Show reasons why an operation is executed in -vv mode, fixes #1063

src/Composer/DependencyResolver/Rule.php

@@ -82,6 +82,16 @@ class Rule
         return $this->job;
     }
 
+    public function getReason()
+    {
+        return $this->reason;
+    }
+
+    public function getReasonData()
+    {
+        return $this->reasonData;
+    }
+
     public function getRequiredPackage()
     {
         if ($this->reason === self::RULE_JOB_INSTALL) {
@@ -200,9 +210,12 @@ class Rule
                 if ($requires) {
                     $requireText = array();
                     foreach ($requires as $require) {
-                        $requireText[] = $require->getPrettyString();
+                        $requireText[$require->getName()][] = $require->getPrettyVersion();
                     }
-                    $text .= ' -> satisfiable by '.implode(', ', $requireText).'.';
+                    foreach ($requireText as $name => $versions) {
+                        $requireText[$name] = $name.'['.implode(', ', $versions).']';
+                    }
+                    $text .= ' -> satisfiable by '.implode(', ', $requireText);
                 } else {
                     $targetName = $this->reasonData->getTarget();
 

src/Composer/Installer.php

@@ -18,6 +18,7 @@ use Composer\DependencyResolver\Operation\UpdateOperation;
 use Composer\DependencyResolver\Operation\UninstallOperation;
 use Composer\DependencyResolver\Pool;
 use Composer\DependencyResolver\Request;
+use Composer\DependencyResolver\Rule;
 use Composer\DependencyResolver\Solver;
 use Composer\DependencyResolver\SolverProblemsException;
 use Composer\Downloader\DownloadManager;
@@ -496,6 +497,21 @@ class Installer
 
             $this->installationManager->execute($localRepo, $operation);
 
+            // output reasons why the operation was ran
+            if ($this->verbose && $this->io->isVeryVerbose()) {
+                $reason = $operation->getReason();
+                if ($reason instanceof Rule) {
+                    switch ($reason->getReason()) {
+                        case Rule::RULE_JOB_INSTALL:
+                            $this->io->write('    REASON: Required to be installed: '.$reason->getRequiredPackage());
+                            break;
+                        case Rule::RULE_PACKAGE_REQUIRES:
+                            $this->io->write('    REASON: '.$reason->getPrettyString());
+                            break;
+                    }
+                }
+            }
+
             $event = 'Composer\Script\ScriptEvents::POST_PACKAGE_'.strtoupper($operation->getJobType());
             if (defined($event) && $this->runScripts) {
                 $this->eventDispatcher->dispatchPackageEvent(constant($event), $this->devMode, $operation);