Fixes for userAgent delay. Retrieved async now. (#236)

* Fixes for userAgent delay.  Retrieved async now.

* Fix test for watchOS/Linux

Author: bsneed

Sources/Segment/Plugins/Context.swift

@@ -108,9 +108,6 @@ public class Context: PlatformPlugin {
             "width": screen.width,
             "height": screen.height
         ]
-        // user-agent
-        let userAgent = device.userAgent
-        context["userAgent"] = userAgent
         // locale
         if Locale.preferredLanguages.count > 0 {
             context["locale"] = Locale.preferredLanguages[0]
@@ -147,6 +144,13 @@ public class Context: PlatformPlugin {
             "wifi": wifi
         ]
 
+        // user-agent
+        // BKS: This use to be in the static section, however it was discovered that on some platforms
+        // there can be a delay in retrieval.  It has to be fetched on the main thread, so we've spun it off
+        // async and cache it when it comes back.
+        let userAgent = device.userAgent
+        context["userAgent"] = userAgent
+
         // other stuff?? ...
     }
 

Sources/Segment/Plugins/Platforms/Vendors/AppleUtils.swift

@@ -19,6 +19,7 @@ import WebKit
 
 internal class iOSVendorSystem: VendorSystem {
     private let device = UIDevice.current
+    @Atomic private static var asyncUserAgent: String? = nil
 
     override var manufacturer: String {
         return "Apple"
@@ -65,17 +66,15 @@ internal class iOSVendorSystem: VendorSystem {
 
     override var userAgent: String? {
         #if !os(tvOS)
-        var userAgent: String?
-        
-        if Thread.isMainThread {
-            userAgent = WKWebView().value(forKey: "userAgent") as? String
-        } else {
-            DispatchQueue.main.sync {
-              userAgent = WKWebView().value(forKey: "userAgent") as? String
+        // BKS: It was discovered that on some platforms there can be a delay in retrieval.
+        // It has to be fetched on the main thread, so we've spun it off
+        // async and cache it when it comes back.
+        if Self.asyncUserAgent == nil {
+            DispatchQueue.main.async {
+                Self.asyncUserAgent = WKWebView().value(forKey: "userAgent") as? String
             }
         }
-
-        return userAgent
+        return Self.asyncUserAgent
         #else
         // webkit isn't on tvos
         return "unknown"
@@ -198,6 +197,7 @@ import WebKit
 
 internal class MacOSVendorSystem: VendorSystem {
     private let device = ProcessInfo.processInfo
+    @Atomic private static var asyncUserAgent: String? = nil
 
     override var manufacturer: String {
         return "Apple"
@@ -238,16 +238,15 @@ internal class MacOSVendorSystem: VendorSystem {
     }
 
     override var userAgent: String? {
-        var userAgent: String?
-        if Thread.isMainThread {
-            userAgent = WKWebView().value(forKey: "userAgent") as? String
-        } else {
-            DispatchQueue.main.sync {
-              userAgent = WKWebView().value(forKey: "userAgent") as? String
+        // BKS: It was discovered that on some platforms there can be a delay in retrieval.
+        // It has to be fetched on the main thread, so we've spun it off
+        // async and cache it when it comes back.
+        if Self.asyncUserAgent == nil {
+            DispatchQueue.main.async {
+                Self.asyncUserAgent = WKWebView().value(forKey: "userAgent") as? String
             }
         }
-        
-        return userAgent
+        return Self.asyncUserAgent
     }
 
     override var connection: ConnectionStatus {

Tests/Segment-Tests/Analytics_Tests.swift

@@ -123,6 +123,14 @@ final class Analytics_Tests: XCTestCase {
         let outputReader = OutputReaderPlugin()
         analytics.add(plugin: outputReader)
 
+#if !os(watchOS) && !os(Linux)
+        // prime the pump for userAgent, since it's retrieved async.
+        let vendorSystem = VendorSystem.current
+        while vendorSystem.userAgent == nil {
+            RunLoop.main.run(until: Date.distantPast)
+        }
+#endif
+        
         waitUntilStarted(analytics: analytics)
 
         // add a referrer