Removed the option to disallowed downgrades and simplifed some places where it was used

src/Composer/DependencyResolver/DefaultPolicy.php

@@ -26,11 +26,6 @@ class DefaultPolicy implements PolicyInterface
         return true;
     }
 
-    public function allowDowngrade()
-    {
-        return true;
-    }
-
     public function versionCompare(PackageInterface $a, PackageInterface $b, $operator)
     {
         $constraint = new VersionConstraint($operator, $b->getVersion());
@@ -39,16 +34,11 @@ class DefaultPolicy implements PolicyInterface
         return $constraint->matchSpecific($version);
     }
 
-    public function findUpdatePackages(Solver $solver, Pool $pool, array $installedMap, PackageInterface $package, $allowAll = false)
+    public function findUpdatePackages(Solver $solver, Pool $pool, array $installedMap, PackageInterface $package)
     {
         $packages = array();
 
         foreach ($pool->whatProvides($package->getName()) as $candidate) {
-            // skip old packages unless downgrades are an option
-            if (!$allowAll && !$this->allowDowngrade() && $this->versionCompare($package, $candidate, '>')) {
-                continue;
-            }
-
             if ($candidate !== $package) {
                 $packages[] = $candidate;
             }

src/Composer/DependencyResolver/PolicyInterface.php

@@ -21,9 +21,8 @@ use Composer\Package\PackageInterface;
 interface PolicyInterface
 {
     function allowUninstall();
-    function allowDowngrade();
     function versionCompare(PackageInterface $a, PackageInterface $b, $operator);
-    function findUpdatePackages(Solver $solver, Pool $pool, array $installedMap, PackageInterface $package, $allowAll);
+    function findUpdatePackages(Solver $solver, Pool $pool, array $installedMap, PackageInterface $package);
     function installable(Solver $solver, Pool $pool, array $installedMap, PackageInterface $package);
     function selectPreferedPackages(Pool $pool, array $installedMap, array $literals);
 }

src/Composer/DependencyResolver/Solver.php

@@ -375,9 +375,9 @@ class Solver
      *                                   be added
      * @param bool             $allowAll Whether downgrades are allowed
      */
-    private function addRulesForUpdatePackages(PackageInterface $package, $allowAll)
+    private function addRulesForUpdatePackages(PackageInterface $package)
     {
-        $updates = $this->policy->findUpdatePackages($this, $this->pool, $this->installedMap, $package, $allowAll);
+        $updates = $this->policy->findUpdatePackages($this, $this->pool, $this->installedMap, $package);
 
         $this->addRulesForPackage($package);
 
@@ -965,7 +965,7 @@ class Solver
         }
 
         foreach ($installedPackages as $package) {
-            $this->addRulesForUpdatePackages($package, true);
+            $this->addRulesForUpdatePackages($package);
         }
 
 
@@ -983,31 +983,15 @@ class Solver
         // solver_addrpmrulesforweak(solv, &addedmap);
 
         foreach ($installedPackages as $package) {
-            // create a feature rule which allows downgrades
-            $updates = $this->policy->findUpdatePackages($this, $this->pool, $this->installedMap, $package, true);
-            $featureRule = $this->createUpdateRule($package, $updates, self::RULE_INTERNAL_ALLOW_UPDATE, (string) $package);
-
-            // create an update rule which does not allow downgrades
-            $updates = $this->policy->findUpdatePackages($this, $this->pool, $this->installedMap, $package, false);
+            $updates = $this->policy->findUpdatePackages($this, $this->pool, $this->installedMap, $package);
             $rule = $this->createUpdateRule($package, $updates, self::RULE_INTERNAL_ALLOW_UPDATE, (string) $package);
 
-            if ($rule->equals($featureRule)) {
-                if ($this->policy->allowUninstall()) {
-                    $featureRule->setWeak(true);
-                    $this->addRule(RuleSet::TYPE_FEATURE, $featureRule);
-                    $this->packageToFeatureRule[$package->getId()] = $rule;
-                } else {
-                    $this->addRule(RuleSet::TYPE_UPDATE, $rule);
-                    $this->packageToUpdateRule[$package->getId()] = $rule;
-                }
-            } else if ($this->policy->allowUninstall()) {
-                $featureRule->setWeak(true);
+            if ($this->policy->allowUninstall()) {
                 $rule->setWeak(true);
-
                 $this->addRule(RuleSet::TYPE_FEATURE, $featureRule);
-                $this->addRule(RuleSet::TYPE_UPDATE, $rule);
-
                 $this->packageToFeatureRule[$package->getId()] = $rule;
+            } else {
+                $this->addRule(RuleSet::TYPE_UPDATE, $rule);
                 $this->packageToUpdateRule[$package->getId()] = $rule;
             }
         }