imp:print:beancount: add a second account name part if needed

Beancount requires account names to have at least two parts.

hledger-lib/Hledger/Write/Beancount.hs

@@ -139,34 +139,34 @@ type BeancountAccountNameComponent = AccountName
 
 -- | Convert a hledger account name to a valid Beancount account name.
 -- 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;
+-- prepends the letter A to any part which doesn't begin with a letter or number;
+-- adds a second :A part if there is only one part;
 -- 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
 -- raises an informative error.
 -- Ref: https://beancount.github.io/docs/beancount_language_syntax.html#accounts
 accountNameToBeancount :: AccountName -> BeancountAccountName
-accountNameToBeancount a =
-  dbg9 "beancount account name" $
-  accountNameFromComponents bs'
+accountNameToBeancount a = b
   where
-    bs =
+    cs1 =
       map accountNameComponentToBeancount $ accountNameComponents $
-      dbg9 "hledger account name  " $
-      a
-    bs' =
-      case bs of
-        b:_ | b `notElem` beancountTopLevelAccounts -> error' e
+      dbg9 "hledger account name  " a
+    cs2 =
+      case cs1 of
+        c:_ | c `notElem` beancountTopLevelAccounts -> error' e
           where
             e = T.unpack $ T.unlines [
-              "bad top-level account: " <> b
-              ,"in beancount account name:           " <> accountNameFromComponents bs
+              "bad top-level account: " <> c
+              ,"in beancount account name:           " <> accountNameFromComponents cs1
               ,"converted from hledger account name: " <> a
               ,"For Beancount, top-level accounts must be (or be --alias'ed to)"
               ,"one of " <> T.intercalate ", " beancountTopLevelAccounts <> "."
               -- ,"and not: " <> b
               ]
-        cs -> cs
+        [c] -> [c, "A"]
+        cs  -> cs
+    b = dbg9 "beancount account name" $ accountNameFromComponents cs2
 
 accountNameComponentToBeancount :: AccountName -> BeancountAccountNameComponent
 accountNameComponentToBeancount acctpart =

hledger/hledger.m4.md

@@ -842,7 +842,8 @@ Here are more details
 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).
+prepending `A` to account name parts which don't begin with a letter or digit,
+and appending `:A` to account names which have only one part).
 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),

hledger/test/print/beancount.test

@@ -9,10 +9,10 @@ $ hledger -f- print -O beancount
 >2 /bad top-level account/
 >=1
 
-# ** 2. Otherwise, accounts are encoded to suit beancount, and open directives are added.
+# ** 2. Otherwise, accounts are modified/encoded to suit beancount, and open directives are added.
 <
 2000-01-01
-  assets:a        0 ABC
+  assets          0 ABC
   equity:$-€:$    0 USD
 
 $ hledger -f- print -O beancount
@@ -34,13 +34,13 @@ $ hledger -f- print -O beancount
   assets    0 "size 2 pencils"
 
 $ hledger -f- print -O beancount
-2000-01-01 open Assets
+2000-01-01 open Assets:A
 
 2000-01-01 *
-    Assets               0 USD
-    Assets                 0 C
-    Assets               0 C21
-    Assets    0 SIZE-2-PENCILS
+    Assets:A               0 USD
+    Assets:A                 0 C
+    Assets:A               0 C21
+    Assets:A    0 SIZE-2-PENCILS
 
 >=
 
@@ -53,9 +53,9 @@ $ hledger -f- print -O beancount
   [c]
 
 $ hledger -f- print -O beancount
-2000-01-01 open Assets
+2000-01-01 open Assets:A
 
 2000-01-01 *
-    Assets           0 USD
+    Assets:A           0 USD
 
 >=