The purchase report in Odoo is not inheritable. All the SQL was written in a single function. See https://github.com/odoo/odoo/blob/a19d2c98f4c80d162a92d08ce4a43ca6021f3bca/addons/purchase/report/purchase_report.py#L52
With the development of this module, the report is now ready for others to extend purchase report. This module also adds received quantity and invoiced quantity into the report
This module may not be needed for the later version of Odoo (i.e. v12+) since Odoo improved the purchase report with the commit 9548d218f19cb344ee961bceb06badf99c9bfd2f: https://github.com/odoo/odoo/commit/9548d218f19cb344ee961bceb06badf99c9bfd2f#diff-7a01ef3634ea769faa887549c442605f
- Community Edition
- Enterprise Edition
This software and associated files (the "Software") may only be used (executed, modified, executed after modifications) if you have purchased a valid license from the authors, typically via Odoo Apps, or if you have received a written agreement from the authors of the Software (see the COPYRIGHT file).
You may develop Odoo modules that use the Software as a library (typically by depending on it, importing it and using its resources), but without copying any source code or material from the Software. You may distribute those modules under the license of your choice, provided that this license is compatible with the terms of the Odoo Proprietary License (For example: LGPL, MIT, or proprietary licenses similar to this one).
It is forbidden to publish, distribute, sublicense, or sell copies of the Software or modified copies of the Software.
The above copyright notice and this permission notice must be included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.