Can't overwrite adminhtml block

Question

I'm trying to rewrite some blocks from adminhtml (Magento 1.9.1.1). Here's my code in my extension's config.xml:

...
<global>
  <blocks>
    <adminhtml>
      <rewrite>
        <report_grid>Mypackage_Myextension_Block_Adminhtml_Report_Grid</report_grid>
        <widget_grid_column_filter_date>Mypackage_Myextension_Block_Adminhtml_Widget_Grid_Column_Filter_Date</widget_grid_column_filter_date>
        <widget_grid_column_renderer_date>Mypackage_Myextension_Block_Adminhtml_Widget_Grid_Column_Renderer_Date</widget_grid_column_renderer_date>
        <widget_grid_column_filter_datetime>Mypackage_Myextension_Block_Adminhtml_Widget_Grid_Column_Filter_Datetime</widget_grid_column_filter_datetime>
        <widget_grid_column_renderer_datetime>Mypackage_Myextension_Block_Adminhtml_Widget_Grid_Column_Renderer_Datetime</widget_grid_column_renderer_datetime>
        <report_sales_grid_column_renderer_date>Mypackage_Myextension_Block_Adminhtml_Report_Sales_Grid_Column_Renderer_Date</report_sales_grid_column_renderer_date>
      </rewrite>
    </adminhtml>
  </blocks>
</global>
...

Oddly enough, all blocks were overwritten except report_grid which is Mage_Adminhtml_Block_Report_Grid.I couldn't find the issue. I have a file called Grid.php in app/code/local/Mypackage/Myextension/Block/Adminhtml/Report. What should I do? Is there any other way to rewrite this block?

UPDATE:

Here's output of Mage::getConfig()->getNode('global/blocks/adminhtml')->asNiceXml();:

<adminhtml>
    <class>Mage_Adminhtml_Block</class>
    <rewrite>
        <report_grid>Mypackage_Myextension_Block_Adminhtml_Report_Grid</report_grid>
        <widget_grid_column_filter_date>Mypackage_Myextension_Block_Adminhtml_Widget_Grid_Column_Filter_Date</widget_grid_column_filter_date>
        <widget_grid_column_renderer_date>Mypackage_Myextension_Block_Adminhtml_Widget_Grid_Column_Renderer_Date</widget_grid_column_renderer_date>
        <widget_grid_column_filter_datetime>Mypackage_Myextension_Block_Adminhtml_Widget_Grid_Column_Filter_Datetime</widget_grid_column_filter_datetime>
        <widget_grid_column_renderer_datetime>Mypackage_Myextension_Block_Adminhtml_Widget_Grid_Column_Renderer_Datetime</widget_grid_column_renderer_datetime>
        <report_sales_grid_column_renderer_date>Mypackage_Myextension_Block_Adminhtml_Report_Sales_Grid_Column_Renderer_Date</report_sales_grid_column_renderer_date>
    </rewrite>
</adminhtml>

And this is my Mypackage_Myextension_Block_Adminhtml_Report_Grid class:

class Mypackage_Myextension_Block_Adminhtml_Report_Grid extends Mage_Adminhtml_Block_Report_Grid
{
    public function __construct() {
        parent::__construct();
        die("Houston the eagle has landed. \o/");
        $this->setTemplate('myextension/report/grid.phtml');
    }
}

But it never called. If I die in Mage_Adminhtml_Block_Report_Grid it will die.

Answer 1

This is very odd, do you have multiple rewrites ? Prefix your name to 'zzzzzzz' and the GLOB (xml files) function will put your rewrite in as last. But maybe check the next line first:

Mage_Core_Model_Config: line(1227)

    $config = $this->_xml->global->{$groupType.'s'}->{$group};
    // First - check maybe the entity class was rewritten
    $className = null;
    if (isset($config->rewrite->$class)) {
        $className = (string)$config->rewrite->$class;
    } 

So, you can do the next test/check:

Test:

<?php

include_once(dirname(dirname(__DIR__)).'/mageInit.php');

mageTest::initMage();
echo Mage::getConfig()->getGroupedClassName('block', 'adminhtml/report_grid');
echo Mage::getConfig()->getNode('global/blocks/adminhtml')->asNiceXml();

Will give me this output when i copy/paste your XML in to my (empty) project:

Mypackage_Myextension_Block_Adminhtml_Report_Grid
<adminhtml>
   <class>Mage_Adminhtml_Block</class>
   <rewrite>
      <report_grid>Mypackage_Myextension_Block_Adminhtml_Report_Grid</report_grid>
      <widget_grid_column_filter_date>Mypackage_Myextension_Block_Adminhtml_Widget_Grid_Column_Filter_Date</widget_grid_column_filter_date>
      <widget_grid_column_renderer_date>Mypackage_Myextension_Block_Adminhtml_Widget_Grid_Column_Renderer_Date</widget_grid_column_renderer_date>
      <widget_grid_column_filter_datetime>Mypackage_Myextension_Block_Adminhtml_Widget_Grid_Column_Filter_Datetime</widget_grid_column_filter_datetime>
      <widget_grid_column_renderer_datetime>Mypackage_Myextension_Block_Adminhtml_Widget_Grid_Column_Renderer_Datetime</widget_grid_column_renderer_datetime>
      <report_sales_grid_column_renderer_date>Mypackage_Myextension_Block_Adminhtml_Report_Sales_Grid_Column_Renderer_Date</report_sales_grid_column_renderer_date>
   </rewrite>
</adminhtml>

The best thing to do is stop using rewrites and the configuration part of Magento. And start using the Event-Driven part of Magento. Especialy if your going to sell your modules to others.

Greating, good luck and happy hacking !