[BUG]: addContent hangs when `DEFAULT_CONTENT_TO_DEFAULT_LANGUAGE=true` causing multilingual contentlets to be re-submitted

[dario-daza]

Problem Statement

When DEFAULT_CONTENT_TO_DEFAULT_LANGUAGE=true, PageResource.render() uses language fallback to return default-language contentlets for entries that have no translation in the requested language.

When we edit the page in dotCMS we are sending the response of PageResource.render() so the editing receives this mixed-language content list and faithfully re-submits it to addContent() (e.g. editing in Spanish, but receiving content that only exists in English). This mixing language scenario causes an IllegalArgumentException.

Since saveContent() in PageResourceHelper is wrapped in @WrapInTransaction, this exception triggered a full transaction rollback. The rollback on a live transaction appeared to the client as an indefinite hang — the HTTP request never returned a response.

Steps to Reproduce

1. Set DEFAULT_CONTENT_TO_DEFAULT_LANGUAGE=true (env var)
2. Create a page in ENG (default language) and the ESP version of the same page (secondary language).
3. Add to the page ENG:
   • A contentlet that exists in both ENG and ESP
   • A contentlet that exists in ENG only
4. Switch to the page ESP and try to add or delete content
5. Observe that when you Delete nothing happens and when you Add content the page stays hanging for a response
6. Inspect the response in the network tab and notice that the resource to edit the page content have failed.

Acceptance Criteria

• entity.containers.<containerId>.contentlets.<uuid> for an ENG render must not include contentlets that have no ENG (or default-language) version
• entity.containers.<containerId>.contentlets.<uuid> for an ESP render correctly includes ESP-only contentlets
• The content list in entity.containers.uuid is consistent with what the rendered HTML displays
• No regression when DEFAULT_CONTENT_TO_DEFAULT_LANGUAGE=false (existing behavior unchanged)

Visual Summary

Bug-multilanguage-page.mp4

Root Cause

Inside overridesMultitreesByPersonalization(), a language-scoped DELETE was used to clean the multi_tree table before re-inserting. This DELETE only removed entries where the child contentlet had a version in the requested language. Because the fallback contentlet (English-only) had no Spanish version, its multi_tree row was not deleted.

When copyMultiTree() then tried to INSERT that same contentlet back, the duplicate check detected the existing row and threw an IllegalArgumentException. Since saveContent() in PageResourceHelper is wrapped in @WrapInTransaction, this exception triggered a full transaction rollback. The rollback on a live transaction appeared to the client as an indefinite hang — the HTTP request never returned a response.

Additional scenario

DEFAULT_CONTENT_TO_DEFAULT_LANGUAGE: entity.containers.uuid includes contentlets from wrong language in render() response

Scenario:

• Default language: English (ENG)
• Secondary language: Spanish (ESP)
• Page content:
  • content1 — ENG only
  • content2 — ENG + ESP
  • content3 — ESP only

Expected behavior:

Request	entity.containers.uuid
render(ENG)	content1(ENG), content2(ENG)
render(ESP)	content1(ENG fallback), content2(ESP), content3(ESP)

Actual behavior:

Request	entity.containers.uuid
render(ENG)	content1(ENG), content2(ENG), content3(ESP) ← wrong
render(ESP)	content1(ENG fallback), content2(ESP), content3(ESP) ✓

The rendered HTML is correct (content3 does not appear in the ENG page HTML), but the JSON metadata is inconsistent with it. This inconsistency can confuse API consumers (e.g. headless/EMA frontends) that rely on entity.containers.uuid to determine which contentlets belong to a page in a given language.

PageRenderUtil.getContentletOrFallback() in dotCMS/src/main/java/com/dotcms/rendering/velocity/services/PageRenderUtil.java.

After findContentletByIdentifierOrFallback() returns empty (content3 has no ENG version and ENG is the default), an additional fallback using findContentletByIdentifierAnyLanguage() returned the ESP version of content3 whenever the content type had languageFallback()=true. This "any language" fallback contradicts the DEFAULT_CONTENT_TO_DEFAULT_LANGUAGE contract (show requested language, or fall back to default language only) and caused the inconsistency between entity.containers.uuid and the rendered HTML.

Fix: Removed the findContentletByIdentifierAnyLanguage fallback from getContentletOrFallback(). When a contentlet has no version in the requested language or the default language, the method now returns null, correctly excluding it from entity.containers.uuid.

dotCMS Version

Latest from main branch

Severity

Medium - Some functionality impacted

Links

NA

[github-actions]

PRs linked to this issue

• 35029 addcontent hangs when default fallback is enabled causing multilingual contentlets to be re submitted by @dario-daza

[dario-daza]

QA Notes

Try out that under the scenario bellow you can add / move / delete content in ether page.

• Set DEFAULT_CONTENT_TO_DEFAULT_LANGUAGE=true
• Create a page in ENG (default language) and the ESP version of the same page (secondary language).
• Add to the page ENG
  • content1 — ENG only
  • content2 — ENG + ESP
• Add to the page ESP
  • content3 — ESP only

Expected behavior:

Request	Render in page
render(ENG)	content1(ENG), content2(ENG)
render(ESP)	content1(ENG fallback), content2(ESP), content3(ESP)

💡 Test this out in Traditional and Headless to verify that both are consistent.
💡 Test this out in more than two languages