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Bulk remove pages fails after 8 pages

See original GitHub issue

In my app, there is a functionality that allows people to “split” a long PDF into two PDFs.

The way it currently works is as follows:

User scrolls through the PDF, and selects the split point. Everything from that point and before will be extracted into a new PDF
Load the PDF, and create an array of every page that needs removing from the source. (e.g. if we make the split point Page 5, the array will be [0 , 1, 2, 3, 4].

This is the code:

// Initiate PDFDocument object
      let pdf = await PDFDocument.create();

      // Now load into a PDFDocument object
      const file = await readFileAsync(filename);

      const source = await PDFDocument.load(file);

       // Make an array of all pages to extract
      let newPages = [];
      for (i = 0; i < splitPoint; i++) {
        newPages.push(i);
      }

      // Copy those pages to a new PDF
      const copiedPages = await pdf.copyPages(source, newPages);
      copiedPages.forEach(page => pdf.addPage(page));
      const newEntry = await pdf.save();

      // Now remove pages from the source document and save back
      newPages.forEach(page => {
        source.removePage(0);
      });
      const newSource = await source.save();

Whenever the newPages array is greater than 8, I always get this error - regardless of the PDF. By this point I have already error checked to see that the “split point” is actually within the document, i.e. that there are in fact at least 9 pages in the document. So this error is not being produced by trying to remove a page when the document doesn’t have that page contained within it.

Error: Index out of bounds: 0/-1 (b)
[0]     at PDFPageTree.removeLeafNode (/Users/me/workspace/app/server/node_modules/pdf-lib/cjs/core/structures/PDFPageTree.js:105:19)
[0]     at PDFPageTree.removeLeafNode (/Users/me/workspace/app/server/node_modules/pdf-lib/cjs/core/structures/PDFPageTree.js:109:20)
[0]     at PDFCatalog.removeLeafNode (/Users/me/workspace/app/server/node_modules/pdf-lib/cjs/core/structures/PDFCatalog.js:27:22)
[0]     at PDFDocument.removePage (/Users/me/workspace/app/server/node_modules/pdf-lib/cjs/api/PDFDocument.js:338:22)
[0]     at /Users/me/workspace/app/server/routes/pdfRoutes.js:73:16
[0]     at Array.forEach (<anonymous>)
[0]     at /Users/me/workspace/app/server/routes/pdfRoutes.js:72:16

Any ideas? Is there a better way to do this?