Gains and different currencies

[Oleg Bulatov]

Hello,

Recently I found a very strange output when I mixed --gain, --exchange, and filters:

~~~
] register Second --gain --exchange XXX
19-Apr-01 Commodities revalued <Revalued> -75.81 XXX 0
19-May-01 Commodities revalued <Revalued> -64.14 XXX 0
19-Jun-01 Commodities revalued <Revalued> -54.97 XXX 0
19-Jun-23 Commodities revalued <Revalued> 0.20 XXX 0
19-Jul-01 Commodities revalued <Revalued> -54.54 XXX -6.70 XXX
19-Aug-01 Commodities revalued <Revalued> -47.51 XXX -12.53 XXX
19-Sep-01 Commodities revalued <Revalued> -47.81 XXX -23.57 XXX
19-Oct-01 Commodities revalued <Revalued> -42.49 XXX -33.37 XXX
~~~

Two unexpected things:

1. The last column contains zeros while the column with posting values
has some values.
2. The first column contains some values for April 2019, but without
--exchange XXX the first record is for 19-Jun-23.

So far I think that the last column with running totals has right
numbers, and I don't understand the posting values.

Is it a bug or don't I understand something fundamental? I tried to
read the expressions for -G [1], but my ledger-fu isn't good enough to
understand them :)

Here's the journal data to reproduce:

~~~
P 2019/03/01 00:00:00 XXX YYY 1.1001
P 2019/04/01 00:00:00 XXX YYY 1.2002
P 2019/05/01 00:00:00 XXX YYY 1.3003
P 2019/06/01 00:00:00 XXX YYY 1.4004
P 2019/07/01 00:00:00 XXX YYY 1.5005
P 2019/08/01 00:00:00 XXX YYY 1.6006
P 2019/09/01 00:00:00 XXX YYY 1.7007
P 2019/10/01 00:00:00 XXX YYY 1.8008

2019/03/01 * Opening Balances
Assets:First 10000.00 XXX
Assets:Second 1000.00 YYY
Equity:Opening Balances

2019/06/23 * Recharge
Assets:Second 140.00 YYY @@ 100.00 XXX
Assets:First -100.00 XXX

2019/08/03 * Recharge
Assets:Second 160.06 YYY @@ 100.00 XXX
Assets:First -100.00 XXX
~~~

[1]: https://github.com/ledger/ledger/blob/0db50b5e31c85437ece1f70d52f8c3420ce35979/src/report.h#L687-L709

Oleg