feat: enumsAsLiterals option (#450)

* feat: add `enumAsConst` option

* chore: add integration/enum-as-const

* feat: handle enumAsConst option

* chore: add integration/enum-as-const-with-string-enums

* fix: rename `enumAsConst` to `enumsAsLiterals`

* chore: update readme

README.markdown

@@ -348,6 +348,8 @@ Generated code will be placed in the Gradle build directory.
 
 - With `--ts_proto_opt=fileSuffix=<SUFFIX>`, ts-proto will emit generated files using the specified suffix. A `helloworld.proto` file with `fileSuffix=.pb` would be generated as `helloworld.pb.ts`. This is common behavior in other protoc plugins and provides a way to quickly glob all the generated files. 
 
+- With `--ts_proto_opt=enumsAsLiterals=true`, the generated enum types will be enum-ish object with `as const`.
+
 ### 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.:

integration/enums-as-literals-with-string-enums/enums-as-literals-with-string-enums.proto

@@ -0,0 +1,12 @@
+syntax = "proto3";
+
+message DividerData {
+    enum DividerType {
+        DOUBLE = 0;
+        SINGLE = 1;
+        DASHED = 2;
+        DOTTED = 3;
+    }
+
+    DividerType type = 1;
+}

integration/enums-as-literals-with-string-enums/enums-as-literals-with-string-enums.ts

@@ -0,0 +1,144 @@
+/* eslint-disable */
+import { util, configure, Writer, Reader } from 'protobufjs/minimal';
+import * as Long from 'long';
+
+export const protobufPackage = '';
+
+export interface DividerData {
+  type: DividerData_DividerType;
+}
+
+export const DividerData_DividerType = {
+  DOUBLE: 'DOUBLE',
+  SINGLE: 'SINGLE',
+  DASHED: 'DASHED',
+  DOTTED: 'DOTTED',
+  UNRECOGNIZED: 'UNRECOGNIZED',
+} as const;
+
+export type DividerData_DividerType = typeof DividerData_DividerType[keyof typeof DividerData_DividerType];
+
+export function dividerData_DividerTypeFromJSON(object: any): DividerData_DividerType {
+  switch (object) {
+    case 0:
+    case 'DOUBLE':
+      return DividerData_DividerType.DOUBLE;
+    case 1:
+    case 'SINGLE':
+      return DividerData_DividerType.SINGLE;
+    case 2:
+    case 'DASHED':
+      return DividerData_DividerType.DASHED;
+    case 3:
+    case 'DOTTED':
+      return DividerData_DividerType.DOTTED;
+    case -1:
+    case 'UNRECOGNIZED':
+    default:
+      return DividerData_DividerType.UNRECOGNIZED;
+  }
+}
+
+export function dividerData_DividerTypeToJSON(object: DividerData_DividerType): string {
+  switch (object) {
+    case DividerData_DividerType.DOUBLE:
+      return 'DOUBLE';
+    case DividerData_DividerType.SINGLE:
+      return 'SINGLE';
+    case DividerData_DividerType.DASHED:
+      return 'DASHED';
+    case DividerData_DividerType.DOTTED:
+      return 'DOTTED';
+    default:
+      return 'UNKNOWN';
+  }
+}
+
+export function dividerData_DividerTypeToNumber(object: DividerData_DividerType): number {
+  switch (object) {
+    case DividerData_DividerType.DOUBLE:
+      return 0;
+    case DividerData_DividerType.SINGLE:
+      return 1;
+    case DividerData_DividerType.DASHED:
+      return 2;
+    case DividerData_DividerType.DOTTED:
+      return 3;
+    default:
+      return 0;
+  }
+}
+
+const baseDividerData: object = { type: DividerData_DividerType.DOUBLE };
+
+export const DividerData = {
+  encode(message: DividerData, writer: Writer = Writer.create()): Writer {
+    if (message.type !== DividerData_DividerType.DOUBLE) {
+      writer.uint32(8).int32(dividerData_DividerTypeToNumber(message.type));
+    }
+    return writer;
+  },
+
+  decode(input: Reader | Uint8Array, length?: number): DividerData {
+    const reader = input instanceof Reader ? input : new Reader(input);
+    let end = length === undefined ? reader.len : reader.pos + length;
+    const message = { ...baseDividerData } as DividerData;
+    while (reader.pos < end) {
+      const tag = reader.uint32();
+      switch (tag >>> 3) {
+        case 1:
+          message.type = dividerData_DividerTypeFromJSON(reader.int32());
+          break;
+        default:
+          reader.skipType(tag & 7);
+          break;
+      }
+    }
+    return message;
+  },
+
+  fromJSON(object: any): DividerData {
+    const message = { ...baseDividerData } as DividerData;
+    message.type =
+      object.type !== undefined && object.type !== null
+        ? dividerData_DividerTypeFromJSON(object.type)
+        : DividerData_DividerType.DOUBLE;
+    return message;
+  },
+
+  toJSON(message: DividerData): unknown {
+    const obj: any = {};
+    message.type !== undefined && (obj.type = dividerData_DividerTypeToJSON(message.type));
+    return obj;
+  },
+
+  fromPartial<I extends Exact<DeepPartial<DividerData>, I>>(object: I): DividerData {
+    const message = { ...baseDividerData } as DividerData;
+    message.type = object.type ?? DividerData_DividerType.DOUBLE;
+    return message;
+  },
+};
+
+type Builtin = Date | Function | Uint8Array | string | number | boolean | undefined;
+
+export type DeepPartial<T> = T extends Builtin
+  ? T
+  : T extends Array<infer U>
+  ? Array<DeepPartial<U>>
+  : T extends ReadonlyArray<infer U>
+  ? ReadonlyArray<DeepPartial<U>>
+  : T extends {}
+  ? { [K in keyof T]?: DeepPartial<T[K]> }
+  : Partial<T>;
+
+type KeysOfUnion<T> = T extends T ? keyof T : never;
+export type Exact<P, I extends P> = P extends Builtin
+  ? P
+  : P & { [K in keyof P]: Exact<P[K], I[K]> } & Record<Exclude<keyof I, KeysOfUnion<P>>, never>;
+
+// If you get a compile-error about 'Constructor<Long> and ... have no overlap',
+// add '--ts_proto_opt=esModuleInterop=true' as a flag when calling 'protoc'.
+if (util.Long !== Long) {
+  util.Long = Long as any;
+  configure();
+}

integration/enums-as-literals-with-string-enums/parameters.txt

@@ -0,0 +1 @@
+stringEnums=true,enumsAsLiterals=true

integration/enums-as-literals/enums-as-literals.proto

@@ -0,0 +1,12 @@
+syntax = "proto3";
+
+message DividerData {
+    enum DividerType {
+        DOUBLE = 0;
+        SINGLE = 1;
+        DASHED = 2;
+        DOTTED = 3;
+    }
+
+    DividerType type = 1;
+}

integration/enums-as-literals/enums-as-literals.ts

@@ -0,0 +1,126 @@
+/* eslint-disable */
+import { util, configure, Writer, Reader } from 'protobufjs/minimal';
+import * as Long from 'long';
+
+export const protobufPackage = '';
+
+export interface DividerData {
+  type: DividerData_DividerType;
+}
+
+export const DividerData_DividerType = {
+  DOUBLE: 0,
+  SINGLE: 1,
+  DASHED: 2,
+  DOTTED: 3,
+  UNRECOGNIZED: -1,
+} as const;
+
+export type DividerData_DividerType = typeof DividerData_DividerType[keyof typeof DividerData_DividerType];
+
+export function dividerData_DividerTypeFromJSON(object: any): DividerData_DividerType {
+  switch (object) {
+    case 0:
+    case 'DOUBLE':
+      return DividerData_DividerType.DOUBLE;
+    case 1:
+    case 'SINGLE':
+      return DividerData_DividerType.SINGLE;
+    case 2:
+    case 'DASHED':
+      return DividerData_DividerType.DASHED;
+    case 3:
+    case 'DOTTED':
+      return DividerData_DividerType.DOTTED;
+    case -1:
+    case 'UNRECOGNIZED':
+    default:
+      return DividerData_DividerType.UNRECOGNIZED;
+  }
+}
+
+export function dividerData_DividerTypeToJSON(object: DividerData_DividerType): string {
+  switch (object) {
+    case DividerData_DividerType.DOUBLE:
+      return 'DOUBLE';
+    case DividerData_DividerType.SINGLE:
+      return 'SINGLE';
+    case DividerData_DividerType.DASHED:
+      return 'DASHED';
+    case DividerData_DividerType.DOTTED:
+      return 'DOTTED';
+    default:
+      return 'UNKNOWN';
+  }
+}
+
+const baseDividerData: object = { type: 0 };
+
+export const DividerData = {
+  encode(message: DividerData, writer: Writer = Writer.create()): Writer {
+    if (message.type !== 0) {
+      writer.uint32(8).int32(message.type);
+    }
+    return writer;
+  },
+
+  decode(input: Reader | Uint8Array, length?: number): DividerData {
+    const reader = input instanceof Reader ? input : new Reader(input);
+    let end = length === undefined ? reader.len : reader.pos + length;
+    const message = { ...baseDividerData } as DividerData;
+    while (reader.pos < end) {
+      const tag = reader.uint32();
+      switch (tag >>> 3) {
+        case 1:
+          message.type = reader.int32() as any;
+          break;
+        default:
+          reader.skipType(tag & 7);
+          break;
+      }
+    }
+    return message;
+  },
+
+  fromJSON(object: any): DividerData {
+    const message = { ...baseDividerData } as DividerData;
+    message.type = object.type !== undefined && object.type !== null ? dividerData_DividerTypeFromJSON(object.type) : 0;
+    return message;
+  },
+
+  toJSON(message: DividerData): unknown {
+    const obj: any = {};
+    message.type !== undefined && (obj.type = dividerData_DividerTypeToJSON(message.type));
+    return obj;
+  },
+
+  fromPartial<I extends Exact<DeepPartial<DividerData>, I>>(object: I): DividerData {
+    const message = { ...baseDividerData } as DividerData;
+    message.type = object.type ?? 0;
+    return message;
+  },
+};
+
+type Builtin = Date | Function | Uint8Array | string | number | boolean | undefined;
+
+export type DeepPartial<T> = T extends Builtin
+  ? T
+  : T extends Array<infer U>
+  ? Array<DeepPartial<U>>
+  : T extends ReadonlyArray<infer U>
+  ? ReadonlyArray<DeepPartial<U>>
+  : T extends {}
+  ? { [K in keyof T]?: DeepPartial<T[K]> }
+  : Partial<T>;
+
+type KeysOfUnion<T> = T extends T ? keyof T : never;
+export type Exact<P, I extends P> = P extends Builtin
+  ? P
+  : P & { [K in keyof P]: Exact<P[K], I[K]> } & Record<Exclude<keyof I, KeysOfUnion<P>>, never>;
+
+// If you get a compile-error about 'Constructor<Long> and ... have no overlap',
+// add '--ts_proto_opt=esModuleInterop=true' as a flag when calling 'protoc'.
+if (util.Long !== Long) {
+  util.Long = Long as any;
+  configure();
+}

integration/enums-as-literals/parameters.txt

@@ -0,0 +1 @@
+enumsAsLiterals=true

src/enums.ts

@@ -19,22 +19,36 @@ export function generateEnum(
   const chunks: Code[] = [];
 
   maybeAddComment(sourceInfo, chunks, enumDesc.options?.deprecated);
-  chunks.push(code`export ${options.constEnums ? 'const ' : ''}enum ${def(fullName)} {`);
+
+  if (options.enumsAsLiterals) {
+    chunks.push(code`export const ${def(fullName)} = {`);
+  } else {
+    chunks.push(code`export ${options.constEnums ? 'const ' : ''}enum ${def(fullName)} {`);
+  }
+
+  const delimiter = options.enumsAsLiterals ? ':' : '=';
 
   enumDesc.value.forEach((valueDesc, index) => {
     const info = sourceInfo.lookup(Fields.enum.value, index);
     maybeAddComment(info, chunks, valueDesc.options?.deprecated, `${valueDesc.name} - `);
     chunks.push(
-      code`${valueDesc.name} = ${options.stringEnums ? `"${valueDesc.name}"` : valueDesc.number.toString()},`
+      code`${valueDesc.name} ${delimiter} ${options.stringEnums ? `"${valueDesc.name}"` : valueDesc.number.toString()},`
     );
   });
 
   if (options.unrecognizedEnum)
     chunks.push(code`
-      ${UNRECOGNIZED_ENUM_NAME} = ${
+      ${UNRECOGNIZED_ENUM_NAME} ${delimiter} ${
       options.stringEnums ? `"${UNRECOGNIZED_ENUM_NAME}"` : UNRECOGNIZED_ENUM_VALUE.toString()
     },`);
-  chunks.push(code`}`);
+
+  if (options.enumsAsLiterals) {
+    chunks.push(code`} as const`);
+    chunks.push(code`\n`);
+    chunks.push(code`export type ${def(fullName)} = typeof ${def(fullName)}[keyof typeof ${def(fullName)}]`);
+  } else {
+    chunks.push(code`}`);
+  }
 
   if (options.outputJsonMethods || (options.stringEnums && options.outputEncodeMethods)) {
     chunks.push(code`\n`);

src/options.ts

@@ -43,6 +43,7 @@ export type Options = {
   outputTypeRegistry: boolean;
   stringEnums: boolean;
   constEnums: boolean;
+  enumsAsLiterals: boolean;
   outputClientImpl: boolean | 'grpc-web';
   outputServices: ServiceOption;
   addGrpcMetadata: boolean;
@@ -76,6 +77,7 @@ export function defaultOptions(): Options {
     outputTypeRegistry: false,
     stringEnums: false,
     constEnums: false,
+    enumsAsLiterals: false,
     outputClientImpl: true,
     outputServices: ServiceOption.DEFAULT,
     returnObservable: false,

tests/options-test.ts

@@ -9,6 +9,7 @@ describe('options', () => {
         "constEnums": false,
         "context": false,
         "emitImportedFiles": true,
+        "enumsAsLiterals": false,
         "env": "both",
         "esModuleInterop": false,
         "exportCommonSymbols": true,