feat: add setLinkTransformer for adding custom links

Author: jsakas

src/notion-to-md.spec.ts

@@ -15,7 +15,7 @@ describe("setCustomTransformer", () => {
       expect.objectContaining({
         type: "test",
         test: { foo: "bar" },
-      })
+      }),
     );
   });
   test("supports only one customTransformer per type ", () => {
@@ -65,4 +65,60 @@ describe("setCustomTransformer", () => {
     });
     expect(md).toBe("---");
   });
+
+  test("setLinkTransformer works", async () => {
+    const n2m = new NotionToMarkdown({ notionClient: {} as any });
+    n2m.setLinkTransformer((text, href) => {
+      return `<a href="${href}" data-testid="my-link">${text}</a>`;
+    });
+    const md = await n2m.blockToMarkdown({
+      id: "test",
+      type: "paragraph",
+      paragraph: {
+        color: "default",
+        rich_text: [
+          {
+            type: "text",
+            text: {
+              content: "Link using at-sign ",
+              link: null,
+            },
+            annotations: {
+              bold: false,
+              italic: false,
+              strikethrough: false,
+              underline: false,
+              code: false,
+              color: "default",
+            },
+            plain_text: "Link using at-sign ",
+            href: null,
+          },
+          {
+            type: "mention",
+            mention: {
+              type: "page",
+              page: {
+                id: "f1b1910b-caec-8014-aecb-d34ee7f50191",
+              },
+            },
+            annotations: {
+              bold: false,
+              italic: false,
+              strikethrough: false,
+              underline: false,
+              code: false,
+              color: "default",
+            },
+            plain_text: "My page",
+            href: "https://www.notion.so/f1b1910bcaec8014aecbd34ee7f50191",
+          },
+        ],
+      },
+      object: "block",
+    });
+    expect(md).toBe(
+      'Link using at-sign <a href="https://www.notion.so/f1b1910bcaec8014aecbd34ee7f50191" data-testid="my-link">My page</a>',
+    );
+  });
 });

src/notion-to-md.ts

@@ -16,6 +16,8 @@ import {
 import * as md from "./utils/md";
 import { getBlockChildren } from "./utils/notion";
 
+type LinkTransformer = (text: string, href: string) => string;
+
 /**
  * Converts a Notion page to Markdown.
  */
@@ -44,6 +46,14 @@ export class NotionToMarkdown {
     return this;
   }
 
+  setLinkTransformer(fn: LinkTransformer) {
+    this.linkTransformer = fn;
+  }
+
+  linkTransformer(text: string, href: string) {
+    return md.link(text, href);
+  }
+
   /**
    * Converts Markdown Blocks to string
    * @param {MdBlock[]} mdBlocks - Array of markdown blocks
@@ -120,8 +130,9 @@ export class NotionToMarkdown {
             mdOutput[pageIdentifier] = mdOutput[pageIdentifier] || "";
             if (mdstr[childPageTitle]) {
               // child page heading followed by child page content
-              mdOutput[pageIdentifier] +=
-                `\n${childPageTitle}\n${mdstr[childPageTitle]}`;
+              mdOutput[
+                pageIdentifier
+              ] += `\n${childPageTitle}\n${mdstr[childPageTitle]}`;
             }
           }
         } else if (mdBlocks.type === "toggle") {
@@ -159,8 +170,7 @@ export class NotionToMarkdown {
           mdOutput[pageIdentifier] += "\n";
         } else if (mdBlocks.type === "callout") {
           // do nothing the callout block is already processed
-        }
-         else {
+        } else {
           let mdstr = this.toMarkdownString(
             mdBlocks.children,
             pageIdentifier,
@@ -375,7 +385,7 @@ export class NotionToMarkdown {
               title = matches ? matches[0] : type;
             }
 
-            return md.link(title, link);
+            return this.linkTransformer(title, link);
           }
         }
         break;
@@ -399,7 +409,8 @@ export class NotionToMarkdown {
             };
           }
 
-          if (blockContent) return md.link(title, blockContent.url);
+          if (blockContent)
+            return this.linkTransformer(title, blockContent.url);
         }
         break;
 
@@ -430,7 +441,7 @@ export class NotionToMarkdown {
           const tableRows = await getBlockChildren(this.notionClient, id, 100);
           let rowsPromise = tableRows?.map(async (row) => {
             const { type } = row as any;
-            if (type !== 'table_row') return
+            if (type !== "table_row") return;
             const cells = (row as any).table_row["cells"];
 
             /**
@@ -490,7 +501,7 @@ export class NotionToMarkdown {
           plain_text = this.annotatePlainText(plain_text, annotations);
 
           if (content["href"])
-            plain_text = md.link(plain_text, content["href"]);
+            plain_text = this.linkTransformer(plain_text, content["href"]);
 
           parsedData += plain_text;
         });
@@ -500,9 +511,11 @@ export class NotionToMarkdown {
     switch (type) {
       case "code":
         {
-            const codeContent = block.code.rich_text.map((t: any) => t.plain_text).join("\n");
-            const language = block.code.language || "plaintext";
-            parsedData = md.codeBlock(codeContent, language);
+          const codeContent = block.code.rich_text
+            .map((t: any) => t.plain_text)
+            .join("\n");
+          const language = block.code.language || "plaintext";
+          parsedData = md.codeBlock(codeContent, language);
         }
         break;