fix: Reduce floating point precision required of extended json implementations (#369)

Updated the outputted extended json format for the BSON Double type
to conform to the reduced precision standard for cross language compatibility

NODE-2431

Author: nbbeeken

Diff for: lib/double.js

@@ -49,9 +49,17 @@ class Double {
       return { $numberDouble: `-${this.value.toFixed(1)}` };
     }
 
-    return {
-      $numberDouble: Number.isInteger(this.value) ? this.value.toFixed(1) : this.value.toString()
-    };
+    let $numberDouble;
+    if (Number.isInteger(this.value)) {
+      $numberDouble = this.value.toFixed(1);
+      if ($numberDouble.length >= 13) {
+        $numberDouble = this.value.toExponential(13).toUpperCase();
+      }
+    } else {
+      $numberDouble = this.value.toString();
+    }
+
+    return { $numberDouble };
   }
 
   /**

Diff for: test/node/bson_corpus_tests.js

@@ -58,9 +58,7 @@ const skipBSON = {
 
 const skipExtendedJSON = {
   'Timestamp with high-order bit set on both seconds and increment':
-    'Current BSON implementation of timestamp/long cannot hold these values - 1 too large.',
-  '1.23456789012345677E+18': 'NODE-2519',
-  '-1.23456789012345677E+18': 'NODE-2519'
+    'Current BSON implementation of timestamp/long cannot hold these values - 1 too large.'
 };
 
 const corpus = require('./tools/bson_corpus_test_loader');

Diff for: test/node/specs/bson-corpus/README.md

@@ -14,16 +14,22 @@
             "canonical_extjson": "{\"a\" : [{\"$numberInt\": \"10\"}]}"
         },
         {
-            "description": "Single Element Array with index set incorrectly",
+            "description": "Single Element Array with index set incorrectly to empty string",
             "degenerate_bson": "130000000461000B00000010000A0000000000",
             "canonical_bson": "140000000461000C0000001030000A0000000000",
             "canonical_extjson": "{\"a\" : [{\"$numberInt\": \"10\"}]}"
         },
         {
-            "description": "Single Element Array with index set incorrectly",
+            "description": "Single Element Array with index set incorrectly to ab",
             "degenerate_bson": "150000000461000D000000106162000A0000000000",
             "canonical_bson": "140000000461000C0000001030000A0000000000",
             "canonical_extjson": "{\"a\" : [{\"$numberInt\": \"10\"}]}"
+        },
+        {
+            "description": "Multi Element Array with duplicate indexes",
+            "degenerate_bson": "1b000000046100130000001030000a000000103000140000000000",
+            "canonical_bson": "1b000000046100130000001030000a000000103100140000000000",
+            "canonical_extjson": "{\"a\" : [{\"$numberInt\": \"10\"}, {\"$numberInt\": \"20\"}]}"
         }
     ],
     "decodeErrors": [

Diff for: test/node/specs/bson-corpus/array.json

@@ -25,6 +25,12 @@
             "description" : "Y10K",
             "canonical_bson" : "1000000009610000DC1FD277E6000000",
             "canonical_extjson" : "{\"a\":{\"$date\":{\"$numberLong\":\"253402300800000\"}}}"
+        },
+        {
+            "description": "leading zero ms",
+            "canonical_bson": "10000000096100D1D6D6CC3B01000000",
+            "relaxed_extjson": "{\"a\" : {\"$date\" : \"2012-12-24T12:15:30.001Z\"}}",
+            "canonical_extjson": "{\"a\" : {\"$date\" : {\"$numberLong\" : \"1356351330001\"}}}"
         }
     ],
     "decodeErrors": [