fs: Missing cb errors are deprecated, not a throw

Commit a804347 makes fs function rethrow errors when the callback is
omitted. While the right thing to do, it's a change from the old v0.8
behavior where such errors were silently ignored.

To give users time to upgrade, temporarily disable that and replace it
with a function that warns once about the deprecated behavior.

Close #5005

1 files changed, 24 insertions, 10 deletions

diff --git a/lib/fs.js b/lib/fs.js
index 3d37a648a7..49bb027376 100644
--- a/lib/fs.js
+++ b/lib/fs.js
@@ -59,22 +59,36 @@ var DEBUG = process.env.NODE_DEBUG && /fs/.test(process.env.NODE_DEBUG);
 function rethrow() {
   // Only enable in debug mode. A backtrace uses ~1000 bytes of heap space and
   // is fairly slow to generate.
+  var callback;
   if (DEBUG) {
     var backtrace = new Error;
-    return function(err) {
-      if (err) {
-        backtrace.message = err.message;
-        err = backtrace;
-        throw err;
-      }
-    };
+    callback = debugCallback;
+  } else
+    callback = missingCallback;
+
+  return callback;
+
+  function debugCallback(err) {
+    if (err) {
+      backtrace.message = err.message;
+      err = backtrace;
+      missingCallback(err);
+    }
   }
 
-  return function(err) {
+  function missingCallback(err) {
     if (err) {
-      throw err;  // Forgot a callback but don't know where? Use NODE_DEBUG=fs
+      if (process.throwDeprecation)
+        throw err;  // Forgot a callback but don't know where? Use NODE_DEBUG=fs
+      else if (!process.noDeprecation) {
+        var msg = 'fs: missing callback ' + (err.stack || err.message);
+        if (process.traceDeprecation)
+          console.trace(msg);
+        else
+          console.error(msg);
+      }
     }
-  };
+  }
 }
 
 function maybeCallback(cb) {