DG: add-a-project use case wrong extension

[Silvernitro]

Extension 2a should be 1a. The app should throw an error before "showing a command result" if the user input is invalid.

[nus-se-bot]

Team's Response

Command result shown by Momentum is the error, the extension builds up on this. Hence there is no problem with the extension.

Items for the Tester to Verify

:question: Issue response

Team chose [response.Rejected]

• [x] I disagree

Reason for disagreement: Extension 2a should most definitely not "build up" on step 2 as mentioned by the team. Besides showing a Command Result, step 2 also updates the project list to show the addition. Since the extension concerns user input error/duplicate projects, it should not occur after step 2. It should occur before step 2 instead, which is why I suggested that the extension should be labelled as 1a since that would mean that the app would validate user input before executing step 2, which actually adds the project to the list. It does not make sense that the erroneous project that the user is trying to add is still created and added to the project list even before the app shows the error message.

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