Add constants to describe error codes from Installer::run

src/Composer/DependencyResolver/SolverProblemsException.php

@@ -21,6 +21,8 @@ use Composer\Package\PackageInterface;
  */
 class SolverProblemsException extends \RuntimeException
 {
+    const ERROR_DEPENDENCY_RESOLUTION_FAILED = 2;
+
     /** @var Problem[] */
     protected $problems;
     /** @var array<Rule[]> */
@@ -35,7 +37,7 @@ class SolverProblemsException extends \RuntimeException
         $this->problems = $problems;
         $this->learnedPool = $learnedPool;
 
-        parent::__construct('Failed resolving dependencies with '.count($problems).' problems, call getPrettyString to get formatted details', 2);
+        parent::__construct('Failed resolving dependencies with '.count($problems).' problems, call getPrettyString to get formatted details', self::ERROR_DEPENDENCY_RESOLUTION_FAILED);
     }
 
     public function getPrettyString(RepositorySet $repositorySet, Request $request, Pool $pool, $isVerbose, $isDevExtraction = false)

src/Composer/Installer.php

@@ -66,6 +66,13 @@ use Composer\Util\Platform;
  */
 class Installer
 {
+    const ERROR_NONE = 0; // no error/success state
+    const ERROR_GENERIC_FAILURE = 1;
+    const ERROR_NO_LOCK_FILE_FOR_PARTIAL_UPDATE = 3;
+    const ERROR_LOCK_FILE_INVALID = 4;
+    // used/declared in SolverProblemsException, carried over here for completeness
+    const ERROR_DEPENDENCY_RESOLUTION_FAILED = 2;
+
     /**
      * @var IOInterface
      */
@@ -209,6 +216,7 @@ class Installer
      *
      * @throws \Exception
      * @return int        0 on success or a positive error code on failure
+     * @phpstan-return self::ERROR_*
      */
     public function run()
     {
@@ -387,7 +395,7 @@ class Installer
         if (($this->updateAllowList || $this->updateMirrors) && !$lockedRepository) {
             $this->io->writeError('<error>Cannot update ' . ($this->updateMirrors ? 'lock file information' : 'only a partial set of packages') . ' without a lock file present. Run `composer update` to generate a lock file.</error>', true, IOInterface::QUIET);
 
-            return 1;
+            return self::ERROR_NO_LOCK_FILE_FOR_PARTIAL_UPDATE;
         }
 
         $this->io->writeError('<info>Loading composer repositories with package information</info>');
@@ -434,7 +442,7 @@ class Installer
             $ghe = new GithubActionError($this->io);
             $ghe->emit($err."\n".$prettyProblem);
 
-            return max(1, $e->getCode());
+            return max(self::ERROR_GENERIC_FAILURE, $e->getCode());
         }
 
         $this->io->writeError("Analyzed ".count($pool)." packages to resolve dependencies", true, IOInterface::VERBOSE);
@@ -603,7 +611,7 @@ class Installer
             $ghe = new GithubActionError($this->io);
             $ghe->emit($err."\n".$prettyProblem);
 
-            return max(1, $e->getCode());
+            return max(self::ERROR_GENERIC_FAILURE, $e->getCode());
         }
 
         $lockTransaction->setNonDevPackages($nonDevLockTransaction);
@@ -661,7 +669,7 @@ class Installer
                 if (0 !== count($lockTransaction->getOperations())) {
                     $this->io->writeError('<error>Your lock file cannot be installed on this system without changes. Please run composer update.</error>', true, IOInterface::QUIET);
 
-                    return 1;
+                    return self::ERROR_LOCK_FILE_INVALID;
                 }
             } catch (SolverProblemsException $e) {
                 $err = 'Your lock file does not contain a compatible set of packages. Please run composer update.';
@@ -673,7 +681,7 @@ class Installer
                 $ghe = new GithubActionError($this->io);
                 $ghe->emit($err."\n".$prettyProblem);
 
-                return max(1, $e->getCode());
+                return max(self::ERROR_GENERIC_FAILURE, $e->getCode());
             }
         }
 

tests/Composer/Test/Fixtures/installer/partial-update-without-lock.test

@@ -33,5 +33,5 @@ update b/unstable
 --EXPECT-OUTPUT--
 Cannot update only a partial set of packages without a lock file present. Run `composer update` to generate a lock file.
 --EXPECT-EXIT-CODE--
-1
+3
 --EXPECT--