[DAFFODIL-2651] CLI pre-start mode - loads schema then accepts commands.

• Type: New Feature
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 3.2.1
• Component/s: CLI
• Assignee: Unassigned
• Reporter: Mike Beckerle
• Created: 08/Feb/22 20:39
• Updated: 08/Feb/22 20:39

Description

Using large schemas we've now found that the startup time of the CLI is becomming problematic for users. This is not only due to schema compilation time. Even loading a pre-compiled DFDL schema takes substantial time. 

Once you have saved a parser via the CLI save-parser command, it would be good to be able to start the CLI in a way that loads that parser, then enters a command line interpreter which assumes the parser being used is the one loaded. You can then issue parse and unparse commands which will execute without the startup cost of loading a parser. 

Another tool with long startup time, sbt, works this way. Rather than issue commands like 'sbt compile publishLocal', you start it up in interactive mode with just 'sbt'. You can then issue sub-commands repeatedly to 'compile' or 'publishLocal' or 'test' or "run' without paying the startup cost again.

This feature is something similar for the Daffodil CLI. An interactive mode where it either compiles or loads a  previously saved compiled schema, then enters an interactive control loop where individual commands can be issued.