terraform_backend_local.go

package terraform_backend

import (
	"fmt"
	"os"
	"path/filepath"

	errUtils "github.com/cloudposse/atmos/errors"
	"github.com/cloudposse/atmos/pkg/perf"
	"github.com/cloudposse/atmos/pkg/schema"
	u "github.com/cloudposse/atmos/pkg/utils"
)

// ReadTerraformBackendLocal reads the Terraform state file from the local backend.
// If the state file does not exist, the function returns `nil`.
//
// According to Terraform local backend behavior:
// - For the default workspace: state is stored at `terraform.tfstate`
// - For named workspaces: state is stored at `terraform.tfstate.d/<workspace>/terraform.tfstate`
//
// See: https://github.com/cloudposse/atmos/issues/1920
func ReadTerraformBackendLocal(
	atmosConfig *schema.AtmosConfiguration,
	componentSections *map[string]any,
	_ *schema.AuthContext, // Auth context not used for local backend.
) ([]byte, error) {
	defer perf.Track(atmosConfig, "terraform_backend.ReadTerraformBackendLocal")()

	workspace := GetTerraformWorkspace(componentSections)
	componentPath := filepath.Join(
		atmosConfig.TerraformDirAbsolutePath,
		GetTerraformComponent(componentSections),
	)

	var tfStateFilePath string
	if workspace == "" || workspace == "default" {
		// Default workspace: state is stored directly at terraform.tfstate.
		tfStateFilePath = filepath.Join(componentPath, "terraform.tfstate")
	} else {
		// Named workspace: state is stored at terraform.tfstate.d/<workspace>/terraform.tfstate.
		tfStateFilePath = filepath.Join(componentPath, "terraform.tfstate.d", workspace, "terraform.tfstate")
	}

	// If the state file does not exist (the component in the stack has not been provisioned yet), return a `nil` result and no error.
	if !u.FileExists(tfStateFilePath) {
		return nil, nil
	}

	content, err := os.ReadFile(tfStateFilePath)
	if err != nil {
		return nil, fmt.Errorf("%w.\npath: `%s`\nerror: %v", errUtils.ErrReadFile, tfStateFilePath, err)
	}

	return content, nil
}