From a303cad131cfffa4028e6ae558f3b2a016487852 Mon Sep 17 00:00:00 2001
From: Juerd Waalboer <juerd@tnx.nl>
Date: Sun, 17 Nov 2024 01:13:01 +0100
Subject: [PATCH] Remove support for unbalanced transaction, release v7.0.0

---
 UPGRADING.md              | 30 ++++++++++++++++++++++++++++++
 lib/RevBank/Cart/Entry.pm | 33 ++++++---------------------------
 plugins/undo              |  1 -
 revbank                   |  2 +-
 4 files changed, 37 insertions(+), 29 deletions(-)

diff --git a/UPGRADING.md b/UPGRADING.md
index 741a9f7..40bebc3 100644
--- a/UPGRADING.md
+++ b/UPGRADING.md
@@ -4,6 +4,36 @@
 2. Make a backup of your RevBank data and code repo(s).
 3. Read this file :)
 
+# (2024-10-18) RevBank 7.0.0
+
+Support for unbalanced entries has been removed, ensuring a pure double-entry
+bookkeeping system. Grep your log for the string `UNBALANCED` if you're not
+sure that all your custom plugins are already well-behaved. Note that since
+unbalanced transactions are no longer supported, transactions from before that
+change can't be reverted with `undo`.
+
+There are no other changes in this version.
+
+Since all transactions are now balanced, the sum of all the balances is
+`revbank.accounts` will remain fixed forever. It is recommended to make that
+sum equal to `0.00` (only once) by adding a dummy account which acts a
+retroactive opening balance:
+
+```sh
+perl -Ilib -MRevBank::Amount -lane'$sum += RevBank::Amount->parse_string($F[1])
+}{ printf "-deposits/balance %s\n", -$sum if $sum;' revbank.accounts >> revbank.accounts
+```
+
+From that point forward, the sum of all the values in the second column of the
+`revbank.accounts` file should forever be 0.00; if it's not, either someone
+tampered with the file or there is data corruption, and the cause should be
+investigated and corrected.
+
+```sh
+perl -Ilib -MRevBank::Amount -lane'$sum += RevBank::Amount->parse_string($F[1])
+}{ print $sum' revbank.accounts
+```
+
 # (2024-01-20) RevBank 6.0.0
 
 Note that the changes to `revbank.products` do NOT apply to `revbank.market`
diff --git a/lib/RevBank/Cart/Entry.pm b/lib/RevBank/Cart/Entry.pm
index 5a407a6..36d14f4 100644
--- a/lib/RevBank/Cart/Entry.pm
+++ b/lib/RevBank/Cart/Entry.pm
@@ -203,51 +203,30 @@ sub user($self, $new = undef) {
 }
 
 sub sanity_check($self) {
-    # Turnover and journals were implicit contras in previous versions of
-    # revbank, but old plugins may need upgrading to the new dual-entry system,
-    # so (for now) a zero sum is not required.
-
     my @contras = $self->contras;
 
     my $sum = RevBank::Amount->new(
         List::Util::sum(map $_->{amount}->cents, $self, @contras)
     );
 
-    # Although unbalanced transactiens are still allowed, a transaction with
-    # contras should at least not try to issue money that does not exist.
-    if ($sum > 0 and @contras and not $self->{FORCE_UNBALANCED}) {
+    if ($sum != 0) {
         local $ENV{REVBANK_DEBUG} = 1;
         my $message = join("\n",
             "BUG! (probably in $self->{caller})",
-            "This adds up to creating money that does not exist:",
+            "Unbalanced transactions are not possible in double-entry bookkeeping.",
             $self->as_printable,
             (
-                $sum == 2 * $self->{amount}
-                ? "Hint for the developer: contras for positive value should be negative values and vice versa."
+                !@contras
+                ? "Use \$entry->add_contra to balance the transaction."
+                : abs($sum) == 2 * abs($self->{amount})
+                ? "Contras for positive value should be negative values and vice versa."
                 : ()
             ),
-            "Cowardly refusing to create $sum out of thin air"
         );
         RevBank::Plugins::call_hooks("log_error", "UNBALANCED ENTRY $message");
         croak $message;
     }
 
-    if ($sum != 0) {
-        local $ENV{REVBANK_DEBUG} = 1;
-        my $forced = $self->{FORCE_UNBALANCED} ? " (FORCED)" : "";
-        RevBank::Plugins::call_hooks(
-            "log_warning",
-            "UNBALANCED ENTRY$forced in $self->{caller}: " . (
-                @contras
-                ? "sum of entry with contras ($sum) != 0.00"
-                : "transaction has no contras"
-            ) . ". This will be a fatal error in a future version of revbank.\n"
-            . "The unbalanced entry is:\n" . join("\n", $self->as_printable)
-        );
-
-        warn "$self->{caller} has created an unbalanced entry, which is deprecated. Support for unbalanced entries will be removed in a future version of RevBank.\n";
-    }
-
     return 1;
 }
 
diff --git a/plugins/undo b/plugins/undo
index 20046b8..08146e3 100644
--- a/plugins/undo
+++ b/plugins/undo
@@ -52,7 +52,6 @@ sub undo :Tab(&tab) ($self, $cart, $tid, @) {
                 my (undef, $user, $delta) = split " ", $line;
 
                 $entry ||= $cart->add(0, $description, { undo_transaction_id => $tid });
-                $entry->{FORCE_UNBALANCED} = 1;
 
                 $entry->add_contra($user, $delta, "Undo $tid");
             }
diff --git a/revbank b/revbank
index bf66a16..4d4d008 100755
--- a/revbank
+++ b/revbank
@@ -17,7 +17,7 @@ use RevBank::Messages;
 use RevBank::Cart;
 use RevBank::Prompt;
 
-our $VERSION = "6.2.4";
+our $VERSION = "7.0.0";
 
 our %HELP1 = (
     "abort" => "Abort the current transaction",