dpg, integrate TCGC getAllModels - basic support

[haolingdong-msft]

TCGC getAllModels() code is already on main. We will need to getAllModels() in emitter to replace the logics in processModels().

Tasks

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1. Check the type mapping from compiler Type to TCGC SDKType
2. Replace logics for intrinsic types. e.g. unkonwn, void, never, any
3. Replace logics for enum type, pay attention to the case on using union express extensible enum for unbranding
4. Replace logics for union type
5. Replace logics for Record type
6. Replace logics for constant type
7. Replace logics for Array type, pay attention to byte array
8. Replace logics for Scalar type, e.g. number, decimal, string, boolean, bytes etc. pay attention to format
9. Replace logics for Model type, basic cases
10. Replace logics for Model type, discriminator and inheritance' cases
11. Replace logics for Model type, additional properties
12. Replace logics for Model type, multipart form data cases
13. Pass all tests cases in typespec-tests/tsp and cadl-ranch
14. TSP, TCGC common layer, use TCGC returned access #2728
    0 of 1
    +0
    
15. TSP, TCGC common layer, use TCGC returned usage #2729
    2 of 2
    +0
    
16. TSP, TCGC common layer, adopt SdkNullableType #2730
    +0
17. TSP, TCGC common layer, use TCGC returned name as much as possible #2731
    +0
18. TSP, TCGC common layer, use TCGC returned description #2732
    +0
    

Possible gaps between TCGC type and compiler type:

1. unkown type in compiler will be converted to any type in TCGC SdkType.
2. void and never is not supported in TCGC SdkType yet. TCGC issue: Enhance typing for intrinsic type typespec-azure#292
3. SdkType does not contain namespace information. Model and enum type from getAllModels does not have namespace typespec-azure#290
4. SdkType.description and SdkType.detail: If both @summary and @doc exist, .description will be the content in @summary and detail will be the content in @doc. If only @doc exists, then description will be the content in @doc.
5. TCGC types does not have concept of @format, it will map the type with @format to an SdkBuiltInType. (expected)
6. Optional literal do not have correct generated name. [TCGC][Bug] getAllModels, Optional literal do not have correct generated name typespec-azure#553
7. Description is not correctly returned for scalar types [TCGC][Bug] getAllModels, description is not correctly returned for scalar types typespec-azure#555
8. discriminator, Returned model properties are not correct when discriminator as @clientName decorator [TCGC][Bug] getAllModels, discriminator, Returned model properties are not correct when discriminator has @clientName decorator typespec-azure#554
9. model is array case not handled correctly： [TCGC][Bug] model is array case not handled correctly typespec-azure#690
10. Type of model property/enum member when it is defined as constant number: Type of model property/enum member when it is defined as constant number microsoft/typespec#3314
11. when should standalone models be generated: [TCGC][Discussion] model types, when should standalone models be generated typespec-azure#823
12. ARM breaking change on UserAssignedIdentity: [TCGC] [ARM] Expected client code on definition model UserAssignedIdentities is Record<UserAssignedIdentity>;  typespec-azure#825

Log Time cost: 10-12 weeks

TCGC dependencies

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1. Enhance typing for intrinsic type typespec-azure#292
   bug getAllModels lib:tcgc +3
   
2. Model and enum type from getAllModels does not have namespace typespec-azure#290
   feature lib:tcgc +2
   
3. [TCGC][Bug] getAllModels, Optional literal do not have correct generated name typespec-azure#553
   getAllModels lib:tcgc +2
   
4. [TCGC][Bug] getAllModels, description is not correctly returned for scalar types typespec-azure#555
   getAllModels lib:tcgc +2
   
5. [TCGC][Bug] getAllModels, discriminator, Returned model properties are not correct when discriminator has @clientName decorator typespec-azure#554
   getAllModels lib:tcgc +2
   
6. Type of model property/enum member when it is defined as constant number microsoft/typespec#3314
   +0
   
7. [TCGC] [ARM] Expected client code on definition model UserAssignedIdentities is Record<UserAssignedIdentity>; typespec-azure#825
   MPG Impact lib:tcgc needs-area needs-team-attention +4
   
8. [TCGC][Discussion] model types, when should standalone models be generated typespec-azure#823
   lib:tcgc needs-area +2

[weidongxu-microsoft]

The Model is get from the raw Type. Use raw in it is meaningless.

[lirenhe]

The Model is get from the raw Type. Use raw in it is meaningless.

Please try to use the real models returned by TCGC instead of raw. And we shall continue reducing the usage of 'raw' in the source code till it is no longer needed.

cc @lmazuel

[weidongxu-microsoft]

The Model is get from the raw Type. Use raw in it is meaningless.

Please try to use the real models returned by TCGC instead of raw. And we shall continue reducing the usage of 'raw' in the source code till it is no longer needed.

cc @lmazuel

I was saying the same thing... "Use raw in it is meaningless."

[weidongxu-microsoft]

never means the whole thing not exist (property: never means no such property). So it is correct that it not map to anything.

[weidongxu-microsoft]

Personally opinion:
You can start (incrementally) merge back to main branch, if you can handle Scalar/Record/Array and Model, preferrable Enum as well (they are major types -- it be fine at this stage to use raw if a nested ModelProperty is e.g. of type Union)

[haolingdong-msft]

I agree, I will try to make the change incrementally and split to seperate mergable pr.

[haolingdong-msft]

Loop page

[haolingdong-msft]

TCGC will deprecate nullable property on type. Only property, dictionary value and additional property has nullable property.