[DahanItamar]

Fixes #300.

The markup pattern captures the attributes together with the whitespace that follows the tag name, but the parser removed only its first character (attributes.slice(1)). When the first attribute sits on its own line, the remaining indentation was kept in rawAttrs, and toString() then added its own separating space:

parse('<button\n   data-primary>Go</button>').toString();
// before: '<button    data-primary>Go</button>'
// after:  '<button data-primary>Go</button>'

This strips all leading whitespace instead. Whitespace between attributes is kept as before, and markup that already had a single space before the first attribute serializes unchanged.

Validation:

• Build passed (tsdown).
• Full suite passed on Node 24: 309 passing, 13 existing pending.
• The new test/tests/issues/300.js covers rawAttrs, newline, tab and multi-space separators, and the unchanged single-space case. Three of its four cases failed before the fix.
• git diff --check passed. ESLint still can't initialize with the locked TypeScript installation, same as noted in fix: preserve table rows with omitted end tags #322.

🤖 Generated with Claude Code