Vite does not work with custom frontend directory

[mcollovati]

Description of the bug

When using Vite is a Spring Boot project with a custom frontend folder configured in vaadin-maven-plugin, the dev server seems to start, but the java application keeps restarting infinitely.

Main problem seems to be that in vite.generated.ts there a root key whose value is hard-coded to 'frontend'.
This can be fixed in vite.config.ts

const customConfig: UserConfigFn = (env) => ({
  // Here you can add custom Vite parameters
  // https://vitejs.dev/config/
  root: 'src/main/frontend'
});

But then there are failure in themes compilation, because they are still using frontend/generated directory instead to be nested into the custom frontend folder.

The workaround for this is to set also the generatedTsFolder setting in vaadin-maven-plugin, pointing to a subfolder of the custom generated frontend dir.

<generatedTsFolder>src/main/frontend/generated</generatedTsFolder>

However this does not make Vite work because there are other issues with custom frontend folder.
This is slightly related to #12880).
For example some hard-coded relative path that assumes files are in frontend/generated (for example ../../target/xyz).

Additional note: vite.generated.ts has the following confiuration that may also be wrong with custom frontend directory

const allowedFrontendFolders = [
  // other settings
  path.resolve(frontendFolder, '../node_modules')
];

Minimal reproducible example

Download an application from start.vaadin.com with Vite enabled and add the following configuration to vaadin-maven-plugin.

<configuration>
    <frontendDirectory>src/main/frontend</frontendDirectory>
</configuration>

Expected behavior

Vite dev serve works as when using default frontend directory

Actual behavior

1. Dev server does not serve frontend files and Java server continously restarts itself
2. If workarounds are applyed, compilation fails due to "file not found" errors because of wrong relative paths

Versions:

- Vaadin / Flow version: 23.1.1
- Java version: 11
- OS version: Ubuntu 21.10
- Browser version (if applicable):
- Application Server (if applicable):
- IDE (if applicable):
- Development mode
- Project from start.vaadin.com

[vaadin-bot]

This ticket/PR has been released with Vaadin 23.1.6.

[vaadin-bot]

This ticket/PR has been released with Vaadin 23.2.0.beta1 and is also targeting the upcoming stable 23.2.0 version.