feat(common): Add json schema const decorator.

packages/common/src/jsonschema/decorators/const.spec.ts

@@ -0,0 +1,28 @@
+import {Const, JsonSchema} from "../../../src/jsonschema";
+import {stubSchemaDecorator} from "./utils";
+
+describe("Const", () => {
+  describe("when const is a string", () => {
+    it("should store data", () => {
+      const decorateStub = stubSchemaDecorator();
+      const schema = new JsonSchema();
+      Const("0");
+      // @ts-ignore
+      decorateStub.getCall(0).args[0](schema);
+      schema.const.should.eq("0");
+      decorateStub.restore();
+    });
+  });
+
+  describe("when const is a boolean", () => {
+    it("should store data", () => {
+      const decorateStub = stubSchemaDecorator();
+      const schema = new JsonSchema();
+      Const(false);
+      // @ts-ignore
+      decorateStub.getCall(0).args[0](schema);
+      schema.const.should.eq(false);
+      decorateStub.restore();
+    });
+  });
+});

packages/common/src/jsonschema/decorators/const.ts

@@ -0,0 +1,66 @@
+import {JSONSchema6Type} from "json-schema";
+import {decoratorSchemaFactory} from "../utils/decoratorSchemaFactory";
+
+/**
+ * The const keyword is used to restrict a value to a fixed value.
+ *
+ *
+ * ## Example
+ * ### With a string
+ *
+ * ```typescript
+ * class Model {
+ *    @Const("value1")
+ *    property: "value1";
+ * }
+ * ```
+ *
+ * Will produce:
+ *
+ * ```json
+ * {
+ *   "type": "object",
+ *   "properties": {
+ *     "property": {
+ *       "type": "string",
+ *       "const": "value1"
+ *     }
+ *   }
+ * }
+ * ```
+ *  * ### With a boolean
+ *
+ * ```typescript
+ * class Model {
+ *    @Const(true)
+ *    property: boolean;
+ * }
+ * ```
+ *
+ * Will produce:
+ *
+ * ```json
+ * {
+ *   "type": "object",
+ *   "properties": {
+ *     "property": {
+ *       "type": "boolean",
+ *       "const": true
+ *     }
+ *   }
+ * }
+ * ```
+ *
+ * @param {string | number | boolean } constValue
+ * @returns {Function}
+ * @decorator
+ * @ajv
+ * @property
+ * @jsonschema
+ * @auto-map The data will be stored on the right place according to the type and collectionType (primitive or collection).
+ */
+export function Const(constValue: JSONSchema6Type | any) {
+  return decoratorSchemaFactory(schema => {
+    schema.mapper.const = constValue;
+  });
+}

packages/common/src/jsonschema/decorators/index.ts

@@ -26,3 +26,4 @@ export * from "./any";
 export * from "./schema";
 export * from "./title";
 export * from "./ignoreProperty";
+export * from "./const";