Fix 'object' enumType types

The enum types exported when using the 'object' enumType would always
just be a string, since the strings used in the enum object would be
widened to just be a 'string' type. This adds 'as const' to the
declaration, to prevent this widening.

See https://www.typescriptlang.org/docs/handbook/release-notes/typescript-3-4.html#const-assertions

generator.ts

@@ -90,7 +90,7 @@ function getEnumTs(
     case "object": {
       const enumValues = enumData.values.map(({ name }) => `  ${name}: "${name}"`).join(",\n");
       const enumName = enumNameMap.get(enumData.name);
-      return `export const ${enumName} = {\n${enumValues}\n};\n\nexport type ${enumName} = (typeof ${enumName})[keyof typeof ${enumName}];`;
+      return `export const ${enumName} = {\n${enumValues}\n} as const;\n\nexport type ${enumName} = (typeof ${enumName})[keyof typeof ${enumName}];`;
     }
     default:
       throw new Error(`Unknown enumType: ${config.enumType}`);

tests/options-behavior/expected/enumTypeObject.ts

@@ -4,7 +4,7 @@ export const Gender = {
   Male: "Male",
   Female: "Female",
   Other: "Other"
-};
+} as const;
 
 export type Gender = (typeof Gender)[keyof typeof Gender];
 
@@ -13,7 +13,7 @@ export const DataTest = {
   Banana: "Banana",
   Orange: "Orange",
   Pear: "Pear"
-};
+} as const;
 
 export type DataTest = (typeof DataTest)[keyof typeof DataTest];
 

tests/options-behavior/expected/enumTypeObjectPrefixSuffix.ts

@@ -4,7 +4,7 @@ export const eGenderEnum = {
   Male: "Male",
   Female: "Female",
   Other: "Other"
-};
+} as const;
 
 export type eGenderEnum = (typeof eGenderEnum)[keyof typeof eGenderEnum];
 
@@ -13,7 +13,7 @@ export const eDataTestEnum = {
   Banana: "Banana",
   Orange: "Orange",
   Pear: "Pear"
-};
+} as const;
 
 export type eDataTestEnum = (typeof eDataTestEnum)[keyof typeof eDataTestEnum];