Check that if one hook is defined the other is too

lib/persistence.js

@@ -34,7 +34,13 @@ function Persistence (options) {
     }
   }
 
-  // After serialization and before deserialization hooks
+  // After serialization and before deserialization hooks with some basic sanity checks
+  if (options.afterSerialization && !options.beforeDeserialization) {
+    throw "Serialization hook defined but deserialization hook undefined, cautiously refusing to start NeDB";
+  }
+  if (!options.afterSerialization && options.beforeDeserialization) {
+    throw "Serialization hook undefined but deserialization hook defined, cautiously refusing to start NeDB";
+  }
   this.afterSerialization = options.afterSerialization || function (s) { return s; };
   this.beforeDeserialization = options.beforeDeserialization || function (s) { return s; };
 

test/persistence.test.js

@@ -268,15 +268,32 @@ describe('Persistence', function () {
     });
   });
   
-  describe('Data can be persisted using serialization hooks', function () {
+  describe.only('Data can be persisted using serialization hooks', function () {
     var as = function (s) { return "before_" + s + "_after"; }
       , bd = function (s) { return s.substring(7, s.length - 6); } 
   
+    it("Declaring only one hook will throw an exception to prevent data loss", function (done) {
+      var hookTestFilename = 'workspace/hookTest.db'
+      Persistence.ensureFileDoesntExist(hookTestFilename, function () {
+        (function () {
+          new Datastore({ filename: hookTestFilename, autoload: true
+                        , afterSerialization: as
+                        });
+        }).should.throw();
+        
+        (function () {
+          new Datastore({ filename: hookTestFilename, autoload: true
+                        , beforeDeserialization: bd
+                        });
+        }).should.throw();
+
+        done();
+      });
+    });
   
     it("A serialization hook can be used to transform data before writing new state to disk", function (done) {
       var hookTestFilename = 'workspace/hookTest.db'
-      fs.unlinkSync(hookTestFilename);
+      Persistence.ensureFileDoesntExist(hookTestFilename, function () {
-      
         var d = new Datastore({ filename: hookTestFilename, autoload: true
                                , afterSerialization: as
                                , beforeDeserialization: bd
@@ -351,11 +368,11 @@ describe('Persistence', function () {
           });
         });
       });
+    });
     
     it("Use serialization hook when persisting cached database or compacting", function (done) {
       var hookTestFilename = 'workspace/hookTest.db'
-      fs.unlinkSync(hookTestFilename);
+      Persistence.ensureFileDoesntExist(hookTestFilename, function () {
-      
         var d = new Datastore({ filename: hookTestFilename, autoload: true
                                , afterSerialization: as
                                , beforeDeserialization: bd
@@ -413,11 +430,11 @@ describe('Persistence', function () {
           });
         });
       });
+    });
     
     it("Deserialization hook is correctly used when loading data", function (done) {
       var hookTestFilename = 'workspace/hookTest.db'
-      fs.unlinkSync(hookTestFilename);
+      Persistence.ensureFileDoesntExist(hookTestFilename, function () {
-      
         var d = new Datastore({ filename: hookTestFilename, autoload: true
                                , afterSerialization: as
                                , beforeDeserialization: bd
@@ -460,6 +477,7 @@ describe('Persistence', function () {
           });
         });
       });
+    });
     
   });