PiT 24.5: prepare-frontend and build-frontend seems to scan classes multiple times

[manolo]

Description of the bug

prepare-frontend and build-frontend scan classes multiple times, and it probably causes wasting some seconds during the build

mvn clean package -Pproduction

[INFO] --- vaadin-maven-plugin:24.5.0.alpha14:prepare-frontend (default) @ bakery-app-starter-flow-spring ---
[INFO] Reflections took 1569 ms to scan 197 urls, producing 10632 keys and 56187 values
[INFO] Reflections took 1236 ms to scan 197 urls, producing 10632 keys and 56187 values
[INFO] Reflections took 1275 ms to scan 197 urls, producing 10632 keys and 56187 values
[INFO] Visited 120 classes. Took 358 ms.
[INFO] Copying frontend resources from jar files ...
[INFO] Visited 201 resources. Took 291 ms.

...
[INFO] --- vaadin-maven-plugin:24.5.0.alpha14:build-frontend (default) @ bakery-app-starter-flow-spring ---
[INFO] Reflections took 1252 ms to scan 197 urls, producing 10632 keys and 56187 values
[INFO] Reflections took 1135 ms to scan 197 urls, producing 10632 keys and 56187 values
[INFO] Scanning classes to find frontend configurations and dependencies...
[INFO] Visited 7475 classes. Took 7552 ms.

Expected behavior

classes are visited once per goal

Minimal reproducible example

Download and compile bakery-app-starter-flow-spring

Versions

• Vaadin / Flow version: 24.5.0.alpha

[mcollovati]

This was changed time ago, to make sure that DevModeInitializer and prepare-fronted behave the same to prevent excessive server restarts during development.
IIRC, the problem was that if you have the application running through the IDE, and you do a maven compilation, then some generated frontend files were removed and not recreated, causing several reloads.

Here's the PR #19011

[mshabarov]

We have to investigate if/how we can cache the scanning results for build-frontend.

[jorgheymans]

Here's the full picture for our build, 9 times at about 1200ms each that's noticeable in a build. Caching the scanning results can be done from maven, see https://github.com/ronmamo/reflections-maven/ for the example.

[INFO] --- vaadin:24.4.12:configure (configure) @ ims ---
[INFO] Reflections took 2346 ms to scan 321 urls, producing 17915 keys and 93773 values
[WARNING] The 'configure' goal is only meant to be used in Hilla projects with endpoints.
[ims] [INFO]
[ims] [INFO] <<< vaadin:24.4.12:prepare-frontend (default) < :configure @ ims <<<
[ims] [INFO]
[ims] [INFO]
[ims] [INFO] --- vaadin:24.4.12:prepare-frontend (default) @ ims ---
[ims] [INFO] Reflections took 1563 ms to scan 321 urls, producing 17915 keys and 93773 values
[ims] [INFO] The globally installed Node.js version 14.18.0 is older than the required minimum version 18.12.0. Using Node.js from /home/afis4/.vaadin.
[ims] [INFO] Reflections took 1203 ms to scan 321 urls, producing 17915 keys and 93773 values
[ims] [INFO] Reflections took 1246 ms to scan 321 urls, producing 17915 keys and 93773 values
[ims] [INFO] Visited 328 classes. Took 672 ms.
[ims] [INFO] Copying frontend resources from jar files ...
[ims] [INFO] Visited 347 resources. Took 250 ms.
[ims] [INFO]
[ims] [INFO] >>> vaadin:24.4.12:build-frontend (default) > :configure @ ims >>>
[INFO]
[INFO] --- vaadin:24.4.12:configure (configure) @ ims ---
[INFO] Reflections took 1244 ms to scan 321 urls, producing 17915 keys and 93773 values
[WARNING] The 'configure' goal is only meant to be used in Hilla projects with endpoints.
[ims] [INFO]
[ims] [INFO] <<< vaadin:24.4.12:build-frontend (default) < :configure @ ims <<<
[ims] [INFO]
[ims] [INFO]
[ims] [INFO] --- vaadin:24.4.12:build-frontend (default) @ ims ---
[ims] [INFO] Reflections took 1242 ms to scan 321 urls, producing 17915 keys and 93773 values
[ims] [INFO] Reflections took 1082 ms to scan 321 urls, producing 17915 keys and 93773 values
[ims] [INFO] Scanning classes to find frontend configurations and dependencies...
[ims] [INFO] Visited 7251 classes. Took 5940 ms.
[ims] [INFO] Checking if a production mode bundle build is needed
[ims] [INFO] Frontend build requested.
[ims] [INFO] Skipping npm install because the frontend packages are already installed in the folder '/home/afis4/src/acd/backends/ims/app/node_modules' and the hash in the file '/home/afis4/src/acd/backends/ims/app/node_modules/.vaadin/vaadin.json' is the same as in 'package.json'
[ims] [INFO] Copying frontend resources from jar files ...
[ims] [INFO] Visited 347 resources. Took 154 ms.
[ims] [INFO] The globally installed Node.js version 14.18.0 is older than the required minimum version 18.12.0. Using Node.js from /home/afis4/.vaadin.
[ims] [INFO] Running Vite ...
[ims] [INFO] Reflections took 1157 ms to scan 321 urls, producing 17915 keys and 93773 values
[ims] [INFO] Reflections took 1128 ms to scan 321 urls, producing 17915 keys and 93773 values
[ims] [INFO] Scanning classes to find frontend configurations and dependencies...
[ims] [INFO] Visited 7251 classes. Took 4594 ms.
[ims] [INFO] Unable to determine Vaadin version. No META-INF/maven/com.vaadin/vaadin-core/pom.properties found
[ims] [INFO] Build frontend completed in 33329 ms.
[ims] [INFO]