43 lines
2.1 KiB
Markdown
43 lines
2.1 KiB
Markdown
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[](https://github.com/dart-lang/tools/actions/workflows/boolean_selector.yaml)
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[](https://pub.dev/packages/boolean_selector)
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[](https://pub.dev/packages/boolean_selector/publisher)
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The `boolean_selector` package defines a simple and flexible syntax for boolean
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expressions. It can be used for filtering based on user-defined expressions. For
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example, the [`test`][test] package uses boolean selectors to allow users to
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define what platforms their tests support.
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[test]: https://github.com/dart-lang/test
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The boolean selector syntax is based on a simplified version of Dart's
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expression syntax. Selectors can contain identifiers, parentheses, and boolean
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operators, including `||`, `&&`, `!`, and `? :`. Any valid Dart identifier is
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allowed, and identifiers may also contain hyphens. For example, `chrome`,
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`chrome || content-shell`, and `js || (vm && linux)` are all valid boolean
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selectors.
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A boolean selector is parsed from a string using
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[`BooleanSelector.parse()`][parse], and evaluated against a set of variables
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using [`BooleanSelector.evaluate()`][evaluate]. The variables are supplied as
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a function that takes a variable name and returns its value. For example:
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[parse]: https://pub.dev/documentation/boolean_selector/latest/boolean_selector/BooleanSelector/BooleanSelector.parse.html
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[evaluate]: https://pub.dev/documentation/boolean_selector/latest/boolean_selector/BooleanSelector/evaluate.html
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```dart
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import 'package:boolean_selector/boolean_selector.dart';
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void main(List<String> args) {
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var selector = BooleanSelector.parse("(x && y) || z");
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print(selector.evaluate((variable) => args.contains(variable)));
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}
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```
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## Versioning
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If this package adds new features to the boolean selector syntax, it will
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increment its major version number. This ensures that packages that expose the
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syntax to their users will be able to update their own minor versions, so their
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users can indicate that they rely on the new syntax.
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