API: Add reference to the mailing list in errors and deprecation warnings

This was suggested at a Developer Summit session as a way to get people
to know about the mailing list.

This also adds a hook so ApiFeatureUsage can mention itself in
deprecation warnings too.

Bug: T148855
Change-Id: I04a7cf89e87e48f6504803dd173e779017a205d0

docs/hooks.txt

@@ -365,6 +365,11 @@ $user: Current user
  * 1.27+: IApiMessage, or a key or key+parameters in ApiBase::$messageMap.
  * Earlier: A key or key+parameters in ApiBase::$messageMap.
 
+'ApiDeprecationHelp': Add messages to the 'deprecation-help' warning generated
+from ApiBase::addDeprecation().
+&$msgs: Message[] Messages to include in the help. Multiple messages will be
+  joined with spaces.
+
 'APIEditBeforeSave': DEPRECATED! Use EditFilterMergedContent instead.
 Before saving a page with api.php?action=edit, after
 processing request parameters. Return false to let the request fail, returning

includes/api/ApiBase.php

@@ -1718,6 +1718,18 @@ abstract class ApiBase extends ContextSource {
 			$this->logFeatureUsage( $feature );
 		}
 		$this->addWarning( $msg, 'deprecation', $data );
+
+		// No real need to deduplicate here, ApiErrorFormatter does that for
+		// us (assuming the hook is deterministic).
+		$msgs = [ $this->msg( 'api-usage-mailinglist-ref' ) ];
+		Hooks::run( 'ApiDeprecationHelp', [ &$msgs ] );
+		if ( count( $msgs ) > 1 ) {
+			$key = '$' . join( ' $', range( 1, count( $msgs ) ) );
+			$msg = ( new RawMessage( $key ) )->params( $msgs );
+		} else {
+			$msg = reset( $msgs );
+		}
+		$this->getMain()->addWarning( $msg, 'deprecation-help' );
 	}
 
 	/**

includes/api/ApiMain.php

@@ -1109,7 +1109,11 @@ class ApiMain extends ApiBase {
 			$result->addContentValue(
 				$path,
 				'docref',
-				$this->msg( 'api-usage-docref', $link )->inLanguage( $formatter->getLanguage() )->text()
+				trim(
+					$this->msg( 'api-usage-docref', $link )->inLanguage( $formatter->getLanguage() )->text()
+					. ' '
+					. $this->msg( 'api-usage-mailinglist-ref' )->inLanguage( $formatter->getLanguage() )->text()
+				)
 			);
 		} else {
 			if ( $config->get( 'ShowExceptionDetails' ) ) {

includes/api/i18n/en.json

@@ -1795,6 +1795,7 @@
 
 	"api-feed-error-title": "Error ($1)",
 	"api-usage-docref": "See $1 for API usage.",
+	"api-usage-mailinglist-ref": "Subscribe to the mediawiki-api-announce mailing list at <https://lists.wikimedia.org/mailman/listinfo/mediawiki-api-announce> for notice of API deprecations and breaking changes.",
 	"api-exception-trace": "$1 at $2($3)\n$4",
 	"api-credits-header": "Credits",
 	"api-credits": "API developers:\n* Yuri Astrakhan (creator, lead developer Sep 2006–Sep 2007)\n* Roan Kattouw (lead developer Sep 2007–2009)\n* Victor Vasiliev\n* Bryan Tong Minh\n* Sam Reed\n* Brad Jorsch (lead developer 2013–present)\n\nPlease send your comments, suggestions and questions to mediawiki-api@lists.wikimedia.org\nor file a bug report at https://phabricator.wikimedia.org/."

includes/api/i18n/qqq.json

@@ -1685,6 +1685,7 @@
 	"apiwarn-wgDebugAPI": "{{doc-apierror}}",
 	"api-feed-error-title": "Used as a feed item title when an error occurs in <kbd>action=feedwatchlist</kbd>.\n\nParameters:\n* $1 - API error code\n{{Identical|Error}}",
 	"api-usage-docref": "\n\nParameters:\n* $1 - URL of the API auto-generated documentation.",
+	"api-usage-mailinglist-ref": "{{doc-apierror}} Also used in the error response.",
 	"api-exception-trace": "\n\nParameters:\n* $1 - Exception class.\n* $2 - File from which the exception was thrown.\n* $3 - Line number from which the exception was thrown.\n* $4 - Exception backtrace.",
 	"api-credits-header": "Header for the API credits section in the API help output\n{{Identical|Credit}}",
 	"api-credits": "API credits text, displayed in the API help output"

tests/phpunit/includes/api/ApiMainTest.php

@@ -546,7 +546,9 @@ class ApiMainTest extends ApiTestCase {
 						[ 'code' => 'existing-error', 'text' => 'existing error', 'module' => 'main' ],
 						[ 'code' => 'ue', 'text' => "Usage exception!", 'data' => [ 'foo' => 'bar' ] ]
 					],
-					'docref' => "See $doclink for API usage.",
+					'docref' => "See $doclink for API usage. Subscribe to the mediawiki-api-announce mailing " .
+						"list at <https://lists.wikimedia.org/mailman/listinfo/mediawiki-api-announce> " .
+						"for notice of API deprecations and breaking changes.",
 					'servedby' => wfHostname(),
 				]
 			],
@@ -564,7 +566,9 @@ class ApiMainTest extends ApiTestCase {
 						[ 'code' => 'sv-error1', 'text' => 'An error', 'module' => 'foo+bar' ],
 						[ 'code' => 'sv-error2', 'text' => 'Another error', 'module' => 'foo+bar' ],
 					],
-					'docref' => "See $doclink for API usage.",
+					'docref' => "See $doclink for API usage. Subscribe to the mediawiki-api-announce mailing " .
+						"list at <https://lists.wikimedia.org/mailman/listinfo/mediawiki-api-announce> " .
+						"for notice of API deprecations and breaking changes.",
 					'servedby' => wfHostname(),
 				]
 			],