rpc: Make ValueFromAmount always return 8 decimals

This is the format that was always returned to JSON clients.
The difference was not noticed before, because VREAL values
are post-processed by univalue.

By implementing the functionality directly it breaks the dependency
of rpcserver on utilmoneystr. FormatMoney is now only used for debugging
purposes.

To test, port over the formatting tests from util_tests.cpp to
rpc_tests.cpp.

src/rpcserver.cpp

@@ -11,7 +11,6 @@
 #include "sync.h"
 #include "ui_interface.h"
 #include "util.h"
-#include "utilmoneystr.h"
 #include "utilstrencodings.h"
 #ifdef ENABLE_WALLET
 #include "wallet/wallet.h"
@@ -133,7 +132,12 @@ CAmount AmountFromValue(const UniValue& value)
 
 UniValue ValueFromAmount(const CAmount& amount)
 {
-    return UniValue(UniValue::VREAL, FormatMoney(amount));
+    bool sign = amount < 0;
+    int64_t n_abs = (sign ? -amount : amount);
+    int64_t quotient = n_abs / COIN;
+    int64_t remainder = n_abs % COIN;
+    return UniValue(UniValue::VNUM,
+            strprintf("%s%d.%08d", sign ? "-" : "", quotient, remainder));
 }
 
 uint256 ParseHashV(const UniValue& v, string strName)

src/test/rpc_tests.cpp

@@ -120,6 +120,29 @@ BOOST_AUTO_TEST_CASE(rpc_format_monetary_values)
     BOOST_CHECK(ValueFromAmount(100000000LL).write() == "1.00000000");
     BOOST_CHECK(ValueFromAmount(2099999999999990LL).write() == "20999999.99999990");
     BOOST_CHECK(ValueFromAmount(2099999999999999LL).write() == "20999999.99999999");
+
+    BOOST_CHECK_EQUAL(ValueFromAmount(0).write(), "0.00000000");
+    BOOST_CHECK_EQUAL(ValueFromAmount((COIN/10000)*123456789).write(), "12345.67890000");
+    BOOST_CHECK_EQUAL(ValueFromAmount(-COIN).write(), "-1.00000000");
+    BOOST_CHECK_EQUAL(ValueFromAmount(-COIN/10).write(), "-0.10000000");
+
+    BOOST_CHECK_EQUAL(ValueFromAmount(COIN*100000000).write(), "100000000.00000000");
+    BOOST_CHECK_EQUAL(ValueFromAmount(COIN*10000000).write(), "10000000.00000000");
+    BOOST_CHECK_EQUAL(ValueFromAmount(COIN*1000000).write(), "1000000.00000000");
+    BOOST_CHECK_EQUAL(ValueFromAmount(COIN*100000).write(), "100000.00000000");
+    BOOST_CHECK_EQUAL(ValueFromAmount(COIN*10000).write(), "10000.00000000");
+    BOOST_CHECK_EQUAL(ValueFromAmount(COIN*1000).write(), "1000.00000000");
+    BOOST_CHECK_EQUAL(ValueFromAmount(COIN*100).write(), "100.00000000");
+    BOOST_CHECK_EQUAL(ValueFromAmount(COIN*10).write(), "10.00000000");
+    BOOST_CHECK_EQUAL(ValueFromAmount(COIN).write(), "1.00000000");
+    BOOST_CHECK_EQUAL(ValueFromAmount(COIN/10).write(), "0.10000000");
+    BOOST_CHECK_EQUAL(ValueFromAmount(COIN/100).write(), "0.01000000");
+    BOOST_CHECK_EQUAL(ValueFromAmount(COIN/1000).write(), "0.00100000");
+    BOOST_CHECK_EQUAL(ValueFromAmount(COIN/10000).write(), "0.00010000");
+    BOOST_CHECK_EQUAL(ValueFromAmount(COIN/100000).write(), "0.00001000");
+    BOOST_CHECK_EQUAL(ValueFromAmount(COIN/1000000).write(), "0.00000100");
+    BOOST_CHECK_EQUAL(ValueFromAmount(COIN/10000000).write(), "0.00000010");
+    BOOST_CHECK_EQUAL(ValueFromAmount(COIN/100000000).write(), "0.00000001");
 }
 
 static UniValue ValueFromString(const std::string &str)