journal: allow prices in balance assertions, but ignore (#824, #958)

hledger-lib/Hledger/Read/Common.hs

@@ -737,9 +737,11 @@ balanceassertionp = do
   char '='
   exact <- optional $ try $ char '='
   lift (skipMany spacenonewline)
-  a <- amountwithoutpricep <?> "unpriced amount (for a balance assertion or assignment)"
+  -- allow this amount to have a price, for compatibility, but discard it
+  a <- amountp <?> "amount (for a balance assertion or assignment)"
+  let a' = a{aprice=NoPrice}
   return BalanceAssertion
-    { baamount = a
+    { baamount = a'
     , baexact = isJust exact
     , baposition = sourcepos
     }

hledger-lib/hledger_journal.m4.md

@@ -439,7 +439,9 @@ One workaround is to isolate each commodity into its own subaccount:
 ### Assertions and prices
 
 Balance assertion (or assignment) amounts should not have a [price](#transaction-prices),
-as the meaning of that would be unclear.
+as the meaning of that is unclear.
+A price written there will be ignored.
+(hledger's [close](/manual.html#close) command used to generate balance assertions with prices.)
 
 ### Assertions and subaccounts