Poor error handling when redirected main document request fails

[connorjclark]

node cli http://localhost:10503\?redirect\=https://idonotexistalsdkjsadlajd.com --view

This requests fails both the mimetype check (as the failing network record mimetype is an empty string), and the interstitial check. The latter takes precedence over the former.

But we also show a "main doc was redirected" warning, which is just noise. We should not emit this warning when we have an error interstitial.

Additionally, the final urls:

finalDisplayedUrl: "chrome-error://chromewebdata/"
mainDocumentUrl: "chrome-error://chromewebdata/"
finalUrl: "chrome-error://chromewebdata/"

are not useful. And aren't really navigable links (the URL-under-test link in the top-left of the report just re-opens the same report document).

[connorjclark]

A related problem is currently seen in LR (only for kohl.com):

In this case, the main document was redirect to the mobile site, which ended up failing. The LHR ends up with a runtime error of NOT_HTML, which is less accurate than emitting a "main document failed" error. I'm not sure why WRS did not redirect to an error interstitial. Instead it was about:blank. caseq says we shouldn't make any assumptions about the url the page ends up on when Page.navigate fails.

[adamraine]

• Interstitial error/warning should have more data
• If the redirect warning must be present, it should be lower than any page load error
• Ideally we can find the "last valid URL" and present that as finalDisplayedUrl
• We should fail with a "main document failed" error instead of a MIME type error for the situation in Poor error handling when redirected main document request fails #15270 (comment)