go: add a way to display upcoming db migrations

modules/db/db.go

@@ -6,6 +6,7 @@ package db
 import (
 	"context"
 	"fmt"
+	"os"
 
 	"git.dotya.ml/mirre-mt/pcmt/ent"
 	"git.dotya.ml/mirre-mt/pcmt/ent/migrate"
@@ -90,6 +91,25 @@ func IsSetUp(ctx context.Context, client *ent.Client) (bool, error) {
 	return false, nil
 }
 
+// PrintMigration prints the upcoming migration to stdout.
+func PrintMigration(ctx context.Context, client *ent.Client) error {
+	slogger := ctx.Value(CtxKey{}).(*slogging.Slogger)
+	log := *slogger
+
+	log.Logger = log.With(
+		slog.Group("pcmt extra", slog.String("module", "modules/db")),
+	)
+
+	log.Info("printing the upcoming migration to stdout")
+
+	if err := client.Schema.WriteTo(ctx, os.Stdout); err != nil {
+		log.Errorf("failed to print schema changes: %v", err)
+		return err
+	}
+
+	return nil
+}
+
 // SetUp attempts to automatically migrate DB schema and creates the set-up
 // record indicating that the DB has been set up. Optionally and only if the DB
 // has not been set up prior, it creates and admin user with the initPasswd and

run.go

@@ -68,6 +68,7 @@ var (
 	licenseFlag        = flag.Bool("license", false, "Print licensing information and exit")
 	versionFlag        = flag.Bool("version", false, "Print version and exit")
 	importFlag         = flag.String("import", "", "Path to import breach data from")
+	printMigrationFlag = flag.Bool("printMigration", false, "Print to stdout what is about to happen during the following database migration (mainly useful for debugging")
 	version            = "dev"
 	// the global logger.
 	slogger *slogging.Slogger
@@ -88,13 +89,21 @@ func run() error { //nolint:gocognit
 		return nil
 	}
 
+	// skip printing program header.
+	skipHeader := false
+
 	var doingImport bool
 
 	if importFlag != nil && *importFlag != "" {
 		doingImport = true
+		skipHeader = true
 	}
 
-	if !doingImport {
+	if *printMigrationFlag {
+		skipHeader = true
+	}
+
+	if !skipHeader {
 		printHeader()
 	}
 
@@ -180,6 +189,11 @@ func run() error { //nolint:gocognit
 
 	ctx := context.WithValue(context.Background(), moddb.CtxKey{}, slogger)
 
+	if *printMigrationFlag {
+		log.Debug("printing the following migration to stdout")
+		return moddb.PrintMigration(ctx, db)
+	}
+
 	log.Info("ensuring the db is set up and attempting to automatically migrate db schema")
 
 	// make sure the database is set up and optionally creates an administrator