(bug 35240) Fix mw.loader state machine.
authorlupo <lupo.bugzilla@gmail.com>
Wed, 9 May 2012 09:01:19 +0000 (11:01 +0200)
committerlupo <lupo.bugzilla@gmail.com>
Wed, 9 May 2012 09:01:19 +0000 (11:01 +0200)
Main changes:

* handlePending() correctly handles "missing" and "error" states
and propagates error states up the dependency tree.

* handlePending() is called whenever a module enters one of the
states "ready", "error", or "missing" (in execute() and
mw.loader.state()).

* load() filters out not only undefined modules, but -- by the logic of
the comment there -- also modules in state "error" or "missing".

Minor changes:

* recurse() renamed to sortDependencies(), also uses a hash for
unresolved now instead of an array.

* execute() was never called with the second parameter "callback", hence
I've removed it.

* simplified the "are all dependencies 'ready'?" test and moved it to
its own function.

The change comes with additional QUnit tests for mw.loader. If I run
these tests against the current mediawiki.js, several of them fail. In
particular test #86 ("mw.loader real missing dependency") is
instructive: if the server returns "missing" for a module, dependent
modules never progress beyond "loaded", and if there are jobs (from
mw.loader.using()) depending on such a missing module (directly or
indirectly), neither ready() nor error() is ever called.

Running the tests against the changed mediawiki.js in this change, they
all succeed for me.

Patchset 2: whitespace changes, $_GET instead of $_REQUEST in
testloader.

Patchset 3: XML::encodeJsVar() in testloader, deepEqual() in Qunit
tests.

Patchset 4: rebase

Patchset 5: Amend commit message only (typo)

Change-Id: Ia67edfc07fc9237def04ed13bb2cee16e519d7af

resources/mediawiki/mediawiki.js
tests/qunit/data/testloader.php [new file with mode: 0644]
tests/qunit/suites/resources/mediawiki/mediawiki.test.js

index 4f345ab..a9fa1fd 100644 (file)
@@ -481,9 +481,19 @@ var mw = ( function ( $, undefined ) {
                        }
 
                        /**
-                        * Recursively resolves dependencies and detects circular references
+                        * Resolves dependencies and detects circular references.
+                        *
+                        * @param module String Name of the top-level module whose dependencies shall be
+                        *   resolved and sorted.
+                        * @param resolved Array Returns a topological sort of the given module and its
+                        *   dependencies, such that later modules depend on earlier modules. The array
+                        *   contains the module names. If the array contains already some module names,
+                        *   this function appends its result to the pre-existing array.
+                        * @param unresolved Object [optional] Hash used to track the current dependency
+                        *   chain; used to report loops in the dependency graph.
+                        * @throws Error if any unregistered module or a dependency loop is encountered
                         */
-                       function recurse( module, resolved, unresolved ) {
+                       function sortDependencies( module, resolved, unresolved ) {
                                var n, deps, len;
 
                                if ( registry[module] === undefined ) {
@@ -497,12 +507,20 @@ var mw = ( function ( $, undefined ) {
                                                registry[module].dependencies = [registry[module].dependencies];
                                        }
                                }
+                               if ( $.inArray( module, resolved ) !== -1 ) {
+                                       // Module already resolved; nothing to do.
+                                       return;
+                               }
+                               // unresolved is optional, supply it if not passed in
+                               if ( !unresolved ) {
+                                       unresolved = {};
+                               }
                                // Tracks down dependencies
                                deps = registry[module].dependencies;
                                len = deps.length;
                                for ( n = 0; n < len; n += 1 ) {
                                        if ( $.inArray( deps[n], resolved ) === -1 ) {
-                                               if ( $.inArray( deps[n], unresolved ) !== -1 ) {
+                                               if ( unresolved[deps[n]] ) {
                                                        throw new Error(
                                                                'Circular reference detected: ' + module +
                                                                ' -> ' + deps[n]
@@ -510,40 +528,37 @@ var mw = ( function ( $, undefined ) {
                                                }
 
                                                // Add to unresolved
-                                               unresolved[unresolved.length] = module;
-                                               recurse( deps[n], resolved, unresolved );
-                                               // module is at the end of unresolved
-                                               unresolved.pop();
+                                               unresolved[module] = true;
+                                               sortDependencies( deps[n], resolved, unresolved );
+                                               delete unresolved[module];
                                        }
                                }
                                resolved[resolved.length] = module;
                        }
 
                        /**
-                        * Gets a list of module names that a module depends on in their proper dependency order
+                        * Gets a list of module names that a module depends on in their proper dependency
+                        * order.
                         *
                         * @param module string module name or array of string module names
                         * @return list of dependencies, including 'module'.
                         * @throws Error if circular reference is detected
                         */
                        function resolve( module ) {
-                               var modules, m, deps, n, resolved;
+                               var m, resolved;
 
                                // Allow calling with an array of module names
                                if ( $.isArray( module ) ) {
-                                       modules = [];
+                                       resolved = [];
                                        for ( m = 0; m < module.length; m += 1 ) {
-                                               deps = resolve( module[m] );
-                                               for ( n = 0; n < deps.length; n += 1 ) {
-                                                       modules[modules.length] = deps[n];
-                                               }
+                                               sortDependencies( module[m], resolved );
                                        }
-                                       return modules;
+                                       return resolved;
                                }
 
                                if ( typeof module === 'string' ) {
                                        resolved = [];
-                                       recurse( module, resolved, [] );
+                                       sortDependencies( module, resolved );
                                        return resolved;
                                }
 
@@ -598,57 +613,107 @@ var mw = ( function ( $, undefined ) {
                        }
 
                        /**
-                        * Automatically executes jobs and modules which are pending with satistifed dependencies.
+                        * Determine whether all dependencies are in state 'ready', which means we may
+                        * execute the module or job now.
+                        *
+                        * @param dependencies Array dependencies (module names) to be checked.
                         *
-                        * This is used when dependencies are satisfied, such as when a module is executed.
+                        * @return Boolean true if all dependencies are in state 'ready', false otherwise
                         */
-                       function handlePending( module ) {
-                               var j, r;
+                       function allReady( dependencies ) {
+                               return filter( 'ready', dependencies ).length === dependencies.length;
+                       }
 
-                               try {
-                                       // Run jobs whose dependencies have just been met
-                                       for ( j = 0; j < jobs.length; j += 1 ) {
-                                               if ( compare(
-                                                       filter( 'ready', jobs[j].dependencies ),
-                                                       jobs[j].dependencies ) )
-                                               {
-                                                       var callback = jobs[j].ready;
-                                                       jobs.splice( j, 1 );
-                                                       j -= 1;
-                                                       if ( $.isFunction( callback ) ) {
-                                                               callback();
+                       /**
+                        * Log a message to window.console, if possible. Useful to force logging of some
+                        * errors that are otherwise hard to detect, even if mw.log is not available. (I.e.,
+                        * this logs also if not in debug mode.)
+                        *
+                        * @param msg String text for the log entry
+                        * @param e   Error [optional] to also log.
+                        */
+                       function log( msg, e ) {
+                               if ( window.console && typeof window.console.log === 'function' ) {
+                                       console.log( msg );
+                                       if ( e ) {
+                                               console.log( e );
+                                       }
+                               }
+                       }
+
+                       /**
+                        * A module has entered state 'ready', 'error', or 'missing'. Automatically update pending jobs
+                        * and modules that depend upon this module. if the given module failed, propagate the 'error'
+                        * state up the dependency tree; otherwise, execute all jobs/modules that now have all their
+                        * dependencies satisfied. On jobs depending on a failed module, run the error callback, if any.
+                        *
+                        * @param module String name of module that entered one of the states 'ready', 'error', or 'missing'.
+                        */
+                       function handlePending( module ) {
+                               var j, job, hasErrors, m, stateChange;
+
+                               // Modules.
+                               if ( $.inArray( registry[module].state, ['error', 'missing'] ) !== -1 ) {
+                                       // If the current module failed, mark all dependent modules also as failed.
+                                       // Iterate until steady-state to propagate the error state upwards in the
+                                       // dependency tree.
+                                       do {
+                                               stateChange = false;
+                                               for ( m in registry ) {
+                                                       if ( $.inArray( registry[m].state, ['error', 'missing'] ) === -1 ) {
+                                                               if ( filter( ['error', 'missing'], registry[m].dependencies ).length > 0 ) {
+                                                                       registry[m].state = 'error';
+                                                                       stateChange = true;
+                                                               }
                                                        }
                                                }
-                                       }
-                                       // Execute modules whose dependencies have just been met
-                                       for ( r in registry ) {
-                                               if ( registry[r].state === 'loaded' ) {
-                                                       if ( compare(
-                                                               filter( ['ready'], registry[r].dependencies ),
-                                                               registry[r].dependencies ) )
-                                                       {
-                                                               execute( r );
+                                       } while ( stateChange );
+                               }
+
+                               // Execute all jobs whose dependencies are either all satisfied or contain at least one failed module.
+                               for ( j = 0; j < jobs.length; j += 1 ) {
+                                       hasErrors = filter( ['error', 'missing'], jobs[j].dependencies ).length > 0;
+                                       if ( hasErrors || allReady( jobs[j].dependencies ) ) {
+                                               // All dependencies satisfied, or some have errors
+                                               job = jobs[j];
+                                               jobs.splice( j, 1 );
+                                               j -= 1;
+                                               try {
+                                                       if ( hasErrors ) {
+                                                               throw new Error ("Module " + module + " failed.");
+                                                       } else {
+                                                               if ( $.isFunction( job.ready ) ) {
+                                                                       job.ready();
+                                                               }
+                                                       }
+                                               } catch ( e ) {
+                                                       if ( $.isFunction( job.error ) ) {
+                                                               try {
+                                                                       job.error( e, [module] );
+                                                               } catch ( ex ) {
+                                                                       // A user-defined operation raised an exception. Swallow to protect
+                                                                       // our state machine!
+                                                                       log( 'mw.loader::handlePending> Exception thrown by job.error()', ex );
+                                                               }
                                                        }
                                                }
                                        }
-                               } catch ( e ) {
-                                       // Run error callbacks of jobs affected by this condition
-                                       for ( j = 0; j < jobs.length; j += 1 ) {
-                                               if ( $.inArray( module, jobs[j].dependencies ) !== -1 ) {
-                                                       if ( $.isFunction( jobs[j].error ) ) {
-                                                               jobs[j].error( e, module );
-                                                       }
-                                                       jobs.splice( j, 1 );
-                                                       j -= 1;
+                               }
+
+                               if ( registry[module].state === 'ready' ) {
+                                       // The current module became 'ready'. Recursively execute all dependent modules that are loaded
+                                       // and now have all dependencies satisfied.
+                                       for ( m in registry ) {
+                                               if ( registry[m].state === 'loaded' && allReady( registry[m].dependencies ) ) {
+                                                       execute( m );
                                                }
                                        }
-                                       throw e;
                                }
                        }
 
                        /**
                         * Adds a script tag to the DOM, either using document.write or low-level DOM manipulation,
-                        * depending on whether document-ready has occured yet and whether we are in async mode.
+                        * depending on whether document-ready has occurred yet and whether we are in async mode.
                         *
                         * @param src String: URL to script, will be used as the src attribute in the script tag
                         * @param callback Function: Optional callback which will be run when the script is done
@@ -725,7 +790,7 @@ var mw = ( function ( $, undefined ) {
                         *
                         * @param module string module name to execute
                         */
-                       function execute( module, callback ) {
+                       function execute( module ) {
                                var style, media, i, script, markModuleReady, nestedAddScript;
 
                                if ( registry[module] === undefined ) {
@@ -766,9 +831,6 @@ var mw = ( function ( $, undefined ) {
                                        markModuleReady = function() {
                                                registry[module].state = 'ready';
                                                handlePending( module );
-                                               if ( $.isFunction( callback ) ) {
-                                                       callback();
-                                               }
                                        };
                                        nestedAddScript = function ( arr, callback, async, i ) {
                                                // Recursively call addScript() in its own callback
@@ -794,11 +856,9 @@ var mw = ( function ( $, undefined ) {
                                } catch ( e ) {
                                        // This needs to NOT use mw.log because these errors are common in production mode
                                        // and not in debug mode, such as when a symbol that should be global isn't exported
-                                       if ( window.console && typeof window.console.log === 'function' ) {
-                                               console.log( 'mw.loader::execute> Exception thrown by ' + module + ': ' + e.message );
-                                               console.log( e );
-                                       }
+                                       log('mw.loader::execute> Exception thrown by ' + module + ': ' + e.message, e);
                                        registry[module].state = 'error';
+                                       handlePending( module );
                                }
                        }
 
@@ -1157,18 +1217,16 @@ var mw = ( function ( $, undefined ) {
                                        if ( registry[module] !== undefined && registry[module].script !== undefined ) {
                                                throw new Error( 'module already implemented: ' + module );
                                        }
-                                       // Mark module as loaded
-                                       registry[module].state = 'loaded';
                                        // Attach components
                                        registry[module].script = script;
                                        registry[module].style = style;
                                        registry[module].messages = msgs;
-                                       // Execute or queue callback
-                                       if ( compare(
-                                               filter( ['ready'], registry[module].dependencies ),
-                                               registry[module].dependencies ) )
-                                       {
-                                               execute( module );
+                                       // The module may already have been marked as erroneous
+                                       if ( $.inArray( registry[module].state, ['error', 'missing'] ) === -1 ) {
+                                               registry[module].state = 'loaded';
+                                               if ( allReady( registry[module].dependencies ) ) {
+                                                       execute( module );
+                                               }
                                        }
                                },
 
@@ -1192,21 +1250,19 @@ var mw = ( function ( $, undefined ) {
                                        }
                                        // Resolve entire dependency map
                                        dependencies = resolve( dependencies );
-                                       // If all dependencies are met, execute ready immediately
-                                       if ( compare( filter( ['ready'], dependencies ), dependencies ) ) {
+                                       if ( allReady( dependencies ) ) {
+                                               // Run ready immediately
                                                if ( $.isFunction( ready ) ) {
                                                        ready();
                                                }
-                                       }
-                                       // If any dependencies have errors execute error immediately
-                                       else if ( filter( ['error'], dependencies ).length ) {
+                                       } else if ( filter( ['error', 'missing'], dependencies ).length ) {
+                                               // Execute error immediately if any dependencies have errors
                                                if ( $.isFunction( error ) ) {
-                                                       error( new Error( 'one or more dependencies have state "error"' ),
+                                                       error( new Error( 'one or more dependencies have state "error" or "missing"' ),
                                                                dependencies );
                                                }
-                                       }
-                                       // Since some dependencies are not yet ready, queue up a request
-                                       else {
+                                       } else {
+                                               // Not all dependencies are ready: queue up a request
                                                request( dependencies, ready, error );
                                        }
                                },
@@ -1225,7 +1281,7 @@ var mw = ( function ( $, undefined ) {
                                 *  be assumed if loading a URL, and false will be assumed otherwise.
                                 */
                                load: function ( modules, type, async ) {
-                                       var filtered, m;
+                                       var filtered, m, module;
 
                                        // Validate input
                                        if ( typeof modules !== 'object' && typeof modules !== 'string' ) {
@@ -1264,24 +1320,29 @@ var mw = ( function ( $, undefined ) {
                                        // an array of unrelated modules, whereas the modules passed to
                                        // using() are related and must all be loaded.
                                        for ( filtered = [], m = 0; m < modules.length; m += 1 ) {
-                                               if ( registry[modules[m]] !== undefined ) {
-                                                       filtered[filtered.length] = modules[m];
+                                               module = registry[modules[m]];
+                                               if ( module !== undefined ) {
+                                                       if ( $.inArray( module.state, ['error', 'missing'] ) === -1 ) {
+                                                               filtered[filtered.length] = modules[m];
+                                                       }
                                                }
                                        }
 
+                                       if (filtered.length === 0) {
+                                               return;
+                                       }
                                        // Resolve entire dependency map
                                        filtered = resolve( filtered );
-                                       // If all modules are ready, nothing dependency be done
-                                       if ( compare( filter( ['ready'], filtered ), filtered ) ) {
+                                       // If all modules are ready, nothing to be done
+                                       if ( allReady( filtered ) ) {
                                                return;
                                        }
-                                       // If any modules have errors
-                                       if ( filter( ['error'], filtered ).length ) {
+                                       // If any modules have errors: also quit.
+                                       if ( filter( ['error', 'missing'], filtered ).length ) {
                                                return;
                                        }
-                                       // Since some modules are not yet ready, queue up a request
+                                       // Since some modules are not yet ready, queue up a request.
                                        request( filtered, null, null, async );
-                                       return;
                                },
 
                                /**
@@ -1302,7 +1363,8 @@ var mw = ( function ( $, undefined ) {
                                        if ( registry[module] === undefined ) {
                                                mw.loader.register( module );
                                        }
-                                       if ( state === 'ready' && registry[module].state !== state) {
+                                       if ( $.inArray(state, ['ready', 'error', 'missing']) !== -1
+                                               && registry[module].state !== state ) {
                                                // Make sure pending modules depending on this one get executed if their
                                                // dependencies are now fulfilled!
                                                registry[module].state = state;
diff --git a/tests/qunit/data/testloader.php b/tests/qunit/data/testloader.php
new file mode 100644 (file)
index 0000000..7f4c48d
--- /dev/null
@@ -0,0 +1,100 @@
+<?php
+/**
+ * ResourceLoader stub working with pre-defined test modules.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ * http://www.gnu.org/copyleft/gpl.html
+ *
+ * @file
+ * @package MediaWiki
+ * @author Lupo
+ * @since 1.20
+ */
+header( 'Content-Type: text/javascript; charset=utf-8' );\r
+
+require_once "../../../includes/Xml.php";
+
+$modules = array (
+       'test.use_missing' => array (
+               'src' => 'mw.loader.implement("test.use_missing", function () {start(); ok(false, "Module test.use_missing should not run.");}, {}, {});',
+               'deps' => array ( 'test.missing' )
+       ),
+       'test.use_missing2' => array (
+               'src' => 'mw.loader.implement("test.use_missing2", function () {start(); ok(false, "Module test.use_missing2 should not run.");}, {}, {});',
+               'deps' => array ( 'test.missing2' )
+       )
+);
+
+// Copied from ResourceLoaderContext
+function expandModuleNames( $modules ) {\r
+       $retval = array();\r
+       // For backwards compatibility with an earlier hack, replace ! with .\r
+       $modules = str_replace( '!', '.', $modules );\r
+       $exploded = explode( '|', $modules );\r
+       foreach ( $exploded as $group ) {\r
+               if ( strpos( $group, ',' ) === false ) {\r
+                       // This is not a set of modules in foo.bar,baz notation\r
+                       // but a single module\r
+                       $retval[] = $group;\r
+               } else {\r
+                       // This is a set of modules in foo.bar,baz notation\r
+                       $pos = strrpos( $group, '.' );\r
+                       if ( $pos === false ) {\r
+                               // Prefixless modules, i.e. without dots\r
+                               $retval = explode( ',', $group );\r
+                       } else {\r
+                               // We have a prefix and a bunch of suffixes\r
+                               $prefix = substr( $group, 0, $pos ); // 'foo'\r
+                               $suffixes = explode( ',', substr( $group, $pos + 1 ) ); // array( 'bar', 'baz' )\r
+                               foreach ( $suffixes as $suffix ) {\r
+                                       $retval[] = "$prefix.$suffix";\r
+                               }\r
+                       }\r
+               }\r
+       }\r
+       return $retval;\r
+}
+
+function addModule ( $moduleName, &$gotten ) {
+       global $modules;
+
+       $result = "";
+       if ( isset( $gotten[$moduleName] ) ) {
+               return $result;
+       }
+       $gotten[$moduleName] = true;
+       if ( isset( $modules[$moduleName] ) ) {
+               $deps = $modules[$moduleName]['deps'];
+               foreach ( $deps as $depName ) {
+                       $result .= addModule( $depName, $gotten ) . "\n";
+               }
+               $result .= $modules[$moduleName]['src'] . "\n";
+       } else {
+               $result .= 'mw.loader.state( ' . Xml::encodeJsVar( $moduleName ) . ', "missing" );' . "\n";
+       }
+       return $result . "\n";
+}
+
+$result = "";
+
+if ( isset( $_GET['modules'] ) ) {
+       $toGet = expandModuleNames( $_GET['modules'] );
+       $gotten = array();
+       foreach ( $toGet as $moduleName ) {
+               $result .= addModule( $moduleName, $gotten );
+       }
+}
+
+echo $result;
index fd4710f..2f11521 100644 (file)
@@ -261,6 +261,129 @@ test( 'mw.loader.implement', function () {
 
 });
 
+test( 'mw.loader erroneous indirect dependency', function() {
+       expect( 3 );
+       mw.loader.register( [
+               ['test.module1', '0'],
+               ['test.module2', '0', ['test.module1']],
+               ['test.module3', '0', ['test.module2']]
+       ] );
+       mw.loader.implement( 'test.module1', function() { throw new Error( 'expected' ); }, {}, {} );
+       strictEqual( mw.loader.getState( 'test.module1' ), 'error', 'Expected "error" state for test.module1' );
+       strictEqual( mw.loader.getState( 'test.module2' ), 'error', 'Expected "error" state for test.module2' );
+       strictEqual( mw.loader.getState( 'test.module3' ), 'error', 'Expected "error" state for test.module3' );
+} );
+
+test( 'mw.loader out-of-order implementation', function() {
+       expect( 9 );
+       mw.loader.register( [
+               ['test.module4', '0'],
+               ['test.module5', '0', ['test.module4']],
+               ['test.module6', '0', ['test.module5']]
+       ] );
+       mw.loader.implement( 'test.module4', function() {}, {}, {} );
+       strictEqual( mw.loader.getState( 'test.module4' ), 'ready', 'Expected "ready" state for test.module4' );
+       strictEqual( mw.loader.getState( 'test.module5' ), 'registered', 'Expected "registered" state for test.module5' );
+       strictEqual( mw.loader.getState( 'test.module6' ), 'registered', 'Expected "registered" state for test.module6' );
+       mw.loader.implement( 'test.module6', function() {}, {}, {} );
+       strictEqual( mw.loader.getState( 'test.module4' ), 'ready', 'Expected "ready" state for test.module4' );
+       strictEqual( mw.loader.getState( 'test.module5' ), 'registered', 'Expected "registered" state for test.module5' );
+       strictEqual( mw.loader.getState( 'test.module6' ), 'loaded', 'Expected "loaded" state for test.module6' );
+       mw.loader.implement( 'test.module5', function() {}, {}, {} );
+       strictEqual( mw.loader.getState( 'test.module4' ), 'ready', 'Expected "ready" state for test.module4' );
+       strictEqual( mw.loader.getState( 'test.module5' ), 'ready', 'Expected "ready" state for test.module5' );
+       strictEqual( mw.loader.getState( 'test.module6' ), 'ready', 'Expected "ready" state for test.module6' );
+} );
+
+test( 'mw.loader missing dependency', function() {
+       expect( 13 );
+       mw.loader.register( [
+               ['test.module7', '0'],
+               ['test.module8', '0', ['test.module7']],
+               ['test.module9', '0', ['test.module8']]
+       ] );
+       mw.loader.implement( 'test.module8', function() {}, {}, {} );
+       strictEqual( mw.loader.getState( 'test.module7' ), 'registered', 'Expected "registered" state for test.module7' );
+       strictEqual( mw.loader.getState( 'test.module8' ), 'loaded', 'Expected "loaded" state for test.module8' );
+       strictEqual( mw.loader.getState( 'test.module9' ), 'registered', 'Expected "registered" state for test.module9' );
+       mw.loader.state( 'test.module7', 'missing' );
+       strictEqual( mw.loader.getState( 'test.module7' ), 'missing', 'Expected "missing" state for test.module7' );
+       strictEqual( mw.loader.getState( 'test.module8' ), 'error', 'Expected "error" state for test.module8' );
+       strictEqual( mw.loader.getState( 'test.module9' ), 'error', 'Expected "error" state for test.module9' );
+       mw.loader.implement( 'test.module9', function() {}, {}, {} );
+       strictEqual( mw.loader.getState( 'test.module7' ), 'missing', 'Expected "missing" state for test.module7' );
+       strictEqual( mw.loader.getState( 'test.module8' ), 'error', 'Expected "error" state for test.module8' );
+       strictEqual( mw.loader.getState( 'test.module9' ), 'error', 'Expected "error" state for test.module9' );
+       mw.loader.using(
+               ['test.module7'],
+               function() {
+                       ok( false, "Success fired despite missing dependency" );
+                       ok( true , "QUnit expected() count dummy" );
+               },
+               function( e, dependencies ) {
+                       strictEqual( $.isArray( dependencies ), true, 'Expected array of dependencies' );
+                       deepEqual( dependencies, ['test.module7'], 'Error callback called with module test.module7' );
+               }
+       );
+       mw.loader.using(
+               ['test.module9'],
+               function() {
+                       ok( false, "Success fired despite missing dependency" );
+                       ok( true , "QUnit expected() count dummy" );
+               },
+               function( e, dependencies ) {
+                       strictEqual( $.isArray( dependencies ), true, 'Expected array of dependencies' );
+                       dependencies.sort();
+                       deepEqual(
+                               dependencies,
+                               ['test.module7', 'test.module8', 'test.module9'],
+                               'Error callback called with all three modules as dependencies'
+                       );
+               }
+       );
+} );
+
+test( 'mw.loader real missing dependency', function() {
+       expect( 6 );
+
+       mw.loader.addSource(
+               'test',
+               {'loadScript' : QUnit.fixurl( mw.config.get( 'wgScriptPath' ) + '/tests/qunit/data/testloader.php' )}
+       );
+       mw.loader.register( [
+               ['test.missing', '0', [], null, 'test'], ['test.missing2', '0', [], null, 'test'],
+               ['test.use_missing', '0', ['test.missing'], null, 'test'],
+               ['test.use_missing2', '0', ['test.missing2'], null, 'test']
+       ] );
+
+       stop();
+       // Asynch ahead
+
+       mw.loader.load( ['test.use_missing'] );
+
+       function verifyModuleStates() {
+               strictEqual( mw.loader.getState( 'test.missing' ), 'missing', 'Module "test.missing" must have state "missing"' );
+               strictEqual( mw.loader.getState( 'test.missing2' ), 'missing', 'Module "test.missing2" must have state "missing"' );
+               strictEqual( mw.loader.getState( 'test.use_missing' ), 'error', 'Module "test.use_missing" must have state "error"' );
+               strictEqual( mw.loader.getState( 'test.use_missing2' ), 'error', 'Module "test.use_missing2" must have state "error"' );
+       }
+
+       mw.loader.using( ['test.use_missing2'],
+               function() {
+                       start();
+                       ok( false, "Success called wrongly." );
+                       ok( true , "QUnit expected() count dummy" );
+                       verifyModuleStates();
+               },
+               function( e, dependencies ) {
+                       start();
+                       ok( true, "Error handler called correctly." );
+                       deepEqual( dependencies, ['test.missing2'], "Dependencies correct." );
+                       verifyModuleStates();
+               }
+       );
+} );
+
 test( 'mw.loader bug29107' , function () {
        expect(2);