Add rootSchema and ajvOptions options

readme.md

@@ -100,6 +100,47 @@ config.set('foo', '1');
 
 **Note:** The `default` value will be overwritten by the `defaults` option if set.
 
+#### rootSchema
+Type: `object`
+
+Top-level properties for the schema. Requires a `schema` option to be provided, and cannot contain a `properties` field.
+
+Example:
+
+```js
+import Conf from 'conf';
+
+const store = new Conf({
+	projectName: 'foo',
+	schema: {},
+	rootSchema: {
+		additionalProperties: false
+	}
+});
+```
+
+#### ajvOptions
+Type: `object`
+
+Options to pass to AJV. Requires a `schema` option to be provided.
+
+Example:
+
+```js
+import Conf from 'conf';
+
+const store = new Conf({
+	projectName: 'foo',
+	schema: {},
+	rootSchema: {
+		additionalProperties: false
+	},
+	ajvOptions: {
+		removeAdditional: true,
+	},
+});
+```
+
 #### migrations
 
 Type: `object`

source/index.ts

@@ -97,12 +97,14 @@ export default class Conf<T extends Record<string, any> = Record<string, unknown
 			const ajv = new Ajv({
 				allErrors: true,
 				useDefaults: true,
+				...options.ajvOptions,
 			});
 			ajvFormats(ajv);
 
 			const schema: JSONSchema = {
 				type: 'object',
 				properties: options.schema,
+				...options.rootSchema,
 			};
 
 			this.#validator = ajv.compile(schema);
@@ -112,6 +114,8 @@ export default class Conf<T extends Record<string, any> = Record<string, unknown
 					this.#defaultValues[key as keyof T] = value.default; // eslint-disable-line @typescript-eslint/no-unsafe-assignment
 				}
 			}
+		} else if (options.rootSchema ?? options.ajvOptions) {
+			throw new TypeError('`schema` option required to use `rootSchema` or `ajvOptions`.');
 		}
 
 		if (options.defaults) {

source/types.ts

@@ -1,5 +1,6 @@
 import {type JSONSchema as TypedJSONSchema} from 'json-schema-typed';
 // eslint-disable unicorn/import-index
+import type {CurrentOptions} from 'ajv/dist/core.js';
 import type Conf from './index.js';
 
 export type Options<T extends Record<string, any>> = {
@@ -50,6 +51,20 @@ export type Options<T extends Record<string, any>> = {
 	*/
 	schema?: Schema<T>;
 
+	/**
+	Top-level properties for the schema.
+
+	Requires a `schema` option to be provided, and cannot contain a `properties` field.
+	*/
+	rootSchema?: Omit<TypedJSONSchema, 'properties'>;
+
+	/**
+	Options to pass to AJV.
+
+	Requires a `schema` option to be provided.
+	*/
+	ajvOptions?: CurrentOptions;
+
 	/**
 	Name of the config file (without extension).
 

test/index.ts

@@ -787,6 +787,43 @@ test('schema - validate Conf default', t => {
 	}, {message: 'Config schema violation: `foo` must be string'});
 });
 
+test('schema - rootSchema without schema', t => {
+	t.throws(() => {
+		new Conf({
+			cwd: temporaryDirectory(),
+			rootSchema: {},
+		});
+	}, {message: '`schema` option required to use `rootSchema` or `ajvOptions`.'});
+});
+
+test('schema - validate rootSchema', t => {
+	t.throws(() => {
+		const config = new Conf({
+			cwd: temporaryDirectory(),
+			schema: {},
+			rootSchema: {
+				additionalProperties: false,
+			},
+		});
+		config.set('foo', 'bar');
+	}, {message: 'Config schema violation: `` must NOT have additional properties'});
+});
+
+test('AJV - validate AJV options', t => {
+	const config = new Conf({
+		cwd: temporaryDirectory(),
+		schema: {},
+		ajvOptions: {
+			removeAdditional: true,
+		},
+		rootSchema: {
+			additionalProperties: false,
+		},
+	});
+	config.set('foo', 'bar');
+	t.is(config.get('foo'), undefined);
+});
+
 test('.get() - without dot notation', t => {
 	t.is(t.context.configWithoutDotNotation.get('foo'), undefined);
 	t.is(t.context.configWithoutDotNotation.get('foo', '🐴'), '🐴');