doc/api/fs.markdown

@@ -63,26 +63,11 @@ Relative path to filename can be used, remember however that this path will be
 relative to `process.cwd()`.
 
 Most fs functions let you omit the callback argument. If you do, a default
-callback is used that rethrows errors. To get a trace to the original call
-site, set the NODE_DEBUG environment variable:
+callback is used that ignores errors, but prints a deprecation
+warning.
 
-    $ cat script.js
-    function bad() {
-      require('fs').readFile('/');
-    }
-    bad();
-
-    $ env NODE_DEBUG=fs node script.js
-    fs.js:66
-            throw err;
-                  ^
-    Error: EISDIR, read
-        at rethrow (fs.js:61:21)
-        at maybeCallback (fs.js:79:42)
-        at Object.fs.readFile (fs.js:153:18)
-        at bad (/path/to/script.js:2:17)
-        at Object.<anonymous> (/path/to/script.js:5:1)
-        <etc.>
+**IMPORTANT**: Omitting the callback is deprecated.  v0.12 will throw the
+errors as exceptions.
 
 
 ## fs.rename(oldPath, newPath, [callback])

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) {

test/simple/test-fs-readfile-error.js

@@ -28,7 +28,7 @@ var callbacks = 0;
 
 function test(env, cb) {
   var filename = path.join(common.fixturesDir, 'test-fs-readfile-error.js');
-  var execPath = process.execPath + ' ' + filename;
+  var execPath = process.execPath + ' --throw-deprecation ' + filename;
   var options = { env: env || {} };
   exec(execPath, options, function(err, stdout, stderr) {
     assert(err);
@@ -53,3 +53,12 @@ test({ NODE_DEBUG: 'fs' }, function(data) {
 process.on('exit', function() {
   assert.equal(callbacks, 2);
 });
+
+(function() {
+  console.error('the warnings are normal here.');
+  // just make sure that this doesn't crash the process.
+  var fs = require('fs');
+  fs.readFile(__dirname);
+  fs.readdir(__filename);
+  fs.unlink('gee-i-sure-hope-this-file-isnt-important-or-existing');
+})();