Improve UX of ROI command

[pandabrun]

Hello all,

First things first, thank you all for this very nice software ! 👍

Few days ago, I suggested via IRC (ping @adept) that the ROI command could be a little bit more ux-friendly by removing the need of the --pnl flag.

Here's an example of how I understand the ROI commands works now

1. Buy assets and record offset of pnl gain/loss

2019-06-20 Gettin' Rich
  Assets:cash   - $300
  Investment:APPL

2020-06-23 pnl valuation
  investment:APPL   = $25
  Unrealized:APPL

2. Enjoy roi

➜ hledger roi --investment='Investment:APPL' --pnl='Unrealized:APPL'
+---++------------+------------++---------------+----------+-------------+-----++-------+-------+
|   ||      Begin |        End || Value (begin) | Cashflow | Value (end) | PnL ||   IRR |   TWR |
+===++============+============++===============+==========+=============+=====++=======+=======+
| 1 || 2019-06-20 | 2020-06-23 ||             0 |      300 |         325 |  25 || 8.22% | 8.21% |
+---++------------+------------++---------------+----------+-------------+-----++-------+-------+

This approach requires to offset pnl of each investments into a dedicated account (eg. Unrealized:APPL in this case), which I found somehow not very practical since it spams my journal by 'not real' transaction.

Moreover, I guess this needs of offseting latest pnl is redundant with the P directive (cf. https://hledger.org/journal.html#declaring-market-prices) since the pnl is only a subtraction of the latest price minus the buying price and then could be easily calculated by the command.

In my opinion, the ROI commands should work this way:

1. Buy assets and record new price with the P directive

2019-06-20 Gettin' Rich ; buy some APPL
  Assets:cash   - $300
  Investment:APPL

P 2020-06-15 APPL  $ 280.80 ; record new price
P 2020-06-15 APPL  $ 290.43 ; same

And then the ROI command should be able to calculate the latest pnl for the selected commodity, maybe with a new flag like that for example

➜ hledger roi --investment='Investment:APPL' --commodity='AAPL'
+---++------------+------------++---------------+----------+-------------+-----++-------+-------+
|   ||      Begin |        End || Value (begin) | Cashflow | Value (end) | PnL ||   IRR |   TWR |
+===++============+============++===============+==========+=============+=====++=======+=======+
| 1 || 2019-06-20 | 2020-06-23 ||             0 |      300 |         325 |  25 || 8.22% | 8.21% |
+---++------------+------------++---------------+----------+-------------+-----++-------+-------+

Curious to have opinon around this wish, let me know if it seems relevant 😳

[simonmichael]

Thanks for the suggestion @pandabrun. Sounds good to me at least. Possibly requires progress on #1029 first ?

[adept]

This approach requires to offset pnl of each investments into a dedicated account (eg. Unrealized:APPL in this case), which I found somehow not very practical since it spams my journal by 'not real' transaction.

I am slightly late to the party with this comment, but I just want to note that there is no need to have a separate pnl account per investment - you use a single one for all of them.

Also, with #1483 roi should that P directives into account automatically, hopefully removing the need for manual valuation transactions (in your use-case, at least)