@picksell/ts-proto

ts-proto

ts-proto transforms your .proto files into strong typed typescript files!

Table of contents

• QuickStart
• Goals
• Example Types
• Highlights
• Current Disclaimers
• Auto-Batching / N+1 Prevention
• Usage
  • Supported options
  • Only Types
  • NestJS Support
• Building
• Assumptions
• Todo
• Typing Approach
• OneOf Handling
• Primitive Types
• Wrapper Types
• Number Types
• Current Status of Optional Values

Overview

ts-proto generates TypeScript types from protobuf schemas.

I.e. given a person.proto schema like:

message Person {
  string name = 1;
}

ts-proto will generate a person.ts file like:

interface Person {
  name: string
}

const Person = {
  encode(person): Writer { ... }
  decode(reader): Person { ... }
  toJSON(person): unknown { ... }
  fromJSON(data): Person { ... }
}

It also knows about services and will generate types for them as well, i.e.:

export interface PingService {
  ping(request: PingRequest): Promise<PingResponse>;
}

It will also generate client implementations of PingService, but currently only Twirp clients are supported (see issue 2 for wider/native GRPC support).

QuickStart

• npm install ts-proto
• protoc --plugin=./node_modules/.bin/protoc-gen-ts_proto --ts_proto_out=. ./simple.proto
  • (Note that the output parameter name, ts_proto_out, is named based on the suffix of the plugin's name, i.e. "ts_proto" suffix in the --plugin=./node_modules/.bin/protoc-gen-ts_proto parameter becomes the _out prefix, per protoc's CLI conventions.)
  • On Windows, use protoc --plugin=protoc-gen-ts_proto=.\node_modules\.bin\protoc-gen-ts_proto.cmd --ts_proto_out=. ./imple.proto

This will generate *.ts source files for the given *.proto types.

If you want to package these source files into an npm package to distribute to clients, just run tsc on them as usual to generate the .js/.d.ts files, and deploy the output as a regular npm package.

Goals

• Idiomatic TypeScript/ES6 types
  • ts-proto is a clean break from either the built-in Google/Java-esque JS code of protoc or the "make .d.ts files the *.js comments" approach of protobufjs
  • (Techically the protobufjs/minimal package is used for actually reading/writing bytes.)
• TypeScript-first output
• Interfaces over classes
  • As much as possible, types are just interfaces, so you can work with messages just like regular hashes/data structures.
• Only supports codegen *.proto-to-*.ts workflow, currently no runtime reflection/loading of dynamic .proto files
• Currently ambivalent about browser support, current focus is on Node/server-side use cases

Example Types

The generated types are "just data", i.e.:

export interface Simple {
  name: string;
  age: number;
  createdAt: Date | undefined;
  child: Child | undefined;
  state: StateEnum;
  grandChildren: Child[];
  coins: number[];
}

Along with encode/decode factory methods:

export const Simple = {
  encode(message: Simple, writer: Writer = Writer.create()): Writer {
    ...
  },

  decode(reader: Reader, length?: number): Simple {
    ...
  },

  fromJSON(object: any): Simple {
    ...
  },

  fromPartial(object: DeepPartial<Simple>): Simple {
    ...
  },

  toJSON(message: Simple): unknown {
    ...
  },
};

This allows idiomatic TS/JS usage like:

const bytes = Simple.encode({ name: ..., age: ..., ... }).finish();
const simple = Simple.decode(Reader.create(bytes));
const { name, age } = simple;

Which can dramatically ease integration when converting to/from other layers without creating a class and calling the right getters/setters.

Highlights

• A poor man's attempt at "please give us back optional types"

  Wrapper types, i.e. google.protobuf.StringValue, are mapped as optional values, i.e. string | undefined, which means for primitives we can kind of pretend that the protobuf type system has optional types.

• Timestamp is mapped as Date

• fromJSON/toJSON support the canonical Protobuf JS format (i.e. timestamps are ISO strings)

Current Disclaimers

ts-proto was originally developed for Twirp, so the clients it generates (if your *.proto files use the GRPC service constructs) assume they're talking to Twirp HTTP endpoints. There is an issue filed (#2) to support GRPC endpoints, but no work currently in progress.

That said, the message/interface types that ts-proto generates are not coupled to Twirp and should be fully usable in other Protobuf environments (either GRPC-based or even just reading protobuf files from disk/etc.). The client-related output can also be disabled (see the Usage section).

ts-proto also does not currently have any infrastructure to help implement the server-side of a GRPC (either Twirp or pure GRPC) service, i.e. built-in Express bindings or something like that. However, again, the types/interfaces that ts-proto generates for your messages and services are still generally very helpful in setting up your own server-side implementations.

Auto-Batching / N+1 Prevention

If you're using ts-proto's (currently Twirp only) clients to call backend micro-services, similar to the N+1 problem in SQL applications, it is easy for micro-service clients to (when serving an individual request) inadvertantly trigger multiple separate RPC calls for "get book 1", "get book 2", "get book 3", that should really be batched into a single "get books [1, 2, 3]" (assuming the backend supports a batch-oriented RPC method).

ts-proto can help with this, and essentially auto-batch your individual "get book" calls into batched "get books" calls.

For ts-proto to do this, you need to implement your service's RPC methods with the batching convention of:

• A method name of Batch<OperationName>
• The Batch<OperationName> input type has a single repeated field (i.e. repeated string ids = 1)
• The Batch<OperationName> output type has either a:
  • A single repeated field (i.e. repeated Foo foos = 1) where the output order is the same as the input ids order, or
  • A map of the input to an output (i.e. map<string, Entity> entities = 1;)

When ts-proto recognizes methods of this pattern, it will automatically create a "non-batch" version of <OperationName> for the client, i.e. client.Get<OperationName>, that takes a single id and returns a single result.

This provides the client code with the illusion that it can make individual Get<OperationName> calls (which is generally preferrable/easier when implementing the client's business logic), but the actual implementation that ts-proto provides will end up making Batch<OperationName> calls to the backend service.

You also need to enable the useContext=true build-time parameter, which gives all client methods a Go-style ctx parameter, with a getDataLoaders method that lets ts-proto cache/resolve request-scoped DataLoaders, which provide the fundamental auto-batch detection/flushing behavior.

See the batching.proto file and related tests for examples/more details.

But the net effect is that ts-proto can provide SQL-/ORM-style N+1 prevention for clients calls, which can be critical especially in high-volume / highly-parallel implementations like GraphQL front-end gateways calling backend micro-services.

Usage

ts-proto is a protoc plugin, so you run it by (either directly in your project, or more likely in your mono-repo schema pipeline, i.e. like Ibotta or Namely):

• Add ts-proto to your package.json
• Run npm install to download it
• Invoke protoc with a plugin parameter like:

protoc --plugin=node_modules/ts-proto/protoc-gen-ts_proto ./batching.proto -I.

Supported options

• With --ts_proto_opt=context=true, the services will have a Go-style ctx parameter, which is useful for tracing/logging/etc. if you're not using node's async_hooks api due to performance reasons.

• With --ts_proto_opt=forceLong=long, all 64 bit numbers will be parsed as instances of Long (using the long library).

  Alternatively, if you pass --ts_proto_opt=forceLong=string, all 64 bit numbers will be outputted as strings.

• With --ts_proto_opt=env=node or browser or both, ts-proto will make environment-specific assumptions in your output. This defaults to both, which makes no environment-specific assumptions.

  Using node changes the types of bytes from Uint8Array to Buffer for easier integration with the node ecosystem which generally uses Buffer.

  Currently browser doesn't have any specific behavior other than being "not node". It probably will soon/at some point.

• With --ts_proto_opt=useOptionals=true, non-scalar fields are declared as optional TypeScript properties, e.g. field?: Message instead of field: Message | undefined.

  ts-proto defaults to useOptionals=false, e.g. field: Message | undefined, because it is the "most-safe" for use cases like:

  interface SomeMessage {
    firstName: string | undefined;
    lastName: string | undefined;
  }
  
  const data = { firstName: 'a', lastTypo: 'b' };
  
  // This will compile even though `lastTypo` means that `lastName` is not assigned
  const message: SomeMessage = {
    ...data,
  };
  

  However, the type-safety of useOptionals=false is admittedly tedious if you have many inherently-unused fields, so you can use useOptionals=true if that trade-off makes sense for your project.

  Eventually if TypesCript supports Exact Types, that should allow ts-proto to switch to useOptionals=true as the default/only behavior, have the generated Message.encode/Message.toPartial/etc. methods accept Exact<T> versions of the message types, and the result would be both safe + succinct.

• With --ts_proto_opt=oneof=unions, oneof fields will be generated as ADTs.

  See the "OneOf Handling" section.

• With --ts_proto_opt=lowerCaseServiceMethods=true, the method names of service methods will be lowered/camel-case, i.e. service.findFoo instead of service.FindFoo.

• With --ts_proto_opt=outputEncodeMethods=false, the Message.encode and Message.decode methods for working with protobuf-encoded/binary data will not be output.

  This is useful if you want "only types".

• With --ts_proto_opt=outputJsonMethods=false, the Message.fromJSON and Message.toJSON methods for working with JSON-coded data will not be output.

  This is also useful if you want "only types".

• With --ts_proto_opt=outputClientImpl=false, the client implementations, i.e. FooServiceClientImpl, that implement the client-side (currently Twirp-only) RPC interfaces will not be output.

• With --ts_proto_opt=returnObservable=true, the return type of service methods will be Observable<T> instead of Promise<T>.

• With--ts_proto_opt=addGrpcMetadata=true, the last argument of service methods will accept the grpc Metadata type, which contains additional information with the call (i.e. access tokens/etc.).

  (Requires nestJs=true.)

• With--ts_proto_opt=addNestjsRestParameter=true, the last argument of service methods will be an rest parameter with type any. This way you can use custom decorators you could normally use in nestjs.

  (Requires nestJs=true.)

• With --ts_proto_opt=nestJs=true, the defaults will change to generate NestJS protobuf friendly types & service interfaces that can be used in both the client-side and server-side of NestJS protobuf implementations. See the nestjs readme for more information and implementation examples.

  Specifically outputEncodeMethods, outputJsonMethods, and outputClientImpl will all be false, and lowerCaseServiceMethods will be true.

  Note that addGrpcMetadata, addNestjsRestParameter and returnObservable will still be false.

Only Types

If you're looking for ts-proto to generate only types for your Protobuf types then passing all three of outputEncodeMethods, outputJsonMethods, and outputClientImpl as false is probably what you want, i.e.:

--ts_proto_opt=outputEncodeMethods=false,outputJsonMethods=false,outputClientImpl=false.

NestJS Support

We have a great way of working together with nestjs. ts-proto generates interfaces and decorators for you controller, client. For more information see the nestjs readme.

Building

ts-proto does not use pbjs at runtime, but we do use it in the ts-proto build process (to bootstrap the types used to parse the incoming protobuf metadata types, as well as for the test suite to ensure the ts-proto implementations match the ts-proto).

After running yarn install, run ./pbjs.sh to create the bootstrap types, and ./integration/pbjs.sh to create the integration test types. These pbjs-generated files are not currently checked in.

After this the tests should pass.

After making changes to ts-proto, you can run cd integration and ./codegen.sh to re-generate the test case *.ts output files that are in each integration/<test-case>/ directory.

The test suite's proto files (i.e. simple.proto, batching.proto, etc.) currently have serialized/.bin copies checked into git (i.e. simple.bin, batching.bin, etc.), so that the test suite can run without having to invoke the protoc build chain. I.e. if you change the simple.proto/etc. files, you'll need to run ./integration/update-bins.sh, which does require having the protoc executable available.

Assumptions

• TS/ES6 module name is the proto package

Todo

• Support the string-based encoding of duration in fromJSON/toJSON
• Support the json_name annotation
• Make oneof=unions the default behavior in 2.0

Typing Approach

• Missing fields on read
  • When decoding from binary, we set default values for all primitives
  • When decoding from JSON, we may have missing keys.
    • We could convert them to our prototype.
  • When using an instantiated object, our types enforce all keys to be set.

OneOf Handling

By default, oneof fields are modeled "flatly" in the message, i.e. oneof either_field { string field_a; string field_b } means that the message will have field_a: string | undefined; field_b: string | undefined.

With this output, you'll have to check both if object.field_a and if object.field_b, and if you set one, you'll have to remember to unset the other.

It's generally recommended to use the oneof=unions option, which will change the output to be an Abstract Data Type/ADT like:

interface YourMessage {
  eitherField: { $case: 'field_a'; field_a: string } | { $case: 'field_b'; field_b: string };
}

As this will automatically enforce only one of field_a or field_b "being set" at a time, because the values are stored in the eitherField field that can only have a single value at a time.

In ts-proto's currently-unplanned 2.x release, oneof=unions will become the default behavior.

Primitive Types

Protobuf has the somewhat annoying behavior that primitives types cannot differentiate between set-to-defalut-value and unset.

I.e. if you have a string name = 1, and set object.name = '', Protobuf will skip sending the tagged name field over the wire, because its understood that readers on the other end will, when they see name is not included in the payload, return empty string.

ts-proto models this behavior, of "unset" values being the primitive's default. (Technically by setting up an object prototype that knows the default values of the message's primitive fields.)

If you want fields where you can model set/unset, see Wrapper Types.

Wrapper Types

In core Protobuf, while unset primitives are read as default values, unset messages are returned as null.

This allows a cute hack where you can model a logical string | null by creating a field that is a message (can be null) and the message has a single string value (for when the value is not null).

Protobuf has several built-in types for this pattern, i.e. google.protobuf.StringValue.

ts-proto understands these wrapper types and will generate google.protobuf.StringValue name = 1 as a name: string | undefined.

This hides some of the StringValue mess and gives a more idiomatic way of using them.

Granted, it's unfortunate this is not as simple as marking the string as optional.

Number Types

Numbers are by default assumed to be plain JavaScript numbers. Since protobuf supports 64 bit numbers, but JavaScript doesn't, default behaviour is to throw an error if a number is detected to be larger than Number.MAX_SAFE_INTEGER. If 64 bit numbers are expected to be used, then use the forceLong option.

Each of the protobuf basic number types maps as following depending on option used.

Protobuf number types	Default Typescript types	forceLong=long types	forceLong=string types
double	number	number	number
float	number	number	number
int32	number	number	number
int64	number*	Long	string
uint32	number	number	number
uint64	number*	Unsigned Long	string
sint32	number	number	number
sint64	number*	Long	string
fixed32	number	number	number
fixed64	number*	Unsigned Long	string
sfixed32	number	number	number
sfixed64	number*	Long	string

Where (*) indicates they might throw an error at runtime.

Current Status of Optional Values

• Required primitives: use as-is, i.e. string name = 1.
• Optional primitives: use wrapper types, i.e. StringValue name = 1.
• Required messages: not available
• Optional primitives: use as-is, i.e. SubMessage message = 1.