Is there a way to easily compare 2 AST structures disregarding position? - node.js

Question

Is there a way to easily compare 2 ast's on babel?
Consider a program like this as the source file:
// example.ts
import { foo } from "bar";
describe("Some test", () => {
let moduleFixture: any;
beforeAll(async () => {
moduleFixture = await foo.createTestingModule({}).compile();
});
afterAll(async () => {
await foo.tearDown();
});
});
And consider the following babel program
const babelParser = require("#babel/parser");
const { default: traverse } = require("#babel/traverse");
const { readFileSync } = require("fs");
const recast = require("recast");
const { default: template } = require("#babel/template");
const source = readFileSync(`./example.ts`, "utf-8");
const buildBeforeAll = template(
` beforeAll(async () => {
moduleFixture = await foo.createTestingModule({}).compile();
}); `,
{
plugins: ["typescript"],
}
);
const beforeAllAst = buildBeforeAll();
const ast = babelParser.parse(source, {
allowImportExportEverywhere: true,
plugins: ["typescript"],
});
traverse(ast, {
enter(path) {
const isBeforeAll = path.isIdentifier({ name: "beforeAll" });
if (isBeforeAll) {
// Somehow compare is beforeAllASt === path
console.log(`found an appropriate beforeall`);
path.replaceWithSourceString(`beforeEach`);
}
},
});
console.log(recast.print(ast).code);
What would be the best way to compare beforeAllAst with a traversed node?

Answer 1

The simplest way to made such modifications will be using 🐊Putout code transformer, I'm working on.
Here is how it looks like:
const source = `
beforeAll(async () => {
moduleFixture = await foo.createTestingModule({}).compile();
});
`;
module.exports.replace = () => ({
[source]: (vars, path) => {
path.node.callee.name = 'beforeEach'
return path;
},
});
This plugin searches for exact mach of beforeAll function call. It uses #putout/compare which can be used directly in your code:
const {compare} = require('#putout/compare');
traverse(ast, {
enter(path) {
const isBeforeAll = path.isIdentifier({ name: "beforeAll" });
if (compare(path, beforeAllAst)) {
// Somehow compare is beforeAllASt === path
console.log(`found an appropriate beforeall`);
path.replaceWithSourceString(`beforeEach`);
}
},
});
#putout/compare compares AST-node with given string or other AST-node