NEW Translatable.enforce_global_unique_urls config setting

See https://github.com/silverstripe/silverstripe-cms/pull/216
and https://github.com/silverstripe/silverstripe-cms/pull/772
for context

code/model/Translatable.php

@@ -205,6 +205,13 @@ class Translatable extends DataExtension implements PermissionProvider {
 	 */
 	protected static $allowed_locales = null;
 
+	/**
+	 * @var boolean Check other languages for URLSegment values (only applies to {@link SiteTree}).
+	 * Turn this off to handle language setting yourself, e.g. through language-specific subdomains
+	 * or URL path prefixes like "/en/mypage".
+	 */
+	private static $enforce_global_unique_urls = true;
+		
 	/**
 	 * Reset static configuration variables to their default values
 	 */
@@ -1743,11 +1750,14 @@ class Translatable extends DataExtension implements PermissionProvider {
      */
 	public function augmentValidURLSegment() {
 		$reEnableFilter = false;
-		if(self::locale_filter_enabled()) {
+		if(!Config::inst()->get('Translatable', 'enforce_global_unique_urls')) {
+			self::enable_locale_filter();
+		} elseif(self::locale_filter_enabled()) {
 			self::disable_locale_filter();
 			$reEnableFilter = true;
 		}
-		$IDFilter     = ($this->owner->ID) ? "AND \"SiteTree\".\"ID\" <> {$this->owner->ID}" :  null;
+
+		$IDFilter = ($this->owner->ID) ? "AND \"SiteTree\".\"ID\" <> {$this->owner->ID}" :  null;
 		$parentFilter = null;
 
 			if($this->owner->ParentID) {
@@ -1759,9 +1769,9 @@ class Translatable extends DataExtension implements PermissionProvider {
 		$existingPage = SiteTree::get()
 			// disable get_one cache, as this otherwise may pick up results from when locale_filter was on
 			->where("\"URLSegment\" = '{$this->owner->URLSegment}' $IDFilter $parentFilter")->First();
-		
 		if($reEnableFilter) self::enable_locale_filter();
 		
+		// By returning TRUE or FALSE, we overrule the base SiteTree->validateURLSegment() logic
 		return !$existingPage;
 	}
 		

docs/en/index.md

@@ -167,12 +167,17 @@ Creating a translation:
 If a child page translation is requested without the parent
 page already having a translation in this language, the extension
 will recursively create translations up the tree.
-Caution: The "URLSegment" property is enforced to be unique across
+
+The `SiteTree.URLSegment` property is enforced to be unique across
 languages by auto-appending the language code at the end.
-You'll need to ensure that the appropriate "reading language" is set
+It ensures that all pages can be reached through their URL without any additional setup.
-before showing links to other pages on a website through $_GET['locale'].
+This behaviour can be turned off through the `Translatable.enforce_global_unique_urls` configuration setting,
-Pages in different languages can have different publication states
+in which case its up to you to ensure the language context can be derived from the URL
-through the `[api:Versioned]` extension.
+(e.g. through a subdomain or a language path prefix like `/en/mypage`).
+
+In either case, you'll need to take care that the appropriate "reading language" is set
+before showing links to other pages on a website, for example through
+a `locale` GET parameter (see `Translatable::choose_site_locale()`).
 
 Note: You can't get Children() for a parent page in a different language
 through set_reading_locale(). Get the translated parent first.
@@ -188,9 +193,7 @@ through set_reading_locale(). Get the translated parent first.
 By default, the URLs generated for a page can only contain western characters ("ASCII").
 You can configure this to accept the whole range of UTF8 characters as well.
 This is a SilverStripe core feature, rather than anything specific to this module.
-Add the following to your `mysite/_config.php`:
+Refer to the `URLSegmentFilter.default_allow_multibyte` configuration setting.
-
-	URLSegmentFilter::$default_allow_multibyte = true;
 
 ### Translating custom properties
 

tests/unit/TranslatableTest.php

@@ -408,10 +408,17 @@ class TranslatableTest extends FunctionalTest {
 		$translatedPage = $origPage->createTranslation('de_DE');
 		$this->assertEquals($translatedPage->URLSegment, 'testpage-de-de');
 	
-		$translatedPage->URLSegment = 'testpage';
+		$translatedPage->URLSegment = 'testpage'; // de_DE clashes with en_US
 		$translatedPage->write();
-	
 		$this->assertNotEquals($origPage->URLSegment, $translatedPage->URLSegment);
+
+		Translatable::set_current_locale('de_DE');
+		Config::inst()->update('Translatable', 'enforce_global_unique_urls', false);
+		$translatedPage->URLSegment = 'testpage'; // de_DE clashes with en_US
+		$translatedPage->write();
+		$this->assertEquals('testpage', $translatedPage->URLSegment);
+		Config::inst()->update('Translatable', 'enforce_global_unique_urls', true);
+		Translatable::set_current_locale('en_US');
 	}
 	
 	function testUpdateCMSFieldsOnSiteTree() {