fix: change parsing of type: null to add nullable: true to oneOf/anyOf (#43)

Author: jonluca

Diff for: package.json

@@ -36,22 +36,22 @@
 	"dependencies": {
 		"@apidevtools/json-schema-ref-parser": "^9.0.9",
 		"json-schema-walker": "^1.1.0",
-		"openapi-types": "^12.0.2",
+		"openapi-types": "^12.1.0",
 		"yargs": "^17.6.2"
 	},
 	"devDependencies": {
 		"@types/json-schema": "^7.0.11",
-		"@typescript-eslint/eslint-plugin": "^5.42.0",
-		"@typescript-eslint/parser": "^5.42.0",
+		"@typescript-eslint/eslint-plugin": "^5.49.0",
+		"@typescript-eslint/parser": "^5.49.0",
 		"c8": "^7.12.0",
-		"eslint": "^8.27.0",
-		"eslint-config-prettier": "^8.5.0",
+		"eslint": "^8.32.0",
+		"eslint-config-prettier": "^8.6.0",
 		"eslint-plugin-prettier": "^4.2.1",
 		"eslint-plugin-unused-imports": "^2.0.0",
-		"nock": "^13.2.9",
-		"prettier": "^2.7.1",
-		"typescript": "^4.8.4",
-		"vitest": "^0.24.5"
+		"nock": "^13.3.0",
+		"prettier": "^2.8.3",
+		"typescript": "^4.9.4",
+		"vitest": "^0.28.1"
 	},
 	"prettier": {
 		"singleQuote": true,

Diff for: src/index.ts

@@ -19,7 +19,7 @@ class InvalidTypeError extends Error {
 
 const oasExtensionPrefix = 'x-';
 
-const handleDefinition = async <T extends JSONSchema = JSONSchema>(
+const handleDefinition = async <T extends JSONSchema4 = JSONSchema4>(
 	def: JSONSchema7Definition | JSONSchema6Definition | JSONSchema4,
 	schema: T
 ) => {
@@ -52,7 +52,8 @@ const handleDefinition = async <T extends JSONSchema = JSONSchema>(
 			delete (<any>walker.rootSchema).definitions;
 		}
 		return walker.rootSchema;
-	} else if (Array.isArray(def)) {
+	}
+	if (Array.isArray(def)) {
 		// if it's an array, we might want to reconstruct the type;
 		const typeArr = def;
 		const hasNull = typeArr.includes('null');
@@ -69,7 +70,7 @@ const handleDefinition = async <T extends JSONSchema = JSONSchema>(
 	return def;
 };
 
-const convert = async <T extends JSONSchema = JSONSchema>(
+const convert = async <T extends object = JSONSchema4>(
 	schema: T,
 	options?: Options
 ): Promise<OpenAPIV3.Document> => {
@@ -108,6 +109,7 @@ function convertSchema(schema: SchemaType | undefined) {
 	schema = convertTypes(schema);
 	schema = rewriteConst(schema);
 	schema = convertDependencies(schema);
+	schema = convertNullable(schema);
 	schema = rewriteIfThenElse(schema);
 	schema = rewriteExclusiveMinMax(schema);
 	schema = convertExamples(schema);
@@ -196,6 +198,30 @@ function convertDependencies(schema: SchemaType) {
 	return schema;
 }
 
+function convertNullable(schema: SchemaType) {
+	for (const key of ['oneOf', 'anyOf'] as const) {
+		const schemas = schema[key] as JSONSchema4[];
+		if (!Array.isArray(schemas)) {
+			return schema;
+		}
+
+		const hasNullable = schemas.some((item) => item.type === 'null');
+
+		if (!hasNullable) {
+			return schema;
+		}
+
+		const filtered = schemas.filter((l) => l.type !== 'null');
+		for (const schemaEntry of filtered) {
+			schemaEntry.nullable = true;
+		}
+
+		schema[key] = filtered;
+	}
+
+	return schema;
+}
+
 function convertTypes(schema: SchemaType) {
 	if (typeof schema !== 'object') {
 		return schema;
@@ -300,11 +326,11 @@ function rewriteIfThenElse(schema: SchemaType) {
 function rewriteExclusiveMinMax(schema: SchemaType) {
 	if (typeof schema.exclusiveMaximum === 'number') {
 		schema.maximum = schema.exclusiveMaximum;
-		schema.exclusiveMaximum = true;
+		(schema as JSONSchema4).exclusiveMaximum = true;
 	}
 	if (typeof schema.exclusiveMinimum === 'number') {
 		schema.minimum = schema.exclusiveMinimum;
-		schema.exclusiveMinimum = true;
+		(schema as JSONSchema4).exclusiveMinimum = true;
 	}
 	return schema;
 }

Diff for: test/default-null.test.ts

@@ -8,8 +8,8 @@ it('supports default values of null', async ({ expect }) => {
 			nullableStringWithDefault: {
 				default: null,
 				oneOf: [{ type: 'string' }, { type: 'null' }],
-			}
-		}
+			},
+		},
 	};
 
 	const result = await convert(schema);
@@ -19,9 +19,9 @@ it('supports default values of null', async ({ expect }) => {
 		properties: {
 			nullableStringWithDefault: {
 				default: null,
-				oneOf: [{ type: 'string' }, { nullable: true }],
-			}
-		}
+				oneOf: [{ type: 'string', nullable: true }],
+			},
+		},
 	};
 
 	expect(result).toEqual(expected);