[BUG] Search suggestions don't work

[stweil]

Description

Search suggestions don't work.

Reproduction

Steps to reproduce the behaviour:

1. Add the search plugin and enable search suggestions.
2. Enter text in the search field (3 or more characters).
3. See error: there are no search suggestions

Expected Behavior

Search suggestions should be shown.

Environment

• OS version: Debian GNU/Linux trixie
• Apache Solr version: 9
• TYPO3 version: 12

[stweil]

Related error in the TYPO3 log (occurs as soon as something is written in the search field):

 Core: Exception handler (WEB): Uncaught TYPO3 Exception: #1476107295: PHP Warning: Undefined array key "solrcore" in /viewer/vendor/kitodo/presentation/Classes/Middleware/SearchSuggest.php line 56 | TYPO3\CMS\Core\Error\Exception thrown in file /viewer/vendor/typo3/cms-core/Classes/Error/ErrorHandler.php in line 141. Requested URL: https://DOMAIN/

[stweil]

The issue still occurs with 6.0.0-rc1. As soon as the third character is typed in the search field, a TYPO3 execption is thrown:

 Core: Exception handler (WEB): Uncaught TYPO3 Exception: #1476107295: PHP Warning: Undefined array key "solrcore" in /viewer/vendor/kitodo/presentation/Classes/Middleware/SearchSuggest.php line 56 | TYPO3\CMS\Core\Error\Exception thrown in file /viewer/vendor/typo3/cms-core/Classes/Error/ErrorHandler.php in line 141. Requested URL: https://DOMAIN/ 

[beatrycze-volk]

I was not able to reproduce it. Do you have value in form field solrcore? The value for this field comes from FlexForm settings.

<f:if condition="{settings.suggest}">
    <f:form.hidden name="solrcore" value="{settings.solrcore}" />
    <f:form.hidden name="uHash" value="{uHash}" />
</f:if>

[stweil]

I see in the logs that the reported exception occurred on 2025-10-09, but not after this date.

Nevertheless I still don't see search suggestions. Solr reports "suggest" requests, but these requests have no results:

curl "http://localhost:8983/solr/dlfCore1/suggest?omitHeader=true&wt=json&json.nl=flat&suggest=true&suggest.q=lade&suggest.count=10&suggest.build=false&suggest.reload=false"
{
  "suggest":{
    "suggest":{
      "lade":{
        "numFound":0,
        "suggestions":[ ]
      }
    }
  }
}

A search for "Ladenburg" has 40922 hits in 12975 documents, so when I enter "Laden" in the search field, it should suggest "Ladenburg".

[stweil]

Search suggestions also don't work on https://digi.bib.uni-mannheim.de/. There "Berl" should suggest "Berlin" which occurs very often in the metadata and in the fulltext.