From 2ea6389bf7069644616b3ab7b9f67002c8554870 Mon Sep 17 00:00:00 2001
From: auto-revert-processor <dev-prod-dag@mongodb.com>
Date: Fri, 21 Jan 2022 06:48:21 +0000
Subject: Revert "SERVER-62322 Allow an empty object to be projected in
 $setWindowFields"

This reverts commit 2dac3294841b0374a94a5823f3726d5d02e27261.
---
 jstests/aggregation/sources/setWindowFields/parse.js        | 12 ++----------
 src/mongo/db/pipeline/document_source_set_window_fields.cpp |  9 +++------
 2 files changed, 5 insertions(+), 16 deletions(-)

diff --git a/jstests/aggregation/sources/setWindowFields/parse.js b/jstests/aggregation/sources/setWindowFields/parse.js
index c61839f27b8..63b92e952e0 100644
--- a/jstests/aggregation/sources/setWindowFields/parse.js
+++ b/jstests/aggregation/sources/setWindowFields/parse.js
@@ -213,7 +213,8 @@ assert.commandWorked(run({
 }));
 
 // Not every accumulator is automatically a window function.
-let err = assert.commandFailedWithCode(run({$setWindowFields: {output: {a: {b: {$sum: "$a"}}}}}),
+
+var err = assert.commandFailedWithCode(run({$setWindowFields: {output: {a: {b: {$sum: "$a"}}}}}),
                                        ErrorCodes.FailedToParse);
 assert.includes(err.errmsg, 'Expected a $-prefixed window function, b');
 
@@ -249,13 +250,4 @@ err = assert.commandFailedWithCode(
     }),
     ErrorCodes.FailedToParse);
 assert.includes(err.errmsg, 'Unrecognized window function, $summ');
-
-// Test that an empty object is a valid projected field.
-assert.commandWorked(coll.insert({}));
-assert.commandWorked(run({$setWindowFields: {output: {v: {$max: {mergeObjects: {}}}}}}));
-
-// However conflicting field paths is always an error.
-err = assert.commandFailedWithCode(
-    run({$setWindowFields: {output: {a: {$sum: 1}, 'a.b': {$sum: 1}}}}), 40176);
-assert.includes(err.errmsg, 'specification contains two conflicting paths');
 })();
diff --git a/src/mongo/db/pipeline/document_source_set_window_fields.cpp b/src/mongo/db/pipeline/document_source_set_window_fields.cpp
index d736f56845d..87cd3ad0267 100644
--- a/src/mongo/db/pipeline/document_source_set_window_fields.cpp
+++ b/src/mongo/db/pipeline/document_source_set_window_fields.cpp
@@ -461,11 +461,9 @@ DocumentSource::GetNextResult DocumentSourceInternalSetWindowFields::doGetNext()
     MutableDocument addFieldsSpec;
     for (auto&& [fieldName, function] : _executableOutputs) {
         try {
-            // Wrap the projected value in a $literal since there are limitations on a user-facing
-            // $addFields that we don't want to enforce here (e.g. empty object). If we hit a
-            // uassert while evaluating expressions on user data, delete the temporary table before
-            // aborting the operation.
-            addFieldsSpec.addField(fieldName, Value(DOC("$literal" << function->getNext())));
+            // If we hit a uassert while evaluating expressions on user data, delete the temporary
+            // table before aborting the operation.
+            addFieldsSpec.addField(fieldName, function->getNext());
         } catch (const DBException&) {
             _iterator.finalize();
             throw;
@@ -508,7 +506,6 @@ DocumentSource::GetNextResult DocumentSourceInternalSetWindowFields::doGetNext()
             _iterator.finalize();
             break;
     }
-
     auto projExec = projection_executor::AddFieldsProjectionExecutor::create(
         pExpCtx, addFieldsSpec.freeze().toBson());
 
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