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Lazily load agents in proxy-agent #327

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Lazily load agents in proxy-agent #327

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5 changes: 5 additions & 0 deletions .changeset/late-berries-rule.md
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Original file line number Diff line number Diff line change
@@ -0,0 +1,5 @@
---
'proxy-agent': minor
---

Lazily load agents in proxy-agent
65 changes: 37 additions & 28 deletions packages/proxy-agent/src/index.ts
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Expand Up @@ -5,47 +5,57 @@ import LRUCache from 'lru-cache';
import { Agent, AgentConnectOpts } from 'agent-base';
import createDebug from 'debug';
import { getProxyForUrl as envGetProxyForUrl } from 'proxy-from-env';
import { PacProxyAgent, PacProxyAgentOptions } from 'pac-proxy-agent';
import { HttpProxyAgent, HttpProxyAgentOptions } from 'http-proxy-agent';
import { HttpsProxyAgent, HttpsProxyAgentOptions } from 'https-proxy-agent';
import { SocksProxyAgent, SocksProxyAgentOptions } from 'socks-proxy-agent';
import type { PacProxyAgent, PacProxyAgentOptions } from 'pac-proxy-agent';
import type { HttpProxyAgent, HttpProxyAgentOptions } from 'http-proxy-agent';
import type { HttpsProxyAgent, HttpsProxyAgentOptions } from 'https-proxy-agent';
import type { SocksProxyAgent, SocksProxyAgentOptions } from 'socks-proxy-agent';

const debug = createDebug('proxy-agent');

const PROTOCOLS = [
...HttpProxyAgent.protocols,
...SocksProxyAgent.protocols,
...PacProxyAgent.protocols,
] as const;
type ValidProtocol =
| (typeof HttpProxyAgent.protocols)[number]
| (typeof HttpsProxyAgent.protocols)[number]
| (typeof SocksProxyAgent.protocols)[number]
| (typeof PacProxyAgent.protocols)[number];

type ValidProtocol = (typeof PROTOCOLS)[number];

type AgentConstructor = new (...args: never[]) => Agent;
type AgentConstructor = new (proxy: string, proxyAgentOptions?: ProxyAgentOptions) => Agent;

type GetProxyForUrlCallback = (url: string) => string | Promise<string>;

/**
* Shorthands for built-in supported types.
* Lazily loaded since some of these imports can be quite expensive
* (in particular, pac-proxy-agent).
*/
const wellKnownAgents = {
http: async () => (await import('http-proxy-agent')).HttpProxyAgent,
https: async () => (await import('https-proxy-agent')).HttpsProxyAgent,
socks: async () => (await import('socks-proxy-agent')).SocksProxyAgent,
pac: async () => (await import('pac-proxy-agent')).PacProxyAgent,
} as const;

/**
* Supported proxy types.
*/
export const proxies: {
[P in ValidProtocol]: [AgentConstructor, AgentConstructor];
[P in ValidProtocol]: [() => Promise<AgentConstructor>, () => Promise<AgentConstructor>];
} = {
http: [HttpProxyAgent, HttpsProxyAgent],
https: [HttpProxyAgent, HttpsProxyAgent],
socks: [SocksProxyAgent, SocksProxyAgent],
socks4: [SocksProxyAgent, SocksProxyAgent],
socks4a: [SocksProxyAgent, SocksProxyAgent],
socks5: [SocksProxyAgent, SocksProxyAgent],
socks5h: [SocksProxyAgent, SocksProxyAgent],
'pac+data': [PacProxyAgent, PacProxyAgent],
'pac+file': [PacProxyAgent, PacProxyAgent],
'pac+ftp': [PacProxyAgent, PacProxyAgent],
'pac+http': [PacProxyAgent, PacProxyAgent],
'pac+https': [PacProxyAgent, PacProxyAgent],
http: [wellKnownAgents.http, wellKnownAgents.https],
https: [wellKnownAgents.http, wellKnownAgents.https],
socks: [wellKnownAgents.socks, wellKnownAgents.socks],
socks4: [wellKnownAgents.socks, wellKnownAgents.socks],
socks4a: [wellKnownAgents.socks, wellKnownAgents.socks],
socks5: [wellKnownAgents.socks, wellKnownAgents.socks],
socks5h: [wellKnownAgents.socks, wellKnownAgents.socks],
'pac+data': [wellKnownAgents.pac, wellKnownAgents.pac],
'pac+file': [wellKnownAgents.pac, wellKnownAgents.pac],
'pac+ftp': [wellKnownAgents.pac, wellKnownAgents.pac],
'pac+http': [wellKnownAgents.pac, wellKnownAgents.pac],
'pac+https': [wellKnownAgents.pac, wellKnownAgents.pac],
};

function isValidProtocol(v: string): v is ValidProtocol {
return (PROTOCOLS as readonly string[]).includes(v);
return Object.keys(proxies).includes(v);
}

export type ProxyAgentOptions = HttpProxyAgentOptions<''> &
Expand Down Expand Up @@ -135,8 +145,7 @@ export class ProxyAgent extends Agent {
throw new Error(`Unsupported protocol for proxy URL: ${proxy}`);
}
const ctor =
proxies[proxyProto][secureEndpoint || isWebSocket ? 1 : 0];
// @ts-expect-error meh…
await proxies[proxyProto][secureEndpoint || isWebSocket ? 1 : 0]();
agent = new ctor(proxy, this.connectOpts);
this.cache.set(cacheKey, agent);
} else {
Expand Down