feature flag approval sending

SignalMessaging/ViewControllers/AttachmentApprovalViewController.swift

@@ -1861,6 +1861,7 @@ class MediaMessageTextToolbar: UIView, UITextViewDelegate {
 
     public func textView(_ textView: UITextView, shouldChangeTextIn range: NSRange, replacementText text: String) -> Bool {
 
+        if !FeatureFlags.sendingMediaWithOversizeText {
             let existingText: String = textView.text ?? ""
             let proposedText: String = (existingText as NSString).replacingCharacters(in: range, with: text)
 
@@ -1903,6 +1904,7 @@ class MediaMessageTextToolbar: UIView, UITextViewDelegate {
 
                 return false
             }
+        }
 
         // Though we can wrap the text, we don't want to encourage multline captions, plus a "done" button
         // allows the user to get the keyboard out of the way while in the attachment approval view.

SignalMessaging/utils/ThreadUtil.m

@@ -113,7 +113,15 @@ NS_ASSUME_NONNULL_BEGIN
     if ([fullMessageText lengthOfBytesUsingEncoding:NSUTF8StringEncoding] < kOversizeTextMessageSizeThreshold) {
         truncatedText = fullMessageText;
     } else {
+        if (SSKFeatureFlags.sendingMediaWithOversizeText) {
             truncatedText = [fullMessageText ows_truncatedToByteCount:kOversizeTextMessageSizeThreshold];
+        } else {
+            // Legacy iOS clients already support receiving long text, but they assume _any_ body
+            // text is the _full_ body text. So until we consider "rollout" complete, we maintain
+            // the legacy sending behavior, which does not include the truncated text in the
+            // websocket proto.
+            truncatedText = nil;
+        }
         DataSource *_Nullable dataSource = [DataSourceValue dataSourceWithOversizeText:fullMessageText];
         if (dataSource) {
             SignalAttachment *oversizeTextAttachment =

SignalServiceKit/src/Util/FeatureFlags.swift

@@ -0,0 +1,22 @@
+//
+//  Copyright (c) 2019 Open Whisper Systems. All rights reserved.
+//
+
+import Foundation
+
+/// By centralizing feature flags here and documenting their rollout plan, it's easier to review
+/// which feature flags are in play.
+@objc(SSKFeatureFlags)
+public class FeatureFlags: NSObject {
+
+    /// iOS has long supported sending oversized text as a sidecar attachment. The other clients
+    /// simply displayed it as a text attachment. As part of the new cross-client long-text feature,
+    /// we want to be able to display long text with attachments as well. Existing iOS clients
+    /// won't properly display this, so we'll need to wait a while for rollout.
+    /// The stakes aren't __too__ high, because legacy clients won't lose data - they just won't
+    /// see the media attached to a long text message until they update their client.
+    @objc
+    public static var sendingMediaWithOversizeText: Bool {
+        return false
+    }
+}