packages/babel-generator/src/index.js
import SourceMap from "./source-map";
import Printer, { type Format } from "./printer";
/**
* Babel's code generator, turns an ast into code, maintaining sourcemaps,
* user preferences, and valid output.
*/
class Generator extends Printer {
constructor(ast, opts = {}, code) {
const format = normalizeOptions(code, opts);
const map = opts.sourceMaps ? new SourceMap(opts, code) : null;
super(format, map);
this.ast = ast;
}
ast: Object;
/**
* Generate code and sourcemap from ast.
*
* Appends comments that weren't attached to any node to the end of the generated output.
*/
generate() {
return super.generate(this.ast);
}
}
/**
* Normalize generator options, setting defaults.
*
* - Detects code indentation.
* - If `opts.compact = "auto"` and the code is over 500KB, `compact` will be set to `true`.
*/
function normalizeOptions(code, opts): Format {
const format = {
auxiliaryCommentBefore: opts.auxiliaryCommentBefore,
auxiliaryCommentAfter: opts.auxiliaryCommentAfter,
shouldPrintComment: opts.shouldPrintComment,
retainLines: opts.retainLines,
retainFunctionParens: opts.retainFunctionParens,
comments: opts.comments == null || opts.comments,
compact: opts.compact,
minified: opts.minified,
concise: opts.concise,
jsonCompatibleStrings: opts.jsonCompatibleStrings,
indent: {
adjustMultilineComment: true,
style: " ",
base: 0,
},
decoratorsBeforeExport: !!opts.decoratorsBeforeExport,
jsescOption: {
quotes: "double",
wrap: true,
...opts.jsescOption,
},
recordAndTupleSyntaxType: opts.recordAndTupleSyntaxType,
};
if (format.minified) {
format.compact = true;
format.shouldPrintComment =
format.shouldPrintComment || (() => format.comments);
} else {
format.shouldPrintComment =
format.shouldPrintComment ||
(value =>
format.comments ||
value.indexOf("@license") >= 0 ||
value.indexOf("@preserve") >= 0);
}
if (format.compact === "auto") {
format.compact = code.length > 500_000; // 500KB
if (format.compact) {
console.error(
"[BABEL] Note: The code generator has deoptimised the styling of " +
`${opts.filename} as it exceeds the max of ${"500KB"}.`,
);
}
}
if (format.compact) {
format.indent.adjustMultilineComment = false;
}
return format;
}
/**
* We originally exported the Generator class above, but to make it extra clear that it is a private API,
* we have moved that to an internal class instance and simplified the interface to the two public methods
* that we wish to support.
*/
export class CodeGenerator {
constructor(ast, opts, code) {
this._generator = new Generator(ast, opts, code);
}
generate() {
return this._generator.generate();
}
}
export default function (ast: Object, opts: Object, code: string): Object {
const gen = new Generator(ast, opts, code);
return gen.generate();
}