Routing to root path does not work correctly when using nested API resources

First off, thanks for this great project!

I'm reporting an issue here I ran into when using API Gateway v1 with a proxy resource.

Repro

I have defined a RestAPI resource triggered on a nested root path and subpaths under a /v1/ path namespace. The SAM template looks like this:

      Events:
        ProxyApiRoot:
          Type: Api
          Properties:
            RestApiId: !Ref ExpressApi
            Path: /v1/
            Method: ANY
        ProxyApiGreedy:
          Type: Api
          Properties:
            RestApiId: !Ref ExpressApi
            Path: /v1/{proxy+}
            Method: ANY

I also have a BasePathMapping defined nesting one level deeper, so the final root path for my app is /routes/v1/.

My express app has a handler defined for the root path:

router.get('/', (req, res) => { ... }

However a request to <host>/routes/v1/ returns a generic 404 from express. The request is routing correctly through API Gateway to my app, but once it gets to express it can't find a matching handler for the / path.

Debugging

I added a handler for the catch-all route * and printed out the currentInvoke to try to track down the problem. I think I narrowed it down to this line:

https://github.com/vendia/serverless-express/blob/4ba9799a6573ea4227939001c3e49e07b75a35ea/src/event-sources/utils.js#L6-L7

The issue is that my request to /routes/v1/ is being handled by ProxyApiRoot, not ProxyApiGreedy. Since ProxyApiRoot doesn't populate a value for event.pathParameters.proxy, the fallback event.path is used. But unlike pathParameters.proxy, event.path includes the full path including the namespaces. So for a request to the root of my app, serverless-express is interpreting the path as event.path == '/routes/v1', not event.path == '/'.

Solution?

There may need to be more smarts added to getPathWithQueryStringParams for stripping out prefixes from the root path.

For example from printing out the currentInvoke I found:

• The base path part is available at event.requestContext.customDomain.basePathMatched == 'routes'
• The v1 part is available at event.resource = '/v1'.

Perhaps these can be used to remove /routes/v1 from the root path when event.pathParameters.proxy is not populated.

Workaround

In the short term I found a workaround by avoiding root paths altogether. My SAM template now looks like:

        ProxyApiGreedy:
          Type: Api
          Properties:
            RestApiId: !Ref ExpressApi
            Path: /{proxy+}
            Method: ANY

and I mount all my express routes at v1 explicitly using app.use('/v1', router).

Commencez dans src/event-sources/utils.js, au niveau de getPathWithQueryStringParams, puis reproduisez les routes imbriquées /v1/ et /v1/{proxy+} de SAM API Gateway avec le mapping de chemin de base /routes/v1/. Suivez les champs de l’événement utilisés pour la requête racine, en particulier event.path, event.resource, event.requestContext.customDomain.basePathMatched et event.pathParameters.proxy. C’est terminé lorsque le gestionnaire racine Express reçoit / au lieu du chemin avec espace de noms.