src,fs: calculate fs times without truncation

also added some missing bits that didn't make it into #12818

PR-URL: https://github.com/nodejs/node/pull/12607
Refs: https://github.com/nodejs/node/pull/12818
Reviewed-By: Timothy Gu <timothygu99@gmail.com>
Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: James M Snell <jasnell@gmail.com>

lib/fs.js

@@ -206,6 +206,8 @@ fs.Stats = Stats;
 // defining the properties in this fashion (explicitly with no loop or factory)
 // has been shown to be the most performant on V8 contemp.
 // Ref: https://github.com/nodejs/node/pull/12818
+// + 0.5 is added to the Dates to protect values from being rounded down
+// Ref: https://github.com/nodejs/node/pull/12607
 Object.defineProperties(Stats.prototype, {
   atime: {
     configurable: true,

src/node_file.cc

@@ -479,9 +479,9 @@ void FillStatsArray(double* fields, const uv_stat_t* s) {
   fields[9] = -1;
 #endif
   // Dates.
-#define X(idx, name)                                                          \
-  fields[idx] = (static_cast<double>(s->st_##name.tv_sec) * 1000) +           \
-                (static_cast<double>(s->st_##name.tv_nsec / 1000000));        \
+#define X(idx, name)                          \
+  fields[idx] = (s->st_##name.tv_sec * 1e3) + \
+                (s->st_##name.tv_nsec / 1e6); \
 
   X(10, atim)
   X(11, mtim)

test/parallel/test-fs-utimes.js

@@ -143,15 +143,21 @@ function testIt(atime, mtime, callback) {
 const stats = fs.statSync(__filename);
 
 // run tests
-const runTest = common.mustCall(testIt, 5);
+const runTest = common.mustCall(testIt, 6);
 
 runTest(new Date('1982-09-10 13:37'), new Date('1982-09-10 13:37'), function() {
   runTest(new Date(), new Date(), function() {
     runTest(123456.789, 123456.789, function() {
       runTest(stats.mtime, stats.mtime, function() {
-        runTest('123456', -1, common.mustCall(function() {
-          // done
-        }));
+        runTest('123456', -1, function() {
+          runTest(
+            new Date('2017-04-08T17:59:38.008Z'),
+            new Date('2017-04-08T17:59:38.008Z'),
+            common.mustCall(function() {
+              // done
+            })
+          );
+        });
       });
     });
   });