Fix infinite loop when parsing MagicMock objects

[sgd2z]

Fix infinite loop when parsing MagicMock objects

Problem

When llsd.parse() receives a MagicMock object (or similar mock objects), it enters an infinite loop that consumes all available memory until the process is killed with OOM.

This commonly occurs when tests incorrectly mock requests.Response without setting the .content attribute - the default MagicMock is passed to llsd.parse() instead of bytes.

Root Cause

In LLSDBaseParser._reset(), the code checked something.seekable() to determine if the input was a seekable stream. For a MagicMock:

• mock.seekable() returns another MagicMock (which is truthy)
• The parser then tries to read from the mock, getting more MagicMock objects recursively
• This causes infinite memory consumption

Solution

Modified _reset() to validate input types properly:

• Check if something is an io.IOBase instance (proper stream type)
• Raise a clear LLSDParseError for invalid input types

Changes

• llsd/base.py: Added proper input validation in _reset() method
• tests/llsd_test.py: Added InvalidInputTypes test class with tests for MagicMock, str, None, and int inputs

Testing

All 96 tests pass.

Before this fix:
llsd.parse(MagicMock()) # Hangs forever, consumes all memory

After this fix:
llsd.parse(MagicMock())

Raises: LLSDParseError: Cannot parse LLSD from MagicMock. Expected bytes or a file-like object (io.IOBase subclass).

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[sgd2z]

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[sgd2z]

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.82%. Comparing base (f00d36b) to head (8a0618f).

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #32      +/-   ##
==========================================
+ Coverage   89.68%   89.82%   +0.13%     
==========================================
  Files           6        6              
  Lines         863      865       +2     
==========================================
+ Hits          774      777       +3     
+ Misses         89       88       -1     

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