docs(stepfunctions): use JsonPath.DISCARD in place of null for input

packages/aws-cdk-lib/aws-stepfunctions/lib/private/json-path.ts

@@ -1,5 +1,6 @@
 import { IntrinsicParser, IntrinsicExpression } from './intrinstics';
 import { captureStackTrace, IResolvable, IResolveContext, Token, Tokenization } from '../../../core';
+import { SPECIFY_NULL } from '../types';
 
 const JSON_PATH_TOKEN_SYMBOL = Symbol.for('@aws-cdk/aws-stepfunctions.JsonPathToken');
 
@@ -40,6 +41,7 @@ export function renderObject(obj: object | undefined): object | undefined {
     handleNumber: renderNumber,
     handleBoolean: renderBoolean,
     handleResolvable: renderResolvable,
+    handleNull: renderNull,
   });
 }
 
@@ -81,6 +83,10 @@ export function findReferencedPaths(obj: object | undefined): Set<string> {
       }
       return {};
     },
+
+    handleNull(_key: string, _x: null) {
+      return {};
+    },
   });
 
   return found;
@@ -124,6 +130,7 @@ interface FieldHandlers {
   handleNumber(key: string, x: number): {[key: string]: number | string};
   handleBoolean(key: string, x: boolean): {[key: string]: boolean};
   handleResolvable(key: string, x: IResolvable): {[key: string]: any};
+  handleNull(key: string, x: null): {[key: string]: null};
 }
 
 export function recurseObject(obj: object | undefined, handlers: FieldHandlers, visited: object[] = []): object | undefined {
@@ -142,7 +149,9 @@ export function recurseObject(obj: object | undefined, handlers: FieldHandlers,
 
   const ret: any = {};
   for (const [key, value] of Object.entries(obj)) {
-    if (typeof value === 'string') {
+    if (value === SPECIFY_NULL) {
+      Object.assign(ret, handlers.handleNull(key, null));
+    } else if (typeof value === 'string') {
       Object.assign(ret, handlers.handleString(key, value));
     } else if (typeof value === 'number') {
       Object.assign(ret, handlers.handleNumber(key, value));
@@ -318,6 +327,14 @@ function pathFromToken(token: IResolvable | undefined) {
   return token && (JsonPathToken.isJsonPathToken(token) ? token.path : undefined);
 }
 
+/**
+ * Render a parameter null value
+ */
+function renderNull(key: string, _value: null): {[key: string]: null} {
+  console.log("YEET");
+  return { [key]: null };
+}
+
 /**
  * Render the string or number value in a valid JSON Path expression.
  *

packages/aws-cdk-lib/aws-stepfunctions/lib/types.ts

@@ -239,3 +239,8 @@ export interface ProcessorConfig {
  * @deprecated use JsonPath.DISCARD
  */
 export const DISCARD = 'DISCARD';
+
+/**
+ * Special string value to drop state
+ */
+export const NULL_SUBSTITUTE = 'NULL_SUBSTITUTE';

packages/aws-cdk-lib/aws-stepfunctions/test/fields.test.ts

@@ -1,4 +1,4 @@
-import { FieldUtils, JsonPath, TaskInput } from '../lib';
+import { SPECIFY_NULL, FieldUtils, JsonPath, TaskInput } from '../lib';
 
 describe('Fields', () => {
   const jsonPathValidationErrorMsg = /exactly '\$', '\$\$', start with '\$.', start with '\$\$.', start with '\$\[', or start with an intrinsic function: States.Array, States.ArrayPartition, States.ArrayContains, States.ArrayRange, States.ArrayGetItem, States.ArrayLength, States.ArrayUnique, States.Base64Encode, States.Base64Decode, States.Hash, States.JsonMerge, States.StringToJson, States.JsonToString, States.MathRandom, States.MathAdd, States.StringSplit, States.UUID, or States.Format./;
@@ -252,6 +252,21 @@ describe('Fields', () => {
       },
     });
   });
+
+  test('null value rendered', () => {
+    const object = {
+      nullParameter: SPECIFY_NULL,
+    };
+    expect(FieldUtils.renderObject(
+      {
+        reference1: object,
+      },
+    )).toStrictEqual({
+      reference1: {
+        nullParameter: null,
+      },
+    });
+  });
 });
 
 describe('intrinsics constructors', () => {