fix nafai's bug: fail on empty account name components, don't just ignore

Ledger/Parse.hs

@@ -17,6 +17,7 @@ import System.IO (stdin)
 import Ledger.Utils
 import Ledger.Types
 import Ledger.Dates
+import Ledger.AccountName (accountNameFromComponents,accountNameComponents)
 import Ledger.Amount
 import Ledger.LedgerTransaction
 import Ledger.Posting
@@ -371,11 +372,17 @@ ledgerposting = do
 transactionaccountname :: GenParser Char LedgerFileCtx AccountName
 transactionaccountname = liftM2 (++) getParentAccount ledgeraccountname
 
--- | account names may have single spaces inside them, and are terminated by two or more spaces
+-- | Account names may have single spaces inside them, and are terminated
+-- by two or more spaces. They should have one or more components of at
+-- least one character, separated by the account separator char.
+
 ledgeraccountname :: GenParser Char st String
 ledgeraccountname = do
-    accountname <- many1 (nonspace <|> singlespace)
-    return $ striptrailingspace accountname
+    a <- many1 (nonspace <|> singlespace)
+    let a' = striptrailingspace a
+    when (accountNameFromComponents (accountNameComponents a') /= a')
+         (fail $ "accountname seems ill-formed: "++a')
+    return a'
     where 
       singlespace = try (do {spacenonewline; do {notFollowedBy spacenonewline; return ' '}})
       -- couldn't avoid consuming a final space sometimes, harmless

Tests.hs

@@ -160,6 +160,14 @@ $ printf "2009-01-01 x\n  a  2\n  b (b) b  -1\n  c\n" | hledger -f - print 2>&1;
 
 @
 
+Nafai's bug:
+@
+$ printf "2009/1/1 x\n a:  13\n b\n" | hledger -f - bal -E 2>&1
+"-" (line 2, column 1):
+unexpected " "
+accountname seems ill-formed: a:
+@
+
 -}
 -- other test tools:
 -- http://hackage.haskell.org/cgi-bin/hackage-scripts/package/test-framework
@@ -597,6 +605,12 @@ tests = [
     assertBool "ledgerTransaction should not include a comment in the description"
                    $ either (const False) ((== "a") . ltdescription) t
 
+  ,"ledgeraccountname" ~: do
+    assertBool "ledgeraccountname parses a normal accountname" $ (isRight $ parsewith ledgeraccountname "a:b:c")
+    assertBool "ledgeraccountname rejects an empty inner component" $ (isLeft $ parsewith ledgeraccountname "a::c")
+    assertBool "ledgeraccountname rejects an empty leading component" $ (isLeft $ parsewith ledgeraccountname ":b:c")
+    assertBool "ledgeraccountname rejects an empty trailing component" $ (isLeft $ parsewith ledgeraccountname "a:b:")
+
   ,"ledgerposting" ~: do
     parseWithCtx ledgerposting rawposting1_str `parseis` rawposting1