perf: optimize Object.keys() checks and optional chaining

[AbdelrahmanHafez]

Summary

• Add utils.hasOwnKeys() helper that checks for empty objects without allocating an array via Object.keys()
• Replace ~50 instances of Object.keys(obj).length pattern with hasOwnKeys(), reading the first key only instead of creating an array for all keys.
• Convert deep property access chains like a && a.b && a.b.c to optional chaining a?.b?.c
• Cache repeated property lookups (e.g., this.$__schema.options, model.db.options)
• Optimize indexOf() calls by caching the result instead of calling twice
• Convert arguments to rest parameters in Query.prototype.slice()
• Optimize Set operations in document.overwrite() and getModelsMapForPopulate()

[Copilot]

Pull request overview

This PR implements several performance optimizations across the Mongoose codebase:

• Introduces a new utils.hasOwnKeys() helper that checks for object keys more efficiently than Object.keys().length
• Converts verbose property access chains to optional chaining syntax
• Caches repeated property lookups to avoid redundant access
• Optimizes indexOf() calls by caching results
• Converts arguments object usage to rest parameters
• Optimizes Set operations for duplicate checking

Reviewed changes

Copilot reviewed 35 out of 35 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
lib/utils.js	Adds hasOwnKeys() helper function and updates isEmptyObject() to use it
lib/types/subdocument.js	Replaces Object.keys(ret).length === 0 with hasOwnKeys()
lib/types/documentArray/methods/index.js	Converts property access chains to optional chaining
lib/types/documentArray/index.js	Converts property access chains to optional chaining
lib/types/array/methods/index.js	Replaces Object.keys() length checks with hasOwnKeys()
lib/types/array/index.js	Converts property access chains to optional chaining
lib/schemaType.js	Simplifies null/undefined check to != null
lib/schema/subdocument.js	Converts to optional chaining and uses hasOwnKeys()
lib/schema/string.js	Simplifies null/undefined checks to != null
lib/schema/number.js	Simplifies null/undefined checks to != null
lib/schema/mixed.js	Replaces Object.keys() check with hasOwnKeys()
lib/schema/map.js	Replaces Object.keys() check with hasOwnKeys()
lib/schema/array.js	Converts property access chain to optional chaining
lib/schema.js	Converts to optional chaining and uses hasOwnKeys()
lib/queryHelpers.js	Converts to optional chaining
lib/query.js	Caches repeated property access, converts to rest parameters, uses hasOwnKeys(), and optional chaining
lib/plugins/trackTransaction.js	Replaces Object.keys() checks with hasOwnKeys()
lib/mongoose.js	Converts to optional chaining and uses hasOwnKeys()
lib/model.js	Converts to optional chaining and uses hasOwnKeys()
lib/helpers/update/castArrayFilters.js	Adds utils import and uses hasOwnKeys()
lib/helpers/update/applyTimestampsToUpdate.js	Adds utils import and uses hasOwnKeys()
lib/helpers/schema/getIndexes.js	Simplifies null/undefined check to != null
lib/helpers/schema/applyWriteConcern.js	Adds utils import, uses optional chaining and hasOwnKeys()
lib/helpers/schema/applyReadConcern.js	Converts to optional chaining
lib/helpers/query/castUpdate.js	Uses hasOwnKeys() for empty object checks
lib/helpers/populate/getModelsMapForPopulate.js	Optimizes duplicate checking with Set, uses optional chaining and hasOwnKeys()
lib/helpers/document/compile.js	Converts to optional chaining and uses hasOwnKeys()
lib/helpers/document/applyVirtuals.js	Adds utils import and uses hasOwnKeys()
lib/helpers/document/applyTimestamps.js	Adds utils import and uses hasOwnKeys()
lib/drivers/node-mongodb-native/connection.js	Converts to optional chaining and uses hasOwnKeys()
lib/drivers/node-mongodb-native/collection.js	Converts to optional chaining
lib/document.js	Optimizes with Set for key deduplication, caches schema options, uses hasOwnKeys()
lib/cursor/changeStream.js	Converts to optional chaining
lib/connection.js	Caches indexOf() results and uses hasOwnKeys()
lib/cast.js	Converts to optional chaining and uses hasOwnKeys()

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