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/snap/node/11691/lib/node_modules/npm/node_modules/http-cache-semantics/index.js
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'use strict'; /** * @typedef {Object} HttpRequest * @property {Record<string, string>} headers - Request headers * @property {string} [method] - HTTP method * @property {string} [url] - Request URL */ /** * @typedef {Object} HttpResponse * @property {Record<string, string>} headers - Response headers * @property {number} [status] - HTTP status code */ /** * Set of default cacheable status codes per RFC 7231 section 6.1. * @type {Set<number>} */ const statusCodeCacheableByDefault = new Set([ 200, 203, 204, 206, 300, 301, 308, 404, 405, 410, 414, 501, ]); /** * Set of HTTP status codes that the cache implementation understands. * Note: This implementation does not understand partial responses (206). * @type {Set<number>} */ const understoodStatuses = new Set([ 200, 203, 204, 300, 301, 302, 303, 307, 308, 404, 405, 410, 414, 501, ]); /** * Set of HTTP error status codes. * @type {Set<number>} */ const errorStatusCodes = new Set([ 500, 502, 503, 504, ]); /** * Object representing hop-by-hop headers that should be removed. * @type {Record<string, boolean>} */ const hopByHopHeaders = { date: true, // included, because we add Age update Date connection: true, 'keep-alive': true, 'proxy-authenticate': true, 'proxy-authorization': true, te: true, trailer: true, 'transfer-encoding': true, upgrade: true, }; /** * Headers that are excluded from revalidation update. * @type {Record<string, boolean>} */ const excludedFromRevalidationUpdate = { // Since the old body is reused, it doesn't make sense to change properties of the body 'content-length': true, 'content-encoding': true, 'transfer-encoding': true, 'content-range': true, }; /** * Converts a string to a number or returns zero if the conversion fails. * @param {string} s - The string to convert. * @returns {number} The parsed number or 0. */ function toNumberOrZero(s) { const n = parseInt(s, 10); return isFinite(n) ? n : 0; } /** * Determines if the given response is an error response. * Implements RFC 5861 behavior. * @param {HttpResponse|undefined} response - The HTTP response object. * @returns {boolean} true if the response is an error or undefined, false otherwise. */ function isErrorResponse(response) { // consider undefined response as faulty if (!response) { return true; } return errorStatusCodes.has(response.status); } /** * Parses a Cache-Control header string into an object. * @param {string} [header] - The Cache-Control header value. * @returns {Record<string, string|boolean>} An object representing Cache-Control directives. */ function parseCacheControl(header) { /** @type {Record<string, string|boolean>} */ const cc = {}; if (!header) return cc; // TODO: When there is more than one value present for a given directive (e.g., two Expires header fields, multiple Cache-Control: max-age directives), // the directive's value is considered invalid. Caches are encouraged to consider responses that have invalid freshness information to be stale const parts = header.trim().split(/,/); for (const part of parts) { const [k, v] = part.split(/=/, 2); cc[k.trim()] = v === undefined ? true : v.trim().replace(/^"|"$/g, ''); } return cc; } /** * Formats a Cache-Control directives object into a header string. * @param {Record<string, string|boolean>} cc - The Cache-Control directives. * @returns {string|undefined} A formatted Cache-Control header string or undefined if empty. */ function formatCacheControl(cc) { let parts = []; for (const k in cc) { const v = cc[k]; parts.push(v === true ? k : k + '=' + v); } if (!parts.length) { return undefined; } return parts.join(', '); } module.exports = class CachePolicy { /** * Creates a new CachePolicy instance. * @param {HttpRequest} req - Incoming client request. * @param {HttpResponse} res - Received server response. * @param {Object} [options={}] - Configuration options. * @param {boolean} [options.shared=true] - Is the cache shared (a public proxy)? `false` for personal browser caches. * @param {number} [options.cacheHeuristic=0.1] - Fallback heuristic (age fraction) for cache duration. * @param {number} [options.immutableMinTimeToLive=86400000] - Minimum TTL for immutable responses in milliseconds. * @param {boolean} [options.ignoreCargoCult=false] - Detect nonsense cache headers, and override them. * @param {any} [options._fromObject] - Internal parameter for deserialization. Do not use. */ constructor( req, res, { shared, cacheHeuristic, immutableMinTimeToLive, ignoreCargoCult, _fromObject, } = {} ) { if (_fromObject) { this._fromObject(_fromObject); return; } if (!res || !res.headers) { throw Error('Response headers missing'); } this._assertRequestHasHeaders(req); /** @type {number} Timestamp when the response was received */ this._responseTime = this.now(); /** @type {boolean} Indicates if the cache is shared */ this._isShared = shared !== false; /** @type {boolean} Indicates if legacy cargo cult directives should be ignored */ this._ignoreCargoCult = !!ignoreCargoCult; /** @type {number} Heuristic cache fraction */ this._cacheHeuristic = undefined !== cacheHeuristic ? cacheHeuristic : 0.1; // 10% matches IE /** @type {number} Minimum TTL for immutable responses in ms */ this._immutableMinTtl = undefined !== immutableMinTimeToLive ? immutableMinTimeToLive : 24 * 3600 * 1000; /** @type {number} HTTP status code */ this._status = 'status' in res ? res.status : 200; /** @type {Record<string, string>} Response headers */ this._resHeaders = res.headers; /** @type {Record<string, string|boolean>} Parsed Cache-Control directives from response */ this._rescc = parseCacheControl(res.headers['cache-control']); /** @type {string} HTTP method (e.g., GET, POST) */ this._method = 'method' in req ? req.method : 'GET'; /** @type {string} Request URL */ this._url = req.url; /** @type {string} Host header from the request */ this._host = req.headers.host; /** @type {boolean} Whether the request does not include an Authorization header */ this._noAuthorization = !req.headers.authorization; /** @type {Record<string, string>|null} Request headers used for Vary matching */ this._reqHeaders = res.headers.vary ? req.headers : null; // Don't keep all request headers if they won't be used /** @type {Record<string, string|boolean>} Parsed Cache-Control directives from request */ this._reqcc = parseCacheControl(req.headers['cache-control']); // Assume that if someone uses legacy, non-standard uncecessary options they don't understand caching, // so there's no point stricly adhering to the blindly copy&pasted directives. if ( this._ignoreCargoCult && 'pre-check' in this._rescc && 'post-check' in this._rescc ) { delete this._rescc['pre-check']; delete this._rescc['post-check']; delete this._rescc['no-cache']; delete this._rescc['no-store']; delete this._rescc['must-revalidate']; this._resHeaders = Object.assign({}, this._resHeaders, { 'cache-control': formatCacheControl(this._rescc), }); delete this._resHeaders.expires; delete this._resHeaders.pragma; } // When the Cache-Control header field is not present in a request, caches MUST consider the no-cache request pragma-directive // as having the same effect as if "Cache-Control: no-cache" were present (see Section 5.2.1). if ( res.headers['cache-control'] == null && /no-cache/.test(res.headers.pragma) ) { this._rescc['no-cache'] = true; } } /** * You can monkey-patch it for testing. * @returns {number} Current time in milliseconds. */ now() { return Date.now(); } /** * Determines if the response is storable in a cache. * @returns {boolean} `false` if can never be cached. */ storable() { // The "no-store" request directive indicates that a cache MUST NOT store any part of either this request or any response to it. return !!( !this._reqcc['no-store'] && // A cache MUST NOT store a response to any request, unless: // The request method is understood by the cache and defined as being cacheable, and ('GET' === this._method || 'HEAD' === this._method || ('POST' === this._method && this._hasExplicitExpiration())) && // the response status code is understood by the cache, and understoodStatuses.has(this._status) && // the "no-store" cache directive does not appear in request or response header fields, and !this._rescc['no-store'] && // the "private" response directive does not appear in the response, if the cache is shared, and (!this._isShared || !this._rescc.private) && // the Authorization header field does not appear in the request, if the cache is shared, (!this._isShared || this._noAuthorization || this._allowsStoringAuthenticated()) && // the response either: // contains an Expires header field, or (this._resHeaders.expires || // contains a max-age response directive, or // contains a s-maxage response directive and the cache is shared, or // contains a public response directive. this._rescc['max-age'] || (this._isShared && this._rescc['s-maxage']) || this._rescc.public || // has a status code that is defined as cacheable by default statusCodeCacheableByDefault.has(this._status)) ); } /** * @returns {boolean} true if expiration is explicitly defined. */ _hasExplicitExpiration() { // 4.2.1 Calculating Freshness Lifetime return !!( (this._isShared && this._rescc['s-maxage']) || this._rescc['max-age'] || this._resHeaders.expires ); } /** * @param {HttpRequest} req - a request * @throws {Error} if the headers are missing. */ _assertRequestHasHeaders(req) { if (!req || !req.headers) { throw Error('Request headers missing'); } } /** * Checks if the request matches the cache and can be satisfied from the cache immediately, * without having to make a request to the server. * * This doesn't support `stale-while-revalidate`. See `evaluateRequest()` for a more complete solution. * * @param {HttpRequest} req - The new incoming HTTP request. * @returns {boolean} `true`` if the cached response used to construct this cache policy satisfies the request without revalidation. */ satisfiesWithoutRevalidation(req) { const result = this.evaluateRequest(req); return !result.revalidation; } /** * @param {{headers: Record<string, string>, synchronous: boolean}|undefined} revalidation - Revalidation information, if any. * @returns {{response: {headers: Record<string, string>}, revalidation: {headers: Record<string, string>, synchronous: boolean}|undefined}} An object with a cached response headers and revalidation info. */ _evaluateRequestHitResult(revalidation) { return { response: { headers: this.responseHeaders(), }, revalidation, }; } /** * @param {HttpRequest} request - new incoming * @param {boolean} synchronous - whether revalidation must be synchronous (not s-w-r). * @returns {{headers: Record<string, string>, synchronous: boolean}} An object with revalidation headers and a synchronous flag. */ _evaluateRequestRevalidation(request, synchronous) { return { synchronous, headers: this.revalidationHeaders(request), }; } /** * @param {HttpRequest} request - new incoming * @returns {{response: undefined, revalidation: {headers: Record<string, string>, synchronous: boolean}}} An object indicating no cached response and revalidation details. */ _evaluateRequestMissResult(request) { return { response: undefined, revalidation: this._evaluateRequestRevalidation(request, true), }; } /** * Checks if the given request matches this cache entry, and how the cache can be used to satisfy it. Returns an object with: * * ``` * { * // If defined, you must send a request to the server. * revalidation: { * headers: {}, // HTTP headers to use when sending the revalidation response * // If true, you MUST wait for a response from the server before using the cache * // If false, this is stale-while-revalidate. The cache is stale, but you can use it while you update it asynchronously. * synchronous: bool, * }, * // If defined, you can use this cached response. * response: { * headers: {}, // Updated cached HTTP headers you must use when responding to the client * }, * } * ``` * @param {HttpRequest} req - new incoming HTTP request * @returns {{response: {headers: Record<string, string>}|undefined, revalidation: {headers: Record<string, string>, synchronous: boolean}|undefined}} An object containing keys: * - revalidation: { headers: Record<string, string>, synchronous: boolean } Set if you should send this to the origin server * - response: { headers: Record<string, string> } Set if you can respond to the client with these cached headers */ evaluateRequest(req) { this._assertRequestHasHeaders(req); // In all circumstances, a cache MUST NOT ignore the must-revalidate directive if (this._rescc['must-revalidate']) { return this._evaluateRequestMissResult(req); } if (!this._requestMatches(req, false)) { return this._evaluateRequestMissResult(req); } // When presented with a request, a cache MUST NOT reuse a stored response, unless: // the presented request does not contain the no-cache pragma (Section 5.4), nor the no-cache cache directive, // unless the stored response is successfully validated (Section 4.3), and const requestCC = parseCacheControl(req.headers['cache-control']); if (requestCC['no-cache'] || /no-cache/.test(req.headers.pragma)) { return this._evaluateRequestMissResult(req); } if (requestCC['max-age'] && this.age() > toNumberOrZero(requestCC['max-age'])) { return this._evaluateRequestMissResult(req); } if (requestCC['min-fresh'] && this.maxAge() - this.age() < toNumberOrZero(requestCC['min-fresh'])) { return this._evaluateRequestMissResult(req); } // the stored response is either: // fresh, or allowed to be served stale if (this.stale()) { // If a value is present, then the client is willing to accept a response that has // exceeded its freshness lifetime by no more than the specified number of seconds const allowsStaleWithoutRevalidation = 'max-stale' in requestCC && (true === requestCC['max-stale'] || requestCC['max-stale'] > this.age() - this.maxAge()); if (allowsStaleWithoutRevalidation) { return this._evaluateRequestHitResult(undefined); } if (this.useStaleWhileRevalidate()) { return this._evaluateRequestHitResult(this._evaluateRequestRevalidation(req, false)); } return this._evaluateRequestMissResult(req); } return this._evaluateRequestHitResult(undefined); } /** * @param {HttpRequest} req - check if this is for the same cache entry * @param {boolean} allowHeadMethod - allow a HEAD method to match. * @returns {boolean} `true` if the request matches. */ _requestMatches(req, allowHeadMethod) { // The presented effective request URI and that of the stored response match, and return !!( (!this._url || this._url === req.url) && this._host === req.headers.host && // the request method associated with the stored response allows it to be used for the presented request, and (!req.method || this._method === req.method || (allowHeadMethod && 'HEAD' === req.method)) && // selecting header fields nominated by the stored response (if any) match those presented, and this._varyMatches(req) ); } /** * Determines whether storing authenticated responses is allowed. * @returns {boolean} `true` if allowed. */ _allowsStoringAuthenticated() { // following Cache-Control response directives (Section 5.2.2) have such an effect: must-revalidate, public, and s-maxage. return !!( this._rescc['must-revalidate'] || this._rescc.public || this._rescc['s-maxage'] ); } /** * Checks whether the Vary header in the response matches the new request. * @param {HttpRequest} req - incoming HTTP request * @returns {boolean} `true` if the vary headers match. */ _varyMatches(req) { if (!this._resHeaders.vary) { return true; } // A Vary header field-value of "*" always fails to match if (this._resHeaders.vary === '*') { return false; } const fields = this._resHeaders.vary .trim() .toLowerCase() .split(/\s*,\s*/); for (const name of fields) { if (req.headers[name] !== this._reqHeaders[name]) return false; } return true; } /** * Creates a copy of the given headers without any hop-by-hop headers. * @param {Record<string, string>} inHeaders - old headers from the cached response * @returns {Record<string, string>} A new headers object without hop-by-hop headers. */ _copyWithoutHopByHopHeaders(inHeaders) { /** @type {Record<string, string>} */ const headers = {}; for (const name in inHeaders) { if (hopByHopHeaders[name]) continue; headers[name] = inHeaders[name]; } // 9.1. Connection if (inHeaders.connection) { const tokens = inHeaders.connection.trim().split(/\s*,\s*/); for (const name of tokens) { delete headers[name]; } } if (headers.warning) { const warnings = headers.warning.split(/,/).filter(warning => { return !/^\s*1[0-9][0-9]/.test(warning); }); if (!warnings.length) { delete headers.warning; } else { headers.warning = warnings.join(',').trim(); } } return headers; } /** * Returns the response headers adjusted for serving the cached response. * Removes hop-by-hop headers and updates the Age and Date headers. * @returns {Record<string, string>} The adjusted response headers. */ responseHeaders() { const headers = this._copyWithoutHopByHopHeaders(this._resHeaders); const age = this.age(); // A cache SHOULD generate 113 warning if it heuristically chose a freshness // lifetime greater than 24 hours and the response's age is greater than 24 hours. if ( age > 3600 * 24 && !this._hasExplicitExpiration() && this.maxAge() > 3600 * 24 ) { headers.warning = (headers.warning ? `${headers.warning}, ` : '') + '113 - "rfc7234 5.5.4"'; } headers.age = `${Math.round(age)}`; headers.date = new Date(this.now()).toUTCString(); return headers; } /** * Returns the Date header value from the response or the current time if invalid. * @returns {number} Timestamp (in milliseconds) representing the Date header or response time. */ date() { const serverDate = Date.parse(this._resHeaders.date); if (isFinite(serverDate)) { return serverDate; } return this._responseTime; } /** * Value of the Age header, in seconds, updated for the current time. * May be fractional. * @returns {number} The age in seconds. */ age() { let age = this._ageValue(); const residentTime = (this.now() - this._responseTime) / 1000; return age + residentTime; } /** * @returns {number} The Age header value as a number. */ _ageValue() { return toNumberOrZero(this._resHeaders.age); } /** * Possibly outdated value of applicable max-age (or heuristic equivalent) in seconds. * This counts since response's `Date`. * * For an up-to-date value, see `timeToLive()`. * * Returns the maximum age (freshness lifetime) of the response in seconds. * @returns {number} The max-age value in seconds. */ maxAge() { if (!this.storable() || this._rescc['no-cache']) { return 0; } // Shared responses with cookies are cacheable according to the RFC, but IMHO it'd be unwise to do so by default // so this implementation requires explicit opt-in via public header if ( this._isShared && (this._resHeaders['set-cookie'] && !this._rescc.public && !this._rescc.immutable) ) { return 0; } if (this._resHeaders.vary === '*') { return 0; } if (this._isShared) { if (this._rescc['proxy-revalidate']) { return 0; } // if a response includes the s-maxage directive, a shared cache recipient MUST ignore the Expires field. if (this._rescc['s-maxage']) { return toNumberOrZero(this._rescc['s-maxage']); } } // If a response includes a Cache-Control field with the max-age directive, a recipient MUST ignore the Expires field. if (this._rescc['max-age']) { return toNumberOrZero(this._rescc['max-age']); } const defaultMinTtl = this._rescc.immutable ? this._immutableMinTtl : 0; const serverDate = this.date(); if (this._resHeaders.expires) { const expires = Date.parse(this._resHeaders.expires); // A cache recipient MUST interpret invalid date formats, especially the value "0", as representing a time in the past (i.e., "already expired"). if (Number.isNaN(expires) || expires < serverDate) { return 0; } return Math.max(defaultMinTtl, (expires - serverDate) / 1000); } if (this._resHeaders['last-modified']) { const lastModified = Date.parse(this._resHeaders['last-modified']); if (isFinite(lastModified) && serverDate > lastModified) { return Math.max( defaultMinTtl, ((serverDate - lastModified) / 1000) * this._cacheHeuristic ); } } return defaultMinTtl; } /** * Remaining time this cache entry may be useful for, in *milliseconds*. * You can use this as an expiration time for your cache storage. * * Prefer this method over `maxAge()`, because it includes other factors like `age` and `stale-while-revalidate`. * @returns {number} Time-to-live in milliseconds. */ timeToLive() { const age = this.maxAge() - this.age(); const staleIfErrorAge = age + toNumberOrZero(this._rescc['stale-if-error']); const staleWhileRevalidateAge = age + toNumberOrZero(this._rescc['stale-while-revalidate']); return Math.round(Math.max(0, age, staleIfErrorAge, staleWhileRevalidateAge) * 1000); } /** * If true, this cache entry is past its expiration date. * Note that stale cache may be useful sometimes, see `evaluateRequest()`. * @returns {boolean} `false` doesn't mean it's fresh nor usable */ stale() { return this.maxAge() <= this.age(); } /** * @returns {boolean} `true` if `stale-if-error` condition allows use of a stale response. */ _useStaleIfError() { return this.maxAge() + toNumberOrZero(this._rescc['stale-if-error']) > this.age(); } /** See `evaluateRequest()` for a more complete solution * @returns {boolean} `true` if `stale-while-revalidate` is currently allowed. */ useStaleWhileRevalidate() { const swr = toNumberOrZero(this._rescc['stale-while-revalidate']); return swr > 0 && this.maxAge() + swr > this.age(); } /** * Creates a `CachePolicy` instance from a serialized object. * @param {Object} obj - The serialized object. * @returns {CachePolicy} A new CachePolicy instance. */ static fromObject(obj) { return new this(undefined, undefined, { _fromObject: obj }); } /** * @param {any} obj - The serialized object. * @throws {Error} If already initialized or if the object is invalid. */ _fromObject(obj) { if (this._responseTime) throw Error('Reinitialized'); if (!obj || obj.v !== 1) throw Error('Invalid serialization'); this._responseTime = obj.t; this._isShared = obj.sh; this._cacheHeuristic = obj.ch; this._immutableMinTtl = obj.imm !== undefined ? obj.imm : 24 * 3600 * 1000; this._ignoreCargoCult = !!obj.icc; this._status = obj.st; this._resHeaders = obj.resh; this._rescc = obj.rescc; this._method = obj.m; this._url = obj.u; this._host = obj.h; this._noAuthorization = obj.a; this._reqHeaders = obj.reqh; this._reqcc = obj.reqcc; } /** * Serializes the `CachePolicy` instance into a JSON-serializable object. * @returns {Object} The serialized object. */ toObject() { return { v: 1, t: this._responseTime, sh: this._isShared, ch: this._cacheHeuristic, imm: this._immutableMinTtl, icc: this._ignoreCargoCult, st: this._status, resh: this._resHeaders, rescc: this._rescc, m: this._method, u: this._url, h: this._host, a: this._noAuthorization, reqh: this._reqHeaders, reqcc: this._reqcc, }; } /** * Headers for sending to the origin server to revalidate stale response. * Allows server to return 304 to allow reuse of the previous response. * * Hop by hop headers are always stripped. * Revalidation headers may be added or removed, depending on request. * @param {HttpRequest} incomingReq - The incoming HTTP request. * @returns {Record<string, string>} The headers for the revalidation request. */ revalidationHeaders(incomingReq) { this._assertRequestHasHeaders(incomingReq); const headers = this._copyWithoutHopByHopHeaders(incomingReq.headers); // This implementation does not understand range requests delete headers['if-range']; if (!this._requestMatches(incomingReq, true) || !this.storable()) { // revalidation allowed via HEAD // not for the same resource, or wasn't allowed to be cached anyway delete headers['if-none-match']; delete headers['if-modified-since']; return headers; } /* MUST send that entity-tag in any cache validation request (using If-Match or If-None-Match) if an entity-tag has been provided by the origin server. */ if (this._resHeaders.etag) { headers['if-none-match'] = headers['if-none-match'] ? `${headers['if-none-match']}, ${this._resHeaders.etag}` : this._resHeaders.etag; } // Clients MAY issue simple (non-subrange) GET requests with either weak validators or strong validators. Clients MUST NOT use weak validators in other forms of request. const forbidsWeakValidators = headers['accept-ranges'] || headers['if-match'] || headers['if-unmodified-since'] || (this._method && this._method != 'GET'); /* SHOULD send the Last-Modified value in non-subrange cache validation requests (using If-Modified-Since) if only a Last-Modified value has been provided by the origin server. Note: This implementation does not understand partial responses (206) */ if (forbidsWeakValidators) { delete headers['if-modified-since']; if (headers['if-none-match']) { const etags = headers['if-none-match'] .split(/,/) .filter(etag => { return !/^\s*W\//.test(etag); }); if (!etags.length) { delete headers['if-none-match']; } else { headers['if-none-match'] = etags.join(',').trim(); } } } else if ( this._resHeaders['last-modified'] && !headers['if-modified-since'] ) { headers['if-modified-since'] = this._resHeaders['last-modified']; } return headers; } /** * Creates new CachePolicy with information combined from the previews response, * and the new revalidation response. * * Returns {policy, modified} where modified is a boolean indicating * whether the response body has been modified, and old cached body can't be used. * * @param {HttpRequest} request - The latest HTTP request asking for the cached entry. * @param {HttpResponse} response - The latest revalidation HTTP response from the origin server. * @returns {{policy: CachePolicy, modified: boolean, matches: boolean}} The updated policy and modification status. * @throws {Error} If the response headers are missing. */ revalidatedPolicy(request, response) { this._assertRequestHasHeaders(request); if (this._useStaleIfError() && isErrorResponse(response)) { return { policy: this, modified: false, matches: true, }; } if (!response || !response.headers) { throw Error('Response headers missing'); } // These aren't going to be supported exactly, since one CachePolicy object // doesn't know about all the other cached objects. let matches = false; if (response.status !== undefined && response.status != 304) { matches = false; } else if ( response.headers.etag && !/^\s*W\//.test(response.headers.etag) ) { // "All of the stored responses with the same strong validator are selected. // If none of the stored responses contain the same strong validator, // then the cache MUST NOT use the new response to update any stored responses." matches = this._resHeaders.etag && this._resHeaders.etag.replace(/^\s*W\//, '') === response.headers.etag; } else if (this._resHeaders.etag && response.headers.etag) { // "If the new response contains a weak validator and that validator corresponds // to one of the cache's stored responses, // then the most recent of those matching stored responses is selected for update." matches = this._resHeaders.etag.replace(/^\s*W\//, '') === response.headers.etag.replace(/^\s*W\//, ''); } else if (this._resHeaders['last-modified']) { matches = this._resHeaders['last-modified'] === response.headers['last-modified']; } else { // If the new response does not include any form of validator (such as in the case where // a client generates an If-Modified-Since request from a source other than the Last-Modified // response header field), and there is only one stored response, and that stored response also // lacks a validator, then that stored response is selected for update. if ( !this._resHeaders.etag && !this._resHeaders['last-modified'] && !response.headers.etag && !response.headers['last-modified'] ) { matches = true; } } const optionsCopy = { shared: this._isShared, cacheHeuristic: this._cacheHeuristic, immutableMinTimeToLive: this._immutableMinTtl, ignoreCargoCult: this._ignoreCargoCult, }; if (!matches) { return { policy: new this.constructor(request, response, optionsCopy), // Client receiving 304 without body, even if it's invalid/mismatched has no option // but to reuse a cached body. We don't have a good way to tell clients to do // error recovery in such case. modified: response.status != 304, matches: false, }; } // use other header fields provided in the 304 (Not Modified) response to replace all instances // of the corresponding header fields in the stored response. const headers = {}; for (const k in this._resHeaders) { headers[k] = k in response.headers && !excludedFromRevalidationUpdate[k] ? response.headers[k] : this._resHeaders[k]; } const newResponse = Object.assign({}, response, { status: this._status, method: this._method, headers, }); return { policy: new this.constructor(request, newResponse, optionsCopy), modified: false, matches: true, }; } };
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