Hledger: generate automated transactions (postings), like ledger

[simonmichael]

_Original author: [email protected] (March 04, 2013 21:06:26)_

We'd like to have automated transactions or postings supported in hledger, eg for automatically generating interest postings based on another posting's amount. We have ledger's design (http://ledger-cli.org/3.0/doc/ledger3.html#Automated-Transactions) but other ideas could be considered.

_Original issue: http://code.google.com/p/hledger/issues/detail?id=99_

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[simonmichael]

I question this. We have hledger-interest which generates explicit transactions, which is more manual but allows much more control and predictability. Needs discussion/developers, closing.

[singpolyma]

This would be very useful for compatibility with ledger. the complexity mostly would come from interpreting the expression language, yes?

[simonmichael]

Yes interpreting the expression language, for a start. That alone seems a really big task. Also there's: finding out what that language is (from the C++ code, as neither the docs nor any person knows all of it). Troubleshooting/fixing/documenting the inevitable incompatibilities in the features that have been implemented. Tracking the language as Ledger evolves over time. Troubleshooting/testing/fixing/documenting all the interesting interactions we'll find between automated transactions and existing features.

Arguably it would be useful to at least specify and implement a compatible subset of it. It sounds like it would be useful for some folks, and it would make us seem more Ledger compatible - right ? But most Ledger users that try it will grumble that it doesn't support essential-thing-they-rely on; hledger users will be constantly asking for just one more feature; and it will add complexity and drag to the project which I'm not sure it will justify, even if we manage to attract a dedicated maintainer for it.

Soo.. that's my reaction today, but I'd love to be proven wrong. How interested are you really ? :-)

[simonmichael]

PS, I said "not sure it will justify" partly because I have philosophical/design doubts too, namely that generating "invisible transactions" adds a level of complexity and error potential for users that is completely absent from the current hledger, where everything is visible and explicit, the journal is readable by humans and accountants even without software, and we do everything we can to make things intuitive and minimise avoidable complexity.

All that said, if someone made it, I'd be first in line to try it and figure out how I can best use it. An add-on script might be a good way to start, for preprocessing journals with automated transactions.

[simonmichael]

The hledger-rewrite script is a way to experiment with this. It generates postings according to rules, but you run it explicitly as part of your command pipeline.

[ony]

@simonmichael, I've tried to use it for automatic budget bucketing. See budget.bash.
Unfortunately for ./budget.sh -f data/sample.journal it generates:

2008/06/03 * eat & shop
    expenses:food                   $1
    expenses:supplies               $1
    assets:cash                    $-2
    (Budget:Expenses:Food)           $-1

Instead of

2008/06/03 * eat & shop
    expenses:food                   $1
    expenses:supplies               $1
    assets:cash                    $-2
    (Budget:Expenses:Food)           $-1
    (Budget:Expenses:Supplies)           $-1

And of course when I remove all not:... that I tried to use to avoid assigning posting to multiple buckets:

2008/06/03 * eat & shop
    expenses:food                       $1
    expenses:supplies                   $1
    assets:cash                        $-2
    (Budget:Expenses:Food)             $-1
    (Budget:Expenses:Supplies)           $-1
    (Budget:Expenses)                  $-1

[simonmichael]

That's a pretty fascinating example of dark bash magic!

[simonmichael]

Noted some rewrite todos.

[simonmichael]

Here's my attempt with the current hledger-rewrite; clunky, but possible:

budget.sh

#!/bin/sh
cat "$@" \
| hledger-rewrite -f- expenses:food     --add-posting '(budget:food)      *-1' \
| hledger-rewrite -f- expenses:supplies --add-posting '(budget:supplies)  *-1' \
| hledger-rewrite -f- expenses:rent     --add-posting '(budget:rent)      *-1' \

$ budget.sh data/sample.journal
2008/01/01 income
    assets:bank:checking            $1
    income:salary                  $-1

2008/06/01 gift
    assets:bank:checking            $1
    income:gifts                   $-1

2008/06/02 save
    assets:bank:saving              $1
    assets:bank:checking           $-1

2008/06/03 * eat & shop
    expenses:food                $1
    expenses:supplies            $1
    assets:cash                 $-2
    (budget:food)               $-1
    (budget:supplies)           $-1

2008/12/31 * pay off
    liabilities:debts               $1
    assets:bank:checking           $-1

[linuxcaffe]

clunky? brilliant!

[ony]

@simonmichael, how you catch all other expenses that have no specific bucket in your budget? They are still expenses and you can't simply ignore them.
I thought I can target them via query expenses and not:expenses:food. But it didn't work out.

[simonmichael]

Hmm, it's difficult. Easier to make hledger-rewrite smarter I think.

[ony]

@simonmichael, I've started work on this ticket in my branch.

Current progress (hledger rewrite)

• Apply for every posting in transaction
• Full syntax of posting (including comments etc).
• ModifierTransactions from journal used for rewriting.
• mtvaluexpr is parsed as Query but it shouldn't refer to a current date. It is used together with command-line query to restrict what transactions being re-written.

See changes to tests/bin/rewrite.test for examples of automated transactions.

[simonmichael]

This functionality was merged in hledger 1.5. Latest docs: https://hledger.org/manual.html#auto-postings-transaction-modifiers .

[albins]

This functionality was merged in hledger 1.5. Latest docs: https://hledger.org/manual.html#auto-postings-transaction-modifiers .

This link is now broken!

[simonmichael]

The new url: https://hledger.org/journal.html#auto-postings-transaction-modifiers