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Traverse an ESTree-compliant AST

License: MIT License

JavaScript 100.00%

estree-walker's Introduction

estree-walker

Simple utility for walking an ESTree-compliant AST, such as one generated by acorn.

Installation

npm i estree-walker

Usage

var walk = require('estree-walker').walk;
var acorn = require('acorn');

ast = acorn.parse(sourceCode, options); // https://github.com/acornjs/acorn

walk(ast, {
  enter(node, parent, prop, index) {
    // some code happens
  },
  leave(node, parent, prop, index) {
    // some code happens
  }
});

Inside the enter function, calling this.skip() will prevent the node's children being walked, or the leave function (which is optional) being called.

Call this.replace(new_node) in either enter or leave to replace the current node with a new one.

Call this.remove() in either enter or leave to remove the current node.

Why not use estraverse?

The ESTree spec is evolving to accommodate ES6/7. I've had a couple of experiences where estraverse was unable to handle an AST generated by recent versions of acorn, because it hard-codes visitor keys.

estree-walker, by contrast, simply enumerates a node's properties to find child nodes (and child lists of nodes), and is therefore resistant to spec changes. It's also much smaller. (The performance, if you're wondering, is basically identical.)

None of which should be taken as criticism of estraverse, which has more features and has been battle-tested in many more situations, and for which I'm very grateful.

License

MIT

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estree-walker's Issues

[Bug Report] Getting an ts error when I build my project(using [email protected])

Version
estree-walker 2.0.2(Be depended on @vue/[email protected])
Node: 14.16.1
typescript: 4.2.4

Describe
Getting an ts error when I build my project
node_modules/estree-walker/types/index.d.ts:13:34 - error TS2307: Cannot find module 'estree' or its corresponding type declarations.

Error [ERR_PACKAGE_PATH_NOT_EXPORTED]: No "exports" main defined in... error

Getting an error when I try to use estree-walker with esbuild:

Error [ERR_PACKAGE_PATH_NOT_EXPORTED]: No "exports" main defined in /Users/sam/Nine/components/node_modules/estree-walker/package.json
    at throwExportsNotFound (internal/modules/esm/resolve.js:290:9)
    at packageExportsResolve (internal/modules/esm/resolve.js:479:7)
    at resolveExports (internal/modules/cjs/loader.js:432:36)
    at Function.Module._findPath (internal/modules/cjs/loader.js:472:31)
    at Function.Module._resolveFilename (internal/modules/cjs/loader.js:867:27)
    at Function.Module._load (internal/modules/cjs/loader.js:725:27)
    at Module.require (internal/modules/cjs/loader.js:952:19)
    at require (internal/modules/cjs/helpers.js:88:18)
    at Object.<anonymous> (/Users/sam/Nine/components/dist/src/main.js:43:39)
    at Module._compile (internal/modules/cjs/loader.js:1063:30) {
  code: 'ERR_PACKAGE_PATH_NOT_EXPORTED'
}

Node Version: v14.15.4

tsconfig.json:

{
  "compilerOptions": {
    "allowSyntheticDefaultImports": true,
    "esModuleInterop": true,
    "allowJs": true,
    "importHelpers": true,
    "alwaysStrict": true,
    "sourceMap": true,
    "forceConsistentCasingInFileNames": true,
    "noFallthroughCasesInSwitch": true,
    "noImplicitReturns": true,
    "noUnusedLocals": true,
    "noUnusedParameters": true,
    "noImplicitAny": false,
    "noImplicitThis": false,
    "strictNullChecks": false
  },
  "include": ["src/**/*", "__tests__/**/*"]
}

1.0.0 (and missing LICENSE file)

Any reason to hold off from a 1.0.0 release? Is this package considered stable?

Also, you unambiguously specify this is under the MIT LICENSE, but, you don't provide the LICENSE yourself in either the npm publication or this repository.

From the MIT LICENSE:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

Where (and what is the contents of) the copyright notice? etc

Move `@types/estree` to dependencies instead of devDeps

As estree is exposed in the types used by estree-walker, when using estree-walker with a strict package manager like yarn pnp, TypeScript warns us that it cannot find the package estree when using estree-walker:

Here is the error I have in TypeScript:

.yarn/cache/estree-walker-npm-3.0.1-f100136724-002ec6bba6.zip/node_modules/estree-walker/types/index.d.ts(18,56): error TS2307: Cannot find module 'estree' or its corresponding type declarations.

Moving @types/estree to the deps would allow other package to directly find estree (as devDeps are not installed by other packages, but deps are)

Packaged v3 doesn't have `dist` folder

It seems that the packaged v3 version of the lib was deployed without the build artifacts 🙈

https://npm-explorer.tk/?p=estree-walker

The usage instructions in the README.md are not working.

When I followed the usage instructions in the README, I received this error message.

Error [ERR_PACKAGE_PATH_NOT_EXPORTED]: No "exports" main defined in /Users/sam/Nine/components/node_modules/estree-walker/package.json
    at throwExportsNotFound (internal/modules/esm/resolve.js:290:9)
    at packageExportsResolve (internal/modules/esm/resolve.js:479:7)
    at resolveExports (internal/modules/cjs/loader.js:432:36)
    at Function.Module._findPath (internal/modules/cjs/loader.js:472:31)
    at Function.Module._resolveFilename (internal/modules/cjs/loader.js:867:27)
    at Function.Module._load (internal/modules/cjs/loader.js:725:27)
    at Module.require (internal/modules/cjs/loader.js:952:19)
    at require (internal/modules/cjs/helpers.js:88:18)
    at Object.<anonymous> (/Users/sam/Nine/components/dist/src/main.js:43:39)
    at Module._compile (internal/modules/cjs/loader.js:1063:30) {
  code: 'ERR_PACKAGE_PATH_NOT_EXPORTED'
}

Could i fix this usage instructions in the README?

index.d.ts file is not part of the npm package

Hi,

I noticed that the index.d.ts file is not included in the NPM package, so the types are not accessible to the users.

Allow to `return` from `enter` and `leave`

Hey y'all

I think it would be great if there was an easy way to break the tree traversal and return something by calling return ....

Then, this code would be possible:

const result = walk(ast, {enter(node) {
    if(node === condition) return something
}})
// Logs the value of something
console.log(result)

What do you think?

Wrong TS types: BaseNode instead of Node

Hey, I'm using the svelte compiler to walk the AST. I'm using Typescript and it seems that the typings are wrong for the node that passed to the walk function - https://github.com/Rich-Harris/estree-walker/blob/master/src/async.js#L4

It's typed as BaseNode, but the possible results are some sort of of Node + INode mixed type (eg. ModuleSpecifier for import statements). The dependencies:

{
    "svelte": "^3.38.2",
    "@types/estree": "^0.0.48",
    "estree-walker": "^3.0.0"
}

P.S. Also Svelte doesn't automatically include those types, you need to install more of the packages. This isn't ideal as you could miss-match the dependency versions. Maybe there is a conventional way to bundle types, without the need for the user to install svelte's sub-dependencies? 🤔

Caching child keys not always valid

I have some code including ES7 decorators parsed by acorn-es7.

ClassDeclaration.decorators is not always present, so caching the keys means that the decorator node is skipped unless the first class encountered happens to have a decorator.

The filter isn't really necessary given the check for value.type later, so removing the cache shouldn't have much of a performance impact.