journal: make balance assertions exact again (#941)

Going with option 1b from the issue: calculated and asserted amounts
are compared exactly, disregarding display precision.
But now balance assertion failure messages show those exact amounts at
full precision, avoiding confusion.

hledger-lib/Hledger/Data/Journal.hs

@@ -583,50 +583,53 @@ checkBalanceAssertion p@Posting{pbalanceassertion=Just (BalanceAssertion{baamoun
                     | otherwise = []
 checkBalanceAssertion _ _ = Right ()
 
--- | Does the difference between the asserted balance
--- and (the corresponding part of) the actual balance
--- appear as zero, when rendered to the greater of
--- 1. the standard display precision for the commodity
--- 2. the full precision of the asserted amount ?
--- The posting is used when creating an error message.
+-- | Are the asserted balance and the actual balance
+-- exactly equal (disregarding display precision) ?
+-- The posting is used for creating an error message.
 checkBalanceAssertionCommodity :: Posting -> Amount -> MixedAmount -> Either String ()
 checkBalanceAssertionCommodity p assertedamt actualbal
-  | isZeroAmount diff = Right ()
-  | True              = Left err
+  | pass      = Right ()
+  | otherwise = Left err
     where
-      diff =
-        -- traceWith (("diff:"++).showAmountDebug) $
+      assertedcomm = acommodity assertedamt
+      actualbalincommodity = fromMaybe nullamt $ find ((== assertedcomm) . acommodity) (amounts actualbal)
+      pass =
+        aquantity
         -- traceWith (("asserted:"++).showAmountDebug)
-        assertedamt -
+        assertedamt ==
+        aquantity
         -- traceWith (("actual:"++).showAmountDebug)
         actualbalincommodity
-      assertedcomm = acommodity assertedamt
-      actualbalincommodity = fromMaybe nullamt $ find ((== assertedcomm) . acommodity) (amounts actualbal)
-      diffplus | isNegativeAmount diff == False = "+"
-               | otherwise = ""
+      diff = aquantity assertedamt - aquantity actualbalincommodity
       err = printf (unlines
-                    [ "balance assertion error%s",
-                      "after posting:",
-                      "%s",
-                      "balance assertion details:",
+                    [ "balance assertion: %s",
+                      "\nassertion details:",
                       "date:       %s",
                       "account:    %s",
                       "commodity:  %s",
-                      "calculated: %s",
-                      "asserted:   %s (difference: %s)"
+                      -- "display precision:  %d",
+                      "calculated: %s", -- (at display precision: %s)",
+                      "asserted:   %s", -- (at display precision: %s)",
+                      "difference: %s"
                     ])
         (case ptransaction p of
-           Nothing -> ":" -- shouldn't happen
-           Just t ->  printf " in %s:\nin transaction:\n%s"
-                      (showGenericSourcePos pos) (chomp $ showTransaction t) :: String
-                        where pos = baposition $ fromJust $ pbalanceassertion p)
-        (showPostingLine p)
+           Nothing -> "?" -- shouldn't happen
+           Just t ->  printf "%s\ntransaction:\n%s"
+                        (showGenericSourcePos pos)
+                        (chomp $ showTransaction t)
+                        :: String
+                        where
+                          pos = baposition $ fromJust $ pbalanceassertion p
+        )
         (showDate $ postingDate p)
         (T.unpack $ paccount p) -- XXX pack
         assertedcomm
-        (showAmount actualbalincommodity)
-        (showAmount assertedamt)
-        (diffplus ++ showAmount diff)
+        -- (asprecision $ astyle actualbalincommodity)  -- should be the standard display precision I think
+        (show $ aquantity actualbalincommodity)
+        -- (showAmount actualbalincommodity)
+        (show $ aquantity assertedamt)
+        -- (showAmount assertedamt)
+        (show diff)
 
 -- | Fill in any missing amounts and check that all journal transactions
 -- balance and all balance assertions pass, or return an error message.

hledger-lib/Hledger/Data/Transaction.hs

@@ -35,7 +35,7 @@ module Hledger.Data.Transaction (
   showTransaction,
   showTransactionUnelided,
   showTransactionUnelidedOneLineAmounts,
-  showPostingLine,
+  -- showPostingLine,
   showPostingLines,
   -- * GenericSourcePos
   sourceFilePath,
@@ -246,14 +246,17 @@ postingAsLines elideamount onelineamounts pstoalignwith p = concat [
       case renderCommentLines (pcomment p) of []   -> ("",[])
                                               c:cs -> (c,cs)
 
--- | Show a posting's status, account name and amount on one line. 
--- Used in balance assertion errors.
-showPostingLine p =
-  indent $
-  if pstatus p == Cleared then "* " else "" ++
-  showAccountName Nothing (ptype p) (paccount p) ++
-  "    " ++
-  showMixedAmountOneLine (pamount p)
+-- | Render a posting, simply. Used in balance assertion errors.
+-- showPostingLine p =
+--   indent $
+--   if pstatus p == Cleared then "* " else "" ++  -- XXX show !
+--   showAccountName Nothing (ptype p) (paccount p) ++
+--   "    " ++
+--   showMixedAmountOneLine (pamount p) ++
+--   assertion
+--   where
+--     -- XXX extract, handle ==
+--     assertion = maybe "" ((" = " ++) . showAmountWithZeroCommodity . baamount) $ pbalanceassertion p
 
 -- | Render a posting, at the appropriate width for aligning with
 -- its siblings if any. Used by the rewrite command. 

hledger-lib/hledger_journal.m4.md

@@ -468,71 +468,11 @@ flag or `real:` query.
 
 ### Assertions and precision
 
-A [commodity directive](http://hledger.org/journal.html#declaring-commodities)
-which limits the display precision, can affect assertions.
-
-In general, hledger balance assertions should pass or fail as you would
-expect from doing visual inspection and manual arithmetic with the amounts
-shown in reports and error messages, ie at display precision.
-
-More specifically, currently assertions pass if the difference between asserted
-and actual amounts appears to be zero, when rendered to the greater of
-the standard display precision and the asserted amount's precision.
-Here are some examples of this in action.
-
-Asserting the exact balance:
-```journal
-commodity $1000.00
-
-2019/01/01
-    (a)             $0.006
-
-2019/01/02
-    (a)             $1.00  = $1.006
-
-; Actual balance:       1.006
-; Asserted balence:     1.006
-; Difference:           0.000
-; Standard & asserted precisions: 2, 3
-; Difference rendered:  0.000
-; Result:               pass
-```
-
-Asserting the balance rounded to fewer decimal places:
-```journal
-commodity $1000.00
-
-2019/01/01
-    (a)             $0.006
-
-2019/01/02
-    (a)             $1.00  = $1.01
-
-; Actual balance:       1.006
-; Asserted balence:     1.01
-; Difference:           0.004
-; Standard & asserted precisions: 2, 2
-; Difference rendered:  0.00
-; Result:               pass
-```
-
-Asserting an inexact balance with too many decimal places (fails):
-```journal
-commodity $1000.00
-
-2019/01/01
-    (a)             $0.006
-
-2019/01/02
-    (a)             $1.00  = $1.0061
-
-; Actual balance:       1.006
-; Asserted balence:     1.0061
-; Difference:           0.0001
-; Standard & asserted precisions: 2, 4
-; Difference rendered:  0.0001
-; Result:               fail
-```
+Balance assertions compare the exactly calculated amounts,
+which are not always what is shown by reports.
+Eg a [commodity directive](http://hledger.org/journal.html#declaring-commodities)
+may limit the display precision, but this will not affect balance assertions.
+Balance assertion failure messages show exact amounts.
 
 ## Balance Assignments
 

tests/journal/balance-assertions.test

@@ -57,7 +57,7 @@ hledger -f - stats
   b   $-1  = $-3
 
 >>>
->>>2 /balance assertion error.*line 11, column 12/
+>>>2 /balance assertion.*line 11, column 12/
 >>>=1
 
 # 4. should also work without commodity symbols
@@ -335,7 +335,7 @@ hledger -f - stats
 
 2016/1/3
     a       0 == $1
->>>2 /balance assertion error.*line 10, column 15/
+>>>2 /balance assertion.*line 10, column 15/
 >>>=1
 
 # 19. Mix different commodities and exact assignments
@@ -366,17 +366,7 @@ hledger -f- stats
 >>>2 /unexpected '@'/
 >>>=1
 
-# 21. With a commodity directive limiting the display precision. 
-# Assertions pass if the difference between asserted and actual amounts
-# appears to be zero, when rendered to the greater of the standard 
-# display precision and the asserted amount's precision. 
-# Here,
-# Actual balance:       1.006
-# Asserted balence:     1.006
-# Difference:           0.000
-# Standard & asserted precisions: 2, 3
-# Difference rendered:  0.000
-# Result:               pass
+# 21. The exact amounts are compared; display precision does not affect assertions.
 hledger -f- stats
 <<<
 commodity $1000.00
@@ -391,13 +381,7 @@ commodity $1000.00
 >>>2
 >>>=0
 
-# 22. A rounded assertion amount can also pass. Here,
-# Actual balance:       1.006
-# Asserted balence:     1.01
-# Difference:           0.004
-# Standard & asserted precisions: 2, 2
-# Difference rendered:  0.00
-# Result:               pass
+# 22. This fails
 hledger -f- stats
 <<<
 commodity $1000.00
@@ -408,17 +392,10 @@ commodity $1000.00
 2019/01/02
     (a)             $1.00  = $1.01
 
->>> /Transactions/
->>>2
->>>=0
+>>>2 /difference: 0\.004/
+>>>=1
 
-# 23. A more precise assertion amount can fail. Here,
-# Actual balance:       1.006
-# Asserted balence:     1.0061
-# Difference:           0.0001
-# Standard & asserted precisions: 2, 4
-# Difference rendered:  0.0001
-# Result:               fail
+# 23. This fails
 hledger -f- stats
 <<<
 commodity $1000.00
@@ -429,6 +406,5 @@ commodity $1000.00
 2019/01/02
     (a)             $1.00  = $1.0061
 
->>>
->>>2 /difference: \+\$0\.0001/
+>>>2 /difference: 0\.0001/
 >>>=1