Support strict:true (#154), AsObject type, add clear_ methods, fix map default values

[Santalov]

In short:

• Solves Support for compilation and usage with strict typescript compiler options. #154 by making nullability typing in fromObject, toObject, getter and setter methods more exact
• Adds AsObject and AsObjectPartial types for every message
• Adds clear_* methods
• Fix toObject not returning a default value for map fields

What exactly changed.

toObject method now returns AsObject type declared inside a message namespace.
fromObject now accepts AsObjectPartial type, that has as many nullable fields as possible, in contrast to AsObject.
These types are useful when dealing with plain objects, which is common in frontend applications.

The data argument of fromObject function became nullable, so it matches the constructor declaration.
The fromObject and constructor arguments are consistent in terms of nullability. To determine, if a field is nullable, the following function is used:

export function canBeCreatedWithoutValue(
  rootDescriptor: descriptor.FileDescriptorProto,
  fieldDescriptor: descriptor.FieldDescriptorProto,
) {
  return (
    isOptional(rootDescriptor, fieldDescriptor) ||
    // Both proto2 and proto3 don't track presence for maps and repeated fields.
    // https://github.com/protocolbuffers/protobuf/blob/main/docs/field_presence.md#presence-in-proto2-apis
    isMap(fieldDescriptor) ||
    isRepeated(fieldDescriptor)
  );
}

This also makes repeated and map fields nullable in constructor (they weren't).

The return type of the toObject method (AsObject) determines if the field is nullable by using this function:

export function canHaveNullValue(
  rootDescriptor: descriptor.FileDescriptorProto,
  fieldDescriptor: descriptor.FieldDescriptorProto,
): boolean {
  return (
    isOptional(rootDescriptor, fieldDescriptor) &&
    !(
      isNumber(fieldDescriptor) ||
      isEnum(fieldDescriptor) ||
      isRepeated(fieldDescriptor) ||
      isBytes(fieldDescriptor) ||
      isString(fieldDescriptor) ||
      isBoolean(fieldDescriptor) ||
      isMap(fieldDescriptor)
    )
    // isRequiredWithoutExplicitDefault is needed, cos
    // protoc-gen-ts does not throw an exception when deserializing a message
    // that does not have some required fields
    // (neither does Google's javascript implementation).
    // Thanks to @tomasz-szypenbejl-td for reference.
  ) || isRequiredWithoutExplicitDefault(rootDescriptor, fieldDescriptor);
  // Fields that are not optional and have explicit default return that default.
  // Fields that are optional and are not messages, i.e.:
  // (
  //   isNumber(fieldDescriptor) ||
  //   isEnum(fieldDescriptor) ||
  //   isRepeated(fieldDescriptor) ||
  //   isBytes(fieldDescriptor) ||
  //   isString(fieldDescriptor) ||
  //   isBoolean(fieldDescriptor) ||
  //   isMap(fieldDescriptor)
  // ) === true
  // return their default value (zero, [], new Unit8Array(), '', false, new Map())
}

These functions have been derived after some discussion in #146 (link to the comment).

toObject returns default values for maps (there was a bug #146 (comment))

Getter and setter types changed, but this will only affect the strict:true users of typescript.

The function above is also responsible for getter and setter type nullability.

Types of getters and setters match exactly. This is ok, cos when a field always has value (!canHaveNullValue), assigning
undefined to it makes no sense: the getter of the field will always return some non-null value, so the code bellow will print 0.

let x = undefined;
msg.int64 = x; // msg.int is a proto3 int64 field
x = msg.int64;
console.log(x); // will print '0', might be confusing

The implication is that you cannot assign undefined to a field, that always returns non-null value (if you are using strict:true). This is a problem when dealing with optional fields, so clear_* methods were introduced. The plugin generates them for all fields, that had has_* method generated. Those methods are described in the official doc https://github.com/protocolbuffers/protobuf/blob/main/docs/field_presence.md

Tsconfig options strict, noFallthroughCasesInSwitch, noImplicitReturns, noPropertyAccessFromIndexSignature, noUncheckedIndexedAccess, noUnusedParameters are enabled in all tests.

Options noFallthroughCasesInSwitch and noImplicitReturns required no changes.

Option noPropertyAccessFromIndexSignature required to change method access in RPC from property access to element access.

Option noUncheckedIndexedAccess required to add non-null assertion operator (!) when accessing elements of #one_of_decls, methods mentioned above, and when returning cases[case] in oneof method. Tests were also adjusted.

Option noUnusedParameters was covered by if statement, checking nullable data argument. Tests were also adjusted.

I skipped some previously planned options.

Option exactOptionalPropertyTypes is supported only by Typescript >= 4.4, so it was skipped.

Option noUnusedLocals conflicts with interfaces, declared for RPC, so it was skipped too.

[Santalov]

Oh, and there is an ambiguous change, previously discussed here

The fromObject argument became nullable and it confilcts with the name of the method suggesting there should be an object. But making it nullable makes fromObject more similar to the constructor.

@thesayyn , We need your decision. If the change needs to be reverted, I will revert a couple of commits.

[thesayyn]

Hey. I am swarmed this week but I'll try to take a proper look.

EDIT: it would help me a lot if you could split each of these changes into their own PR.

[Santalov]

Hey. I am swarmed this week but I'll try to take a proper look.

EDIT: it would help me a lot if you could split each of these changes into their own PR.

No problem, I will split the PR.

[Santalov]

Hey. I am swarmed this week but I'll try to take a proper look.

EDIT: it would help me a lot if you could split each of these changes into their own PR.

I have not figured out a way to make new PRs independent, cos there are merge conflicts in generated files (maybe we should add them to gitignore). So PRs need to be merged in the following order:

• fix: toObject returns a default value for map fields. Tests. #158
• Support strict true, AsObject and AsObjectPartial types #159
• Support noPropertyAccessFromIndexSignature tsconfig option #160
• Support noUncheckedIndexedAccess tsconfig option #161
• Nullable fromObject argument #162
• Consistent field nullability in the constructor and fromObject method #163
• Presence clear methods #164

[Santalov]

Closing this PR, it duplicates ones listed in the comment above