There's a slight mismatch between what users experience as a command,
and how commands are defined in RevBank. Specifically, the common input
"<productid> <username>" is two separate commands: the first adds the
product to the cart, the second finalizes the transaction. This also
means that "<productid> <username> <productid> <username>" was four
separate commands, resulting in TWO transactions.
That's all fine and useful, but when using this advanced input method,
where input is split on whitespace, it lead to unexpected results if
there are insufficient arguments for the follow-up questions of a
command. For example, "take jantje 10 take pietje 10" will interpret the
second "take" as the description, then "pietje" als the first command of
a new transaction, and finally, "10" which is typically not a valid
command. It is much more likely that the user intended two separate
"take" commands and just forgot to provide the description argument, but
RevBank had no way of inferring that intent.
From this commit on, whenever the user intends to enter further input
words beyond the one that finalizes a transaction ($cart->checkout), a
';' is required. If trailing input is present, the checkout is refused
and the user gets a retry prompt.
Similarly, if the user indicates the intention of having finished a
command by inserting a ';' while there are insufficient words in the
command line to satisfy all follow-up prompts (command arguments), the
rest of the command line is rejected with a retry prompt.
There is, however, still no specific requirement for a ';' separator
after a command that does not finalize a transaction (e.g. "<productid>
<username>" or even "<productid> x2 <productid> <username>" remains
valid), or for a command that precedes a ';' to finalize a transaction
(e.g. "<productid>; <username>;" is also valid).
This change catches many, but not all, mistakes.
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