Previously, the `startSourceSpan` property could be null
but in reality it is always well defined - except for a legacy
case in the old i18n extraction/merging code, where the
typings for source-spans are already being undermined.
Making this property non-null, simplifies code elsewhere
in the project.
PR Close#38581
HTML is very lenient when it comes to closing elements, so Angular's parser has
rules that specify which elements are implicitly closed when closing a tag.
The parser keeps track of the nesting of tag names using a stack and parsing
a closing tag will pop as many elements off the stack as possible, provided
that the elements can be implicitly closed.
For example, consider the following templates:
- `<div><br></div>`, the `<br>` is implicitly closed when parsing `</div>`,
because `<br>` is a void element.
- `<div><p></div>`, the `<p>` is implicitly closed when parsing `</div>`,
as `<p>` is allowed to be closed by the closing of its parent element.
- `<ul><li>A <li>B</ul>`, the first `<li>` is implicitly closed when parsing
the second `<li>`, whereas the second `<li>` would be implicitly closed when
parsing the `</ul>`.
In all the cases above the parsed structure would be correct, however the source
span of the closing `</div>` would incorrectly be assigned to the element that
is implicitly closed. The problem was that closing an element would associate
the source span with the element at the top of the stack, however this may not
be the element that is actually being closed if some elements would be
implicitly closed.
This commit fixes the issue by assigning the end source span with the element
on the stack that is actually being closed. Any implicitly closed elements that
are popped off the stack will not be assigned an end source span, as the
implicit closing implies that no ending element is present.
Note that there is a difference between self-closed elements such as `<input/>`
and implicitly closed elements such as `<input>`. The former does have an end
source span (identical to its start source span) whereas the latter does not.
Fixes#36118
Resolves FW-2004
PR Close#38126
Pete Bacon Darwin
JoostK
Joey Perrott
Alex Rickabaugh
Olivier Combe
Miško Hevery
Jason Aden