`element_children()` error in `flattenKeys()` on scalar keyword input

[bobchristenson]

🐛 Bug: element_children() error in flattenKeys() on scalar keyword input

Project: search_api_solr
Backdrop CMS version: 1.x (tested on 1.27.2)
Module version: 1.x (latest dev)
Search backend: OpenSolr (hosted Solr service)

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Summary

When performing certain keyword searches, this module throws a fatal error:

User error: "0" is an invalid render array key in element_children() 
in element_children() (line 7548 of core/includes/common.inc)

The error occurs in the method SearchApiSolrService::flattenKeys() in includes/service.inc. It incorrectly assumes that $keys is a render array and passes it to element_children(), even though $keys may contain scalars with numeric keys.

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Steps to Reproduce

1. Configure a Solr server using OpenSolr.
2. Create a Search API index and attach it to a View.
3. Add a fulltext keyword filter to the View.
4. Perform a keyword search using a simple word (e.g., christmas).

In some cases, the $keys array passed into flattenKeys() looks like this:

[
  0 => 'christmas',
  '#conjunction' => 'OR',
]

This causes element_children() to throw an error, as 0 => 'christmas' is not a valid child in a render array.

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Why This Happens

The function element_children() is only intended for render arrays. Here, $keys is just a structured array of search conditions and not meant for rendering. Calling element_children() on such data will break when numeric or scalar values are included.

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Proposed Fix

Replace this line:

foreach (element_children($keys) as $i) {

With this:

foreach ($keys as $i => $key) {
  if (strpos($i, '#') === 0) {
    continue; // Skip metadata keys like #conjunction
  }

This change avoids element_children() entirely, filters metadata manually, and is safe for scalar/non-render values.

---

Patch

A working patch is attached below:
✅ Prevents the error
✅ Keeps all original behavior
✅ Safe for scalar + nested array input

```diff diff --git a/includes/service.inc b/includes/service.inc index 1234567..abcdef0 100644 --- a/includes/service.inc +++ b/includes/service.inc @@ protected function flattenKeys(array $keys) { - foreach (element_children($keys) as $i) { + foreach ($keys as $i => $key) { + if (strpos($i, '#') === 0) { + continue; // Skip metadata keys like #conjunction or #negation + } ```

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Recommendation

• ✅ Consider removing all usage of element_children() on non-render data for future robustness.
• 🔍 This issue is exposed by OpenSolr, but the underlying logic bug could affect any site given the right input structure.

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📎 Patch File (Download)

Patch file is attached

search_api_solr-flattenKeys-fix.patch

[herbdool]

@bobchristenson I think it's the same error as this one: #14. Do you want to test that solution? I'm not sure which is better approach.