deptracpy

What is DepTracPy?

DepTracPy is a static code analysis tool for Python that helps you communicate, visualize and enforce architectural decisions in your projects. You can freely define your architectural layers over modules and which rules should apply to them. It is a sister project to a same tool written for PHP - Deptrac.

For example, you can use DepTracPy to ensure that packages/modules in your project are truly independent of each other to make them easier to test and reuse.

DepTracPy can be used in a CI pipeline to make sure a pull request does not violate any of the architectural rules you defined. With the optional Graphviz formatter you can visualize your layers, rules and violations.

Example: DepTracPy analyses DepTracPy

Optional Dependency: Graphviz

If you want to create graphical diagrams with your class dependencies, you will also need the dot command provided by Graphviz.

Graphviz can be installed using common package managers:

# for macos + brew
brew install graphviz

# for ubuntu and debian
sudo apt-get install graphviz

Graphviz is also available for Windows. Install the current stable release and append the binary path on the environment variable Path (e.g. C:\Program Files (x86)\Graphviz2.38\bin).

Getting Started

In order to get started with DepTracPy you will need a configuration file. This configuration file is written in YAML and, by default, is stored with the name deptracpy.yaml in your project’s root directory.

The main purpose of this file is:

  1. Define in which directories DepTracPy will search for your code
  2. Define your architectural layers using so-called collectors.
  3. Define a ruleset describing which layers can communicate with each other.

You can find out more about the Core Concepts in the docs.

Configuration

Let’s have a look at the generated file:

# deptracpy.yaml
paths:
  - src

layers:
  - name: Analyser
    collectors:
      - type: ModuleRecursive
        path: 'deptracpy.Core.Analyser'
  - name: Ast
    collectors:
      - type: ModuleRecursive
        path: 'deptracpy.Core.Ast'
  - name: Layer
    collectors:
      - type: ModuleRecursive
        path: 'deptracpy.Core.Layer'
  - name: References
    collectors:
      - type: ModuleRecursive
        path: 'deptracpy.Core.References'
  - name: Contract
    collectors:
      - type: ModuleRecursive
        path: 'deptracpy.Contract'
      - type: Module
        path: 'deptracpy'


rulesets:
  Analyser:
    - Ast
    - Layer
    - References
    - Contract
  References:
    - Ast
    - Contract
  Layer:
    - Contract

DepTracPy will search your project’s src/ directory for modules and packages.

We then define 5 layers by searching for module names in the files found by DepTracPy. Any file in the module and submodules of deptracpy.Core.Analyser will be grouped in a layer with the same name. The same happens for Ast, Layer and Refe)rences in their name. For Contract layer, any files in deptracpy.Contract and its submodules as well as files directly in the deptracpy module (like __init__.py) will be grouped.

The ruleset will then allow files in the Analyser-layer to communicate - i.e. use files from - the Ast, Layer, References and Contract layers. Files grouped in the References layer may not use files from the Analyser layer, but they can use files from the Ast and Contract layers. Files inside the Layer layer may only use files from the Contract layer. Files in the Contract layer may not use any files from any other layer.

You can learn more about the file in the Configuration reference.

Run DepTracPy

Once you have set up the config file you can run DepTracPy to analyse your code and check for violations.

deptracpy

The generated output will roughly look like this:

                                                           Supportive                                                            
┌───────────┬───────────────────────────────────────────────────────────────────────────────────────────────────────────────────┐
│ Violation │ OutputFormatter: deptracpy.Supportive.entrypoint cannot depend on deptracpy.OutputFormatter.format.format_output. │
└───────────┴───────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘
       Results        
┏━━━━━━━━━━━━┳━━━━━━━┓
┃            ┃ Count ┃
┡━━━━━━━━━━━━╇━━━━━━━┩
│ Allowed    │ 114   │
│ Warning    │ 0     │
│ Violations │ 1     │
│ Errors     │ 0     │
└────────────┴───────┘
0 errors and 1 violations found in the analysis.

Process finished with exit code 1

This is a report generated by DepTracPy. At the top you can see a list of violations, if there are any. A violation means that a layer uses a layer that is prohibited by the configured ruleset. In this case, a file from the Supportive layer uses a file from the OutputFormatter layer.

The table on the bottom gives you an overview over:

You can also change the output format itself by using one of the many provided Output Formatters.

Contribute

DepTracPy is in active development. We are looking for your suggestions and help to make it better.

Feel free to open an issue if you encounter bugs, have suggestions or would like to add a new feature to DepTracPy.

Please feel free to improve this documentation, fix bugs, or work on a suggested feature by making a pull request on GitHub. Don’t hesitate to ask for support, if you need help at any point.

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