I see the point of waiting for subtree modifications, however I don't like
`when_dom_changes` because it's inherently flaky - in the `SearchPage` example,
the DOM changes could very well be finished before the test has had a chance to
call `autocomplete_results`, and you'd see a timeout even though the app
behaves correctly.
This is why WebDriver has `StaleElementReferenceErrors` (and one of the reaons
why I use watir-webdriver with `Watir.always_locate = false`).
To avoid this problem, the waiting should happen in the method that also
triggers the search results:
```ruby
class SearchPage
def search_for(term)
old_results = autocomplete_element.wd
search_field.set(term)
# wait for the DOM change
Wait.until do
begin
old_results.enabled? # could be any call - just need to force a
staleness check in webdriver
false
rescue Selenium::WebDriver::Error::StaleElementReferenceError => ex
true
end
end
end
def autocomplete_results
autocomplete_element.as.map(&:text)
end
private
def search_field
browser.text_field(:id => "search_field")
end
def autocomplete_element
browser.div(:id => "autocomplete")
end
end
```
As the verbosity of the example shows, it's not easy with Watir currently. In
part this is because of Watir's lazy locating of elements, but here we need to
get a reference to the element that will change, before it goes stale. One hack
would be to do something like:
```ruby
old_results = autocomplete_element
old_results.exist? # with Watir.always_locate = false, the element reference
is now cached - which is definitely not obvious to a normal user
search_field.set(term)
wait_until { old_results.stale? } # new method: Element#stale? - but it can
only work when Watir.always_locate = false, and the element is cached /
previously located`
```
I would support a change that makes this easier, but I don't think
`.when_dom_changes` does the job correctly, since you can't set it up before
triggering the action that performs the modification.
---
Reply to this email directly or view it on GitHub:
https://github.com/watir/watir-webdriver/issues/193#issuecomment-18463730
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