feat: pass HTML serializer children as string

src/asHTML.ts

@@ -2,8 +2,9 @@ import {
 	serialize,
 	Element,
 	composeSerializers,
-	wrapMapSerializer,
 	RichTextFunctionSerializer,
+	RichTextMapSerializer,
+	wrapMapSerializer,
 } from "@prismicio/richtext";
 import { RichTextField } from "@prismicio/types";
 
@@ -75,6 +76,37 @@ const createDefaultHTMLSerializer = (
 	};
 };
 
+/**
+ * Wraps a map serializer into a regular function serializer. The given map
+ * serializer should accept children as a string, not as an array of strings
+ * like `@prismicio/richtext`'s `wrapMapSerializer`.
+ *
+ * @param mapSerializer - Map serializer to wrap
+ *
+ * @returns A regular function serializer
+ */
+const wrapMapSerializerWithStringChildren = (
+	mapSerializer: HTMLMapSerializer,
+): RichTextFunctionSerializer<string> => {
+	const modifiedMapSerializer = {} as RichTextMapSerializer<string>;
+
+	for (const tag in mapSerializer) {
+		const tagSerializer = mapSerializer[tag as keyof typeof mapSerializer];
+
+		if (tagSerializer) {
+			modifiedMapSerializer[tag as keyof typeof mapSerializer] = (payload) => {
+				return tagSerializer({
+					...payload,
+					// @ts-expect-error - merging blockSerializer types causes TS to bail to a never type
+					children: payload.children.join(""),
+				});
+			};
+		}
+	}
+
+	return wrapMapSerializer(modifiedMapSerializer);
+};
+
 /**
  * Serializes a rich text or title field to an HTML string
  *
@@ -96,8 +128,9 @@ export const asHTML = (
 	if (htmlSerializer) {
 		serializer = composeSerializers(
 			typeof htmlSerializer === "object"
-				? wrapMapSerializer(htmlSerializer)
-				: htmlSerializer,
+				? wrapMapSerializerWithStringChildren(htmlSerializer)
+				: (type, node, text, children, key) =>
+						htmlSerializer(type, node, text, children.join(""), key),
 			createDefaultHTMLSerializer(linkResolver),
 		);
 	} else {

src/types.ts

@@ -2,6 +2,7 @@ import type { FilledLinkToDocumentField } from "@prismicio/types";
 import {
 	RichTextFunctionSerializer,
 	RichTextMapSerializer,
+	RichTextMapSerializerFunction,
 } from "@prismicio/richtext";
 
 /**
@@ -21,13 +22,78 @@ export type LinkResolverFunction<ReturnType = string> = (
 /**
  * Serializes a node from a rich text or title field with a function to HTML
  *
+ * Unlike a typical `@prismicio/richtext` function serializer, this serializer
+ * converts the `children` argument to a single string rather than an array of strings.
+ *
  * @see Templating rich text and title fields from Prismic {@link https://prismic.io/docs/technologies/templating-rich-text-and-title-fields-javascript}
  */
-export type HTMLFunctionSerializer = RichTextFunctionSerializer<string>;
+export type HTMLFunctionSerializer = (
+	type: Parameters<RichTextFunctionSerializer<string>>[0],
+	node: Parameters<RichTextFunctionSerializer<string>>[1],
+	text: Parameters<RichTextFunctionSerializer<string>>[2],
+	children: Parameters<RichTextFunctionSerializer<string>>[3][number],
+	key: Parameters<RichTextFunctionSerializer<string>>[4],
+) => string | null | undefined;
 
 /**
  * Serializes a node from a rich text or title field with a map to HTML
  *
+ * Unlike a typical `@prismicio/richtext` map serializer, this serializer
+ * converts the `children` property to a single string rather than an array of strings.
+ *
  * @see Templating rich text and title fields from Prismic {@link https://prismic.io/docs/technologies/templating-rich-text-and-title-fields-javascript}
  */
-export type HTMLMapSerializer = RichTextMapSerializer<string>;
+export type HTMLMapSerializer = {
+	[P in keyof RichTextMapSerializer<string>]: (payload: {
+		type: Parameters<HTMLMapSerializerFunction<P>>[0]["type"];
+		node: Parameters<HTMLMapSerializerFunction<P>>[0]["node"];
+		text: Parameters<HTMLMapSerializerFunction<P>>[0]["text"];
+		children: Parameters<HTMLMapSerializerFunction<P>>[0]["children"][number];
+		key: Parameters<HTMLMapSerializerFunction<P>>[0]["key"];
+	}) => string | null | undefined;
+};
+
+/**
+ * A {@link RichTextMapSerializerFunction} type specifically for {@link HTMLMapSerializer}.
+ *
+ * @typeParam BlockName - The serializer's Rich Text block type.
+ */
+type HTMLMapSerializerFunction<
+	BlockType extends keyof RichTextMapSerializer<string>,
+> = RichTextMapSerializerFunction<
+	string,
+	ExtractNodeGeneric<RichTextMapSerializer<string>[BlockType]>,
+	ExtractTextTypeGeneric<RichTextMapSerializer<string>[BlockType]>
+>;
+
+/**
+ * Returns the `Node` generic from {@link RichTextMapSerializerFunction}.
+ *
+ * @typeParam T - The `RichTextMapSerializerFunction` containing the needed
+ *   `Node` generic.
+ */
+type ExtractNodeGeneric<T> = T extends RichTextMapSerializerFunction<
+	// eslint-disable-next-line @typescript-eslint/no-explicit-any
+	any,
+	infer U,
+	// eslint-disable-next-line @typescript-eslint/no-explicit-any
+	any
+>
+	? U
+	: never;
+
+/**
+ * Returns the `TextType` generic from {@link RichTextMapSerializerFunction}.
+ *
+ * @typeParam T - The `RichTextMapSerializerFunction` containing the needed
+ *   `TextType` generic.
+ */
+type ExtractTextTypeGeneric<T> = T extends RichTextMapSerializerFunction<
+	// eslint-disable-next-line @typescript-eslint/no-explicit-any
+	any,
+	// eslint-disable-next-line @typescript-eslint/no-explicit-any
+	any,
+	infer U
+>
+	? U
+	: never;

test/__testutils__/htmlFunctionSerializer.ts

@@ -9,7 +9,7 @@ export const htmlFunctionSerializer: HTMLFunctionSerializer = (
 ) => {
 	switch (node.type) {
 		case Element.heading1: {
-			return `<h2>${children.join("")}</h2>`;
+			return `<h2>${children}</h2>`;
 		}
 	}
 

test/__testutils__/htmlMapSerializer.ts

@@ -1,5 +1,7 @@
 import { HTMLMapSerializer } from "../../src";
 
 export const htmlMapSerializer: HTMLMapSerializer = {
-	heading1: ({ children }) => `<h2>${children.join("")}</h2>`,
+	heading1: ({ children }) => `<h2>${children}</h2>`,
+	// `undefined` serializers should be treated the same as not including it.
+	heading2: undefined,
 };