GX2019: one id on two elements of a component

Cause#

An id names one element of a document. With one id on two elements, a label for, a link to #intro and a patch of Gx reach only the first one.

Gx gives no finding for two elements in two branches of one if or switch: one render holds one of them.

Example#

package page

<main>
  <section id="intro">One</section>
  <section id="intro">Two</section>
</main>

gx check reports:

page/Page.gx:5:3: GX2019: the id "intro" is on two elements of the component: an id names one element

Fix#

1. Give each element its own id.
2. For an element in a loop, use a keyed fragment: <li #row(key string) key={key}>. Gx then makes one id for each key.