What is the purpose of metadata json files?

The metadata.json file can be treated as a diagram of the overall structure of a decorator's metadata, represented as an abstract syntax tree(AST). During the analysis phase, the AOT collector scan the metadata recorded in the Angular decorators and outputs metadata information in .metadata.json files, one per .d.ts file.

Practical Code Example

// Purpose of .metadata.json files:
// Legacy pre-Ivy artifact that recorded decorator metadata for AOT compilation across libraries.
// Deprecated in modern Ivy engine.