Bug: Negative slice index in populate subdocPath calculation

[maniktyagi04]

Description

When calculating subdocPath in populate operations with nested paths, if schema.path.length + 1 is greater than or equal to options.path.length, the slice operation results in a negative index. This causes slice() to count from the end of the string instead of the beginning, leading to incorrect path calculations.

Affected Code

lib/helpers/populate/getModelsMapForPopulate.js - Lines 242, 304, and 325

Current Behavior

const subdocPath = options.path.slice(0, options.path.length - schema.path.length - 1);

When schema.path.length + 1 >= options.path.length, the second argument becomes negative or zero, causing incorrect subdocPath extraction.

Expected Behavior

The slice index should never be negative. The subdocPath should be correctly extracted even in edge cases where the schema path is longer than or equal to the options path.

Proposed Fix

Add Math.max(0, ...) to prevent negative indices:

const subdocPath = options.path.slice(0, Math.max(0, options.path.length - schema.path.length - 1));

Impact

This bug affects populate operations with nested paths and could cause populate to fail or use incorrect paths in edge cases.

Testing

All existing populate tests pass with this fix (305 tests in test/model.populate.test.js).

[AbdelrahmanHafez]

@maniktyagi04
Can you please come up with a repro script similar to the one in #12250 (comment)? This would help us better explain the issue you're facing.