Revert "SERVER-38909 Permit empty update modifiers, treating as a no-op rather than an error"

This reverts commit 957febbf065a51cc278c66c72f5a81ff2630201c.

2 files changed, 12 insertions, 2 deletions

diff --git a/src/mongo/db/update/update_driver.cpp b/src/mongo/db/update/update_driver.cpp
index 2e0754b3f92..e0cf8dafb4c 100644
--- a/src/mongo/db/update/update_driver.cpp
+++ b/src/mongo/db/update/update_driver.cpp
@@ -73,6 +73,13 @@ modifiertable::ModifierType validateMod(BSONElement mod) {
                           << " not {" << mod << "}",
             mod.type() == BSONType::Object);
 
+    uassert(ErrorCodes::FailedToParse,
+            str::stream() << "'" << mod.fieldName()
+                          << "' is empty. You must specify a field like so: "
+                             "{"
+                          << mod.fieldName() << ": {<field>: ...}}",
+            !mod.embeddedObject().isEmpty());
+
     return modType;
 }
 
diff --git a/src/mongo/db/update/update_driver_test.cpp b/src/mongo/db/update/update_driver_test.cpp
index 743d3fbe67d..5c736122c65 100644
--- a/src/mongo/db/update/update_driver_test.cpp
+++ b/src/mongo/db/update/update_driver_test.cpp
@@ -121,8 +121,11 @@ TEST(Parse, EmptyMod) {
     boost::intrusive_ptr<ExpressionContextForTest> expCtx(new ExpressionContextForTest());
     UpdateDriver driver(expCtx);
     std::map<StringData, std::unique_ptr<ExpressionWithPlaceholder>> arrayFilters;
-    // Verifies that {$set: {}} is accepted.
-    ASSERT_DOES_NOT_THROW(driver.parse(fromjson("{$set: {}}"), arrayFilters));
+    ASSERT_THROWS_CODE_AND_WHAT(
+        driver.parse(fromjson("{$set:{}}"), arrayFilters),
+        AssertionException,
+        ErrorCodes::FailedToParse,
+        "'$set' is empty. You must specify a field like so: {$set: {<field>: ...}}");
 }
 
 TEST(Parse, WrongMod) {