checker.rb in strong_migrations-0.6.3

- old
+ new

@@ -99,17 +99,54 @@
 
           if type.to_s == "json" && postgresql?
             raise_error :add_column_json
           end
         when :change_column
-          table, column, type = args
+          table, column, type, options = args
+          options ||= {}
 
           safe = false
-          # assume Postgres 9.1+ since previous versions are EOL
-          if postgresql? && type.to_s == "text"
-            found_column = connection.columns(table).find { |c| c.name.to_s == column.to_s }
-            safe = found_column && found_column.type == :string
+          existing_column = connection.columns(table).find { |c| c.name.to_s == column.to_s }
+          if existing_column
+            sql_type = existing_column.sql_type.split("(").first
+            if postgresql?
+              case type.to_s
+              when "string", "text"
+                # safe to change limit for varchar
+                safe = ["character varying", "text"].include?(sql_type)
+              when "numeric", "decimal"
+                # numeric and decimal are equivalent and can be used interchangably
+                safe = ["numeric", "decimal"].include?(sql_type) &&
+                  (
+                    (
+                      # unconstrained
+                      !options[:precision] && !options[:scale]
+                    ) || (
+                      # increased precision, same scale
+                      options[:precision] && existing_column.precision &&
+                      options[:precision] >= existing_column.precision &&
+                      options[:scale] == existing_column.scale
+                    )
+                  )
+              when "datetime", "timestamp", "timestamptz"
+                safe = ["timestamp without time zone", "timestamp with time zone"].include?(sql_type) &&
+                  postgresql_version >= Gem::Version.new("12") &&
+                  connection.select_all("SHOW timezone").first["TimeZone"] == "UTC"
+              end
+            elsif mysql? || mariadb?
+              case type.to_s
+              when "string"
+                # https://dev.mysql.com/doc/refman/5.7/en/innodb-online-ddl-operations.html
+                # https://mariadb.com/kb/en/innodb-online-ddl-operations-with-the-instant-alter-algorithm/#changing-the-data-type-of-a-column
+                # increased limit, but doesn't change number of length bytes
+                # 1-255 = 1 byte, 256-65532 = 2 bytes, 65533+ = too big for varchar
+                limit = options[:limit] || 255
+                safe = ["varchar"].include?(sql_type) &&
+                  limit >= existing_column.limit &&
+                  (limit <= 255 || existing_column.limit > 255)
+              end
+            end
           end
           raise_error :change_column unless safe
         when :create_table
           table, options = args
           options ||= {}
@@ -323,10 +360,11 @@
       if vars[:append]
         vars[:append] = vars[:append].gsub(/%(?!{)/, "%%") % vars
       end
 
       # escape % not followed by {
-      @migration.stop!(message.gsub(/%(?!{)/, "%%") % vars, header: header || "Dangerous operation detected")
+      message = message.gsub(/%(?!{)/, "%%") % vars if message.include?("%")
+      @migration.stop!(message, header: header || "Dangerous operation detected")
     end
 
     def constraint_str(statement, identifiers)
       # not all identifiers are tables, but this method of quoting should be fine
       code = statement % identifiers.map { |v| connection.quote_table_name(v) }