Revert "fs: Missing cb errors are deprecated, not a throw"

This reverts commits 6bd8b7e5405e1cdc9f56214f5f6b741806c32e5f
and fa05e8a2706e20a191942fe2b2273481605a1f14.

doc/api/fs.markdown

@@ -63,11 +63,26 @@ 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 ignores errors, but prints a deprecation
-warning.
+callback is used that rethrows errors. To get a trace to the original call
+site, set the NODE_DEBUG environment variable:
 
-**IMPORTANT**: Omitting the callback is deprecated.  v0.12 will throw the
-errors as exceptions.
+    $ 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.>
 
 
 ## fs.rename(oldPath, newPath, [callback])

lib/fs.js

@@ -59,36 +59,22 @@ 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;
-    callback = debugCallback;
-  } else
-    callback = missingCallback;
-
-  return callback;
-
-  function debugCallback(err) {
-    if (err) {
-      backtrace.message = err.message;
-      err = backtrace;
-      missingCallback(err);
-    }
-  }
-
-  function missingCallback(err) {
-    if (err) {
-      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);
+    return function(err) {
+      if (err) {
+        backtrace.message = err.message;
+        err = backtrace;
+        throw err;
       }
-    }
+    };
   }
+
+  return function(err) {
+    if (err) {
+      throw err;  // Forgot a callback but don't know where? Use NODE_DEBUG=fs
+    }
+  };
 }
 
 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 + ' --throw-deprecation ' + filename;
+  var execPath = process.execPath + ' ' + filename;
   var options = { env: env || {} };
   exec(execPath, options, function(err, stdout, stderr) {
     assert(err);
@@ -53,12 +53,3 @@ 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');
-})();