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370 lines
10 KiB
370 lines
10 KiB
2 years ago
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import {parseExpression, ParserOptions} from '@babel/parser';
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import * as b from '@babel/types';
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import binaryOperation from './binaryOperation';
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export {ParserOptions as BabylonOptions};
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export interface ExpressionToConstantOptions {
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constants?: any;
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}
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export interface Options extends ExpressionToConstantOptions {
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babylon?: ParserOptions;
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}
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export function expressionToConstant(
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expression: b.Expression,
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options: ExpressionToConstantOptions = {},
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): {constant: true; result: any} | {constant: false; result?: void} {
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let constant = true;
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function toConstant(expression: b.Expression): any {
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if (!constant) return;
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if (b.isArrayExpression(expression)) {
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const result = [];
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for (let i = 0; constant && i < expression.elements.length; i++) {
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const element = expression.elements[i];
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if (b.isSpreadElement(element)) {
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const spread = toConstant(element.argument);
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if (!(isSpreadable(spread) && constant)) {
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constant = false;
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} else {
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result.push(...spread);
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}
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} else if (b.isExpression(element)) {
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result.push(toConstant(element));
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} else {
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constant = false;
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}
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}
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return result;
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}
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if (b.isBinaryExpression(expression)) {
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const left = toConstant(expression.left);
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const right = toConstant(expression.right);
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return constant && binaryOperation(expression.operator, left, right);
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}
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if (b.isBooleanLiteral(expression)) {
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return expression.value;
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}
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if (b.isCallExpression(expression)) {
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const args = [];
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for (let i = 0; constant && i < expression.arguments.length; i++) {
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const arg = expression.arguments[i];
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if (b.isSpreadElement(arg)) {
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const spread = toConstant(arg.argument);
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if (!(isSpreadable(spread) && constant)) {
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constant = false;
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} else {
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args.push(...spread);
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}
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} else if (b.isExpression(arg)) {
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args.push(toConstant(arg));
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} else {
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constant = false;
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}
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}
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if (!constant) return;
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if (b.isMemberExpression(expression.callee)) {
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const object = toConstant(expression.callee.object);
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if (!object || !constant) {
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constant = false;
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return;
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}
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const member = expression.callee.computed
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? toConstant(expression.callee.property)
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: b.isIdentifier(expression.callee.property)
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? expression.callee.property.name
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: undefined;
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if (member === undefined && !expression.callee.computed) {
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constant = false;
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}
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if (!constant) return;
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if (canCallMethod(object, '' + member)) {
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return object[member].apply(object, args);
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}
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} else {
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if (!b.isExpression(expression.callee)) {
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constant = false;
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return;
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}
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const callee = toConstant(expression.callee);
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if (!constant) return;
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return callee.apply(null, args);
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}
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}
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if (b.isConditionalExpression(expression)) {
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const test = toConstant(expression.test);
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return test
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? toConstant(expression.consequent)
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: toConstant(expression.alternate);
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}
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if (b.isIdentifier(expression)) {
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if (
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options.constants &&
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{}.hasOwnProperty.call(options.constants, expression.name)
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) {
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return options.constants[expression.name];
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}
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}
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if (b.isLogicalExpression(expression)) {
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const left = toConstant(expression.left);
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const right = toConstant(expression.right);
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if (constant && expression.operator === '&&') {
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return left && right;
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}
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if (constant && expression.operator === '||') {
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return left || right;
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}
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}
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if (b.isMemberExpression(expression)) {
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const object = toConstant(expression.object);
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if (!object || !constant) {
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constant = false;
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return;
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}
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const member = expression.computed
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? toConstant(expression.property)
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: b.isIdentifier(expression.property)
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? expression.property.name
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: undefined;
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if (member === undefined && !expression.computed) {
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constant = false;
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}
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if (!constant) return;
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if ({}.hasOwnProperty.call(object, '' + member) && member[0] !== '_') {
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return object[member];
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}
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}
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if (b.isNullLiteral(expression)) {
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return null;
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}
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if (b.isNumericLiteral(expression)) {
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return expression.value;
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}
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if (b.isObjectExpression(expression)) {
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const result: any = {};
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for (let i = 0; constant && i < expression.properties.length; i++) {
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const property = expression.properties[i];
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if (b.isObjectProperty(property)) {
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if (property.shorthand) {
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constant = false;
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return;
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}
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const key = property.computed
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? toConstant(property.key)
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: b.isIdentifier(property.key)
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? property.key.name
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: b.isStringLiteral(property.key)
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? property.key.value
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: undefined;
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if (!key || key[0] === '_') {
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constant = false;
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}
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if (!constant) return;
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if (b.isExpression(property.value)) {
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const value = toConstant(property.value);
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if (!constant) return;
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result[key] = value;
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} else {
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constant = false;
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}
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} else if (b.isObjectMethod(property)) {
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constant = false;
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} else if (b.isSpreadProperty(property)) {
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const argument = toConstant(property.argument);
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if (!argument) constant = false;
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if (!constant) return;
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Object.assign(result, argument);
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}
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}
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return result;
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}
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if (b.isParenthesizedExpression(expression)) {
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return toConstant(expression.expression);
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}
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if (b.isRegExpLiteral(expression)) {
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return new RegExp(expression.pattern, expression.flags);
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}
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if (b.isSequenceExpression(expression)) {
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for (let i = 0; i < expression.expressions.length - 1 && constant; i++) {
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toConstant(expression.expressions[i]);
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}
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return toConstant(
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expression.expressions[expression.expressions.length - 1],
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);
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}
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if (b.isStringLiteral(expression)) {
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return expression.value;
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}
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// TODO: TaggedTemplateExpression
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if (b.isTemplateLiteral(expression)) {
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let result = '';
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for (let i = 0; i < expression.quasis.length; i++) {
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const quasi = expression.quasis[i];
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result += quasi.value.cooked;
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if (i < expression.expressions.length) {
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result += '' + toConstant(expression.expressions[i]);
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}
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}
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return result;
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}
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if (b.isUnaryExpression(expression)) {
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const argument = toConstant(expression.argument);
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if (!constant) {
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return;
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}
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switch (expression.operator) {
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case '-':
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return -argument;
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case '+':
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return +argument;
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case '!':
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return !argument;
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case '~':
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return ~argument;
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case 'typeof':
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return typeof argument;
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case 'void':
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return void argument;
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}
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}
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constant = false;
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}
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const result = toConstant(expression);
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return constant ? {constant: true, result} : {constant: false};
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}
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function isSpreadable(value: any): boolean {
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return (
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typeof value === 'string' ||
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Array.isArray(value) ||
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(typeof Set !== 'undefined' && value instanceof Set) ||
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(typeof Map !== 'undefined' && value instanceof Map)
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);
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}
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function shallowEqual(a: any, b: any) {
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if (a === b) return true;
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if (a && b && typeof a === 'object' && typeof b === 'object') {
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for (let key in a) {
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if (a[key] !== b[key]) {
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return false;
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}
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}
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for (let key in b) {
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if (a[key] !== b[key]) {
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return false;
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}
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}
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return true;
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}
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return false;
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}
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function canCallMethod(object: any, member: string): boolean {
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switch (typeof object) {
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case 'boolean':
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switch (member) {
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case 'toString':
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return true;
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default:
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return false;
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}
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case 'number':
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switch (member) {
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case 'toExponential':
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case 'toFixed':
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case 'toPrecision':
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case 'toString':
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return true;
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default:
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return false;
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}
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case 'string':
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switch (member) {
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case 'charAt':
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case 'charCodeAt':
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case 'codePointAt':
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case 'concat':
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case 'endsWith':
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case 'includes':
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case 'indexOf':
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case 'lastIndexOf':
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case 'match':
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case 'normalize':
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case 'padEnd':
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case 'padStart':
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case 'repeat':
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case 'replace':
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case 'search':
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case 'slice':
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case 'split':
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case 'startsWith':
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case 'substr':
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case 'substring':
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case 'toLowerCase':
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case 'toUpperCase':
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case 'trim':
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return true;
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default:
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return false;
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}
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default:
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if (object instanceof RegExp) {
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switch (member) {
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case 'test':
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case 'exec':
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return true;
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default:
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return false;
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}
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}
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return {}.hasOwnProperty.call(object, member) && member[0] !== '_';
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}
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}
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const EMPTY_OBJECT = {};
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let lastSrc = '';
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let lastConstants = EMPTY_OBJECT;
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let lastOptions = EMPTY_OBJECT;
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let lastResult: any = null;
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let lastWasConstant = false;
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export function isConstant(
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src: string,
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constants: any = EMPTY_OBJECT,
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options: ParserOptions = EMPTY_OBJECT,
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) {
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if (
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lastSrc === src &&
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shallowEqual(lastConstants, constants) &&
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shallowEqual(lastOptions, options)
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) {
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return lastWasConstant;
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}
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lastSrc = src;
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lastConstants = constants;
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let ast: b.Expression | void;
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try {
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ast = parseExpression(src, options);
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} catch (ex) {
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return (lastWasConstant = false);
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}
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const {result, constant} = expressionToConstant(ast, {constants});
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lastResult = result;
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return (lastWasConstant = constant);
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}
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export function toConstant(
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src: string,
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constants: any = EMPTY_OBJECT,
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options: ParserOptions = EMPTY_OBJECT,
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) {
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if (!isConstant(src, constants, options)) {
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throw new Error(JSON.stringify(src) + ' is not constant.');
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}
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return lastResult;
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}
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export default isConstant;
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module.exports = isConstant;
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module.exports.default = isConstant;
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module.exports.expressionToConstant = expressionToConstant;
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module.exports.isConstant = isConstant;
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module.exports.toConstant = toConstant;
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