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Level 5 / Project 05 - Plugin Style Transformer

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— This project — — Flashcards — Browser

Estimated time: 70 minutes

Focus

  • extensible transform dispatch

Why this project exists

This project gives you level-appropriate practice in a realistic operations context. Goal: run the baseline, alter behavior, break one assumption, recover safely, and explain the fix.

Run (copy/paste)

Use <repo-root> as the folder containing this repository's README.md.

cd <repo-root>/projects/level-5/05-plugin-style-transformer
python project.py --input data/sample_input.json --output data/transformed.json --plugins uppercase,trim_whitespace,add_timestamp
pytest -q

Expected terminal output

Applied 3 plugins to 4 records
9 passed

Expected artifacts

  • data/transformed.json
  • Passing tests
  • Updated notes.md

Checkpoint: Baseline code runs and all tests pass. Commit your work before continuing.

Alter it (required) — Extension

  1. Write a new plugin class that reverses string values and register it in the registry.
  2. Add a --list-plugins flag that prints all registered plugin names and exits.
  3. Add execution order tracking so each record shows which plugins were applied.
  4. Re-run script and tests.

Break it (required) — Core

  1. Request a plugin name that does not exist in the registry (e.g. --plugins nonexistent).
  2. Pass an input file where a record is missing the fields your plugins expect.
  3. Capture the first failing test or visible bad output.

Fix it (required) — Core

  1. Raise a clear error listing available plugins when a requested one is not found.
  2. Make plugins skip fields that are missing rather than crashing.
  3. Add tests for unknown plugin names and missing fields.
  4. Re-run until output and tests are deterministic.

Checkpoint: All modifications done, tests still pass. Good time to review your changes.

Explain it (teach-back)

  1. How does the plugin registry pattern decouple new transforms from the core pipeline?
  2. What is the role of the TransformPlugin base class?
  3. Why does apply_plugins iterate plugins in order?
  4. Where do you see plugin architectures in real systems (webpack, pytest, Flask extensions)?

Mastery check

You can move on when you can: - run baseline without docs, - explain one core function line-by-line, - break and recover in one session, - keep tests passing after your change.

Stuck? Ask AI

If you are stuck after trying for 20 minutes, use one of these prompts:

  • "I am working on Plugin Style Transformer. I got this error: [paste error]. Can you explain what this error means without giving me the fix?"
  • "I am trying to build a plugin system where new transforms can be registered without modifying existing code. Can you explain the registry pattern with a simple example?"
  • "Can you explain how to use a dictionary to dispatch different functions based on a string key?"
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