Fixed Improper Method Call: Replaced NotImplementedError with NotImplemented

[fazledyn-or]

Details

1. In file: _csc.py, class: csc_matrix, there is a special method __mul__ that raises a NotImplementedError. If a special method supporting a binary operation is not implemented it should return NotImplemented. On the other hand, NotImplementedError should be raised from abstract methods inside user defined base classes to indicate that derived classes should override those methods. iCR suggested that the special method __mul__ should return NotImplemented instead of raising an exception.

2. In file: _csr.py, class: csr_matrix, there is a special method __truediv__ that raises a NotImplementedError. If a special method supporting a binary operation is not implemented it should return NotImplemented. On the other hand, NotImplementedError should be raised from abstract methods inside user defined base classes to indicate that derived classes should override those methods. iCR suggested that the special method __truediv__ should return NotImplemented instead of raising an exception.

An example of how NotImplemented helps the interpreter support a binary operation is shown here.

Notes

• Both the class csr_matrix and csc_matrix inherits the following classes as below. Among them, a binary operation method, such as __mul__ is already defined and implemented in class _base.spmatrix. As a result, it's suggested that NotImplemented should be used instead of raising an exception.

  - csr_matrix
      - _compressed._compressed_sparse_matrix
    	  - sparse_data._data_matrix
    		  - _base.spmatrix
    			  ```
    		    	    def __mul__(self, other):
        			        return self.tocsr().__mul__(other)
    			  ```
                  - sparse_data._minmax_mixin
                	  - object
                  - _index.IndexMixin
                	  - object
  
  - csc_matrix
      - _compressed._compressed_sparse_matrix (SAME as above)
  

• However, for special custom methods, one can opt-in to use raise NotImplementedError.

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Sponsorship and Support:

This work is done by the security researchers from OpenRefactory and is supported by the Open Source Security Foundation (OpenSSF): Project Alpha-Omega. Alpha-Omega is a project partnering with open source software project maintainers to systematically find new, as-yet-undiscovered vulnerabilities in open source code - and get them fixed – to improve global software supply chain security.

The bug is found by running the Intelligent Code Repair (iCR) tool by OpenRefactory and then manually triaging the results.

[asi1024]

/test mini

[kmaehashi]

As per the definition of NotImplemented:

A special value which should be returned by the binary special methods (e.g. eq(), lt(), add(), rsub(), etc.) to indicate that the operation is not implemented with respect to the other type;

I think

                else:
                    raise NotImplementedError

should be replaced by raise AssertionError, not return NotImplemented. These else clauses are tests against cuSPARSE's feature availability (not testing "with respect to the other type"), and never expected to reach.

[fazledyn-or]

@kmaehashi In that case, let's use AssertionError instead of NotImplemented in the mentioned code. Since I have no prior knowledge regarding the Cupy codebase, I had no idea. Also, what should be the message inside the error ?

Let me add new commits to this PR.

[kmaehashi]

I guess just doing raise AssertionError is fine here, this is the case where users should never see.

[fazledyn-or]

I've replaced return NotImplemented with raise AssertionError except at the following method -

def __rtruediv__(self, other):
    return NotImplemented

in _csr.py since the method isn't even implemented at all.

[kmaehashi]

LGTM!

[asi1024]

/test mini

[asi1024]

/test mini

[asi1024]

@fazledyn-or LGTM. Thanks for your contribution!