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

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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.

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

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