Custom Middleware Reusability

[cschuff]

Expected Behavior

Defining a custom middleware once should allow to reuse it in customMiddleware more than once. This might be achieved by giving middlewares an id (to reference custom middlewares) and a name (used for order and display).

Current Behavior

It fails with duplicate middleware name:

Error: Failed to add custom middleware proxy. A middleware with the same name is already known.
    at MiddlewareManager.addCustomMiddleware (/XXX/node_modules/@ui5/cli/node_modules/@ui5/server/lib/middleware/MiddlewareManager.js:159:11)
npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! XXX@1.0.0 start: `ui5 serve -p 3000`
npm ERR! Exit status 1
npm ERR! 
npm ERR! Failed at the XXX@1.0.0 start script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.

Steps to reproduce the issue

1. Create a simple custom middleware
2. Register as custom middleware in ui5.yaml
3. Use the newly registered middleware twice in ui5.yaml

Affected components (if known)

• ui5-builder
• ui5-server
• ui5-cli
• ui5-fs
• ui5-project
• ui5-logger

Log Output / Stack Trace

Error: Failed to add custom middleware proxy. A middleware with the same name is already known.
    at MiddlewareManager.addCustomMiddleware (/XXX/node_modules/@ui5/cli/node_modules/@ui5/server/lib/middleware/MiddlewareManager.js:159:11)
npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! XXX@1.0.0 start: `ui5 serve -p 3000`
npm ERR! Exit status 1
npm ERR! 
npm ERR! Failed at the XXX@1.0.0 start script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.

[RandomByte]

Hey @cschuff,

Could you please add some details on your use case? We discussed generating unique IDs for custom middlewares during their implementation. However, we were concerned how one could reference the middleware in the "customMiddleware" configuration without knowing the generated ID.

Why do you need the same middleware to be added multiple times? Is it to use different mount paths? Or a different order?

Thanks!

[cschuff]

I have a generic proxy middleware that I re-use to proxy different backends. And yes, they need different mount paths. That's about it.

[vobu]

tried it out - see SAP/ui5-server#246 (comment)
didn't work at first shot, probably did sth wrong though