include P amounts in canonicalisation (fixes #131)

Since market price amounts didn't contribute to the canonical commodity
styles, they were being reset to the null style. And this propagated to
the reported amounts when -V was in effect, causing much confusion.
Now, market prices contribute to canonicalisation and the expected
styles are preserved even with -V.

cf https://github.com/simonmichael/hledger/issues/131#issuecomment-133545140

hledger-lib/Hledger/Data/Journal.hs

@@ -583,13 +583,23 @@ journalConvertAmountsToCost j@Journal{jtxns=ts} = j{jtxns=map fixtransaction ts}
 --               Just (UnitPrice ma)  -> c:(concatMap amountCommodities $ amounts ma)
 --               Just (TotalPrice ma) -> c:(concatMap amountCommodities $ amounts ma)
 
--- | Get all this journal's (mixed) amounts, in the order parsed.
-journalMixedAmounts :: Journal -> [MixedAmount]
-journalMixedAmounts = map pamount . journalPostings
-
--- | Get all this journal's component amounts, roughly in the order parsed.
+-- | Get an ordered list of the amounts in this journal which will
+-- influence amount style canonicalisation. These are:
+--
+-- * amounts in market price directives (in parse order)
+-- * amounts in postings (in parse order)
+--
+-- Amounts in default commodity directives also influence
+-- canonicalisation, but earlier, as amounts are parsed.
+-- Amounts in posting prices are not used for canonicalisation.
+--
 journalAmounts :: Journal -> [Amount]
-journalAmounts = concatMap flatten . journalMixedAmounts where flatten (Mixed as) = as
+journalAmounts j =
+  concat
+   [map mpamount $ jmarketprices j
+   ,concatMap flatten $ map pamount $ journalPostings j
+   ]
+  where flatten (Mixed as) = as
 
 -- | The fully specified date span enclosing the dates (primary or secondary)
 -- of all this journal's transactions and postings, or DateSpan Nothing Nothing

tests/journal/market-prices.test

@@ -0,0 +1,25 @@
+# market prices defined with the P directive are used by -V/--value.
+
+# 1. market prices (a) are affected by D directives and (b) contribute
+# to amount style canonicalisation.
+# (https://github.com/simonmichael/hledger/issues/131#issuecomment-133545140)
+
+hledger -f- balance -V
+<<<
+D 1000.00 H
+
+P 2015/08/14 EEEE   41.66
+P 2015/08/14 FFFF   74.62
+P 2015/08/14 GGGG  32.39
+
+2015/08/15
+    a  2.4120 EEEE @@ 100
+    a  0.3350 FFFF @@ 25
+    a  0.7718 GGGG @@ 25
+    b
+>>>
+            150.48 H  a
+           -150.00 H  b
+--------------------
+              0.48 H
+>>>=0