print: show all decimal places in assertion/assignment amounts (#1465)

Overriding the commodity style, per https://hledger.org/hledger.html#commodity-display-style.

hledger-lib/Hledger/Data/Journal.hs

@@ -981,7 +981,8 @@ journalApplyCommodityStyles j@Journal{jtxns=ts, jpricedirectives=pds} =
         fixtransaction t@Transaction{tpostings=ps} = t{tpostings=map fixposting ps}
         fixposting p = p{pamount=styleMixedAmount styles $ pamount p
                         ,pbalanceassertion=fixbalanceassertion <$> pbalanceassertion p}
-        fixbalanceassertion ba = ba{baamount=styleAmount styles $ baamount ba}
+        -- balance assertion amounts are always displayed, eg by print, at full precision, per docs
+        fixbalanceassertion ba = ba{baamount=setFullPrecision $ styleAmount styles $ baamount ba}
         fixpricedirective pd@PriceDirective{pdamount=a} = pd{pdamount=styleAmountExceptPrecision styles a}
 
 -- | Get the canonical amount styles for this journal, whether (in order of precedence):

hledger/test/journal/amounts-and-commodities.test

@@ -195,3 +195,18 @@ $ hledger -f - print
     (b)          2.00 $
 
 >=
+
+# Balance assertion amounts are always displayed at their full precision,
+# overriding commodity styles. (#1465)
+<
+commodity A 1.
+
+2021-01-01
+  (a)   0.001A
+  (a)   1.122A = 1.123A
+$ hledger -f - print
+2021-01-01
+    (a)               0
+    (a)             A 1 = A 1.123
+
+>=