Add edit link to gadget definition in Special:Gadgets

When using the Gadget definition: namespace, link to the definition
pages from Special:Gadgets. Also change the wording of the links
to edit the names of the gadgets, to disambiguate them.

Change-Id: I327a4cfa9846edec60e1aaafc674cd66f4e0beae

i18n/en.json

@@ -19,6 +19,8 @@
 	"gadgets-definition": "",
 	"gadgets-title": "Gadgets",
 	"gadgets-pagetext": "Below is a list of special gadgets users can enable on their [[Special:Preferences#mw-prefsection-gadgets|preferences page]], as defined by the [[MediaWiki:Gadgets-definition|definitions]].\nThis overview provides easy access to the system message pages that define each gadget's description and code.",
+	"gadgets-editdescription": "Edit description",
+	"gadgets-viewdescription": "View description",
 	"gadgets-uses": "Uses",
 	"gadgets-required-rights": "Requires the following {{PLURAL:$2|right|rights}}:\n\n$1",
 	"gadgets-required-skins": "Available on the {{PLURAL:$2|$1 skin|following skins: $1}}.",

i18n/qqq.json

@@ -32,6 +32,8 @@
 	"gadgets-definition": "{{notranslate}}",
 	"gadgets-title": "{{Identical|Gadgets}}",
 	"gadgets-pagetext": "Used as intro text in [[Special:Gadgets]].",
+	"gadgets-editdescription": "Link for editing the gadget description shown in Special:Preferences. Used on [[Special:Gadgets]].",
+	"gadgets-viewdescription": "Link for viewing the gadget description shown in Special:Preferences. Used on [[Special:Gadgets]] instead of {{msg-mw|Gadgets-editname}} when the user does not have permissions to edit.",
 	"gadgets-uses": "This is used as a verb in third-person singular. It appears in front of a script name. Example: \"''Uses: Gadget-UTCLiveClock.js''\"\n\nSee [[meta:Special:Gadgets|Gadgets page in meta.wikimedia.org]]\n{{Identical|Use}}",
 	"gadgets-required-rights": "Parameters:\n* $1 - a list in wikitext.\n* $2 - the number of items in list $1 for PLURAL use.",
 	"gadgets-required-skins": "Parameters:\n* $1 - a comma separated list.\n* $2 - the number of items in list $1 for PLURAL use.",

includes/GadgetDefinitionNamespaceRepo.php

@@ -105,6 +105,13 @@ class GadgetDefinitionNamespaceRepo extends GadgetRepo {
 		$this->wanCache->touchCheckKey( $this->getGadgetIdsKey() );
 	}
 
+	/**
+	 * @inheritDoc
+	 */
+	public function getGadgetDefinitionTitle( string $id ): ?Title {
+		return Title::makeTitleSafe( NS_GADGET_DEFINITION, $id );
+	}
+
 	/**
 	 * @param string $id
 	 * @throws InvalidArgumentException

includes/GadgetRepo.php

@@ -66,6 +66,18 @@ abstract class GadgetRepo {
 	public function handlePageDeletion( LinkTarget $target ) {
 	}
 
+	/**
+	 * Given a gadget ID, return the title of the page where the gadget is
+	 * defined (or null if the given repo does not have per-gadget definition
+	 * pages).
+	 *
+	 * @param string $id
+	 * @return Title|null
+	 */
+	public function getGadgetDefinitionTitle( string $id ): ?Title {
+		return null;
+	}
+
 	/**
 	 * Get a list of gadgets sorted by category
 	 *

includes/SpecialGadgets.php

@@ -63,9 +63,12 @@ class SpecialGadgets extends SpecialPage {
 
 		$listOpen = false;
 
-		$editInterfaceMessage = $this->getUser()->isAllowed( 'editinterface' )
+		$editDefinitionMessage = $this->getUser()->isAllowed( 'gadgets-definition-edit' )
 			? 'edit'
 			: 'viewsource';
+		$editInterfaceMessage = $this->getUser()->isAllowed( 'editinterface' )
+			? 'gadgets-editdescription'
+			: 'gadgets-viewdescription';
 
 		$linkRenderer = $this->getLinkRenderer();
 		$skinFactory = $services->getSkinFactory();
@@ -99,6 +102,15 @@ class SpecialGadgets extends SpecialPage {
 				}
 
 				$links = [];
+				$definitionTitle = GadgetRepo::singleton()->getGadgetDefinitionTitle( $name );
+				if ( $definitionTitle ) {
+					$links[] = $linkRenderer->makeLink(
+						$definitionTitle,
+						$this->msg( $editDefinitionMessage )->text(),
+						[],
+						[ 'action' => 'edit' ]
+					);
+				}
 				$links[] = $linkRenderer->makeLink(
 					$t,
 					$this->msg( $editInterfaceMessage )->text(),