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Review Checklists for Extension Safety

Concept Position

flowchart TD
  family["Python Programming"] --> program["Python Object-Oriented Programming"]
  program --> module["Module 09: Public APIs, Extension Seams, and Governance"]
  module --> concept["Review Checklists for Extension Safety"]
  concept --> capstone["Capstone pressure point"]
flowchart TD
  problem["Start with the design or failure question"] --> example["Study the worked example and trade-offs"]
  example --> boundary["Name the boundary this page is trying to protect"]
  boundary --> proof["Carry that question into code review or the capstone"]

Read the first diagram as a placement map: this page is one concept inside its parent module, not a detached essay, and the capstone is the pressure test for whether the idea holds. Read the second diagram as the working rhythm for the page: name the problem, study the example, identify the boundary, then carry one review question forward.

Purpose

Give reviewers a repeatable way to evaluate API and plugin changes before accidental surface area or unsafe extension patterns become permanent.

1. Checklists Reduce Blind Spots

Useful review questions include:

  • is this surface truly public
  • who will depend on it
  • what invariants remain protected
  • how would we deprecate it later
  • what tests and docs prove the contract

2. Review Should Cover Behavior, Not Only Types

A plugin hook may look small in code while still exposing timing, ordering, or thread-safety assumptions that become public obligations.

3. Safety Includes Failure Semantics

Ask what happens when an extension:

  • raises an error
  • blocks too long
  • returns malformed data
  • is missing at startup

Extension safety is incomplete without these cases.

4. Make the Checklist Reusable

The goal is not bureaucracy. The goal is to keep high-impact reviews consistent across different maintainers and future iterations.

Practical Guidelines

  • Review extension surfaces with a standard set of compatibility and safety questions.
  • Include failure semantics and lifecycle concerns in the checklist.
  • Tie checklist items to docs and tests where possible.
  • Keep the checklist short enough to be used consistently.

Exercises for Mastery

  1. Draft a six-question review checklist for a new plugin hook.
  2. Use it on one existing extension surface and note the gaps.
  3. Add one missing failure-path test discovered by the checklist.