Retrieve requests for node, user, comment file resource return empty result

Version 6.x-3.x-dev 30th July (as well as rc-2)
PHP 5.3.6
OS: OSX

Steps to recreate

Enable services under admin/build/services/list/rest_services/resources. Assuming that you configured your services to use REST and services/rest as an endpoint.

Call:
/services/rest/node -- this will work correctly and return list of nodes available on your site

Now call:
/services/rest/node/NID --- privide some valid node id. You will get empty result.

The same applies for other resources like: file, comment, user.

Bug in Code

There are at least two issues here:

1. First is the problematic use of isset() funciton in _RESOURCE_NAME_resource_access() functions inside RESOURCE_NAME_resource.inc files.
2. Second is the fact that getControllerArguments() method of RESTServer does not use information about arguments type to convert it to appropriate type.

Ad. 1

At the very top the funciton is checking condition like:

<?php
if (isset($args[0]['account']) || isset($args[0]['data'])) {
    ...
}
?>

This will always return true if only the $args[0] is defined as string (and it is as described in second issue). PHP behaves a bit unexpectedly here. Array whose elements are strings can be accessed with array notation $arr[0][0], $arr[0][1] etc. What's worse $arr[0]['any_string'] will also work as 'any_string' will be converted to integer causing isset() to always return TRUE as shown in the example code below.

<?php
$arr = array(
  '1234'    
);

print_r($arr);

if (isset($arr[0]['node'])) {
  echo PHP_EOL;
  echo 'non-existent key "node" $arr[0]["node"]';
  echo 'has value: '. $arr[0]['node'].PHP_EOL;
  echo PHP_EOL;
  echo 'string key representing number is converted to number:'.PHP_EOL;
  echo '$arr[0]["0"] = '. $arr[0]['0'].PHP_EOL;
  echo '$arr[0]["1"] = '. $arr[0]['1'].PHP_EOL;
  echo '$arr[0]["2"] = '. $arr[0]['2'].PHP_EOL;
  echo '$arr[0]["3"] = '. $arr[0]['3'].PHP_EOL;
}
?>

Outputs:

Array
(
    [0] => 1234
)

non-existent key "node" $arr[0]["node"]has value: 1

string key representing number is converted to number:
$arr[0]["0"] = 1
$arr[0]["1"] = 2
$arr[0]["2"] = 3
$arr[0]["3"] = 4

To solve this it's enough to replace current if statements with "array friendly" ones like:

<?php
if (is_array($args[0]) && key_exists('node', $args[0])) {
  ...
?>

On the other hand fixing second issue will automatically resolve this one.

Ad. 2

Inside getControllerArguments() in line 225 of RESTServer.inc the $arguments array is being pushed values of arguments. This $arguments array is being used in handler() method where it's being passed to different callback functions among them the above __resource_access().
If the proper conversion based on the type of arument happened than the variable $args[0] from first issue would be integer not a string and isset() function could be safely used.