exception-control

Perform limited static analysis for uncaught exceptions in a Python file.

This is a ⚠️WIP⚠️. Check out tested behavior, untested behavior and limitations.

Usage

To check for uncaught exceptions in a Python file:

python3 main.py [filename]

Multiple files support is limited, but you can try this:

python3 main.py <(cat [file1] [file2]...)

Tested behavior

The following behavior has been verified for the included test files tests/test.py and tests/test2.py:

• Detects exceptions manually raised by functions (raise Exception).
• Detects exceptions raised by calling functions outside try-except blocks, including user-defined functions that raise exceptions, as well as some built-in Python functions like open().
• Detects exceptions raised by using operators like indexing arr[index] and dividing a / b or a // b.
• Excludes exceptions caught in except Exception: clauses from the report and understands the Exception Hierarchy.
• Excludes exceptions documented in function docstrings from the report.

Untested behavior

• May fail with nested try/except blocks.
• More extensive testing needs to be done to detect additional limitations.

Limitations

• Will miss a lot of exceptions:
  • Due to Python being a dynamic language with duck typing, there are many exceptions that cannot be detected statically.
  • The exceptions raised by most popular functions are undocumented and therefore not visible from the outside.
  • Exceptions are stored by name. If there are multiple TypeError in a function, only the last one will be reported.
• Will report exceptions even if they will never be raised in execution:
  • Due to it being a static analysis tool, it does not follow a variable along the code or determine its possible values.
  • That is why, exceptions will be reported for any indexing or division operations regardless if they are "safe" or not.
• Does not work well with classes or custom exceptions:
  • There can be many classes in a single document with methods in different classes sharing the same name.
  • There are many ways to instantiate a class and call its methods.
  • It is, in some cases, impossible to determine the class of a variable and the function called using static analysis.
• Does not support external libraries:
  • External libraries are unsupported, but the code is extensible enough to make it possible to include them in the future.
• Support for multiple files is limited:
  • Support for multiple files is done through Bash Process Substitution. python3 main.py <(cat [file1] [file2]...)
  • Line numbers will be relative to the merged files and not per file.
  • Functions are searched by name, so renamed functions from <module> import <function> as <new_name> will not be detected.