Issue 5279 - Fix broken I/O in non-Firefox applications

lib/io.js

Index: lib/io.js
===================================================================
--- a/lib/io.js
+++ b/lib/io.js
@@ -71,16 +71,55 @@ function callLegacy(method, ...args)
 
 function legacyFile(fileName)
 {
   let file = LegacyIO.resolveFilePath("adblockplus");
   file.append(fileName);
   return file;
 }
 
+let fallback = {
+  readFromFile(fileName, listener)
+  {
+    let wrapper = {
+      process(line)
+      {
+        if (line !== null)
+          listener(line);
+      }
+    };
+    return callLegacy("readFromFile", legacyFile(fileName), wrapper);
+  },
+
+  writeToFile(fileName, data)
+  {
+    return callLegacy("writeToFile", legacyFile(fileName), data);
+  },
+
+  copyFile(fromFile, toFile)
+  {
+    return callLegacy("copyFile", legacyFile(fromFile), legacyFile(toFile));
+  },
+
+  renameFile(fromFile, newName)
+  {
+    return callLegacy("renameFile", legacyFile(fromFile), newName);
+  },
+
+  removeFile(fileName)
+  {
+    return callLegacy("removeFile", legacyFile(fileName));
+  },
+
+  statFile(fileName)
+  {
+    return callLegacy("statFile", legacyFile(fileName));
+  }
+};
+
 exports.IO =
 {
   /**
    * @callback TextSink
    * @param {string} line
    */
 
   /**
@@ -111,30 +150,16 @@ exports.IO =
               return;
             }
           }
           resolve();
         }
 
         processBatch();
       });
-    }).catch(error =>
-    {
-      if (error == "NoSuchFile")
-      {
-        let wrapper = {
-          process(line)
-          {
-            if (line !== null)
-              listener(line);
-          }
-        };
-        return callLegacy("readFromFile", legacyFile(fileName), wrapper);
-      }
-      throw error;
     });
   },
 
   /**
    * Writes text lines to a file.
    * @param {string} fileName
    *    Name of the file to be written
    * @param {Iterable.<string>} data
@@ -154,58 +179,43 @@ exports.IO =
    *    Name of the file to be copied
    * @param {string} toFile
    *    Name of the file to be written, will be overwritten if exists
    * @return {Promise}
    *    Promise to be resolved or rejected once the operation is completed
    */
   copyFile(fromFile, toFile)
   {
-    return callWebExt("copyFile", fromFile, toFile).catch(error =>
-    {
-      if (error == "NoSuchFile")
-        return callLegacy("copyFile", legacyFile(fromFile), legacyFile(toFile));
-      throw error;
-    });
+    return callWebExt("copyFile", fromFile, toFile);
   },
 
   /**
    * Renames a file.
    * @param {string} fromFile
    *    Name of the file to be renamed
    * @param {string} newName
    *    New file name, will be overwritten if exists
    * @return {Promise}
    *    Promise to be resolved or rejected once the operation is completed
    */
   renameFile(fromFile, newName)
   {
-    return callWebExt("renameFile", fromFile, newName).catch(error =>
-    {
-      if (error == "NoSuchFile")
-        return callLegacy("renameFile", legacyFile(fromFile), newName);
-      throw error;
-    });
+    return callWebExt("renameFile", fromFile, newName);
   },
 
   /**
    * Removes a file.
    * @param {string} fileName
    *    Name of the file to be removed
    * @return {Promise}
    *    Promise to be resolved or rejected once the operation is completed
    */
   removeFile(fileName)
   {
-    return callWebExt("removeFile", fileName).catch(error =>
-    {
-      if (error == "NoSuchFile")
-        return callLegacy("removeFile", legacyFile(fileName));
-      throw error;
-    });
+    return callWebExt("removeFile", fileName);
   },
 
   /**
    * @typedef StatData
    * @type {object}
    * @property {boolean} exists
    *    true if the file exists
    * @property {number} lastModified
@@ -217,16 +227,42 @@ exports.IO =
    * @param {string} fileName
    *    Name of the file to be looked up
    * @return {Promise.<StatData>}
    *    Promise to be resolved with file metadata once the operation is
    *    completed
    */
   statFile(fileName)
   {
-    return callWebExt("statFile", fileName).catch(error =>
-    {
-      if (error == "NoSuchFile")
-        return callLegacy("statFile", legacyFile(fileName));
-      throw error;
-    });
+    return callWebExt("statFile", fileName);
   }
 };
+
+let {application} = require("info");
+if (application != "firefox" && application != "fennec2")
+{
+  // Currently, only Firefox has a working WebExtensions implementation, other
+  // applications should just use the fallback.
+  exports.IO = fallback;
+}
+else
+{
+  // Add fallbacks to IO methods - fall back to legacy I/O if file wasn't found.
+  for (let name of Object.getOwnPropertyNames(exports.IO))
+  {
+    // No fallback for writeToFile method, new data should always be stored to
+    // new storage only.
+    if (name == "writeToFile")
+      continue;
+
+    let method = exports.IO[name];
+    let fallbackMethod = fallback[name];
+    exports.IO[name] = (...args) =>
+    {
+      return method(...args).catch(error =>
+      {
+        if (error == "NoSuchFile")
+          return fallbackMethod(...args);
+        throw error;
+      });
+    };
+  }
+}