Format checkboxes

GitHub task lists are represented in HTML as unordered lists with
checkboxes.  These checkboxes are currently ignored when converting the
HTML to text.  This affects PRs with task lists (e.g.
git/git#1359); the resulting text list has no
indication anymore whether an item was checked (done) or not.

Format checkboxes by turning checked ones into "[x]" and unchecked
ones into "[ ]" to retain that information during the conversion.

Helped-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: René Scharfe <l.s.r@web.de>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

Author: rscharfe

lib/markdown-renderer.ts

@@ -36,6 +36,10 @@ export function md2text(markdown: string, columns = 76): string {
                         .replace(/(^|\n)(\n)(?!$)/g, "$1>$2"); // quote empty
                     }});
             },
+            checkBoxFormatter: (elem, _walk, builder) => {
+                const attribs = elem.attribs as { checked?: string };
+                builder.addInline(attribs.checked === undefined ? "[ ]" : "[x]");
+            },
         },
         selectors: [
             {
@@ -72,6 +76,10 @@ export function md2text(markdown: string, columns = 76): string {
                 },
                 format: "blockFormatter"
             },
+            {
+                selector: "input[type=checkbox]",
+                format: "checkBoxFormatter"
+            },
         ],
     };
 

tests/markdown-renderer.test.ts

@@ -109,3 +109,13 @@ const bq7 = `Over 56 levels still has 20 char (exact):
 >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> 3 5 7 9 1 3 5 7 9 1
 >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> 3 5 7`);
 });
+
+test("task lists are rendered correctly", () => {
+    const taskList = `This is a task list:
+* [x] done item
+* [ ] item still to do`;
+    expect(md2text(taskList)).toEqual(`This is a task list:
+
+ * [x] done item
+ * [ ] item still to do`);
+});