "name": "beforeSend",
                         "relativePath": "lib/src/posthog_config.dart",
-                        "typeName": "List<FutureOr<PostHogLogRecord?> Function(PostHogLogRecord)>"
+                        "typeName": "List<PostHogLogRecord? Function(PostHogLogRecord)>"
                     }
                 ],
                 "isDeprecated": false,
@@ -6118,7 +6118,7 @@
         ],
         "typeAliasDeclarations": [
             {
-                "aliasedTypeName": "FutureOr<PostHogEvent?> Function(PostHogEvent)",
+                "aliasedTypeName": "PostHogEvent? Function(PostHogEvent)",
                 "entryPoints": [
                     "posthog_flutter.dart"
                 ],
@@ -6128,7 +6128,7 @@
                 "relativePath": "lib/src/posthog_config.dart"
             },
             {
-                "aliasedTypeName": "FutureOr<PostHogLogRecord?> Function(PostHogLogRecord)",
+                "aliasedTypeName": "PostHogLogRecord? Function(PostHogLogRecord)",
                 "entryPoints": [
                     "posthog_flutter.dart"
                 ],

posthog_flutter/MIGRATION.md

@@ -181,6 +181,26 @@ config.dataMode = PostHogDataMode.any;
 
 They serialized the internal platform-channel format and have no replacement. `toMap()` is gone from `PostHogConfig`, `PostHogBootstrapConfig`, `PostHogLogsConfig`, `PostHogRageClickConfig`, `PostHogSessionReplayConfig`, `PostHogErrorTrackingConfig` and `PostHogExceptionStepsConfig`. To build a result, for example in a test, call the `PostHogFeatureFlagResult` constructor, which stays public.
 
+### `beforeSend` callbacks are synchronous
+
+`BeforeSendCallback` is now `PostHogEvent? Function(PostHogEvent)`, and `BeforeSendLogCallback` is `PostHogLogRecord? Function(PostHogLogRecord)`. An `async` callback is a compile error. Load what it needs ahead of time and read it synchronously.
+
+```dart
+// Before
+config.beforeSend = [
+  (event) async {
+    final allowed = await loadAllowList();
+    return allowed.contains(event.event) ? event : null;
+  },
+];
+
+// After
+final allowed = await loadAllowList();
+config.beforeSend = [
+  (event) => allowed.contains(event.event) ? event : null,
+];
+```
+
 ### Platform interface changes
 
 These affect only code that calls, extends or fakes `PosthogFlutterPlatformInterface`, `PosthogFlutterIO` or `PosthogFlutterWeb` directly, such as test mocks. `Posthog().optIn()` and `optOut()` are unaffected.