Lint your architecture

 

 

 

David Seddon

david@seddonym.me

Blog: http://seddonym.me

Please note: this talk was given for an
earlier version of Layer Linter.

 

Check the latest docs before attempting to implement.

 

layer-linter.readthedocs.io

This talk

1. The shape of a code base
2. A tool to stay in shape

How many modules in
your code base?

a. Less than 10
b. 10s

c. 100s
d. 1,000s +

'Accidental complexity'

How much does accidental complexity
affect your productivity?

a. Not at all
b. A little

c. Somewhat

d. A lot

1. The shape of a
code base

Graph

Directed Graph

# pets/dogs.py

from . import cats

Your modules form a Directed Graph

What is your application
shaped like?

"The goal of an architect is to minimize the human resources required to build and maintain the required system.

"What is it that saps this kind of
people-power? Coupling."
 

'Uncle Bob' Martin, Clean Architecture, 2018 (p. 160)

Using layers to
reduce coupling

Layers

 

An ordered
list of Python modules.

No layer import from a layer above it.

Layers between components

Layers within components

Layers between and
within components

Do your applications have
designed dependency flows?

If you do, is the design
always adhered to?

2. A tool to stay
in shape

layer-lint pets
layers.yml

Contract

Contract

Text

$ layer-lint pets

============
Layer Linter
============

---------
Contracts
---------

Analyzed 23 files, 44 dependencies.
-----------------------------------

My layer contract KEPT

Contracts: 1 kept, 0 broken.

 

 

 

 

 

 

 

 

 

 

Text

$ layer-lint pets

============
Layer Linter
============

---------
Contracts
---------

Analyzed 23 files, 44 dependencies.
-----------------------------------

My layer contract BROKEN

Contracts: 0 kept, 1 broken.

----------------
Broken contracts
----------------

My layer contract
-----------------

1. pets.cats.fur imports pets.dogs.walkies:

    pets.cats.fur <-
    pets.utils <-
    pets.dogs.walkies

 

Top level layers:
    packages:
        - pets
    layers:
        - dogs
        - cats
        - rabbits
layers.yml
Layers within components:
    packages:
        - pets.dogs
        - pets.cats
        - pets.rabbits
    layers:
        - personality
        - traits
        - physical
Layers within components:
    packages:
        - pets.dogs
        - pets.cats
        - pets.rabbits
    layers:
        - personality
        - traits
        - physical


Top level layers:
    packages:
        - pets
    layers:
        - dogs
        - cats
        - rabbits

Text

Top level layers:
    packages:
        - pets
    layers:
        - dogs
        - cats
        - rabbits
    whitelisted_paths:
        - pets.cats.whiskers <- pets.utils

Whitelisted paths

Upcoming features

  • Closed layers

  • Independent layers

Design

Whitelist

Reduce whitelist

How to begin

Feedback wanted!

In summary

  • Think of your code base as a
    directed graph.
     
  • Be an architect! Reduce coupling by imposing constraints on this graph.
     
  • Layer Linter can help you do this.

Layer Linter

layer-linter.readthedocs.io

 

This talk's slides:

slides.com/davidseddon/lint-your-architecture

 

My blog:

seddonym.me

 

Work at Octopus Energy:

octopus.energy/careers/

 

 

David Seddon

david@seddonym.me
@seddonym
seddonym.me

 

Graphs of well
known codebases

http://www.grokcode.com/864/snakefooding-python-code-for-complexity-visualization/

Requests

http://www.grokcode.com/864/snakefooding-python-code-for-complexity-visualization/

Flask

http://www.grokcode.com/864/snakefooding-python-code-for-complexity-visualization/

Celery

http://www.grokcode.com/864/snakefooding-python-code-for-complexity-visualization/

Django

Lint your architecture

By David Seddon

Lint your architecture

Code bases have a nasty habit of becoming a complicated web of circular dependencies. To stop this happening, you need constraints on your project's structure. Meet Layer Linter, a tool to control the dependencies between modules in your Python project. https://layer-linter.readthedocs.io/

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