inferred amounts use the cost commodity if known, like ledger (#69)

hledger-lib/Hledger/Data/Transaction.hs

@@ -141,17 +141,20 @@ isTransactionBalanced canonicalcommoditymap t =
       bvsum' = canonicaliseMixedAmountCommodity canonicalcommoditymap $ costOfMixedAmount bvsum
 
 -- | Ensure this transaction is balanced, possibly inferring a missing
--- amount or a conversion price first, or return an error message.
+-- amount or conversion price, or return an error message.
 --
--- Balancing is affected by the provided commodities' display precisions.
+-- Balancing is affected by commodity display precisions, so those may
+-- be provided.
 --
--- We can infer an amount when there are multiple real postings and
+-- We can infer a missing real amount when there are multiple real
--- exactly one of them is amountless; likewise for balanced virtual
+-- postings and exactly one of them is amountless (likewise for
--- postings. Inferred amounts are converted to cost basis when possible.
+-- balanced virtual postings). Inferred amounts are converted to cost
+-- basis when possible.
 --
--- We can infer a price when all amounts were specified and the sum of
+-- We can infer a conversion price when all real amounts are specified
--- real postings' amounts is exactly two non-explicitly-priced amounts in
+-- and the sum of real postings' amounts is exactly two
--- different commodities; likewise for balanced virtual postings.
+-- non-explicitly-priced amounts in different commodities (likewise
+-- for balanced virtual postings).
 balanceTransaction :: Maybe (Map.Map String Commodity) -> Transaction -> Either String Transaction
 balanceTransaction canonicalcommoditymap t@Transaction{tpostings=ps}
     | length rwithoutamounts > 1 || length bvwithoutamounts > 1
@@ -166,8 +169,8 @@ balanceTransaction canonicalcommoditymap t@Transaction{tpostings=ps}
       bvamounts = map pamount bvwithamounts
       t' = t{tpostings=map inferamount ps}
           where 
-            inferamount p | not (hasAmount p) && isReal p            = p{pamount = (- sum ramounts)}
+            inferamount p | not (hasAmount p) && isReal p            = p{pamount = costOfMixedAmount (- sum ramounts)}
-                          | not (hasAmount p) && isBalancedVirtual p = p{pamount = (- sum bvamounts)}
+                          | not (hasAmount p) && isBalancedVirtual p = p{pamount = costOfMixedAmount (- sum bvamounts)}
                           | otherwise                             = p
 
       -- maybe infer conversion prices, for real postings

tests/precision.test

@@ -1,21 +1,35 @@
 # http://code.google.com/p/hledger/issues/detail?id=23
 #
-# 1. with explicit price:
+# 1. original test case, this should balance since price precisions do
-# prices' commodities are unobserved, so $'s display precision here should be 2 not 4
+# not affect the canonical display precisions used for display and balancing
-bin/hledger -f - print --cost
+bin/hledger -f - print
 <<<
-2010/1/1
+2010/1/1 x
-   a  $0.00
+   A  55.3653 C @ 30.92189512 D
-   a  1C @ $1.0049
+   A  -1712 D
-   a
 >>>
-2010/01/01
+2010/01/01 x
-    a             0
+    A  55.3653 C @ 30.92189512 D
-    a         $1.00
+    A       -1712 D
-    a        $-1.00
 
 >>>=0
 
+## 1b. here $'s canonical display precision should be 2 not 4
+## XXX no, because the inferred amount $1.0049 is observed
+# bin/hledger -f - print --cost
+# <<<
+# 2010/1/1
+#    a  $0.00
+#    a  1C @ $1.0049
+#    a
+# >>>
+# 2010/01/01
+#     a             0
+#     a         $1.00
+#     a        $-1.00
+#
+# >>>=0
+
 # 2. and here the price should be printed with its original precision, not
 # the canonical display precision
 bin/hledger -f - print
@@ -28,7 +42,7 @@ bin/hledger -f - print
 2010/01/01
     a             0
     a  1C @ $1.0049
-    a  -1C @ $1.0049
+    a      $-1.0049
 
 >>>=0
 

tests/prices.test

@@ -8,7 +8,7 @@ bin/hledger -f- print
 >>>
 2011/01/01
     expenses:foreign currency  €100 @ $1.35
-    assets                     €-100 @ $1.35
+    assets                         $-135.00
 
 >>>=0
 
@@ -50,7 +50,7 @@ bin/hledger -f - print
 >>>
 2011/01/01
     expenses:foreign currency  €100 @@ $135
-    assets                     €-100 @@ $135
+    assets                            $-135
 
 >>>=0