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Babel AST transform drops Recast's original property #12882
Description
Bug Report
Maybe you don't consider this a bug, but I thought I'd flag it anyway.
Current behavior
Recast (0.20.4) works by attaching an original property to AST nodes. babel.transformFromAst drops that property, preventing Recast from working as expected.
This is demonstrated by the following script:
const babel = require('@babel/core');
const recast = require('recast');
const _ = require('lodash');
const filename = 'file.js';
const source = `
function f(
a,
b,
c
) {
return d;
}
`;
const babelOpts = {
filename,
ast: true
};
const parser = {
parse(source, opts) {
return babel.parse(source, {
...babelOpts,
..._.omit(
opts,
'jsx', 'loc', 'locations', 'range', 'comment', 'onComment', 'tolerant', 'ecmaVersion'
)
});
}
};
const ast = recast.parse(source, {parser});
const result = babel.transformFromAstSync(ast, source, babelOpts);
const printedFromRecastParse = recast.print(ast).code;
const printedFromBabelTransform = recast.print(result.ast).code;
console.log('printedFromRecastParse', printedFromRecastParse);
console.log();
console.log('printedFromBabelTransform', printedFromBabelTransform);This produces:
printedFromRecastParse
function f(
a,
b,
c
) {
return d;
}
printedFromBabelTransform "use strict";
function f(a, b, c) {
return d;
}
Expected behavior
Program output:
printedFromRecastParse
"use strict";
function f(
a,
b,
c
) {
return d;
}
printedFromBabelTransform "use strict";
function f(
a,
b,
c
) {
return d;
}
Environment
System:
OS: macOS 11.2.1
Binaries:
Node: 12.14.0 - ~/.nvm/versions/node/v12.14.0/bin/node
Yarn: 1.22.5 - /usr/local/bin/yarn
npm: 6.13.4 - ~/.nvm/versions/node/v12.14.0/bin/npm
npmPackages:
@babel/core: 7.13.1 => 7.13.1
@babel/plugin-syntax-pipeline-operator: 7.12.13 => 7.12.13
@babel/plugin-transform-typescript: 7.13.0 => 7.13.0
@babel/preset-env: 7.11.5 => 7.11.5
@babel/preset-typescript: 7.10.4 => 7.10.4
babel-jest: 26.3.0 => 26.3.0
eslint: 7.9.0 => 7.9.0
jest: 26.4.2 => 26.4.2
- Monorepo: no
- How you are using Babel: Standalone
Possible Solution
This workaround addresses the issue, but it's a bit cumbersome. Here's the snippet above with the workaround applied:
const babel = require('@babel/core');
const recast = require('recast');
const _ = require('lodash');
const filename = 'file.js';
const source = `
function f(
a,
b,
c
) {
return d;
}
`;
const babelOpts = {
filename,
ast: true,
code: false
};
const parser = {
parse(source, opts) {
return babel.parse(source, {
...babelOpts,
..._.omit(
opts,
'jsx', 'loc', 'locations', 'range', 'comment', 'onComment', 'tolerant', 'ecmaVersion'
)
});
}
};
const ast = recast.parse(source, {parser});
const setAst = babel => ({
visitor: {
Program(path) {
path.replaceWith(ast.program);
}
}
});
const result = babel.transformSync('', {
...babelOpts,
plugins: [setAst]
});
const printedFromRecastParse = recast.print(ast).code;
const printedFromBabelTransform = recast.print(result.ast).code;
console.log('printedFromRecastParse', printedFromRecastParse);
console.log();
console.log('printedFromBabelTransform', printedFromBabelTransform);Additional context
Activity
babel-bot commentedon Feb 23, 2021
Hey @NickHeiner! We really appreciate you taking the time to report an issue. The collaborators on this project attempt to help as many people as possible, but we're a limited number of volunteers, so it's possible this won't be addressed swiftly.
If you need any help, or just have general Babel or JavaScript questions, we have a vibrant Slack community that typically always has someone willing to help. You can sign-up here for an invite."
nicolo-ribaudo commentedon Feb 23, 2021
You can try passing
cloneInputAst: falsetotransformFromAst's options.NickHeiner commentedon Feb 24, 2021
That fixes it! Thanks.