**Problem**: When using `wblistentityusage` as a value of the `list` parameter in an API query action, results are added to the `query.pages` key in the response object. However, this key is reserved for usage with any of the following parameters: `generator` / `titles` / `pageids` / `revids`. This could lead to a collision when using alongside one of the parameters listed and potentially cause a runtime exception.
```lang=json,counterexample
{
"error": {
"code": "internal_api_error_RuntimeException",
"info": "[267db349-f489-482e-9a01-1d2e6e66654d] Caught exception of type RuntimeException",
"errorclass": "RuntimeException"
},
"servedby": "mw1392"
}
```
**Example**:
See this output for [list=wblistentityusage, list=allpages, titles=Q1](https://www.wikidata.org/w/api.php?action=query&format=json&list=wblistentityusage%7Callpages&titles=Q1&wbeuentities=Q1&wbeulimit=1&aplimit=1). It is evident from the response that `list=allpages`’ output is under `allpages`; `pages` contains two pages that look different and come from different sources, `Q1` from `titles=Q1` and `User:Yiyi` from `list=wblistentityusage`.
**Desired behavior:**
Results from usage of `wblistentityusage` are added under a different key than `query.pages`, potentially: `query.entityusage`
---
==== Error ====
* mwversion: `1.38.0-wmf.19`
* url: https://www.wikidata.org/w/api.php?action=query&format=json&list=wblistentityusage&titles=User_talk%3AEp%C3%ACdosis%2FArchive%2F2019&wbeuentities=Q1000011
* reqId: `267db349-f489-482e-9a01-1d2e6e66654d`
* [[ https://logstash.wikimedia.org/app/dashboards#/view/AXFV7JE83bOlOASGccsT?_g=(time:(from:'2022-01-29T15:44:12.000Z',to:'2022-01-31T12:36:07.698Z'))&_a=(query:(query_string:(query:'reqId:%22267db349-f489-482e-9a01-1d2e6e66654d%22'))) | Find reqId in Logstash ]]
```name=normalized_message
[{reqId}] {exception_url} RuntimeException: Conflicting keys (pageid, ns, title) when attempting to merge element 63735107
```
```name=exception.trace,lines=10
from /srv/mediawiki/php-1.38.0-wmf.19/includes/api/ApiResult.php(304)
#0 /srv/mediawiki/php-1.38.0-wmf.19/includes/api/ApiResult.php(412): ApiResult::setValue(array, integer, array, integer)
#1 /srv/mediawiki/php-1.38.0-wmf.19/extensions/Wikibase/client/includes/Api/ApiListEntityUsage.php(132): ApiResult->addValue(array, integer, array)
#2 /srv/mediawiki/php-1.38.0-wmf.19/extensions/Wikibase/client/includes/Api/ApiListEntityUsage.php(111): Wikibase\Client\Api\ApiListEntityUsage->formatPageData(stdClass, string, array, ApiResult)
#3 /srv/mediawiki/php-1.38.0-wmf.19/extensions/Wikibase/client/includes/Api/ApiListEntityUsage.php(57): Wikibase\Client\Api\ApiListEntityUsage->formatResult(Wikimedia\Rdbms\MysqliResultWrapper, integer, array, NULL)
#4 /srv/mediawiki/php-1.38.0-wmf.19/extensions/Wikibase/client/includes/Api/ApiListEntityUsage.php(46): Wikibase\Client\Api\ApiListEntityUsage->run()
#5 /srv/mediawiki/php-1.38.0-wmf.19/includes/api/ApiQuery.php(629): Wikibase\Client\Api\ApiListEntityUsage->execute()
#6 /srv/mediawiki/php-1.38.0-wmf.19/includes/api/ApiMain.php(1889): ApiQuery->execute()
#7 /srv/mediawiki/php-1.38.0-wmf.19/includes/api/ApiMain.php(868): ApiMain->executeAction()
#8 /srv/mediawiki/php-1.38.0-wmf.19/includes/api/ApiMain.php(839): ApiMain->executeActionWithErrorHandling()
#9 /srv/mediawiki/php-1.38.0-wmf.19/api.php(90): ApiMain->execute()
#10 /srv/mediawiki/php-1.38.0-wmf.19/api.php(45): wfApiMain()
#11 /srv/mediawiki/w/api.php(3): require(string)
#12 {main}
```