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REPL Console

Interactive Gwen shell​

Gwen comes with a REPL (Read-Eval-Print-Loop) console. This is a command line shell that prompts you for steps, evaluates them, and outputs their status in real time. It enables you to experiment and observe the execution of steps as you enter (or paste) them which is very useful for debugging and analysis. Everything you enter is stored in a local history file and you can use the up and down arrow keys to recall previous inputs.

   __ ___      _____ _ __     _    
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Welcome to gwen-web v<version>
gweninterpreter.org

INFO - Default Gherkin feature dialect is: en
INFO - Environment context initialised
INFO - gwen-web.sh 

REPL Console

Enter steps to evaluate or type exit to quit..

gwen>

Starting the REPL​

To start a REPL session, invoke the Gwen CLI without specifying the -b (or --batch) switch.

Open REPL

To open a new REPL session:

npm run gwen

To load meta and open the REPL:

npm run gwen -- -m path/to/file.meta

To execute a feature and open the REPL:

npm run gwen path/to/file.feature

REPL Commands​

Once in the REPL, you can type help at the gwen> prompt to list the available commands.

Gwen REPL commands:

help
  Displays this help text

env [switch] ["filter"]
  Lists attributes in the current environment
    Only lists visible attributes if no options are specified
    switch : (optional)
      -a : to list all attributes in all scopes
      -f : to list all attributes in the feature (global) scope
    filter : (optional) literal string or regex filter expression

:paste|paste
   Enters paste mode (for evaluating multiline steps)

history
  Lists all previously entered commands

!#
  Executes a previously entered command (history bang operator)
    # : the history command number

Given|When|Then|And|But step-expression
  Evaluates a step
    step-expression : the step expression

exit|quit|bye
  Closes the REPL session and exits

ctrl-D
   If in paste mode: exits paste mode and interprets provided steps
   Otherwise: Closes REPL session and exits

tab
  Press the tab key for tab completion

Tab Completion​

You can press the tab key at any time to lookup and select available commands, DSL Steps and custom StepDefs.

Paste Mode​

Should you attempt to enter a multiline step into the REPL, you will quickly discover that the first line will execute and fail as soon as you enter it without waiting for you to enter the remaining lines first. To address this, we have introduced a paste mode.

To enable paste mode, type :paste into the REPL prompt. The following will appear..

gwen> :paste

REPL Console (paste mode)

Enter or paste steps and press ctrl-D to evaluate..

You will then be able to enter or paste a multiple step without anything being executed when you press the enter key for each new line. For example, you could enter the following without any lines being executed prematurely:

 When the following items are added
      | Item          |
      | Get the milk  |
      | Walk the dog  |

Then when you're ready to execute or want to exit the paste mode, insert a new empty line at the end and press press cntl-D. The REPL will then evaluate the step you entered before the empty line and return to the standard prompt when done.

Exiting paste mode, interpreting now..

gwen>  When the following items are added
            | Item          |
            | Get the milk  |
            | Walk the dog  |

INFO - Evaluating Step: When the following items are added
..
REPL Console

Enter steps to evaluate or type exit to quit..

gwen>

Exiting the REPL​

To exit the REPL, enter exit, quit, or bye or press ctrl-D at the gwen prompt.