forked from babel/babel
/
valueToNode.ts
131 lines (113 loc) · 3.32 KB
/
valueToNode.ts
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import isValidIdentifier from "../validators/isValidIdentifier";
import {
identifier,
booleanLiteral,
nullLiteral,
stringLiteral,
numericLiteral,
regExpLiteral,
arrayExpression,
objectProperty,
objectExpression,
unaryExpression,
binaryExpression,
} from "../builders/generated";
import type * as t from "..";
export default valueToNode as {
(value: undefined): t.Identifier; // TODO: This should return "void 0"
(value: boolean): t.BooleanLiteral;
(value: null): t.NullLiteral;
(value: string): t.StringLiteral;
// Infinities and NaN need to use a BinaryExpression; negative values must be wrapped in UnaryExpression
(value: number): t.NumericLiteral | t.BinaryExpression | t.UnaryExpression;
(value: RegExp): t.RegExpLiteral;
(value: ReadonlyArray<unknown>): t.ArrayExpression;
// this throws with objects that are not plain objects,
// or if there are non-valueToNode-able values
(value: object): t.ObjectExpression;
(value: unknown): t.Expression;
};
const objectToString: (value: object) => string = Function.call.bind(
Object.prototype.toString,
);
function isRegExp(value): value is RegExp {
return objectToString(value) === "[object RegExp]";
}
function isPlainObject(value): value is object {
if (
typeof value !== "object" ||
value === null ||
Object.prototype.toString.call(value) !== "[object Object]"
) {
return false;
}
const proto = Object.getPrototypeOf(value);
// Object.prototype's __proto__ is null. Every other class's __proto__.__proto__ is
// not null by default. We cannot check if proto === Object.prototype because it
// could come from another realm.
return proto === null || Object.getPrototypeOf(proto) === null;
}
function valueToNode(value: unknown): t.Expression {
// undefined
if (value === undefined) {
return identifier("undefined");
}
// boolean
if (value === true || value === false) {
return booleanLiteral(value);
}
// null
if (value === null) {
return nullLiteral();
}
// strings
if (typeof value === "string") {
return stringLiteral(value);
}
// numbers
if (typeof value === "number") {
let result;
if (Number.isFinite(value)) {
result = numericLiteral(Math.abs(value));
} else {
let numerator;
if (Number.isNaN(value)) {
// NaN
numerator = numericLiteral(0);
} else {
// Infinity / -Infinity
numerator = numericLiteral(1);
}
result = binaryExpression("/", numerator, numericLiteral(0));
}
if (value < 0 || Object.is(value, -0)) {
result = unaryExpression("-", result);
}
return result;
}
// regexes
if (isRegExp(value)) {
const pattern = value.source;
const flags = value.toString().match(/\/([a-z]+|)$/)[1];
return regExpLiteral(pattern, flags);
}
// array
if (Array.isArray(value)) {
return arrayExpression(value.map(valueToNode));
}
// object
if (isPlainObject(value)) {
const props = [];
for (const key of Object.keys(value)) {
let nodeKey;
if (isValidIdentifier(key)) {
nodeKey = identifier(key);
} else {
nodeKey = stringLiteral(key);
}
props.push(objectProperty(nodeKey, valueToNode(value[key])));
}
return objectExpression(props);
}
throw new Error("don't know how to turn this value into a node");
}