automatically enable tracing when there are listeners

lib/sqlite3.js

 var sqlite3 = module.exports = exports = require('./sqlite3_bindings');
+var EventEmitter = require('events').EventEmitter;
 
 var Database = sqlite3.Database;
 var Statement = sqlite3.Statement;
@@ -90,6 +91,23 @@ Statement.prototype.map = function() {
 
 var isVerbose = false;
 
+Database.prototype.addListener = Database.prototype.on = function(event) {
+    if (event === 'trace') {
+        this.configure('trace', true);
+    }
+
+    EventEmitter.prototype.addListener.apply(this, arguments);
+};
+
+Database.prototype.removeListener = function(event) {
+    if (event === 'trace') {
+        this.configure('trace', false);
+    }
+
+    EventEmitter.prototype.removeListener.apply(this, arguments);
+};
+
+
 // Save the stack trace over EIO callbacks.
 sqlite3.verbose = function() {
     if (!isVerbose) {

test/trace.test.js

@@ -9,8 +9,6 @@ exports['test Database tracing'] = function(beforeExit) {
     var create = false;
     var select = false;
 
-    db.configure('trace', true);
-
     db.on('trace', function(sql) {
         if (sql.match(/^SELECT/)) {
             assert.ok(!select);