This project is very far from production-ready. Use at your own risk.

Permit A38

Permit A38 is a linting tool which leverages JSONPath to create declarative rules executed over a TypeScript abstract syntax tree.

Usage

Currently it's only possible to use this project as a library with a single interesting method in the API, namely:

checkRuleForSource(source: string, rule: Rule): boolean

which accepts the following parameters:

• source - the source code that is being checked.
• rule a rule object as defined in src/types.ts with fields:
  • select - JSONPath which queries for nodes that will be selected for checking.
  • filter - JSONPath filtering the selected nodes.
  • matchType - 'all' or 'none' indicating that for the check to pass all or none of the nodes respectively have to match the filtering query.

Example

const noReadonly = `
  class TestClass {
    field1: string;
    readonly field2: string;
  }
`;

const result = checkRuleForSource(noReadonly, {
    select: '$..[?(PropertyDeclaration)]',
    filter: '$..modifiers[?(ReadonlyKeyword)]',
    matchType: 'none',
    type: 'single-select-filter'
});

Check out https://astexplorer.net to see the AST JSON over which the queries are executed.

The rule above selects nodes having PropertyDeclaration as their SyntaxKind. The resulting array is then queried for nodes which have a modifier with the SyntaxKind ReadonlyKeyword. matchType: 'none' indicates that in order for the rule to pass no node must meet this criterion.

See the tests for more examples.

Aliases and extensions

SyntaxKind

SyntaxKind keys are aliased with @.kind===0000, where 0000 is the respective enum value. The ? prefix drops the @ from the beginning of this substitution.

Examples:

• PropertySignature is an alias for @.kind===161
• @.expression?ParenthesizedExpression turns into @.expression.kind===204

Previous

Each node that is part of an array in the AST(object properties, class members, function paremeters etc.) is decorated with a __previous property pointing to a copy of the previous node, but with its own __previous field not present so as to avoid deep routes.

Comments

Comments are not normally part of the AST, but this library decorates the nodes appropriately. The fields are named the same as in https://astexplorer.net, but the nodes to which the comments are attached may be different.