In HTML to MFM, use angle bracket if needed (#6817)

test/mfm.ts

@@ -12,6 +12,7 @@ import * as assert from 'assert';
 
 import { parse, parsePlain } from '../src/mfm/parse';
 import { toHtml } from '../src/mfm/to-html';
+import { fromHtml } from '../src/mfm/from-html';
 import { toString } from '../src/mfm/to-string';
 import { createTree as tree, createLeaf as leaf, MfmTree } from '../src/mfm/prelude';
 import { removeOrphanedBrackets } from '../src/mfm/language';
@@ -1199,3 +1200,37 @@ describe('MFM', () => {
 		});
 	});
 });
+
+describe('fromHtml', () => {
+	it('br', () => {
+		assert.deepStrictEqual(fromHtml('<p>abc<br><br/>d</p>'), 'abc\n\nd');
+	});
+
+	it('link with different text', () => {
+		assert.deepStrictEqual(fromHtml('<p>a <a href="https://example.com/b">c</a> d</p>'), 'a [c](https://example.com/b) d');
+	});
+
+	it('link with same text', () => {
+		assert.deepStrictEqual(fromHtml('<p>a <a href="https://example.com/b">https://example.com/b</a> d</p>'), 'a https://example.com/b d');
+	});
+
+	it('link with same text, but not encoded', () => {
+		assert.deepStrictEqual(fromHtml('<p>a <a href="https://example.com/ä">https://example.com/ä</a> d</p>'), 'a <https://example.com/ä> d');
+	});
+
+	it('link with no url', () => {
+		assert.deepStrictEqual(fromHtml('<p>a <a href="b">c</a> d</p>'), 'a [c](b) d');
+	});
+
+	it('link without href', () => {
+		assert.deepStrictEqual(fromHtml('<p>a <a>c</a> d</p>'), 'a c d');
+	});
+
+	it('mention', () => {
+		assert.deepStrictEqual(fromHtml('<p>a <a href="https://example.com/@user" class="u-url mention">@user</a> d</p>'), 'a @user@example.com d');
+	});
+
+	it('hashtag', () => {
+		assert.deepStrictEqual(fromHtml('<p>a <a href="https://example.com/tags/a">#a</a> d</p>', ['#a']), 'a #a d');
+	});
+});