Need to check what current behaviour is here. Probably not the same as in March 2014.

I just tried it again on MediaWiki 1.25 (trying to import an API: page of mediawiki.org) and the page was imported without a warning

I dont think T43969 is enough. Sometimes there are many namespaces missing on the target wiki, and they should all be discarded or dumped into one 'junk' namespace.

Creating the 'original' namespaces temporarily means the logs are problematic when the 'original' namespace is deleted.

What if the user was able to select a 'junk' namespace, where any source pages without a target namespace will be put.

The 'junk' namespace could default to 0 to reproduce the existing behaviour.
On wikis with an "Interwiki" namespace, that would be an appropriate default.

The user could also select to not import these pages, which under the covers could be a mapping to namespace -1.

This approach would allow all pages to be easily imported without pre-parsing the XML to create a namespace mapping.

Hi , I have big problem, the "no alert", "no notice" (even with --debug) about *namespaces* cause crash in the importation process. The maintenance/importDump.php must show a message to say "hey You need to define namespaces in the LocalSettings.php"

In T64111#3034109, @Krauss wrote:

Hi , I have big problem, the "no alert", "no notice" (even with --debug) about *namespaces* cause crash in the importation process.

What are the details of the crash? Which dump is causing the problem - if possible could you upload it here, if it is small enough?

Thanks @TTO , was a fast comment, perhaps the best is to split the problem in two, 1) the "Warnings functionality for the import process" (as T113472); 2) the crash.

The most important is 1, that avoid the crash. You can simulate the "no warnings problem" in any importDump that use other namespace... Or as in my case, a Mediawiki without this namespace specific declaration,

define("NS_DOO", 3000);
define("NS_DOO_TALK", 3001);
$wgExtraNamespaces[NS_DOO] = "doo";
$wgExtraNamespaces[NS_DOO_TALK] = "doo_talk";

when I add it at LocalSettings.php the importation works fine, but before it, --dry-run and normal import (and --debug), no one show warnings about that "DOO:title" pages... XML with <namespace key="3000">.