function addBoolAttribute() {
            results.template += `${needsSpacing ? " " : ""}${key.slice(5)}`;
            needsSpacing = true;
          }
TODO: Unfortunately, `attr:onclick` changes too many tests, as we are working in
`minor/next` it will mess up merging. This condition `key !== "onclick" &&` to be
removed once we reach Solid 2.0, which will change a lot of tests.