[MFM] Improve hashtag detection

Resolve #3387

src/mfm/parser.ts

@@ -112,6 +112,7 @@ const mfm = P.createLanguage({
 			const text = input.substr(i);
 			const match = text.match(/^#([^\s\.,!\?#]+)/i);
 			if (!match) return P.makeFailure(i, 'not a hashtag');
+			if (match[1].match(/[0-9]+/)) return P.makeFailure(i, 'not a hashtag');
 			if (input[i - 1] != '\n' && input[i - 1] != ' ' && input[i - 1] != null) return P.makeFailure(i, 'require space before "#"');
 			return P.makeSuccess(i + match[0].length, makeNode('hashtag', { hashtag: match[1] }));
 		}),

test/mfm.ts

@@ -204,6 +204,13 @@ describe('Text', () => {
 					text('!'),
 				], tokens);
 			});
+
+			it('disallow number only', () => {
+				const tokens = analyze('#123');
+				assert.deepEqual([
+					text('#123'),
+				], tokens);
+			});
 		});
 
 		describe('quote', () => {