feat(core): Serve a fixed managed tunnel path from a relative tunnel on the server

A relative `tunnel` can't be a transport URL on the server, so it now names the
path the server serves, and `TunnelOptions.path` overrides the DSN-derived path.
`tunnel: '/monitor'` on both sides then gives a fixed path the same way
`tunnel: true` gives the DSN-derived one.

Author: logaretm

packages/core/src/types/options.ts

@@ -661,6 +661,9 @@ export interface TunnelOptions {
    */
   allowedDsns?: string[];
 
+  /** A fixed tunnel path instead of the one derived from the DSN. A relative `tunnel` string sets this. */
+  path?: string;
+
   /** Path prefix the app is served under, e.g. `/docs`. Set the same value in the browser and the server `init`. */
   basePath?: string;
 

packages/core/src/utils/tunnel.ts

@@ -27,10 +27,15 @@ export function resolveServerTunnelOption(tunnel: string | true | TunnelOptions
   tunnel: string | undefined;
   _managedTunnel?: TunnelOptions;
 } {
-  if (typeof tunnel === 'string' || !tunnel) {
+  if (!tunnel) {
     return { tunnel };
   }
 
+  if (typeof tunnel === 'string') {
+    // A relative path can't be a transport URL on the server, so it names the path to serve instead.
+    return tunnel.startsWith('/') ? { tunnel: undefined, _managedTunnel: { path: tunnel } } : { tunnel };
+  }
+
   return { tunnel: undefined, _managedTunnel: tunnel === true ? {} : tunnel };
 }
 
@@ -77,6 +82,10 @@ export function getTunnelPaths(options?: TunnelOptions): string[] {
     return [];
   }
 
+  if (tunnelOptions.path) {
+    return [tunnelOptions.path];
+  }
+
   return resolveAllowedDsns(tunnelOptions.allowedDsns)
     .map(dsn => getTunnelPath(dsn))
     .filter((path): path is string => !!path);

packages/core/test/lib/utils/tunnel.test.ts

@@ -295,6 +295,13 @@ describe('getTunnelPaths', () => {
     ]);
   });
 
+  it('returns a fixed path instead of the DSN-derived ones', () => {
+    expect(getTunnelPaths({ path: '/monitor', allowedDsns: [TEST_DSN] })).toEqual(['/monitor']);
+    expect(isTunnelRequest({ method: 'POST', url: '/monitor' }, { path: '/monitor', allowedDsns: [TEST_DSN] })).toBe(
+      true,
+    );
+  });
+
   it('uses the managed tunnel config of the active client', () => {
     expect(getTunnelPaths()).toEqual([]);
 
@@ -366,6 +373,10 @@ describe('resolveServerTunnelOption', () => {
     });
   });
 
+  it('serves a relative path instead of using it as the transport tunnel', () => {
+    expect(resolveServerTunnelOption('/monitor')).toEqual({ tunnel: undefined, _managedTunnel: { path: '/monitor' } });
+  });
+
   it('leaves everything off when unset', () => {
     expect(resolveServerTunnelOption(undefined)).toEqual({ tunnel: undefined });
   });