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Contributing

Thank you for contributing! Please follow these steps before preparing a pull request

Prerequisites

You need docker installed. This is because the build process uses docker to build wasm files.

Run the tests

npm install
npm test

Manual testing

If you need to test your changes in an editor, use VSCode. See cucumber/vscode/CONTRIBUTING.md for details.

Add support for a new programming language

If your contribution is to add support for a new programming language, follow these steps:

  1. Read and understand tree-sitter. Its job is to query the source code of whatever language you are trying to add support for. By doing this we can find the specific functions or methods that correspond to that language's Cucumber support. This allows the language-service to abstract away the language specific components and allows the rest of the program to work in more universal Gherkin space.
  2. Run npm install -E tree-sitter-{language}
  3. Update languages in scripts/build.js and add it to cucumber/vscode/README.md.
  4. Run npm install - this should build a wasm for the new language into dist/{language}.wasm
  5. Add test/language/testdata/{language}/StepDefinitions.{ext}, porting the names and expressions from one of the existing implementations.
  6. If the Cucumber implementation supports Cucumber Expressions, add test/language/testdata/{language}/ParameterTypes.{ext}.
  7. Add a new src/language/{language}Language.ts file
    • If the Cucumber implementation does not support Cucumber Expressions, make defineParameterTypeQueries an empty array
  8. Add the name of the new language to the LanguageNames type
  9. Update languageByName in src/language/language.ts
  10. Add a new case statement in src/tree-sitter-node/NodeParserAdapter.ts
  11. Update cucumberExpressionsSupport in test/language/ExpressionBuilder.test.ts to include the new language if it supports Cucumber Expressions
  12. Run tests

As you are working on step 5-7 - use tree-sitter playground to build your query. The queries must have capturing nodes:

  • defineParameterTypeQueries: @expression, @name and @root
  • defineStepDefinitionQueries: @expression and @root

Changing the names of these aliases will result in test failures, even if they work within the tree-sitter playground.

Snippets

Languages should contain a snippet in their respective src/language/{language}Language.ts.

Below is the canonical Ruby example:

{{ keyword }}('{{ expression }}') do |{{ #parameters }}{{ #seenParameter }}, {{ /seenParameter }}{{ name }}{{ /parameters }}|
  // {{ blurb }}
end

This is a Mustache Template. Here is the documentation

Here there are a number of properties to use:

  • keyword is Given, When or Then.
  • expression is the suggested Cucumber Expression for the undefined step.
  • blurb is the comment you should put inside the step definition body.
  • parameters is an array of parameters to use in the function/method/block signature. Each item has three properties:
    • name is the name of the parameter.
    • type is the type of the parameter (for statically typed languages).
    • seenParameter is a boolean which is false for the first parameter and true for the following ones. Useful for adding a ,.

One last thing

Please make sure all code is formatted before submitting a pull request

npm run eslint-fix