122 lines
4.7 KiB
JavaScript
122 lines
4.7 KiB
JavaScript
/**
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* 严格 JSON 输出边界。
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*
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* 为什么要有这层：宿主要在渲染前校验工具结果，而 `JSON.stringify` 遇到
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* BigInt 直接抛、遇到 undefined 静默丢字段、遇到循环引用抛、遇到 accessor
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* 触发取值副作用。任何一条都可能让一个本来成功的操作变成 500，或者更糟——
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* 让「看起来成功」的响应其实丢了关键字段。
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*
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* 规则（与 IG5 的 source/json_output.js 同一套判据）：
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* - 可选对象的 undefined 字段省略；null 保留
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* - 数字必须有限，且不能是 -0
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* - 拒绝：BigInt / Symbol / Function / 循环引用 / accessor / 非普通对象 /
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* 数组空洞 / 带额外属性的数组 / 非可枚举字段
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* - 深度与节点数有上限，超限抛错而不是截断
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*
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* 对外两个入口：
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* projectJson(value, opts) —— 严格投影，非 JSON 就抛
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* safeProject(value, opts) —— 投影失败时降级成带标记的对象，永不抛
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*/
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const MAX_DEPTH_DEFAULT = 64;
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const MAX_NODES_DEFAULT = 200000;
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function fail(at, reason) {
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const error = new TypeError(`dsh-purge JSON at ${at} is not lossless: ${reason}`);
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error.code = "INVALID_PLUGIN_OUTPUT";
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error.at = at;
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return error;
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}
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/**
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* @param {unknown} value
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* @param {{ maxDepth?: number, maxNodes?: number }} [opts]
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*/
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export function projectJson(value, opts = {}) {
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const maxDepth = Number.isFinite(opts.maxDepth) ? opts.maxDepth : MAX_DEPTH_DEFAULT;
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const maxNodes = Number.isFinite(opts.maxNodes) ? opts.maxNodes : MAX_NODES_DEFAULT;
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const ancestors = new WeakSet();
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let nodes = 0;
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function visit(item, at, depth) {
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if (depth > maxDepth) throw fail(at, `maximum nesting ${maxDepth} exceeded`);
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if (++nodes > maxNodes) throw fail(at, `maximum node count ${maxNodes} exceeded`);
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if (item === null) return null;
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const type = typeof item;
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if (type === "string" || type === "boolean") return item;
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if (type === "number") {
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if (!Number.isFinite(item) || Object.is(item, -0)) throw fail(at, "non-lossless number");
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return item;
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}
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if (type !== "object") throw fail(at, `unsupported ${type}`);
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if (ancestors.has(item)) throw fail(at, "circular reference");
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ancestors.add(item);
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try {
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if (Array.isArray(item)) {
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if (Object.getPrototypeOf(item) !== Array.prototype) throw fail(at, "non-plain array");
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const own = Reflect.ownKeys(item);
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if (own.length !== item.length + 1) throw fail(at, "sparse or decorated array");
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const out = new Array(item.length);
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for (let index = 0; index < item.length; index += 1) {
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const descriptor = Object.getOwnPropertyDescriptor(item, String(index));
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if (!descriptor || !("value" in descriptor)) throw fail(`${at}[${index}]`, "missing or accessor item");
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out[index] = visit(descriptor.value, `${at}[${index}]`, depth + 1);
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}
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return out;
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}
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const prototype = Object.getPrototypeOf(item);
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if (prototype !== null && prototype !== Object.prototype) throw fail(at, "non-plain object");
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const out = {};
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for (const key of Reflect.ownKeys(item)) {
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if (typeof key !== "string") throw fail(at, "symbol key");
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const descriptor = Object.getOwnPropertyDescriptor(item, key);
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if (!descriptor.enumerable) throw fail(`${at}.${key}`, "non-enumerable field");
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if (!("value" in descriptor)) throw fail(`${at}.${key}`, "accessor field");
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if (descriptor.value === undefined) continue;
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Object.defineProperty(out, key, {
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value: visit(descriptor.value, `${at}.${key}`, depth + 1),
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enumerable: true,
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writable: true,
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configurable: true,
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});
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}
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return out;
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} finally {
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ancestors.delete(item);
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}
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}
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return visit(value, "$", 0);
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}
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/**
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* 永不抛的版本：投影失败时返回 `{ __invalid: true, __reason, __at }`，
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* 让 HTTP 层仍能给出可诊断的 200/500，而不是把异常冒到宿主。
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*/
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export function safeProject(value, opts = {}) {
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try {
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return { ok: true, value: projectJson(value, opts) };
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} catch (error) {
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return {
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ok: false,
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value: {
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__invalid: true,
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__reason: String(error && error.message ? error.message : error),
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__at: String(error && error.at ? error.at : "$"),
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},
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};
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}
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}
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/** 把任意值编码成可安全写出的 JSON 文本；绝不抛。 */
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export function stringifySafe(value, opts = {}) {
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const projected = safeProject(value, opts);
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try {
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return JSON.stringify(projected.value);
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} catch (error) {
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return JSON.stringify({ __invalid: true, __reason: String(error && error.message ? error.message : error) });
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}
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}
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