The current behavior of `routerLink` for `null` and `undefined` inputs is to treat
the input the same as `[]`. This creates several unresolvable issues with
correctly disabling the links because `commands = []` does _not_ behave the same
as disabling a link. Instead, it navigates to the current page, but will also
clear any fragment and/or query params.
The new behavior of the `routerLink` input will be to completely disable navigation
for `null` and `undefined` inputs. For HTML Anchor elements, this will also mean
removing the `href` attribute.
Fixes#21457Fixes#13980Fixes#31154
BREAKING CHANGE:
Previously `null` and `undefined` inputs for `routerLink` were
equaivalent to empty string and there was no way to disable the link's
navigation.
In addition, the `href` is changed from a property `HostBinding()` to an
attribute binding (`HostBinding('attr.href')`). The effect of this
change is that `DebugElement.properties['href']` will now return the
`href` value returned by the native element which will be the full URL
rather than the internal value of the `RouterLink` `href` property.
PR Close#43087
ccb09b4558