feat(lib-dynamodb): add support for imprecise numbers and custom number retrieval (#6644)

Author: RanVaknin

lib/lib-dynamodb/README.md

@@ -120,15 +120,26 @@ export interface marshallOptions {
    * but false if directly using the marshall function (backwards compatibility).
    */
   convertTopLevelContainer?: boolean;
+  /**
+   * Whether to allow numbers beyond Number.MAX_SAFE_INTEGER during marshalling.
+   * When set to true, allows numbers that may lose precision when converted to JavaScript numbers.
+   * When false (default), throws an error if a number exceeds Number.MAX_SAFE_INTEGER to prevent
+   * unintended loss of precision. Consider using the NumberValue type from @aws-sdk/lib-dynamodb
+   * for precise handling of large numbers.
+   */
+  allowImpreciseNumbers?: boolean;
 }
 
 export interface unmarshallOptions {
   /**
-   * Whether to return numbers as a string instead of converting them to native JavaScript numbers.
+   * Whether to modify how numbers are unmarshalled from DynamoDB.
+   * When set to true, returns numbers as NumberValue instances instead of native JavaScript numbers.
    * This allows for the safe round-trip transport of numbers of arbitrary size.
+   *
+   * If a function is provided, it will be called with the string representation of numbers to handle
+   * custom conversions (e.g., using BigInt or decimal libraries).
    */
-  wrapNumbers?: boolean;
-
+  wrapNumbers?: boolean | ((value: string) => number | bigint | NumberValue | any);
   /**
    * When true, skip wrapping the data in `{ M: data }` before converting.
    *
@@ -235,10 +246,59 @@ const response = await client.get({
 const value = response.Item.bigNumber;
 ```
 
+You can also provide a custom function to handle number conversion during unmarshalling:
+
+```typescript
+const client = DynamoDBDocument.from(new DynamoDB({}), {
+  unmarshallOptions: {
+    // Use BigInt for all numbers
+    wrapNumbers: (str) => BigInt(str),
+  },
+});
+
+const response = await client.get({
+  Key: { id: 1 },
+});
+
+// Numbers in response will be BigInt instead of NumberValue or regular numbers
+```
+
 `NumberValue` does not provide a way to do mathematical operations on itself.
 To do mathematical operations, take the string value of `NumberValue` by calling
 `.toString()` and supply it to your chosen big number implementation.
 
+The client protects against precision loss by throwing an error on large numbers, but you can either
+allow imprecise values with `allowImpreciseNumbers` or maintain exact precision using `NumberValue`.
+
+```typescript
+const preciseValue = "34567890123456789012345678901234567890";
+
+// 1. Default behavior - will throw error
+await client.send(
+  new PutCommand({
+    TableName: "Table",
+    Item: {
+      id: "1",
+      number: Number(preciseValue), // Throws error: Number is greater than Number.MAX_SAFE_INTEGER
+    },
+  })
+);
+
+// 2. Using allowImpreciseNumbers - will store but loses precision (mimics the v2 implicit behavior)
+const impreciseClient = DynamoDBDocumentClient.from(new DynamoDBClient({}), {
+  marshallOptions: { allowImpreciseNumbers: true },
+});
+await impreciseClient.send(
+  new PutCommand({
+    TableName: "Table",
+    Item: {
+      id: "2",
+      number: Number(preciseValue), // Loses precision 34567890123456790000000000000000000000n
+    },
+  })
+);
+```
+
 ### Client and Command middleware stacks
 
 As with other AWS SDK for JavaScript v3 clients, you can apply middleware functions

packages/util-dynamodb/src/convertToAttr.spec.ts

@@ -595,4 +595,32 @@ describe("convertToAttr", () => {
       expect(convertToAttr(new Date(), { convertClassInstanceToMap: true })).toEqual({ M: {} });
     });
   });
+
+  describe("imprecise numbers", () => {
+    const impreciseNumbers = [
+      { val: 1.23e40, str: "1.23e+40" }, // https://github.com/aws/aws-sdk-js-v3/issues/6571
+      { val: Number.MAX_VALUE, str: Number.MAX_VALUE.toString() },
+      { val: Number.MAX_SAFE_INTEGER + 1, str: (Number.MAX_SAFE_INTEGER + 1).toString() },
+    ];
+
+    describe("without allowImpreciseNumbers", () => {
+      impreciseNumbers.forEach(({ val }) => {
+        it(`throws for imprecise number: ${val}`, () => {
+          expect(() => {
+            convertToAttr(val);
+          }).toThrowError(
+            `Number ${val.toString()} is greater than Number.MAX_SAFE_INTEGER. Use NumberValue from @aws-sdk/lib-dynamodb.`
+          );
+        });
+      });
+    });
+
+    describe("with allowImpreciseNumbers", () => {
+      impreciseNumbers.forEach(({ val, str }) => {
+        it(`allows imprecise number: ${val}`, () => {
+          expect(convertToAttr(val, { allowImpreciseNumbers: true })).toEqual({ N: str });
+        });
+      });
+    });
+  });
 });

packages/util-dynamodb/src/convertToAttr.ts

@@ -37,7 +37,7 @@ export const convertToAttr = (data: NativeAttributeValue, options?: marshallOpti
   } else if (typeof data === "boolean" || data?.constructor?.name === "Boolean") {
     return { BOOL: data.valueOf() };
   } else if (typeof data === "number" || data?.constructor?.name === "Number") {
-    return convertToNumberAttr(data);
+    return convertToNumberAttr(data, options);
   } else if (data instanceof NumberValue) {
     return data.toAttributeValue();
   } else if (typeof data === "bigint") {
@@ -91,7 +91,7 @@ const convertToSetAttr = (
   } else if (typeof item === "number") {
     return {
       NS: Array.from(setToOperate)
-        .map(convertToNumberAttr)
+        .map((num) => convertToNumberAttr(num, options))
         .map((item) => item.N),
     };
   } else if (typeof item === "bigint") {
@@ -160,17 +160,20 @@ const validateBigIntAndThrow = (errorPrefix: string) => {
   throw new Error(`${errorPrefix} Use NumberValue from @aws-sdk/lib-dynamodb.`);
 };
 
-const convertToNumberAttr = (num: number | Number): { N: string } => {
+const convertToNumberAttr = (num: number | Number, options?: marshallOptions): { N: string } => {
   if (
     [Number.NaN, Number.POSITIVE_INFINITY, Number.NEGATIVE_INFINITY]
       .map((val) => val.toString())
       .includes(num.toString())
   ) {
     throw new Error(`Special numeric value ${num.toString()} is not allowed`);
-  } else if (num > Number.MAX_SAFE_INTEGER) {
-    validateBigIntAndThrow(`Number ${num.toString()} is greater than Number.MAX_SAFE_INTEGER.`);
-  } else if (num < Number.MIN_SAFE_INTEGER) {
-    validateBigIntAndThrow(`Number ${num.toString()} is lesser than Number.MIN_SAFE_INTEGER.`);
+  } else if (!options?.allowImpreciseNumbers) {
+    // Only perform these checks if allowImpreciseNumbers is false
+    if (num > Number.MAX_SAFE_INTEGER) {
+      validateBigIntAndThrow(`Number ${num.toString()} is greater than Number.MAX_SAFE_INTEGER.`);
+    } else if (num < Number.MIN_SAFE_INTEGER) {
+      validateBigIntAndThrow(`Number ${num.toString()} is lesser than Number.MIN_SAFE_INTEGER.`);
+    }
   }
   return { N: num.toString() };
 };

packages/util-dynamodb/src/convertToNative.spec.ts

@@ -92,6 +92,17 @@ describe("convertToNative", () => {
         }).toThrowError(`${numString} can't be converted to BigInt. Set options.wrapNumbers to get string value.`);
       });
     });
+
+    it("handles custom wrapNumbers function", () => {
+      expect(
+        convertToNative(
+          { N: "124" },
+          {
+            wrapNumbers: (str: string) => Number(str) / 2,
+          }
+        )
+      ).toEqual(62);
+    });
   });
 
   describe("binary", () => {

packages/util-dynamodb/src/convertToNative.ts

@@ -43,10 +43,12 @@ export const convertToNative = (data: AttributeValue, options?: unmarshallOption
 };
 
 const convertNumber = (numString: string, options?: unmarshallOptions): number | bigint | NumberValue => {
+  if (typeof options?.wrapNumbers === "function") {
+    return options?.wrapNumbers(numString);
+  }
   if (options?.wrapNumbers) {
     return NumberValue.from(numString);
   }
-
   const num = Number(numString);
   const infinityValues = [Number.POSITIVE_INFINITY, Number.NEGATIVE_INFINITY];
   const isLargeFiniteNumber =

packages/util-dynamodb/src/marshall.ts

@@ -28,6 +28,14 @@ export interface marshallOptions {
    * but false if directly using the marshall function (backwards compatibility).
    */
   convertTopLevelContainer?: boolean;
+  /**
+   * Whether to allow numbers beyond Number.MAX_SAFE_INTEGER during marshalling.
+   * When set to true, allows numbers that may lose precision when converted to JavaScript numbers.
+   * When false (default), throws an error if a number exceeds Number.MAX_SAFE_INTEGER to prevent
+   * unintended loss of precision. Consider using the NumberValue type from @aws-sdk/lib-dynamodb
+   * for precise handling of large numbers.
+   */
+  allowImpreciseNumbers?: boolean;
 }
 
 /**

packages/util-dynamodb/src/unmarshall.ts

@@ -2,17 +2,21 @@ import { AttributeValue } from "@aws-sdk/client-dynamodb";
 
 import { convertToNative } from "./convertToNative";
 import { NativeAttributeValue } from "./models";
+import { NumberValue } from "./NumberValue";
 
 /**
  * An optional configuration object for `convertToNative`
  */
 export interface unmarshallOptions {
   /**
-   * Whether to return numbers as a string instead of converting them to native JavaScript numbers.
+   * Whether to modify how numbers are unmarshalled from DynamoDB.
+   * When set to true, returns numbers as NumberValue instances instead of native JavaScript numbers.
    * This allows for the safe round-trip transport of numbers of arbitrary size.
+   *
+   * If a function is provided, it will be called with the string representation of numbers to handle
+   * custom conversions (e.g., using BigInt or decimal libraries).
    */
-  wrapNumbers?: boolean;
-
+  wrapNumbers?: boolean | ((value: string) => number | bigint | NumberValue | any);
   /**
    * When true, skip wrapping the data in `{ M: data }` before converting.
    *