Merge pull request #1564 from erikbrinkman/jsonschematype-improvements

Some improvements to JSONSchemaType for records

lib/types/json-schema.ts

@@ -88,20 +88,24 @@ export type JSONSchemaType<T, _partial extends boolean = false> = (
           // "properties" are optional for more concise dictionary schemas
           // "patternProperties" and can be only used with interfaces that have string index
           type: JSONType<"object", _partial>
-          // "required" type does not guarantee that all required properties are listed
-          // it only asserts that optional cannot be listed
-          required: _partial extends true ? Readonly<(keyof T)[]> : Readonly<RequiredMembers<T>[]>
           additionalProperties?: boolean | JSONSchemaType<T[string]>
           unevaluatedProperties?: boolean | JSONSchemaType<T[string]>
           properties?: _partial extends true ? Partial<PropertiesSchema<T>> : PropertiesSchema<T>
           patternProperties?: {[Pattern in string]?: JSONSchemaType<T[string]>}
-          propertyNames?: JSONSchemaType<string>
+          propertyNames?: Omit<JSONSchemaType<string>, "type"> & {type?: "string"}
           dependencies?: {[K in keyof T]?: Readonly<(keyof T)[]> | PartialSchema<T>}
           dependentRequired?: {[K in keyof T]?: Readonly<(keyof T)[]>}
           dependentSchemas?: {[K in keyof T]?: PartialSchema<T>}
           minProperties?: number
           maxProperties?: number
-        }
+        } & (// "required" type does not guarantee that all required properties
+        // are listed it only asserts that optional cannot be listed.
+        // "required" is not necessary if it's a non-partial type with no required keys
+        _partial extends true
+          ? {required: Readonly<(keyof T)[]>}
+          : [RequiredMembers<T>] extends [never]
+          ? {required?: Readonly<RequiredMembers<T>[]>}
+          : {required: Readonly<RequiredMembers<T>[]>})
       : T extends null
       ? {
           nullable: true

spec/types/json-schema.spec.ts

@@ -145,6 +145,8 @@ const invalidSchema: JSONSchemaType<MyData> = {
   type: [],
 }
 
+type MyEnumRecord = Record<"a" | "b" | "c" | "d", number | undefined>
+
 describe("JSONSchemaType type and validation as a type guard", () => {
   const ajv = new _Ajv({allowUnionTypes: true})
 
@@ -259,6 +261,35 @@ describe("JSONSchemaType type and validation as a type guard", () => {
       should.not.exist(ajv.errors)
     })
   })
+
+  describe("schema should be simple for record types", () => {
+    it("typechecks a valid type without required", () => {
+      const myEnumRecordSchema: JSONSchemaType<MyEnumRecord> = {
+        type: "object",
+        propertyNames: {enum: ["a", "b", "c", "d"]},
+        additionalProperty: {type: "number"},
+      }
+      // eslint-disable-next-line no-void
+      void myEnumRecordSchema
+    })
+
+    it("requires required for non-optional types", () => {
+      // @ts-expect-error missing required
+      const requiredSchema: JSONSchemaType<{a: number}> = {
+        type: "object",
+      }
+      // eslint-disable-next-line no-void
+      void requiredSchema
+    })
+
+    it("doesn't require required for optional types", () => {
+      const optionalSchema: JSONSchemaType<{a?: number}> = {
+        type: "object",
+      }
+      // eslint-disable-next-line no-void
+      void optionalSchema
+    })
+  })
 })
 
 // eslint-disable-next-line no-void