In this article, we review what is ESTree. We will look at:
@types/estree package
ESTree dev dependency in Ripple
ESTree usage in Ripple
I found references to ESTree in Ripple codebase.
@types/estree package
This package contains type definitions for estree. Files were exported from https://github.com/DefinitelyTyped/DefinitelyTyped/tree/master/types/estree.
ESTree is a specification that defines the standard structure (format) for representing JavaScript code as an Abstract Syntax Tree (AST).
Below is a comment picked from DefinitelyTyped/types/estree/index.d.ts.
// This definition file follows a somewhat unusual format. ESTree allows // runtime type checks based on the `type` parameter. In order to explain this // to typescript we want to use discriminated union types: // https://github.com/Microsoft/TypeScript/pull/9163 // // For ESTree this is a bit tricky because the high level interfaces like // Node or Function are pulling double duty. We want to pass common fields down // to the interfaces that extend them (like Identifier or // ArrowFunctionExpression), but you can't extend a type union or enforce // common fields on them. So we've split the high level interfaces into two // types, a base type which passes down inherited fields, and a type union of // all types which extend the base type. Only the type union is exported, and // the union is how other types refer to the collection of inheriting types. // // This makes the definitions file here somewhat more difficult to maintain, // but it has the notable advantage of making ESTree much easier to use as // an end user. When JavaScript code is parsed by tools like Babel, ESLint, or TypeScript, it’s converted into an AST, which is a tree-like representation of the code’s syntax. Different tools initially had different AST formats, so ESTree was created to provide a consistent structure for interoperability.
ESTree dev dependency in Ripple
I found @types/estree in devDepencies in package.json:
ESTree usage in Ripple
ESTree is used in a lot of places in Ripple codebase.
Below is one reference picked from ripple/utils/ast.js.
/** * @param {ESTree.AssignmentOperator} operator * @param {ESTree.Identifier | ESTree.MemberExpression} left * @param {ESTree.Expression} right */ export function build_assignment_value(operator, left, right) { return operator === '=' ? right : // turn something like x += 1 into x = x + 1 b.binary(/** @type {ESTree.BinaryOperator} */ (operator.slice(0, -1)), left, right); } Here ESTree is used indicate type of parameters used in functions.
Below is another reference picked from ripple/utils/builders.js.
/** @type {ESTree.DebuggerStatement} */ const debugger_builder = { type: 'DebuggerStatement' }; About me:
Hey, my name is Ramu Narasinga. I study codebase architecture in large open-source projects.
Email: ramu.narasinga@gmail.com
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