util: add internal function _deprecationWarning()

lib/os.js

@@ -37,12 +37,8 @@ exports.platform = function() {
   return process.platform;
 };
 
-var warnNetworkInterfaces = true;
 exports.getNetworkInterfaces = function() {
-  if (warnNetworkInterfaces) {
-    console.error("os.getNetworkInterfaces() is deprecated - use os.networkInterfaces()");
-    console.trace();
-    warnNetworkInterfaces = false;
-  }
+  require('util')._deprecationWarning('os',
+    'os.getNetworkInterfaces() is deprecated - use os.networkInterfaces()');
   return exports.networkInterfaces();
 };

lib/sys.js

@@ -21,15 +21,8 @@
 
 var util = require('util');
 
-var sysWarning;
-if (!sysWarning) {
-  sysWarning = 'The "sys" module is now called "util". ' +
-               'It should have a similar interface.';
-  if (process.env.NODE_DEBUG && process.env.NODE_DEBUG.indexOf('sys') != -1)
-    console.trace(sysWarning);
-  else
-    console.error(sysWarning);
-}
+util._deprecationWarning('sys',
+  'The "sys" module is now called "util". It should have a similar interface.');
 
 exports.print = util.print;
 exports.puts = util.puts;

lib/util.js

@@ -518,3 +518,19 @@ exports.inherits = function(ctor, superCtor) {
     }
   });
 };
+
+var deprecationWarnings;
+
+exports._deprecationWarning = function(moduleId, message) {
+  if (!deprecationWarnings)
+    deprecationWarnings = {};
+  else if (message in deprecationWarnings)
+    return;
+
+  deprecationWarnings[message] = true;
+
+  if ((new RegExp('\\b' + moduleId + '\\b')).test(process.env.NODE_DEBUG))
+    console.trace(message);
+  else
+    console.error(message);
+};