protogen: add field number prop

[Kybxd]

• close protogen: guarantee message field's Tag Number compatibility #218

[codecov]

Codecov Report

Attention: Patch coverage is 92.68293% with 3 lines in your changes missing coverage. Please review.

Project coverage is 71.25%. Comparing base (745037b) to head (22db647).
Report is 6 commits behind head on master.

Files with missing lines	Patch %	Lines
internal/protogen/exporter.go	91.89%	0 Missing and 3 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #230      +/-   ##
==========================================
+ Coverage   71.15%   71.25%   +0.09%     
==========================================
  Files          80       81       +1     
  Lines       10293    10360      +67     
==========================================
+ Hits         7324     7382      +58     
- Misses       2402     2411       +9     
  Partials      567      567              

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[wenchy]

For Go, In/Out parameter reuse is confusing, error-prone, and not recommended.
Please return the next tagid instead if you want to return the next one (just like cursor).

exportField(depth int, tagid int, field *internalpb.Field, prefix string) (int, error)

[Kybxd]

done

[Kybxd]

Is this acceptable, or we may find another way to distinguish the number prop works on the list/map, or the first subfield of the list/map?

[wenchy]

• I think we'd better distinguish them. Add new prop subnumber (just likesubsep) to specify first sub-field's number of the list/map element.
• Also need to improve comment below.

  // Specify field number (unique numbered tag).
  // All fields without numbers specified will use a sequence starting from 1 by default.
  // Besides, auto generated field numbers will not reuse explicitly specified field numbers.
  //
  // Refer to [protobuf: Assigning Field Numbers](https://protobuf.dev/programming-guides/proto3/#assigning)
  int32 number = 16;
  // Specify first sub-field's number of the list-element/map-value/struct.
  int32 subnumber = 17;

[Kybxd]

We fixed the field number of message's first field to 1. So it's no need to consider subnumber now.

[wenchy]

1. Should remove the prop number:10 as it is already used to specify tag id, no useless to keep it.
2. If specified prop number, then the other auto generated tag id MUST not use it again in the same nesting level. Add test case to cover it.

[Kybxd]

1. done
2. a new algorithm is introduced to guarantee auto generated field numbers do not conflict with specified ones.

[wenchy]

• I think we'd better distinguish them. Add new prop subnumber (just likesubsep) to specify first sub-field's number of the list/map element.
• Also need to improve comment below.

  // Specify field number (unique numbered tag).
  // All fields without numbers specified will use a sequence starting from 1 by default.
  // Besides, auto generated field numbers will not reuse explicitly specified field numbers.
  //
  // Refer to [protobuf: Assigning Field Numbers](https://protobuf.dev/programming-guides/proto3/#assigning)
  int32 number = 16;
  // Specify first sub-field's number of the list-element/map-value/struct.
  int32 subnumber = 17;

[wenchy]

It's too verbose to specify field number for each column.

Another solution is automation (auto keep compatibilty), when compared with the old protoconf file:

1. Auto keep field number by unique column name.
2. If new field name occured, then assign the the max field number plus 1 in the same level.

This can avoid field number overwriting for different column names.