cli: common backend for init and upgrade apply commands (#2449)

* Use common 'apply' backend for init and upgrades
* Move unit tests to new apply backend
* Only perform Terraform migrations if state exists in cwd (#2457)
* Rework skipPhases logic

---------

Signed-off-by: Daniel Weiße <dw@edgeless.systems>
Co-authored-by: Moritz Sanft <58110325+msanft@users.noreply.github.com>

cli/internal/cmd/applyterraform.go

@@ -0,0 +1,115 @@
+/*
+Copyright (c) Edgeless Systems GmbH
+
+SPDX-License-Identifier: AGPL-3.0-only
+*/
+
+package cmd
+
+import (
+	"fmt"
+	"path/filepath"
+
+	"github.com/edgelesssys/constellation/v2/cli/internal/cloudcmd"
+	"github.com/edgelesssys/constellation/v2/cli/internal/state"
+	"github.com/edgelesssys/constellation/v2/internal/config"
+	"github.com/edgelesssys/constellation/v2/internal/constants"
+	"github.com/spf13/cobra"
+)
+
+// runTerraformApply checks if changes to Terraform are required and applies them.
+func (a *applyCmd) runTerraformApply(cmd *cobra.Command, conf *config.Config, stateFile *state.State, upgradeDir string) error {
+	a.log.Debugf("Checking if Terraform migrations are required")
+	migrationRequired, err := a.planTerraformMigration(cmd, conf)
+	if err != nil {
+		return fmt.Errorf("planning Terraform migrations: %w", err)
+	}
+
+	if !migrationRequired {
+		a.log.Debugf("No changes to infrastructure required, skipping Terraform migrations")
+		return nil
+	}
+
+	a.log.Debugf("Migrating terraform resources for infrastructure changes")
+	postMigrationInfraState, err := a.migrateTerraform(cmd, conf, upgradeDir)
+	if err != nil {
+		return fmt.Errorf("performing Terraform migrations: %w", err)
+	}
+
+	// Merge the pre-upgrade state with the post-migration infrastructure values
+	a.log.Debugf("Updating state file with new infrastructure state")
+	if _, err := stateFile.Merge(
+		// temporary state with post-migration infrastructure values
+		state.New().SetInfrastructure(postMigrationInfraState),
+	); err != nil {
+		return fmt.Errorf("merging pre-upgrade state with post-migration infrastructure values: %w", err)
+	}
+
+	// Write the post-migration state to disk
+	if err := stateFile.WriteToFile(a.fileHandler, constants.StateFilename); err != nil {
+		return fmt.Errorf("writing state file: %w", err)
+	}
+	return nil
+}
+
+// planTerraformMigration checks if the Constellation version the cluster is being upgraded to requires a migration.
+func (a *applyCmd) planTerraformMigration(cmd *cobra.Command, conf *config.Config) (bool, error) {
+	a.log.Debugf("Planning Terraform migrations")
+	vars, err := cloudcmd.TerraformUpgradeVars(conf)
+	if err != nil {
+		return false, fmt.Errorf("parsing upgrade variables: %w", err)
+	}
+	a.log.Debugf("Using Terraform variables:\n%+v", vars)
+
+	// Check if there are any Terraform migrations to apply
+
+	// Add manual migrations here if required
+	//
+	// var manualMigrations []terraform.StateMigration
+	// for _, migration := range manualMigrations {
+	// 	  u.log.Debugf("Adding manual Terraform migration: %s", migration.DisplayName)
+	// 	  u.upgrader.AddManualStateMigration(migration)
+	// }
+
+	return a.clusterUpgrader.PlanClusterUpgrade(cmd.Context(), cmd.OutOrStdout(), vars, conf.GetProvider())
+}
+
+// migrateTerraform migrates an existing Terraform state and the post-migration infrastructure state is returned.
+func (a *applyCmd) migrateTerraform(cmd *cobra.Command, conf *config.Config, upgradeDir string) (state.Infrastructure, error) {
+	// Ask for confirmation first
+	fmt.Fprintln(cmd.OutOrStdout(), "The upgrade requires a migration of Constellation cloud resources by applying an updated Terraform template. Please manually review the suggested changes below.")
+	if !a.flags.yes {
+		ok, err := askToConfirm(cmd, "Do you want to apply the Terraform migrations?")
+		if err != nil {
+			return state.Infrastructure{}, fmt.Errorf("asking for confirmation: %w", err)
+		}
+		if !ok {
+			cmd.Println("Aborting upgrade.")
+			// User doesn't expect to see any changes in his workspace after aborting an "upgrade apply",
+			// therefore, roll back to the backed up state.
+			if err := a.clusterUpgrader.RestoreClusterWorkspace(); err != nil {
+				return state.Infrastructure{}, fmt.Errorf(
+					"restoring Terraform workspace: %w, restore the Terraform workspace manually from %s ",
+					err,
+					filepath.Join(upgradeDir, constants.TerraformUpgradeBackupDir),
+				)
+			}
+			return state.Infrastructure{}, fmt.Errorf("cluster upgrade aborted by user")
+		}
+	}
+	a.log.Debugf("Applying Terraform migrations")
+
+	a.spinner.Start("Migrating Terraform resources", false)
+	infraState, err := a.clusterUpgrader.ApplyClusterUpgrade(cmd.Context(), conf.GetProvider())
+	a.spinner.Stop()
+	if err != nil {
+		return state.Infrastructure{}, fmt.Errorf("applying terraform migrations: %w", err)
+	}
+
+	cmd.Printf("Infrastructure migrations applied successfully and output written to: %s\n"+
+		"A backup of the pre-upgrade state has been written to: %s\n",
+		a.flags.pathPrefixer.PrefixPrintablePath(constants.StateFilename),
+		a.flags.pathPrefixer.PrefixPrintablePath(filepath.Join(upgradeDir, constants.TerraformUpgradeBackupDir)),
+	)
+	return infraState, nil
+}