fix: harden global fetch proxy handling

tests/unit/utils/fetch-proxy-setup.test.ts

@@ -0,0 +1,89 @@
+import { afterEach, beforeEach, describe, expect, it } from 'bun:test';
+import * as http from 'node:http';
+import { fetch, getGlobalDispatcher, setGlobalDispatcher } from 'undici';
+import { applyGlobalFetchProxy } from '../../../src/utils/fetch-proxy-setup';
+
+const PROXY_ENV_KEYS = [
+  'http_proxy',
+  'HTTP_PROXY',
+  'https_proxy',
+  'HTTPS_PROXY',
+  'all_proxy',
+  'ALL_PROXY',
+  'no_proxy',
+  'NO_PROXY',
+] as const;
+
+describe('global fetch proxy setup', () => {
+  const originalEnv = new Map<string, string | undefined>();
+  const originalDispatcher = getGlobalDispatcher();
+
+  beforeEach(() => {
+    for (const key of PROXY_ENV_KEYS) {
+      originalEnv.set(key, process.env[key]);
+      delete process.env[key];
+    }
+    setGlobalDispatcher(originalDispatcher);
+  });
+
+  afterEach(() => {
+    setGlobalDispatcher(originalDispatcher);
+    for (const key of PROXY_ENV_KEYS) {
+      const value = originalEnv.get(key);
+      if (value === undefined) {
+        delete process.env[key];
+      } else {
+        process.env[key] = value;
+      }
+    }
+  });
+
+  it('does not fail when proxy configuration is invalid', () => {
+    process.env.HTTP_PROXY = 'not-a-valid-url';
+
+    expect(applyGlobalFetchProxy()).toEqual({
+      enabled: false,
+      error: 'Invalid URL',
+    });
+  });
+
+  it('bypasses loopback fetches even when HTTP_PROXY is set', async () => {
+    process.env.HTTP_PROXY = 'http://127.0.0.1:9';
+
+    const server = http.createServer((_req, res) => {
+      res.writeHead(200, { 'content-type': 'text/plain' });
+      res.end('ok');
+    });
+
+    await new Promise<void>((resolve) => server.listen(0, '127.0.0.1', resolve));
+    const address = server.address();
+    if (!address || typeof address === 'string') {
+      throw new Error('Failed to bind test server');
+    }
+
+    try {
+      expect(applyGlobalFetchProxy()).toEqual({ enabled: true });
+
+      const response = await fetch(`http://127.0.0.1:${address.port}/health`);
+      expect(response.status).toBe(200);
+      expect(await response.text()).toBe('ok');
+    } finally {
+      await new Promise<void>((resolve, reject) => {
+        server.close((error) => (error ? reject(error) : resolve()));
+      });
+    }
+  });
+
+  it('supports ALL_PROXY as a fetch proxy fallback', () => {
+    process.env.ALL_PROXY = 'http://127.0.0.1:8080';
+
+    expect(applyGlobalFetchProxy()).toEqual({ enabled: true });
+  });
+
+  it('falls back to ALL_PROXY when HTTP_PROXY is invalid', () => {
+    process.env.HTTP_PROXY = 'not-a-valid-url';
+    process.env.ALL_PROXY = 'http://127.0.0.1:8080';
+
+    expect(applyGlobalFetchProxy()).toEqual({ enabled: true });
+  });
+});