janiussyafiq opened a new pull request, #13065:
URL: https://github.com/apache/apisix/pull/13065
### Description
<!-- Please include a summary of the change and which issue is fixed. -->
<!-- Please also include relevant motivation and context. -->
Fixes asymmetric PATCH behavior when converting `upstream.nodes` between
array and hash table formats.
#### Problem Statement
The Admin API exhibits inconsistent behavior when patching a route's
`upstream.nodes` field:
- Converting from **array → hash table** works
- Converting from **hash table → array** fails with validation error:
`{"error_msg":"invalid configuration: property \"upstream\" validation
failed: property \"nodes\" validation failed: object matches none of the
required"}`
This happens despite both formats being officially supported by the schema.
#### Root Cause
The `merge()` function in `apisix/core/table.lua` only checks if the
**origin** value is an array before deciding whether to replace or recursively
merge:
```lua
if _M.nkeys(origin[k]) ~= #origin[k] then
merge(origin[k] or {}, extend[k] or {}) -- Merge if origin is hash
else
origin[k] = v -- Replace if origin is array
end
```
When patching from hash table → array:
- Origin is hash table, so it tries to merge
- This creates an invalid mixed structure with both string keys (from
hash) and numeric indexes (from array)
- Validation fails because it's neither a valid hash nor a valid array
#### Solution
Modified the merge logic to check both the origin and incoming values:
- If either is an array → replace (prevents invalid mixed structures)
- If both are hash tables → merge (safe to combine)
#### Which issue(s) this PR fixes:
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Usage: `Fixes #<issue number>`, or `Fixes (paste link of issue)`.
-->
Fixes #13045
### Checklist
- [x] I have explained the need for this PR and the problem it solves
- [x] I have explained the changes or the new features added to this PR
- [x] I have added tests corresponding to this change
- [ ] I have updated the documentation to reflect this change
- [x] I have verified that this change is backward compatible (If not,
please discuss on the [APISIX mailing
list](https://github.com/apache/apisix/tree/master#community) first)
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