Fix input validation for missing child blocks (#2942)

.changeset/new-cherries-provide.md

@@ -0,0 +1,5 @@
+---
+"@comet/blocks-api": patch
+---
+
+Fix input validation for missing child blocks

packages/api/blocks-api/src/blocks/decorators/child-block-input.test.ts

@@ -0,0 +1,35 @@
+import { BlockData, BlockDataInterface, BlockInput, createBlock, ExtractBlockData, ExtractBlockInput, inputToData } from "../block";
+import { createRichTextBlock } from "../createRichTextBlock";
+import { ExternalLinkBlock } from "../ExternalLinkBlock";
+import { ChildBlock } from "./child-block";
+import { ChildBlockInput } from "./child-block-input";
+
+const RichTextBlock = createRichTextBlock({ link: ExternalLinkBlock });
+
+class HeadlineBlockData extends BlockData {
+    @ChildBlock(RichTextBlock)
+    headline: ExtractBlockData<typeof RichTextBlock>;
+}
+
+class HeadlineBlockInput extends BlockInput {
+    @ChildBlockInput(RichTextBlock)
+    headline: ExtractBlockInput<typeof RichTextBlock>;
+
+    transformToBlockData(): BlockDataInterface {
+        return inputToData(HeadlineBlockData, this);
+    }
+}
+
+const HeadlineBlock = createBlock(HeadlineBlockData, HeadlineBlockInput, "Headline");
+
+describe("ChildBlockInput", () => {
+    it("should fail if no value is provided", () => {
+        // `@Transform()` allows any value, so we use any here.
+        // eslint-disable-next-line @typescript-eslint/no-explicit-any
+        const plain: any = {};
+
+        expect(() => {
+            HeadlineBlock.blockInputFactory(plain);
+        }).toThrowError(`Missing child block input for 'headline' (RichText)`);
+    });
+});

packages/api/blocks-api/src/blocks/decorators/child-block-input.ts

@@ -1,4 +1,4 @@
-import { Transform } from "class-transformer";
+import { Expose, Transform } from "class-transformer";
 import { ValidateNested } from "class-validator";
 
 import { Block, isBlockInputInterface } from "../block";
@@ -22,13 +22,23 @@ export function ChildBlockInput(block: Block, options?: ChildBlockInputOptions):
             ValidateNested()(target, key); // by default valdidate all child blocks
         }
         BlockField({ type: "block", block, nullable })(target, key);
+        // We need add `@Expose()` to make sure that `@Transform()` is called even when no value is provided.
+        // See https://github.com/typestack/class-transformer/issues/1599#issuecomment-2094934401.
+        Expose()(target, key);
         Transform(
-            ({ value }) =>
-                isBlockInputInterface(value)
-                    ? value
-                    : nullable && (value === undefined || value === null)
-                    ? undefined
-                    : block.blockInputFactory(value),
+            ({ value }) => {
+                if (isBlockInputInterface(value)) {
+                    return value;
+                } else if (nullable && value == null) {
+                    return undefined;
+                } else {
+                    if (value == null) {
+                        throw new Error(`Missing child block input for '${key as string}' (${block.name})`);
+                    }
+
+                    return block.blockInputFactory(value);
+                }
+            },
             {
                 toClassOnly: true,
             },