Magento 2 contains a number of class files that are either pre-generated, or are generated on the fly. They live in
These generated files include factory classes. From the documentation, it's my understanding that a programmer uses factory classes to instantiate "non-injectable" objects. A "non-injectable" object is an object that can't be added via
__constructor dependency injection, usually because it requires user input to instantiate.
What's not clear from the documentation is how Magento 2 knows it needs to generate a factory class. This bit
If a non-existent factory is encountered by object manager in runtime mode or compiler, the object manager generates the factory.
makes it sound like if I use a factory class in the object manager (or, by extension, in the dependency injection __constructors), that Magento 2 will generate it for me. But how does the object manager know the thing I'm requesting is a factory?
Also, there seems to be two commands for automatically generating (or "compiling") all the generated classes. Running either of these commands generates a large number of Factory classes. What configuration and/or code files are these commands looking at to generate the needed factory objects?
I know that tracing the object manager and/or command code all the way down would reveal this, but I'm hoping to avoid that long and arduous journey.