logging: return serialization error to callback instead of throwing (#2081)

Author: stephenplusplus

handwritten/logging/src/log.js

@@ -630,9 +630,17 @@ Log.prototype.decorateEntries_ = function(entries, callback) {
       entry = self.entry(entry);
     }
 
-    var decoratedEntry = entry.toJSON({
-      removeCircular: self.removeCircular_
-    });
+    var decoratedEntry;
+
+    try {
+      decoratedEntry = entry.toJSON({
+        removeCircular: self.removeCircular_
+      });
+    } catch(e) {
+      callback(e);
+      return;
+    }
+
     decoratedEntry.logName = self.formattedName_;
 
     self.metadata_.assignDefaultResource(decoratedEntry, function(err, entry) {

handwritten/logging/test/log.js

@@ -696,6 +696,20 @@ describe('Log', function() {
       log.decorateEntries_([entry], assert.ifError);
     });
 
+    it('should exec callback with error from serialization', function(done) {
+      var error = new Error('Error.');
+
+      var entry = new Entry();
+      entry.toJSON = function() {
+        throw error;
+      };
+
+      log.decorateEntries_([entry], function(err) {
+        assert.strictEqual(err, error);
+        done();
+      });
+    });
+
     it('should assign the log name', function(done) {
       log.decorateEntries_([{}], function(err, decoratedEntries) {
         assert.ifError(err);