server(export): export Markdown using ATX heading syntax (closes #1251)

spec/support/utils.ts

@@ -1,3 +1,35 @@
+/**
+ * Reads the level of indentation of the first line and trims the identation for all the text by that amount.
+ *
+ * For example, for:
+ *
+ * ```json
+ *          {
+ *              "hello": "world"
+ *          }
+ * ```
+ *
+ * it results in:
+ *
+ * ```json
+ * {
+ *     "hello": "world"
+ * }
+ * ```
+ *
+ * This is meant to be used as a template string, where it allows the indentation of the template without affecting whitespace changes.
+ *
+ * @example const html = trimIndentation`\
+ *           <h1>Heading 1</h1>
+ *           <h2>Heading 2</h2>
+ *           <h3>Heading 3</h3>
+ *           <h4>Heading 4</h4>
+ *           <h5>Heading 5</h5>
+ *           <h6>Heading 6</h6>
+ *       `;
+ * @param strings
+ * @returns
+ */
 export function trimIndentation(strings: TemplateStringsArray) {
     const str = strings.toString();
 

src/services/export/md.spec.ts

@@ -74,4 +74,28 @@ describe("Markdown export", () => {
         const expected = "~~hello~~Hello ~~world~~";
         expect(markdownExportService.toMarkdown(html)).toBe(expected);
     });
+
+    it("exports headings properly", () => {
+        const html = trimIndentation`\
+            <h1>Heading 1</h1>
+            <h2>Heading 2</h2>
+            <h3>Heading 3</h3>
+            <h4>Heading 4</h4>
+            <h5>Heading 5</h5>
+            <h6>Heading 6</h6>
+        `;
+        const expected = trimIndentation`\
+            # Heading 1
+
+            ## Heading 2
+
+            ### Heading 3
+
+            #### Heading 4
+
+            ##### Heading 5
+
+            ###### Heading 6`;
+        expect(markdownExportService.toMarkdown(html)).toBe(expected);
+    });
 });

src/services/export/md.ts

@@ -24,7 +24,10 @@ const fencedCodeBlockFilter: TurndownService.Rule = {
 
 function toMarkdown(content: string) {
     if (instance === null) {
-        instance = new TurndownService({ codeBlockStyle: "fenced" });
+        instance = new TurndownService({
+            headingStyle: "atx",
+            codeBlockStyle: "fenced"
+        });
         // Filter is heavily based on: https://github.com/mixmark-io/turndown/issues/274#issuecomment-458730974
         instance.addRule("fencedCodeBlock", fencedCodeBlockFilter);
         instance.use(turndownPluginGfm.gfm);