Find files on file system using a file pattern

[bhufmann]

To find traces programmatically in the file system where the source code (language server) is. For this I'd like to issue a command on a folder and search for file/directories with a given file pattern. For example:
"From a start directory, find all files with the file suffix *.log"
"From a start directory, find all directories that contains a file called metadata"

[paul-marechal]

If running from the frontend (browser), you might want to setup a small backend (node) service that will do the search and return the results.

The idea is that the frontend doesn't have direct access to the remote fs. You'd have to use the FileSystem proxy, but if you want to filter files, doing it from the frontend would be sub-optimal.

So this means making a new proxy, where the server would do the filtering based on some input filter, and just return what is of interest.

To implement such a service, you can inspire yourself from the following code:

1. A "protocol" file with the interfaces your services are going to implement, as well as the unique path that will be used to query said service:
   https://github.com/eclipse-theia/theia/blob/9481af8e21f3be4b2e6658854327d8fa2b390da3/packages/core/src/common/env-variables/env-variables-protocol.ts
   Note how this file is located somewhere under common.
2. An actual implementation of said interfaces:
   https://github.com/eclipse-theia/theia/blob/9481af8e21f3be4b2e6658854327d8fa2b390da3/packages/core/src/node/env-variables/env-variables-server.ts
   Note how this file is located somewhere under node, because this is code that will run in the node server process.
3. Register your service as a ConnectionHandler on the backend:
   https://github.com/eclipse-theia/theia/blob/9481af8e21f3be4b2e6658854327d8fa2b390da3/packages/core/src/node/backend-application-module.ts#L72-L78
4. Register a proxy to your service from the frontend:
   https://github.com/eclipse-theia/theia/blob/9481af8e21f3be4b2e6658854327d8fa2b390da3/packages/core/src/browser/frontend-application-module.ts#L281-L284
   Note how we don't need an implementation on the browser side: the implementation lives on the backend, we just create a proxy that will forward calls for us.

To help you with your actual use case, I would see the following protocol:

export traceFinderPath = '/services/traceFinder'

export interface TraceFinder {

    /**
     * Returns traces under the provided paths (must be directories)
     */
    findTraceRecursive(paths: string[]): Promise<string[]>

}

Then from the frontend, you can remotely call this function by passing the workspace roots to it as paths to find all traces under these folders.

[bhufmann]

Thank you very much for the detailed information. Makes sense to separate the backend and frontend for such a search feature. I'll give it a try.