Salesforce Inherited sharing

As of Winter ’19, we can use inherited sharing in an apex class signature. The “Inherited Sharing” feature allows us to run our apex code either with or without sharing settings, depending on the context in which it was called.

1. This allows the class to run in the same mode as the class which called it. Apex classes with Inherited Sharing that are called from other classes with no sharing settings will run in no sharing mode.
2. Assures that privileged Apex code is not used in unexpected or insecure ways and passes security review.
3. If a class is declared as Inherited Sharing, it runs as with sharing by default.

public inherited sharing class InheritedSharingClass {     
     public List<Contact> getAllTheSecrets() {
         return [SELECT Id,Name FROM Contact];     
} }

Note When an Apex class has inherited sharing, it differs from one that has omitted sharing. Class entry points are treated as “without sharing” if a sharing declaration is omitted. However, inherited sharing makes it default to run as it does with sharing. A class declared as inherited sharing only runs without sharing if it is explicitly called from a context that already exists without sharing.

Some of the basic concepts we should be to analyze. The below points taken from (https://salesforce.stackexchange.com/questions/264509/inherited-sharing-vs-no-sharing-declaration)

• If a class with without sharing is calling the method of a class with inherited sharing, then it will run in without sharing mode.
• If a class with with sharing is calling the method of a class with inherited sharing, then it will run in with sharing mode.
• If a class with omitted sharing (i.e. no sharing is mentioned) is calling the method of a class with inherited sharing, then it will run in without sharing mode as the default sharing mode of the omitted sharing is to run in without sharing mode (This is because the calling class is established as a without sharing context). A class declared as inherited sharing runs as without sharing only when explicitly called from an already established without sharing context.
• If a class with with sharing is calling a method of a class with omitted sharing which in turn calls a method of a class with inherited sharing, then it will run in with sharing mode, as the calling class is in with sharing mode and omitted class is established as with sharing context.
• If a class with without sharing is calling a method of a class with omitted sharing which in turn calls a method of a class with inherited sharing, then it will run in without sharing mode, as the calling class is in without sharing mode and the omitted class is established as without sharing context.
• If the class is used as the entry point to an Apex transaction, an omitted sharing declaration runs as without sharing.
• If the class is used as the entry point to an Apex transaction, inherited sharing ensures that the default is to run as with sharing.