imp:print:beancount output: more robust account/commodity encoding

Unsupported chars are now hex-encoded, not just converted to dashes.
This helps keep account and commodity names unique, especially with
the equity conversion account names generated by --infer-equity when
using currency symbols.
(Those could also be converted to ISO 4217 codes, in theory, but
for now we just hex encode them, which is easier to make robust.)

Also, Beancount commodity symbols are no longer enclosed in
hledger-style double quotes.

hledger-lib/Hledger/Write/Beancount.hs

@@ -26,6 +26,7 @@ import qualified Data.Text.Lazy as TL
 import qualified Data.Text.Lazy.Builder as TB
 import Safe (maximumBound)
 import Text.DocLayout (realLength)
+import Text.Printf
 import Text.Tabular.AsciiWide hiding (render)
 
 import Hledger.Utils
@@ -109,7 +110,7 @@ postingAsLinesBeancount elideamount acctwidth amtwidth p =
       | elideamount = [mempty]
       | otherwise   = showMixedAmountLinesB displayopts a'
         where
-          displayopts = defaultFmt{ displayZeroCommodity=True, displayForceDecimalMark=True }
+          displayopts = defaultFmt{ displayZeroCommodity=True, displayForceDecimalMark=True, displayQuotes=False }
           a' = mapMixedAmount amountToBeancount $ pamount p
     thisamtwidth = maximumBound 0 $ map wbWidth shownAmounts
 
@@ -137,12 +138,12 @@ type BeancountAccountName = AccountName
 type BeancountAccountNameComponent = AccountName
 
 -- | Convert a hledger account name to a valid Beancount account name.
--- It replaces non-supported characters with a dash, it prepends the letter B
--- to any part which doesn't begin with a letter or number, and it capitalises each part.
--- It's possible this could generate the same beancount name for distinct hledger account names.
+-- It replaces spaces with dashes and other non-supported characters with C<HEXBYTES>;
+-- prepends the letter A- to any part which doesn't begin with a letter or number;
+-- and capitalises each part.
 -- It also checks that the first part is one of the required english
 -- account names Assets, Liabilities, Equity, Income, or Expenses, and if not
--- it raises an informative error suggesting --alias.
+-- raises an informative error.
 -- Ref: https://beancount.github.io/docs/beancount_language_syntax.html#accounts
 accountNameToBeancount :: AccountName -> BeancountAccountName
 accountNameToBeancount a =
@@ -174,16 +175,19 @@ accountNameComponentToBeancount acctpart =
     Nothing -> ""
     Just (c,cs) ->
       textCapitalise $
-      T.map (\d -> if isBeancountAccountChar d then d else '-') $ T.cons c cs
+      T.concatMap (\d -> if isBeancountAccountChar d then (T.singleton d) else T.pack $ charToBeancount d) $ T.cons c cs
   where
     prependStartCharIfNeeded t =
       case T.uncons t of
         Just (c,_) | not $ isBeancountAccountStartChar c -> T.cons beancountAccountDummyStartChar t
         _ -> t
 
--- | Dummy valid starting character to prepend to Beancount account name parts if needed (B).
+-- | Dummy valid starting character to prepend to Beancount account name parts if needed (A).
 beancountAccountDummyStartChar :: Char
-beancountAccountDummyStartChar = 'B'
+beancountAccountDummyStartChar = 'A'
+
+charToBeancount :: Char -> String
+charToBeancount c = if isSpace c then "-" else printf "C%x" c
 
 -- XXX these probably allow too much unicode:
 
@@ -222,25 +226,24 @@ type BeancountCommoditySymbol = CommoditySymbol
 -- That is: 2-24 uppercase letters / digits / apostrophe / period / underscore / dash,
 -- starting with a letter, and ending with a letter or digit.
 -- Ref: https://beancount.github.io/docs/beancount_language_syntax.html#commodities-currencies
--- So this: removes any enclosing double quotes,
--- replaces some common currency symbols with currency codes,
+-- So this:
+-- replaces common currency symbols with their ISO 4217 currency codes,
 -- capitalises all letters,
--- replaces any invalid characters with a dash (-),
--- prepends a B if the first character is not a letter,
--- and appends a B if the last character is not a letter or digit.
--- It's possible this could generate unreadable commodity names,
--- or the same beancount name for distinct hledger commodity names.
+-- replaces spaces with dashes and other invalid characters with C<HEXBYTES>,
+-- prepends a C if the first character is not a letter,
+-- appends a C if the last character is not a letter or digit,
+-- and disables hledger's enclosing double quotes.
 --
 -- >>> commodityToBeancount ""
--- "B"
+-- "C"
 -- >>> commodityToBeancount "$"
 -- "USD"
 -- >>> commodityToBeancount "Usd"
 -- "USD"
 -- >>> commodityToBeancount "\"a1\""
 -- "A1"
 -- >>> commodityToBeancount "\"A 1!\""
--- "A-1-B"
+-- "A-1C21"
 --
 commodityToBeancount :: CommoditySymbol -> BeancountCommoditySymbol
 commodityToBeancount com =
@@ -251,16 +254,16 @@ commodityToBeancount com =
     Nothing ->
       com'
       & T.toUpper
-      & T.map (\d -> if isBeancountCommodityChar d then d else '-')
+      & T.concatMap (\d -> if isBeancountCommodityChar d then T.singleton d else T.pack $ charToBeancount d)
       & fixstart
       & fixend
   where
     fixstart bcom = case T.uncons bcom of
       Just (c,_) | isBeancountCommodityStartChar c -> bcom
-      _ -> "B" <> bcom
+      _ -> "C" <> bcom
     fixend bcom = case T.unsnoc bcom of
       Just (_,c) | isBeancountCommodityEndChar c -> bcom
-      _ -> bcom <> "B"
+      _ -> bcom <> "C"
 
 -- | Is this a valid character in the middle of a Beancount commodity name (a capital letter, digit, or '._-) ?
 isBeancountCommodityChar :: Char -> Bool

hledger/hledger.m4.md

@@ -834,38 +834,29 @@ hledger will try to adjust your data to suit Beancount.
 If you plan to export often, you may want to follow Beancount's conventions in your hledger data,
 to ease conversion. Eg use Beancount-friendly account names, currency codes instead of currency symbols,
 and avoid virtual postings, redundant cost notation, etc.
-
-Here are more details, included here for now
+Here are more details
 (see also "hledger and Beancount" <https://hledger.org/beancount.html>).
 
 #### Beancount account names
 
-hledger will try adjust your account names, if needed, to
-[Beancount account names](https://beancount.github.io/docs/beancount_language_syntax.html#accounts),
-by capitalising, replacing unsupported characters with `-`, and
-prepending `B` to parts which don't begin with a letter or digit.
-(It's possible for this to convert distinct hledger account names to the same beancount name.
-Eg, hledger's automatic equity conversion accounts can have currency symbols in their name,
-so `equity:conversion:$-€` becomes `equity:conversion:B---`.)
-
-In addition, you must ensure that the top level account names are `Assets`, `Liabilities`, `Equity`, `Income`, and `Expenses`,
-which Beancount requires.
+hledger will adjust your account names when needed, to make valid
+[Beancount account names](https://beancount.github.io/docs/beancount_language_syntax.html#accounts)
+(capitalising, replacing spaces with `-`, replacing other unsupported characters with `C<HEXBYTES>`,
+and prepending `A` to account name parts which don't begin with a letter or digit).
+However, you must ensure that all top level account names are one of the five required by Beancount:
+`Assets`, `Liabilities`, `Equity`, `Income`, or `Expenses`.
 If yours are named differently, you can use [account aliases](#alias-directive),
 usually in the form of `--alias` options, possibly stored in a [config file](#config-file).
 (An example: [hledger2beancount.conf](https://github.com/simonmichael/hledger/blob/master/examples/hledger2beancount.conf))
 
 #### Beancount commodity names
 
-hledger will adjust your commodity names, if needed, to
+hledger will adjust commodity names when needed, to make valid
 [Beancount commodity/currency names](https://beancount.github.io/docs/beancount_language_syntax.html#commodities-currencies),
-which must be 2-24 uppercase letters, digits, or `'`, `.`, `_`, `-`,
-beginning with a letter and ending with a letter or digit.
-hledger will convert known currency symbols to [ISO 4217 currency codes](https://en.wikipedia.org/wiki/ISO_4217#Active_codes).
-Otherwise, it will capitalise letters,
-replace unsupported characters with a dash (-),
-and prepend/append a "B" when needed.
-(It's possible for this to generate unreadable commodity names,
-or to convert distinct hledger commodity names to the same beancount name.)
+(which must be 2-24 uppercase letters, digits, or `'`, `.`, `_`, `-`, beginning with a letter and ending with a letter or digit).
+hledger will convert known currency symbols to [ISO 4217 currency codes](https://en.wikipedia.org/wiki/ISO_4217#Active_codes),
+capitalise letters, replace spaces with `-`, replace other unsupported characters with `C<HEXBYTES>`,
+and prepend/append a "C" when needed.
 
 #### Beancount virtual postings
 

hledger/test/print/beancount.test

@@ -0,0 +1,46 @@
+# * print command's beancount output format
+
+# ** 1. Unrecognised top level account names are rejected.
+<
+2000-01-01
+  other        0 ABC
+
+$ hledger -f- print -O beancount
+>2 /bad top-level account/
+>=1
+
+# ** 2. Otherwise, accounts are encoded to suit beancount, and open directives are added.
+<
+2000-01-01
+  assets:a        0 ABC
+  equity:$-€:$    0 USD
+
+$ hledger -f- print -O beancount
+2000-01-01 open Assets:A
+2000-01-01 open Equity:C24-C20ac:C24
+
+2000-01-01 *
+    Assets:A                       0 ABC
+    Equity:C24-C20ac:C24           0 USD
+
+>=
+
+# ** 3. Commodity symbols are converted to ISO 4217 codes, or encoded, to suit beancount.
+<
+2000-01-01
+  assets    $0
+  assets    0
+  assets    0!
+  assets    0 "size 2 pencils"
+
+$ hledger -f- print -O beancount
+2000-01-01 open Assets
+
+2000-01-01 *
+    Assets               0 USD
+    Assets                 0 C
+    Assets               0 C21
+    Assets    0 SIZE-2-PENCILS
+
+>=
+