Also known as

Code Smell Incomplete Library Class

Signs and Symptoms

Sooner or later, libraries stop meeting user needs. The only solution to the problem – changing the library – is often impossible since the library is read-only.

Reasons for the Problem

The author of the library has not provided the features you need or has refused to implement them.



  • Reduces code duplication (instead of creating your own library from scratch, you can still piggy-back off an existing one).

When to Ignore

  • Extending a library can generate additional work if the changes to the library involve changes in code.

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