lib: journal: Add support for exact assertions

hledger-lib/Hledger/Data/Journal.hs

@@ -568,11 +568,22 @@ journalCheckBalanceAssertions j =
 -- | Check a posting's balance assertion and return an error if it
 -- fails.
 checkBalanceAssertion :: Posting -> MixedAmount -> Either String ()
-checkBalanceAssertion p@Posting{ pbalanceassertion = Just ass } bal
+checkBalanceAssertion p@Posting{ pbalanceassertion = Just ass } bal =
+  foldl' fold (Right ()) amts
+    where fold (Right _) cass = checkBalanceAssertionCommodity p cass bal
+          fold err _ = err
+          amt = baamount ass
+          amts = amt : if baexact ass
+            then map (\a -> a{ aquantity = 0 }) $ amounts $ filterMixedAmount (\a -> acommodity a /= assertedcomm) bal
+            else []
+          assertedcomm = acommodity amt
+checkBalanceAssertion _ _ = Right ()
+
+checkBalanceAssertionCommodity :: Posting -> Amount -> MixedAmount -> Either String ()
+checkBalanceAssertionCommodity p amt bal
   | isReallyZeroAmount diff = Right ()
   | True    = Left err
-    where amt = baamount ass
-          assertedcomm = acommodity amt
+    where assertedcomm = acommodity amt
           actualbal = fromMaybe nullamt $ find ((== assertedcomm) . acommodity) (amounts bal)
           diff = amt - actualbal
           diffplus | isNegativeAmount diff == False = "+"
@@ -600,7 +611,6 @@ checkBalanceAssertion p@Posting{ pbalanceassertion = Just ass } bal
             (showAmount actualbal)
             (showAmount amt)
             (diffplus ++ showAmount diff)
-checkBalanceAssertion _ _ = Right ()
 
 -- | Fill in any missing amounts and check that all journal transactions
 -- balance, or return an error message. This is done after parsing all
@@ -720,7 +730,10 @@ checkInferAndRegisterAmounts (Right oldTx) = do
     inferFromAssignment p = do
       let acc = paccount p
       case pbalanceassertion p of
-        Just ba -> do
+        Just ba | baexact ba -> do
+          diff <- setMixedBalance acc $ Mixed [baamount ba]
+          fullPosting diff p
+        Just ba | otherwise -> do
           old <- liftModifier $ \Env{ eBalances = bals } -> HT.lookup bals acc
           let amt = baamount ba
               assertedcomm = acommodity amt

hledger-lib/Hledger/Data/Posting.hs

@@ -105,6 +105,7 @@ nullsourcepos = JournalSourcePos "" (1,1)
 nullassertion, assertion :: BalanceAssertion
 nullassertion = BalanceAssertion
                   {baamount=nullamt
+                  ,baexact=False
                   ,baposition=nullsourcepos
                   }
 assertion = nullassertion

hledger-lib/Hledger/Data/Types.hs

@@ -236,8 +236,11 @@ instance Show Status where -- custom show.. bad idea.. don't do it..
   show Pending   = "!"
   show Cleared   = "*"
 
+-- | The amount to compare an account's balance to, to verify that the history
+-- leading to a given point is correct or to set the account to a known value.
 data BalanceAssertion = BalanceAssertion {
-      baamount   :: Amount,
+      baamount   :: Amount,             -- ^ the expected value of a particular commodity
+      baexact    :: Bool,               -- ^ whether the assertion is exclusive, and doesn't allow other commodities alongside 'baamount'
       baposition :: GenericSourcePos
     } deriving (Eq,Typeable,Data,Generic,Show)
 

hledger-lib/Hledger/Read/Common.hs

@@ -721,10 +721,12 @@ balanceassertionp :: JournalParser m BalanceAssertion
 balanceassertionp = do
   sourcepos <- genericSourcePos <$> lift getSourcePos
   char '='
+  exact <- optional $ try $ char '='
   lift (skipMany spacenonewline)
   a <- amountp <?> "amount (for a balance assertion or assignment)" -- XXX should restrict to a simple amount
   return BalanceAssertion
     { baamount = a
+    , baexact = isJust exact
     , baposition = sourcepos
     }
 

hledger-lib/Hledger/Read/CsvReader.hs

@@ -752,7 +752,7 @@ transactionFromCsvRecord sourcepos rules record = t
         ,posting {paccount=account2, pamount=amount2, ptransaction=Just t}
         ]
       }
-    toAssertion (a, b) = BalanceAssertion{
+    toAssertion (a, b) = assertion{
       baamount   = a,
       baposition = b
       }

hledger-lib/Hledger/Read/JournalReader.hs

@@ -730,6 +730,8 @@ tests_JournalReader = tests "JournalReader" [
     ,test "quoted commodity symbol with digits" $ expectParse (postingp Nothing) "  a  1 \"DE123\"\n"
 
     ,test "balance assertion and fixed lot price" $ expectParse (postingp Nothing) "  a  1 \"DE123\" =$1 { =2.2 EUR} \n"
+
+    ,test "balance assertion over entire contents of account" $ expectParse (postingp Nothing) "  a  $1 == $1\n"
     ]
 
   ,tests "transactionmodifierp" [

tests/journal/balance-assertions.test

@@ -308,3 +308,51 @@ hledger -f - stats
 >>> /Transactions/
 >>>2
 >>>=0
+
+# 17. Exact assertions parse correctly
+hledger -f - stats
+<<<
+2016/1/1
+    a      $1
+    b
+
+2016/1/2
+    a         == $1
+>>> /Transactions/
+>>>2
+>>>=0
+
+# 18. Exact assertions consider entire account
+hledger -f - stats
+<<<
+2016/1/1
+    a      $1
+    b
+
+2016/1/2
+    a       1 zorkmids
+    b
+
+2016/1/3
+    a       0 == $1
+>>>2 /balance assertion error.*line 10, column 15/
+>>>=1
+
+# 19. Mix different commodities and exact assignments
+hledger -f - stats
+<<<
+2016/1/1
+    a      $1
+    a      -1 zorkmids
+    b
+
+2016/1/2
+    a         == $1
+    b      -1 zorkmids
+
+2016/1/3
+    b       0 = $-1
+    b       0 = 0 zorkmids
+>>> /Transactions/
+>>>2
+>>>=0