feat(codegen): create object mapper

packages/smithy-client/src/index.ts

@@ -9,6 +9,7 @@ export * from "./extended-encode-uri-component";
 export * from "./get-array-if-single-item";
 export * from "./get-value-from-text-node";
 export * from "./lazy-json";
+export * from "./object-mapping";
 export * from "./parse-utils";
 export * from "./ser-utils";
 export * from "./split-every";

packages/smithy-client/src/object-mapping.spec.ts

@@ -0,0 +1,45 @@
+import { map, ObjectMappingInstructions } from "./object-mapping";
+
+describe("object mapping", () => {
+  const example: ObjectMappingInstructions = {
+    lazyValue1: [, , () => 1],
+    lazyValue2: ["lazyValue2AltKey", , () => 2],
+    lazyValue3: [, , () => 3],
+    lazyConditionalValue1: [, () => true, () => 4],
+    lazyConditionalValue2: ["lazyConditionalValue2AltKey", () => true, () => 5],
+    lazyConditionalValue3: [, true, () => 6],
+    lazyConditionalValue4: [, false, () => 44],
+    lazyConditionalValue5: ["lazyConditionalValue5AltKey", () => false, () => 55],
+    lazyConditionalValue6: [, "", () => 66],
+    simpleValue1: [, , 7],
+    simpleValue2: ["simpleValueAltKey", , 8],
+    simpleValue3: [, , 9],
+    conditionalValue1: [, () => true, 10],
+    conditionalValue2: ["conditionalValue2AltKey", () => true, 11],
+    conditionalValue3: [, {}, 12],
+    conditionalValue4: [, false, 110],
+    conditionalValue5: ["conditionalValue5AltKey", () => false, 121],
+    conditionalValue6: [, "", 132],
+  };
+
+  const exampleResult: Record<string, any> = {
+    lazyValue1: 1,
+    lazyValue2AltKey: 2,
+    lazyValue3: 3,
+    lazyConditionalValue1: 4,
+    lazyConditionalValue2AltKey: 5,
+    lazyConditionalValue3: 6,
+    simpleValue1: 7,
+    simpleValueAltKey: 8,
+    simpleValue3: 9,
+    conditionalValue1: 10,
+    conditionalValue2AltKey: 11,
+    conditionalValue3: 12,
+  };
+
+  describe("map function", () => {
+    it("should map various values according to their instruction sets", () => {
+      expect(map({}, example)).toEqual(exampleResult);
+    });
+  });
+});

packages/smithy-client/src/object-mapping.ts

@@ -0,0 +1,120 @@
+/**
+ * A set of instructions for multiple keys.
+ * The aim is to provide a concise yet readable way to map and filter values
+ * onto a target object.
+ *
+ * @example
+ * ```javascript
+ * const example: ObjectMappingInstructions = {
+ *   lazyValue1: [, , () => 1],
+ *   lazyValue2: ["lazyValue2AltKey", , () => 2],
+ *   lazyValue3: [, , () => 3],
+ *   lazyConditionalValue1: [, () => true, () => 4],
+ *   lazyConditionalValue2: ["lazyConditionalValue2AltKey", () => true, () => 5],
+ *   lazyConditionalValue3: [, true, () => 6],
+ *   lazyConditionalValue4: [, false, () => 44],
+ *   lazyConditionalValue5: ["lazyConditionalValue5AltKey", () => false, () => 55],
+ *   lazyConditionalValue6: [, "", () => 66],
+ *   simpleValue1: [, , 7],
+ *   simpleValue2: ["simpleValueAltKey", , 8],
+ *   simpleValue3: [, , 9],
+ *   conditionalValue1: [, () => true, 10],
+ *   conditionalValue2: ["conditionalValue2AltKey", () => true, 11],
+ *   conditionalValue3: [, {}, 12],
+ *   conditionalValue4: [, false, 110],
+ *   conditionalValue5: ["conditionalValue5AltKey", () => false, 121],
+ *   conditionalValue6: [, "", 132],
+ * };
+ *
+ * const exampleResult: Record<string, any> = {
+ *   lazyValue1: 1,
+ *   lazyValue2AltKey: 2,
+ *   lazyValue3: 3,
+ *   lazyConditionalValue1: 4,
+ *   lazyConditionalValue2AltKey: 5,
+ *   lazyConditionalValue3: 6,
+ *   simpleValue1: 7,
+ *   simpleValueAltKey: 8,
+ *   simpleValue3: 9,
+ *   conditionalValue1: 10,
+ *   conditionalValue2AltKey: 11,
+ *   conditionalValue3: 12,
+ * };
+ * ```
+ */
+export type ObjectMappingInstructions = Record<string, ObjectMappingInstruction>;
+
+/**
+ * An instruction set for assigning a value to a target object.
+ */
+export type ObjectMappingInstruction =
+  | LazyValueInstruction
+  | ConditionalLazyValueInstruction
+  | SimpleValueInstruction
+  | ConditionalValueInstruction;
+
+/**
+ * [Key map or use same key, filter evaluation, value provider]
+ */
+export type LazyValueInstruction = [string | void, FilterEvaluation, () => any];
+
+/**
+ * [Key map or use same key, filter function, value provider]
+ */
+export type ConditionalLazyValueInstruction = [string | void, () => boolean, () => any];
+
+/**
+ * [Key map or use same key, filter evaluation, value]
+ */
+export type SimpleValueInstruction = [string | void, FilterEvaluation, any];
+
+/**
+ * [Key map or use same key, filter function on the value, value]
+ */
+export type ConditionalValueInstruction = [string | void, (value?: any) => boolean, any];
+
+/**
+ * Filter is considered passed if
+ * 1. It is a boolean true.
+ * 2. It is not undefined and is itself truthy.
+ * 3. It is undefined and the corresponding _value_ is neither null nor undefined.
+ */
+export type FilterEvaluation = boolean | unknown | void;
+
+/**
+ * Transfer a set of keys from [source] to [target].
+ * The check [sourceTransferCondition] is applied to values from the source,
+ * and values are transferred only upon passing the check.
+ */
+export const map = (target: any, instructions: Record<string, ObjectMappingInstruction>): typeof target => {
+  for (const key of Object.keys(instructions)) {
+    // eslint-disable-next-line prefer-const
+    let [targetKey, filter, value]: [void | string, ((_?: any) => boolean) | unknown, any] = instructions[key];
+
+    if (targetKey === undefined) {
+      targetKey = key;
+    }
+
+    if (typeof value === "function") {
+      let _value: any;
+      const defaultFilterPassed = filter === undefined && (_value = value()) != null;
+      const customFilterPassed =
+        (typeof filter === "function" && !!filter(void 0)) || (typeof filter !== "function" && !!filter);
+
+      if (defaultFilterPassed) {
+        target[targetKey as string] = _value;
+      } else if (customFilterPassed) {
+        target[targetKey as string] = value();
+      }
+    } else {
+      const defaultFilterPassed = filter === undefined && value != null;
+      const customFilterPassed =
+        (typeof filter === "function" && !!filter(value)) || (typeof filter !== "function" && !!filter);
+
+      if (defaultFilterPassed || customFilterPassed) {
+        target[targetKey as string] = value;
+      }
+    }
+  }
+  return target;
+};