Embedded matching in Mongoid failed to match documents where hashes with numeric keys were nested under arrays. For example:

  document: 
    foo:
      -
        '42':
          bar: 1
  query:
    foo.42.bar: 1

In this case, 42 is meant to be interpreted as the hash key, not as an array index.

https://jira.mongodb.org/browse/MONGOID-5063 earlier repaired a related problem of numeric keys being not matchable when they were in simple hashes (without array expansion being involved).

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Original report:

Mongoid::Matcher.expand_attribute() does not correctly handle numeric hash keys inside expanded arrays. This PR provides the fix + test cases: https://github.com/mongodb/mongoid/pull/4969