Item histories are truncated

[seabelis]

Problem

Item histories do not list all pages. Footer pagination is missing and navigation arrows navigate to a mostly blank page.

https://openlibrary.org/works/OL16282945W/Cinder?m=history&b=21

https://openlibrary.org/works/OL16282945W/Cinder?m=history&b=21&page=2

This example jumps from v22 to v1:
https://openlibrary.org/works/OL8407305W/Casenote_Legal_Briefs?m=history

https://openlibrary.org/works/OL8407305W/Casenote_Legal_Briefs?m=history&page=2

Reproducing the bug

1. Go to ...https://openlibrary.org/works/OL8407305W/Casenote_Legal_Briefs?m=history
2. Do ...Try to get history between v1 and v22.

• Expected behavior: History should be available.
• Actual behavior: History jumps from v22 to v1.

Context

• Browser (Chrome, Safari, Firefox, etc):
• OS (Windows, Mac, etc):
• Logged in (Y/N):
• Environment (prod, dev, local): prod

Breakdown

Implementation Details (for maintainers)

Requirements Checklist

• [ ]

Related files

Stakeholders

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[mekarpeles]

⚠️ Contributors, this issue will be ready to work on once:

• Triage — maintainers will add Priority: * and Lead: @* to replace Needs: Triage and Needs: Lead
• Needs: Breakdown — concrete implementation steps needed (see suggested breakdown below)

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Context

The root cause is an off-by-one indexing mismatch introduced by PR #12169 (merged 2026-03-27), which migrated history pagination from the old Pager macro to the ol-pagination web component.

Backend (vendor/infogami/infogami/core/code.py:191–192) uses 0-indexed pages:

i = web.input(page=0)          # no param → page 0 = first page
offset = 20 * safeint(i.page)  # ?page=2 → offset=40 (items 41–60, not 21–40)

Template (openlibrary/templates/history.html:78–79) reads the URL's page value and adds +1 before passing to the component:

$ page_num = safeint(query_param("page", "0"))
$:macros.OlPaginationArrows(page_num + 1, len(h) == 20)

OlPagination component (openlibrary/components/lit/OlPagination.js:184–191) is 1-indexed and generates:

• page 1 → deletes page param (no ?page in URL)
• page 2 → ?page=2
• page 3 → ?page=3

Net effect: From page 1 (no page param), the template passes 0 + 1 = 1 to the component. Clicking Next generates ?page=2. The backend reads page=2 → offset = 40, skipping 20 items entirely. From ?page=2, the template passes 2 + 1 = 3 to the component, so its Next generates ?page=4 → offset=80. Pages double-skip with each click, which is why history appears to "jump" from recent revisions to v1.

A secondary issue: len(h) == 20 is a brittle has_next_page check — if the last page has exactly 20 items, a spurious next arrow appears.

Issue #12398 (prev arrow on history page links to same page) is a separate symptom of the same root cause.

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Issue Assessment

Open questions

• Should the fix change the infogami backend (vendor/infogami/infogami/core/code.py) to use 1-indexed pages, or work around the mismatch entirely within the OpenLibrary template layer?
• Does the &b= URL parameter (bookmark/revision anchor used in some history URLs) interact with the page offset calculation? Needs verification after any fix.

Suggested breakdown

• Fix vendor/infogami/infogami/core/code.py:191–192 to use 1-indexed pages: i = web.input(page=1) and offset = 20 * max(0, safeint(i.page) - 1). This aligns the backend with the component's URL scheme (?page=2 = second page).
• Fix openlibrary/templates/history.html:78 to default page to "1" (not "0") and remove the + 1 in line 79, so the page number passed to the component matches the URL value: $:macros.OlPaginationArrows(page_num, len(h) > 20).
• Fix has_next_page detection: fetch limit + 1 items in the handler, check len(history) > limit, then trim to limit before rendering — eliminates the spurious next arrow on exact-20 pages.
• Verify that all history URL variants (?m=history, ?m=history&b=N, ?m=history&page=N) navigate correctly after the fix.
• Confirm issue Pagination previous arrow on history page links to the same page #12398 (prev arrow links to same page) is resolved by the same fix.

Full triage checklist (maintainers / Pam)

• Triage — correct labels applied or removed: Needs: Breakdown, Needs: Investigation, Needs: Design, Needs: Staff Decision, Needs: Staff / Admin, Good First Issue, Blocked, Blocker
• Problem / opportunity — problem is clear, audience identified, actionable
• Scope — issue is well-scoped; addresses a single regression
• Justification — regression from a known merged PR; impact is clear
• Success & testing criteria — defines what "done" looks like, verifiable by a contributor without asking; what must be tested
• Proposal & breakdown — concrete plan present; checklist or sub-issues actionable for a contributor
• If bug: environment & repro steps — prod environment confirmed; reproduction steps and URLs provided
• Risks, concerns, open questions — identified and surfaced (no security or privacy implications)
• Pam context — relevant code, commits, PRs reviewed; related issue Pagination previous arrow on history page links to the same page #12398 identified; regression source (PR Migrate all pagination to ol-pagination web component #12169) confirmed
• References — screenshots and reproduction URLs present

Note

This comment was automatically generated by Pam, Open Library's Project AI Manager, on behalf of @mekarpeles. Pam is designed to provide status visibility, perform basic project management functions and relevant codebase research, and provide actionable feedback so contributors aren't left waiting.

[cdrini]

I believe this is a duplicate of #12398

[cdrini]

Ah these are subtly different ; reopening

[akramcodez]

Hi team, I’d like to work on this issue if it’s available.

[tfmorris]

As a stop gap, you can work around this by editing the URL to point to page 1 (ie the second page due to the off-by-one error) https://openlibrary.org/works/OL8407305W/Casenote_Legal_Briefs?m=history&page=1

p.s. it seems like a dupe of #12398 to me.