From c2ea02fd24c9f0775fd5ff51a58df38078060e87 Mon Sep 17 00:00:00 2001
From: hackademix
Date: Sat, 5 Oct 2019 10:56:00 +0200
Subject: Fallback to local storage for any item exceeding limits (fixes
 persistence problems on Chromium).

---
 src/common/Storage.js | 44 ++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 42 insertions(+), 2 deletions(-)

diff --git a/src/common/Storage.js b/src/common/Storage.js
index 4555a28..0e8181e 100644
--- a/src/common/Storage.js
+++ b/src/common/Storage.js
@@ -1,16 +1,47 @@
 var Storage = {
 
   async safeOp(op, type, keys) {
+    let sync = type === "sync";
+    if (sync && op === "get") {
+      let localFallback = await this.localFallback();
+      if (localFallback.size) {
+        for (let k of Array.isArray(keys) ? keys : [keys]) {
+          if (localFallback.has(k)) {
+            type = "local";
+            break;
+          }
+        }
+      }
+    }
     try {
-      return await browser.storage[type][op](keys);
+      let ret = await browser.storage[type][op](keys);
+      if (sync && op === "set") {
+        let localFallback = await this.localFallback();
+        let size = localFallback.size;
+        if (size > 0) {
+          for (let k of Object.keys(keys)) {
+            localFallback.delete(k);
+          }
+          if (size > localFallback.size) this.localFallback(localFallback);
+        }
+      }
+      return ret;
     } catch (e) {
-      if (type === "sync") {
+      if (sync) {
         debug("Sync disabled? Falling back to local storage (%s %o)", op, keys);
+        let localFallback = await this.localFallback();
+        let failedKeys = Array.isArray(keys) ? keys
+          : typeof keys === "string" ? [keys] : Object.keys(keys);
+        for (let k of failedKeys) {
+          localFallback.add(k);
+        }
+        await this.localFallback(localFallback);
       } else {
         error(e);
         throw e;
       }
     }
+
     return await browser.storage.local[op](keys);
   },
 
@@ -20,5 +51,14 @@ var Storage = {
 
   async set(type, keys) {
     return await this.safeOp("set", type, keys);
+  },
+
+  async localFallback(keys) {
+    let name = "__fallbackKeys";
+    if (keys) {
+      return await browser.storage.local.set({[name]: [...keys]});
+    }
+    let fallbackKeys = (await browser.storage.local.get(name))[name];
+    return new Set(Array.isArray(fallbackKeys) ? fallbackKeys : []);
   }
 }
-- 
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