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Héctor Ramos 7e7706cb7d Codegen: Generate ObjC structs for type aliases

Summary:
**Motivation:**

Match the old codegen's behavior when generating structs for type alias derived objects.

**Problem description:**

Take, for example, the following spec:

```
export type MyTypeAlias = { /* ... */ }
export interface Spec extends TurboModule {
  // ...
  +myMethod: (paramName: MyTypeAlias) => void;
  // ...
}
```

The codegen needs to generate a struct to expose the properties of the type alias object. The codegen was producing the following output:

```
- (void)myMethod:(JS::MyModule::SpecMyMethodParamName &)paramName;
```

...which does not match the output from the original codegen:

```
- (void)myMethod:(JS::MyModule::MyTypeAlias &)paramName;
```

The original codegen generates a struct using the type alias name, while the new codegen was generating a struct that uses a combination of the property and parameter names.

Now that type alias names are exposed in the schema, the new codegen can match the original codegen's behavior.

**De-duplication of structs:**

Prior to these changes, type aliases were expanded into regular object types. This meant that any spec that used a type alias more than once would lead to redundant structs getting created. With these changes, we only generate the one struct per type alias, matching the old codegen.

**Expansion of type aliases:**

A new type was introduced in D22200700 (https://github.com/facebook/react-native/commit/e261f022fe6a7653b79330f878fed143725f5324), TypeAliasTypeAnnotation:

```
export type TypeAliasTypeAnnotation = $ReadOnly<{|
  type: 'TypeAliasTypeAnnotation',
  name: string,
|}>;
```

This type may now appear in several locations where a `{| type: 'ObjectTypeAnnotation', properties: [] |}` otherwise would have been used. A `getTypeAliasTypeAnnotation` function is introduced which, given an alias name and an array of aliases provided by the module, will produce the actual object type annotation for the given property parameter.

Changelog: [Internal]

Reviewed By: RSNara

Differential Revision: D22244323

fbshipit-source-id: 125fbf0d6d887bd05a99bf8b81b30bdda4f1682b

2020-07-01 23:39:44 -07:00