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resolves gmertes#29
tested with cadium-playercore 6.0033.414.911, 6.0034.588.911, 6.0038.181.911

src/nflxmultisubs.js

@@ -22,6 +22,28 @@ const hookJsonParseAndAddCallback = function(_window) {
 hookJsonParseAndAddCallback(window);
 
 
+// Hook JSON.stringify() to intercept and modify manifest requests
+const hookJsonStringify = function(_window) {
+  const _stringify = JSON.stringify;
+  _window.JSON.stringify = (...args) => {
+    if (args[0] && (args[0].url === 'licensedManifest' || args[0].url === 'manifest')) {
+      // key name is different for different cadium-playercore versions
+      // so we check each one by testing two common properties
+      for (let i in args[0]) {
+        if (args[0][i] && args[0][i].viewableId && args[0][i].manifestVersion) {
+          args[0][i].showAllSubDubTracks = true;
+          args[0][i].supportsPartialHydration = false;
+          console.log(`Modified manifest request to unlock all sub/dub tracks`);
+        }
+      }
+    }
+    const result = _stringify.call(JSON, ...args);
+    return result;
+  };
+};
+hookJsonStringify(window);
+
+
 // hook `history.pushState()` as there is not "pushstate" event in DOM API
 // Because Netflix preload manifests when the user hovers mouse over movies on index page,
 // our .updateManifest() won't be trigger after user clicks a movie to start watching (they must reload the player page)
@@ -1396,4 +1418,4 @@ window.addEventListener('keyup', (event) => {
 
     primary.style.visibility = secondary.style.visibility = (visible) ? 'hidden' : 'visible';
   }
-}, true);
+}, true);