Fix database double type precision bug (#709)

* Fix VariantToJson double data precision issue

* format the code

* add readme

* restore messaging test

* restore messaging integration test

* fix the test typo

* Update review feedback

Co-authored-by: Cynthia Jiang <cynthiajiang@google.com>

Author: cynthiajoan

app/src/variant_util.cc

@@ -55,7 +55,10 @@ static bool VariantToJson(const Variant& variant, bool prettyPrint,
       break;
     }
     case Variant::kTypeDouble: {
-      *ss << variant.double_value();
+      // IEEE 754 double-precision binary floating-point format: binary64 — The
+      // 53-bit significand precision gives from 15 to 17 significant decimal
+      // digits Default 32-bit only keeps 7 digit precision
+      *ss << std::setprecision(17) << variant.double_value();
       break;
     }
     case Variant::kTypeBool: {

database/integration_test/src/integration_test.cc

@@ -391,6 +391,7 @@ static const int kSimpleInt = 2;
 static const int kSimplePriority = 100;
 static const double kSimpleDouble = 3.4;
 static const bool kSimpleBool = true;
+static const double kLongDouble = 0.123456789876543;
 
 TEST_F(FirebaseDatabaseTest, TestSetAndGetSimpleValues) {
   const char* test_name = test_info_->name();
@@ -415,12 +416,15 @@ TEST_F(FirebaseDatabaseTest, TestSetAndGetSimpleValues) {
         ref.Child(test_name)
             .Child("IntAndPriority")
             .SetValueAndPriority(kSimpleInt, kSimplePriority);
+    firebase::Future<void> f7 =
+        ref.Child(test_name).Child("LongDouble").SetValue(kLongDouble);
     WaitForCompletion(f1, "SetSimpleString");
     WaitForCompletion(f2, "SetSimpleInt");
     WaitForCompletion(f3, "SetSimpleDouble");
     WaitForCompletion(f4, "SetSimpleBool");
     WaitForCompletion(f5, "SetSimpleTimestamp");
     WaitForCompletion(f6, "SetSimpleIntAndPriority");
+    WaitForCompletion(f7, "SetLongDouble");
   }
 
   // Get the values that we just set, and confirm that they match what we
@@ -439,12 +443,15 @@ TEST_F(FirebaseDatabaseTest, TestSetAndGetSimpleValues) {
         ref.Child(test_name).Child("Timestamp").GetValue();
     firebase::Future<firebase::database::DataSnapshot> f6 =
         ref.Child(test_name).Child("IntAndPriority").GetValue();
+    firebase::Future<firebase::database::DataSnapshot> f7 =
+        ref.Child(test_name).Child("LongDouble").GetValue();
     WaitForCompletion(f1, "GetSimpleString");
     WaitForCompletion(f2, "GetSimpleInt");
     WaitForCompletion(f3, "GetSimpleDouble");
     WaitForCompletion(f4, "GetSimpleBool");
     WaitForCompletion(f5, "GetSimpleTimestamp");
     WaitForCompletion(f6, "GetSimpleIntAndPriority");
+    WaitForCompletion(f7, "GetLongDouble");
 
     // Get the current time to compare to the Timestamp.
     int64_t current_time_milliseconds =
@@ -458,6 +465,7 @@ TEST_F(FirebaseDatabaseTest, TestSetAndGetSimpleValues) {
                 TimestampIsNear(current_time_milliseconds));
     EXPECT_EQ(f6.result()->value().AsInt64(), kSimpleInt);
     EXPECT_EQ(f6.result()->priority().AsInt64(), kSimplePriority);
+    EXPECT_EQ(f7.result()->value().AsDouble(), kLongDouble);
   }
 }
 

release_build_files/readme.md

@@ -567,6 +567,10 @@ workflow use only during the development of your app, not for publicly shipping
 code.
 
 ## Release Notes
+### Next Release
+-   Changes
+    -   General: Variant double type now support 64-bit while saving to json.
+        ([#1133](https://github.com/firebase/quickstart-unity/issues/1133)).
 
 ### 8.6.0
 -   Changes