CONTRIBUTING.md

Developing

Custom rules for each linter are implemented differently based on the tool capabilities and the limitations of the underlying language parser. Below are the details on which classes to extend for each linter.

graph LR
  A[<i>Checkstyle</i>] --> B{Is the rule<br>about Javadoc?};
  B --> |No| C[Is it achievable<br>using AST?];
  C --> |No| D[<b>AbstractFileSetCheck</b>];
  C --> |Yes| E[<b>AbstractCheck</b>];
  B --> |Yes| F[<b>AbstractJavadocCheck</b>];

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graph LR
  A[<i>CodeNarc</i>] --> B{Is the rule<br>about imports?};
  B --> |No| C[Is it achievable<br>using AST?];
  C --> |No| D[<b>AbstractRule</b>];
  C --> |Yes| E[<b>AbstractAstVisitorRule</b>];
  B --> |Yes| F[<b>AbstractImportRule</b>];

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graph LR
  A[<i>Ktlint</i>] --> B[<b>Rule</b> supports AST and raw file];

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graph LR
  A[<i>Cppcheck</i>] --> B{Is it achievable<br>using AST?};
  B --> |No| C[Is it achievable<br>using tokens?];
  C --> |No| D[<b>Read raw file</b>];
  C --> |Yes| E[<b>Use tokens</b>];
  B --> |Yes| F[<b>Use scopes</b>];

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graph LR
  A[<i>Pylint</i>] --> B{Is it achievable<br>using AST?};
  B --> |No| C[Is it achievable<br>using tokens?];
  C --> |No| D[<b>BaseRawFileChecker</b>];
  C --> |Yes| E[<b>BaseTokenChecker</b>];
  B --> |Yes| F[<b>BaseChecker</b>];

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graph LR
  A[<i>ESLint</i>] --> B[<b>Rule</b> supports AST and source code];

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Configuration file

Rule message templates are stored in configuration files, distinct for each source language.

Source language	Target language	File extension
Kotlin	Java, Groovy, Kotlin	.properties
Python	C/C++, Python	.cnf
TypeScript	JavaScript, TypeScript	.json

Debugging

Printing the AST tree to the console is possible with Checkstyle and Ktlint.

Checkstyle

checkstyle -T $file
checkstyle -J $file # for javadoc

Ktlint

This command is no longer available in newer versions of Ktlint, use version 0.47.0.

ktlint --color printAST $file

Cppcheck

cppcheck --dump $file