[skip-changelog] Recover from interrupted builtin tool installation

arduino/cores/packagemanager/loader_test.go

@@ -170,6 +170,8 @@ arduino_zero_edbg.serial.disableRTS=true
 func TestLoadDiscoveries(t *testing.T) {
 	// Create all the necessary data to load discoveries
 	fakePath := paths.New("fake-path")
+	require.NoError(t, fakePath.Join("LICENSE").MkdirAll())
+	defer fakePath.RemoveAll()
 
 	createTestPackageManager := func() *PackageManager {
 		pmb := NewBuilder(fakePath, fakePath, fakePath, fakePath, "test")
@@ -277,6 +279,8 @@ func TestLoadDiscoveries(t *testing.T) {
 		require.Contains(t, discoveries, "teensy")
 		pmeRelease()
 	}
+
+	require.NoError(t, fakePath.RemoveAll())
 }
 
 func TestConvertUploadToolsToPluggableDiscovery(t *testing.T) {

arduino/cores/packagemanager/package_manager_test.go

@@ -457,6 +457,8 @@ func TestPackageManagerClear(t *testing.T) {
 func TestFindToolsRequiredFromPlatformRelease(t *testing.T) {
 	// Create all the necessary data to load discoveries
 	fakePath := paths.New("fake-path")
+	require.NoError(t, fakePath.Join("LICENSE").MkdirAll())
+	defer fakePath.RemoveAll()
 
 	pmb := NewBuilder(fakePath, fakePath, fakePath, fakePath, "test")
 	pack := pmb.GetOrCreatePackage("arduino")

arduino/cores/tools.go

@@ -106,7 +106,11 @@ func (tool *Tool) String() string {
 
 // IsInstalled returns true if the ToolRelease is installed
 func (tr *ToolRelease) IsInstalled() bool {
-	return tr.InstallDir != nil
+	if tr.InstallDir == nil {
+		return false
+	}
+	dirContent, _ := tr.InstallDir.ReadDir()
+	return dirContent.Len() != 0
 }
 
 func (tr *ToolRelease) String() string {

internal/integrationtest/board/board_test.go

@@ -558,3 +558,27 @@ func TestBoardSearchWithOutdatedCore(t *testing.T) {
 	// Installed version must be older than latest
 	require.True(t, installedVersion.LessThan(latestVersion))
 }
+
+func TestBoardListWithFailedBuiltinInstallation(t *testing.T) {
+	env, cli := integrationtest.CreateArduinoCLIWithEnvironment(t)
+	defer env.CleanUp()
+
+	_, _, err := cli.Run("core", "update-index")
+	require.NoError(t, err)
+
+	// board list to install builtin tools
+	_, _, err = cli.Run("board", "list")
+	require.NoError(t, err)
+
+	// remove files from serial-discovery directory to simulate a failed installation
+	serialDiscovery, err := cli.DataDir().Join("packages", "builtin", "tools", "serial-discovery").ReadDir()
+	require.NoError(t, err)
+	require.NoError(t, serialDiscovery[0].Join("LICENSE.txt").Remove())
+	require.NoError(t, serialDiscovery[0].Join("serial-discovery.exe").Remove())
+
+	// board list should install serial-discovery again
+	stdout, stderr, err := cli.Run("board", "list")
+	require.NoError(t, err)
+	require.Empty(t, stderr)
+	require.Contains(t, string(stdout), "Downloading missing tool builtin:serial-discovery")
+}