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# gRPC Protobuf Loader
A utility package for loading `.proto` files for use with gRPC, using the latest Protobuf.js package.
Please refer to [protobuf.js' documentation](https://github.com/dcodeIO/protobuf.js/blob/master/README.md)
to understands its features and limitations.
## Installation
```sh
npm install @grpc/proto-loader
```
## Usage
```js
const protoLoader = require('@grpc/proto-loader');
const grpcLibrary = require('grpc');
// OR
const grpcLibrary = require('@grpc/grpc-js');
protoLoader.load(protoFileName, options).then(packageDefinition => {
const packageObject = grpcLibrary.loadPackageDefinition(packageDefinition);
});
// OR
const packageDefinition = protoLoader.loadSync(protoFileName, options);
const packageObject = grpcLibrary.loadPackageDefinition(packageDefinition);
```
The options parameter is an object that can have the following optional properties:
| Field name | Valid values | Description
|------------|--------------|------------
| `keepCase` | `true` or `false` | Preserve field names. The default is to change them to camel case.
| `longs` | `String` or `Number` | The type to use to represent `long` values. Defaults to a `Long` object type.
| `enums` | `String` | The type to use to represent `enum` values. Defaults to the numeric value.
| `bytes` | `Array` or `String` | The type to use to represent `bytes` values. Defaults to `Buffer`.
| `defaults` | `true` or `false` | Set default values on output objects. Defaults to `false`.
| `arrays` | `true` or `false` | Set empty arrays for missing array values even if `defaults` is `false` Defaults to `false`.
| `objects` | `true` or `false` | Set empty objects for missing object values even if `defaults` is `false` Defaults to `false`.
| `oneofs` | `true` or `false` | Set virtual oneof properties to the present field's name. Defaults to `false`.
| `json` | `true` or `false` | Represent `Infinity` and `NaN` as strings in `float` fields, and automatically decode `google.protobuf.Any` values. Defaults to `false`
| `includeDirs` | An array of strings | A list of search paths for imported `.proto` files.
The following options object closely approximates the existing behavior of `grpc.load`:
```js
const options = {
keepCase: true,
longs: String,
enums: String,
defaults: true,
oneofs: true
}
```
## Generating TypeScript types
The `proto-loader-gen-types` script distributed with this package can be used to generate TypeScript type information for the objects loaded at runtime. More information about how to use it can be found in [the *@grpc/proto-loader TypeScript Type Generator CLI Tool* proposal document](https://github.com/grpc/proposal/blob/master/L70-node-proto-loader-type-generator.md). The arguments mostly match the `load` function's options; the full usage information is as follows:
```console
proto-loader-gen-types.js [options] filenames...
Options:
--help Show help [boolean]
--version Show version number [boolean]
--keepCase Preserve the case of field names
[boolean] [default: false]
--longs The type that should be used to output 64 bit
integer values. Can be String, Number
[string] [default: "Long"]
--enums The type that should be used to output enum fields.
Can be String [string] [default: "number"]
--bytes The type that should be used to output bytes
fields. Can be String, Array
[string] [default: "Buffer"]
--defaults Output default values for omitted fields
[boolean] [default: false]
--arrays Output default values for omitted repeated fields
even if --defaults is not set
[boolean] [default: false]
--objects Output default values for omitted message fields
even if --defaults is not set
[boolean] [default: false]
--oneofs Output virtual oneof fields set to the present
field's name [boolean] [default: false]
--json Represent Infinity and NaN as strings in float
fields. Also decode google.protobuf.Any
automatically [boolean] [default: false]
--includeComments Generate doc comments from comments in the original
files [boolean] [default: false]
-I, --includeDirs Directories to search for included files [array]
-O, --outDir Directory in which to output files
[string] [required]
--grpcLib The gRPC implementation library that these types
will be used with. If not provided, some types will
not be generated [string]
--inputTemplate Template for mapping input or "permissive" type
names [string] [default: "%s"]
--outputTemplate Template for mapping output or "restricted" type
names [string] [default: "%s__Output"]
--inputBranded Output property for branded type for "permissive"
types with fullName of the Message as its value
[boolean] [default: false]
--outputBranded Output property for branded type for "restricted"
types with fullName of the Message as its value
[boolean] [default: false]
--targetFileExtension File extension for generated files.
[string] [default: ".ts"]
--importFileExtension File extension for import specifiers in generated
code. [string] [default: ""]
```
### Example Usage
Generate the types:
```sh
$(npm bin)/proto-loader-gen-types --longs=String --enums=String --defaults --oneofs --grpcLib=@grpc/grpc-js --outDir=proto/ proto/*.proto
```
Consume the types:
```ts
import * as grpc from '@grpc/grpc-js';
import * as protoLoader from '@grpc/proto-loader';
import type { ProtoGrpcType } from './proto/example.ts';
import type { ExampleHandlers } from './proto/example_package/Example.ts';
const exampleServer: ExampleHandlers = {
// server handlers implementation...
};
const packageDefinition = protoLoader.loadSync('./proto/example.proto');
const proto = (grpc.loadPackageDefinition(
packageDefinition
) as unknown) as ProtoGrpcType;
const server = new grpc.Server();
server.addService(proto.example_package.Example.service, exampleServer);
```
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