display non-simple commodity names with double-quotes

This ensures print's output remains parseable. The other commands also
double-quote them, for consistency, like c++ ledger.

hledger-lib/Hledger/Data/Amount.hs

@@ -106,9 +106,10 @@ showAmount :: Amount -> String
 showAmount (Amount (Commodity {symbol="AUTO"}) _ _) = "" -- can appear in an error message
 showAmount a@(Amount (Commodity {symbol=sym,side=side,spaced=spaced}) _ pri) =
     case side of
-      L -> printf "%s%s%s%s" sym space quantity price
-      R -> printf "%s%s%s%s" quantity space sym price
+      L -> printf "%s%s%s%s" sym' space quantity price
+      R -> printf "%s%s%s%s" quantity space sym' price
     where
+      sym' = quoteCommoditySymbolIfNeeded sym
       space = if spaced then " " else ""
       quantity = showAmount' a
       price = case pri of (Just pamt) -> " @ " ++ showMixedAmount pamt

hledger-lib/Hledger/Data/Commodity.hs

@@ -16,6 +16,9 @@ import Data.Map ((!))
 
 nonsimplecommoditychars = "0123456789-.@;\n \""
 
+quoteCommoditySymbolIfNeeded s | any (`elem` nonsimplecommoditychars) s = "\"" ++ s ++ "\""
+                               | otherwise = s
+
 -- convenient amount and commodity constructors, for tests etc.
 
 unknown = Commodity {symbol="",   side=L,spaced=False,comma=False,precision=0}

tests/commodities.test

@@ -7,7 +7,7 @@ bin/hledger -f- print
    b
 >>>2 /parse error.*unexpected "0"/
 >>>= 1
-# 2. with quotes
+# 2. with quotes, ok; quotes appear in print output
 bin/hledger -f- print
 <<<
 2010-04-05 x
@@ -15,6 +15,17 @@ bin/hledger -f- print
    b
 >>>
 2010/04/05 x
-    a  10 DE0002635307
-    b  -10 DE0002635307
+    a  10 "DE0002635307"
+    b  -10 "DE0002635307"
 
+# 3. and in other reports too, I guess
+bin/hledger -f- balance
+<<<
+2010-04-05 x
+   a   10 "DE0002635307"
+   b
+>>>
+   10 "DE0002635307"  a
+  -10 "DE0002635307"  b
+--------------------
+    0 "DE0002635307"