Change root.dev-requirement to root.dev in installed.php as the root is not required per se, and this simply tracks the dev mode at install time

src/Composer/InstalledVersions.php

@@ -189,7 +189,7 @@ class InstalledVersions
 
     /**
      * @return array
-     * @psalm-return array{name: string, version: string, reference: string, pretty_version: string, aliases: string[]}
+     * @psalm-return array{name: string, version: string, reference: string, pretty_version: string, aliases: string[], dev: bool}
      */
     public static function getRootPackage()
     {
@@ -202,7 +202,7 @@ class InstalledVersions
      * Returns the raw installed.php data for custom implementations
      *
      * @return array[]
-     * @psalm-return array{root: array{name: string, version: string, reference: string, pretty_version: string, aliases: string[]}, versions: array<string, array{pretty_version?: string, version?: string, aliases?: string[], reference?: string, replaced?: string[], provided?: string[]}>}
+     * @psalm-return array{root: array{name: string, version: string, reference: string, pretty_version: string, aliases: string[], dev: bool}, versions: array<string, array{dev-requirement: bool, pretty_version?: string, version?: string, aliases?: string[], reference?: string, replaced?: string[], provided?: string[]}>}
      */
     public static function getRawData()
     {
@@ -225,7 +225,7 @@ class InstalledVersions
      * @param  array[] $data A vendor/composer/installed.php data set
      * @return void
      *
-     * @psalm-param array{root: array{name: string, version: string, reference: string, pretty_version: string, aliases: string[]}, versions: array<string, array{pretty_version?: string, version?: string, aliases?: string[], reference?: string, replaced?: string[], provided?: string[]}>} $data
+     * @psalm-param array{root: array{name: string, version: string, reference: string, pretty_version: string, aliases: string[], dev: bool}, versions: array<string, array{dev-requirement: bool, pretty_version?: string, version?: string, aliases?: string[], reference?: string, replaced?: string[], provided?: string[]}>} $data
      */
     public static function reload($data)
     {
@@ -235,7 +235,7 @@ class InstalledVersions
 
     /**
      * @return array[]
-     * @psalm-return list<array{root: array{name: string, version: string, reference: string, pretty_version: string, aliases: string[]}, versions: array<string, array{pretty_version?: string, version?: string, aliases?: string[], reference?: string, replaced?: string[], provided?: string[]}>}>
+     * @psalm-return list<array{root: array{name: string, version: string, reference: string, pretty_version: string, aliases: string[], dev: bool}, versions: array<string, array{dev-requirement: bool, pretty_version?: string, version?: string, aliases?: string[], reference?: string, replaced?: string[], provided?: string[]}>}>
      */
     private static function getInstalled()
     {

src/Composer/Repository/FilesystemRepository.php

@@ -179,8 +179,9 @@ class FilesystemRepository extends WritableArrayRepository
             );
             if ($package instanceof RootPackageInterface) {
                 $versions['root'] = $versions['versions'][$package->getName()];
+                unset($versions['root']['dev-requirement']);
                 $versions['root']['name'] = $package->getName();
-                $versions['root']['dev-requirement'] = $devMode;
+                $versions['root']['dev'] = $devMode;
             }
         }
 

tests/Composer/Test/Repository/Fixtures/installed.php

@@ -18,8 +18,8 @@ return array(
             '1.10.x-dev',
         ),
         'reference' => 'sourceref-by-default',
-        'dev-requirement' => true,
         'name' => '__root__',
+        'dev' => true,
     ),
     'versions' => array(
         '__root__' => array(