From eda5c7c568a611394135e3c8c0b06ff23ee4818d Mon Sep 17 00:00:00 2001
From: Arun Banala <arun.banala@mongodb.com>
Date: Thu, 20 May 2021 12:55:12 +0100
Subject: SERVER-57605 Expose Decimal128 equality comparison helper to shell

(cherry picked from commit 66f3c41018ac1850c98c0bef87eda74ff95a00de)
---
 jstests/decimal/decimal_constructors.js | 10 ++++++++++
 src/mongo/shell/shell_utils.cpp         | 14 ++++++++++++++
 src/mongo/shell/types.js                |  4 ++++
 3 files changed, 28 insertions(+)

diff --git a/jstests/decimal/decimal_constructors.js b/jstests/decimal/decimal_constructors.js
index 387a1bee1a9..8af1b6d0f62 100644
--- a/jstests/decimal/decimal_constructors.js
+++ b/jstests/decimal/decimal_constructors.js
@@ -37,4 +37,14 @@ assert.eq(col.find({'d': NumberLong(1)}).count(), '4');
 assert.eq(col.find({'d': NumberInt(1)}).count(), '4');
 // NaN and -NaN are both evaluated to NaN
 assert.eq(col.find({'d': NumberDecimal('NaN')}).count(), 2);
+
+// Verify that shell 'assert.eq' considers precision during comparison.
+assert.neq(NumberDecimal('1'), NumberDecimal('1.000'));
+assert.neq(NumberDecimal('0'), NumberDecimal('-0'));
+
+// Verify the behavior of 'numberDecimalsEqual' helper.
+assert(numberDecimalsEqual(NumberDecimal('10.20'), NumberDecimal('10.2')));
+assert.throws(
+    () => numberDecimalsEqual(NumberDecimal('10.20'), NumberDecimal('10.2'), "Third parameter"));
+assert.throws(() => numberDecimalsEqual(NumberDecimal('10.20'), "Wrong parameter type"));
 }());
diff --git a/src/mongo/shell/shell_utils.cpp b/src/mongo/shell/shell_utils.cpp
index 84e4c1ef4fd..396ca6ab655 100644
--- a/src/mongo/shell/shell_utils.cpp
+++ b/src/mongo/shell/shell_utils.cpp
@@ -461,6 +461,19 @@ BSONObj isInteractive(const BSONObj& a, void*) {
     return BSON("" << shellGlobalParams.runShell);
 }
 
+BSONObj numberDecimalsEqual(const BSONObj& input, void*) {
+    uassert(5760500, "numberDecimalsEqual expects two arguments", input.nFields() == 2);
+
+    BSONObjIterator i(input);
+    auto first = i.next();
+    auto second = i.next();
+    uassert(5760501,
+            "Both the arguments of numberDecimalsEqual should be of type 'NumberDecimal'",
+            first.type() == BSONType::NumberDecimal && second.type() == BSONType::NumberDecimal);
+
+    return BSON("" << first.numberDecimal().isEqual(second.numberDecimal()));
+}
+
 void installShellUtils(Scope& scope) {
     scope.injectNative("getMemInfo", JSGetMemInfo);
     scope.injectNative("_replMonitorStats", replMonitorStats);
@@ -474,6 +487,7 @@ void installShellUtils(Scope& scope) {
     scope.injectNative("convertShardKeyToHashed", convertShardKeyToHashed);
     scope.injectNative("fileExists", fileExistsJS);
     scope.injectNative("isInteractive", isInteractive);
+    scope.injectNative("numberDecimalsEqual", numberDecimalsEqual);
 
 #ifndef MONGO_SAFE_SHELL
     // can't launch programs
diff --git a/src/mongo/shell/types.js b/src/mongo/shell/types.js
index faaa5d00499..c371c3a6b95 100644
--- a/src/mongo/shell/types.js
+++ b/src/mongo/shell/types.js
@@ -389,6 +389,10 @@ if (typeof NumberDecimal !== 'undefined') {
     NumberDecimal.prototype.tojson = function() {
         return this.toString();
     };
+
+    NumberDecimal.prototype.equals = function(other) {
+        return compareNumberDecimals(this, other);
+    };
 }
 
 // ObjectId
-- 
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