[BUG] mainURL can not be updated automatically.

[Dookoen]

Describe the bug
If the mainURL of a paper is missing or invalid (the pdf file is renamed of deleted), when dragging a same PDF with a different file name (user-defined) into Paperlib, the corresponding paper entry dose not update its mainURL.
The import does not work too.
I have to use choose button to relocated the new pdf file for the existing paper entry, then Paperlib will create a new pdf file with a fixed file name and use it as mainURL.
Now i have to delete the old pdf with user-defined file name.

The line paperEntityDraft.setValue("mainURL", payload.value); in pdf-entry-scraper.ts of entry-scrape-extension seems can update mainURL , but it does not work.

To Reproduce
Steps to reproduce the behavior:

1. Import a pdf
2. Rename the pdf
3. The mainURL is invalid and 'Preview' does not work
4. Drag or import the renamed pdf into Paperlib
5. The mainURL is not updated and the 'Preview' does not work

Screenshots or Log
None

System (please complete the following information):

• OS: [macOS arm]
• Paperlib Version [3.0.9]
• paperlib-entry-scrape-extension Version [0.0.27]

Additional context
None

[GeoffreyChen777]

Hi, thanks for your donation.

This is not a bug. Everything is expected.

1. Please never rename PDFs in finder. The filename is managed by Paperlib. We store the filename in database, and use it to access files. In preference, we provide multiple renaming formats. You can even create your own customized format.

2. To replace the main file of a paper, you cannot directly drag it into the main UI as Paperlib will find that the paper is duplicated. You should use this import button, or drag it into this box:

It will never keep your manually renamed filename as Paperlib renames the file according to the renaing format setting.

[GeoffreyChen777]

Paperlib's design philosophy is that Paperlib is the sole entry for papers, and users should hardly ever need to open a file explorer to access their papers.

[Dookoen]

Thanks for you detailed explanation! Is there a method available to retrieve the existing entry or entries when a user drags PDFs into the main UI? I've reviewed the developer documentation, but it appears there's no API provided for obtaining this information. Paperlib is incredibly convenient and robust, and I'd like to incorporate this as an extension for users who wish to replace PDFs in a batched way.

[GeoffreyChen777]

Emm, are you trying to check if there are any duplicated papers to your to-be-import PDFs in the library?

[Dookoen]

Not only check, i want to get id of existing entry of to-be-imported pdfs and update their mainURL.

[GeoffreyChen777]

So basically, what you want to do is that:

1. Drag PDFs into paperlib.
2. If a PDF's corresponding paper exists in Paperlib already, then replace the original PDF.

Right?

[Dookoen]

Yeap. U r right.

[GeoffreyChen777]

OK. So there is no API for this, but I think you can do it by combining multiple APIs.

1. To get the newly imported papers before being imported to database, you can use this hook: https://paperlib.app/en/extension-doc/process-hook.html#afterscrapemetadata
2. Then in your extension, you can check the library with PLAPI.paperService.load(). The first arg of this API is a querySentence, for example, you use title == '123' to get papers with a title 123. If the results is empty, it means that there is no duplicated paper. Otherwise, you can get the duplicated paper.

For querySentence, it's similar to the smartfilter, you can explore it there: