feat: publish v1.0.0-rc.36-custom.1

model/migration_dialector.go

@@ -0,0 +1,71 @@
+package model
+
+import (
+	"strings"
+
+	"github.com/shopspring/decimal"
+	"gorm.io/driver/mysql"
+	"gorm.io/driver/postgres"
+	"gorm.io/gorm"
+	"gorm.io/gorm/schema"
+)
+
+// Embed the concrete dialectors to retain their transaction/savepoint and other
+// optional GORM interfaces. Only schema comparison needs normalization.
+type mysqlMigrationDialector struct{ mysql.Dialector }
+
+func (d mysqlMigrationDialector) Migrator(db *gorm.DB) gorm.Migrator {
+	return mysqlSchemaMigrator{d.Dialector.Migrator(db).(mysql.Migrator)}
+}
+
+type mysqlSchemaMigrator struct{ mysql.Migrator }
+
+func (m mysqlSchemaMigrator) MigrateColumn(value any, field *schema.Field, column gorm.ColumnType) error {
+	if !field.HasDefaultValue || !strings.EqualFold(column.DatabaseTypeName(), "decimal") {
+		return m.Migrator.MigrateColumn(value, field, column)
+	}
+	stored, ok := column.DefaultValue()
+	if !ok {
+		return m.Migrator.MigrateColumn(value, field, column)
+	}
+	storedNumber, storedErr := decimal.NewFromString(stored)
+	modelNumber, modelErr := decimal.NewFromString(field.DefaultValue)
+	if storedErr != nil || modelErr != nil || !storedNumber.Equal(modelNumber) {
+		return m.Migrator.MigrateColumn(value, field, column)
+	}
+	// MySQL pads decimal defaults (0 -> 0.000000). Skip only the equivalent
+	// default comparison, retaining type/size/null checks. AlterColumn still
+	// reads the original model, including its default.
+	comparisonField := *field
+	comparisonField.HasDefaultValue = false
+	comparisonField.DefaultValue = ""
+	comparisonField.DefaultValueInterface = nil
+	return m.Migrator.MigrateColumn(value, &comparisonField, columnWithoutDefault{column})
+}
+
+type migrationColumnType interface{ gorm.ColumnType }
+
+type columnWithoutDefault struct{ migrationColumnType }
+
+func (columnWithoutDefault) DefaultValue() (string, bool) { return "", false }
+
+type postgresMigrationDialector struct{ postgres.Dialector }
+
+func (d postgresMigrationDialector) Migrator(db *gorm.DB) gorm.Migrator {
+	return postgresSchemaMigrator{d.Dialector.Migrator(db).(postgres.Migrator)}
+}
+
+type postgresSchemaMigrator struct{ postgres.Migrator }
+
+func (m postgresSchemaMigrator) MigrateColumn(value any, field *schema.Field, column gorm.ColumnType) error {
+	if column.DatabaseTypeName() == "bpchar" && strings.HasPrefix(strings.ToLower(string(field.DataType)), "char(") {
+		// PostgreSQL reports CHAR(n) as bpchar. Normalize the name, retaining
+		// Length() so a real CHAR length change still triggers migration.
+		column = charColumnType{column}
+	}
+	return m.Migrator.MigrateColumn(value, field, column)
+}
+
+type charColumnType struct{ migrationColumnType }
+
+func (charColumnType) DatabaseTypeName() string { return "char" }