SERVER-29676 arrayToObject should not error out on explicit value of null or undefined for value

Closes #1158

Signed-off-by: Tess Avitabile <tess.avitabile@mongodb.com>
(cherry picked from commit 21f0ae2d10531d0897c55c7be16f783abb6a8e1d)

2 files changed, 42 insertions, 28 deletions

diff --git a/jstests/aggregation/expressions/arrayToObject.js b/jstests/aggregation/expressions/arrayToObject.js
index 9e3b4614665..5ec450a79eb 100644
--- a/jstests/aggregation/expressions/arrayToObject.js
+++ b/jstests/aggregation/expressions/arrayToObject.js
@@ -52,48 +52,62 @@
     result = coll.aggregate([{$match: {_id: 6}}, array_to_object_expr]).toArray();
     assert.eq(result, [{_id: 6, collapsed: null}]);
 
-    assert.writeOK(coll.insert({_id: 7, expanded: [{"k": "price", "v": 24}, ["item", "apple"]]}));
-    assertErrorCode(coll, [{$match: {_id: 7}}, array_to_object_expr], 40391);
+    assert.writeOK(coll.insert({_id: 7, expanded: [{"k": "price", "v": null}]}));
+    result = coll.aggregate([{$match: {_id: 7}}, array_to_object_expr]).toArray();
+    assert.eq(result, [{_id: 7, collapsed: {"price": null}}]);
 
-    assert.writeOK(coll.insert({_id: 8, expanded: [["item", "apple"], {"k": "price", "v": 24}]}));
-    assertErrorCode(coll, [{$match: {_id: 8}}, array_to_object_expr], 40396);
+    assert.writeOK(coll.insert({_id: 8, expanded: [{"k": "price", "v": undefined}]}));
+    result = coll.aggregate([{$match: {_id: 8}}, array_to_object_expr]).toArray();
+    assert.eq(result, [{_id: 8, collapsed: {"price": undefined}}]);
 
-    assert.writeOK(coll.insert({_id: 9, expanded: "string"}));
-    assertErrorCode(coll, [{$match: {_id: 9}}, array_to_object_expr], 40386);
+    assert.writeOK(coll.insert({_id: 9, expanded: [{"k": "price", "v": 24}, ["item", "apple"]]}));
+    assertErrorCode(coll, [{$match: {_id: 9}}, array_to_object_expr], 40391);
 
-    assert.writeOK(coll.insert({_id: 10, expanded: ObjectId()}));
-    assertErrorCode(coll, [{$match: {_id: 10}}, array_to_object_expr], 40386);
+    assert.writeOK(coll.insert({_id: 10, expanded: [["item", "apple"], {"k": "price", "v": 24}]}));
+    assertErrorCode(coll, [{$match: {_id: 10}}, array_to_object_expr], 40396);
 
-    assert.writeOK(coll.insert({_id: 11, expanded: NumberLong(0)}));
+    assert.writeOK(coll.insert({_id: 11, expanded: "string"}));
     assertErrorCode(coll, [{$match: {_id: 11}}, array_to_object_expr], 40386);
 
-    assert.writeOK(coll.insert({_id: 12, expanded: [0]}));
-    assertErrorCode(coll, [{$match: {_id: 12}}, array_to_object_expr], 40398);
+    assert.writeOK(coll.insert({_id: 12, expanded: ObjectId()}));
+    assertErrorCode(coll, [{$match: {_id: 12}}, array_to_object_expr], 40386);
 
-    assert.writeOK(coll.insert({_id: 13, expanded: [["missing_value"]]}));
-    assertErrorCode(coll, [{$match: {_id: 13}}, array_to_object_expr], 40397);
+    assert.writeOK(coll.insert({_id: 13, expanded: NumberLong(0)}));
+    assertErrorCode(coll, [{$match: {_id: 13}}, array_to_object_expr], 40386);
 
-    assert.writeOK(coll.insert({_id: 14, expanded: [[321, 12]]}));
-    assertErrorCode(coll, [{$match: {_id: 14}}, array_to_object_expr], 40395);
+    assert.writeOK(coll.insert({_id: 14, expanded: [0]}));
+    assertErrorCode(coll, [{$match: {_id: 14}}, array_to_object_expr], 40398);
 
-    assert.writeOK(coll.insert({_id: 15, expanded: [["key", "value", "offset"]]}));
+    assert.writeOK(coll.insert({_id: 15, expanded: [["missing_value"]]}));
     assertErrorCode(coll, [{$match: {_id: 15}}, array_to_object_expr], 40397);
 
-    assert.writeOK(coll.insert({_id: 16, expanded: {y: []}}));
-    assertErrorCode(coll, [{$match: {_id: 16}}, array_to_object_expr], 40386);
+    assert.writeOK(coll.insert({_id: 16, expanded: [[321, 12]]}));
+    assertErrorCode(coll, [{$match: {_id: 16}}, array_to_object_expr], 40395);
 
-    assert.writeOK(coll.insert({_id: 17, expanded: [{y: "x", x: "y"}]}));
-    assertErrorCode(coll, [{$match: {_id: 17}}, array_to_object_expr], 40393);
+    assert.writeOK(coll.insert({_id: 17, expanded: [["key", "value", "offset"]]}));
+    assertErrorCode(coll, [{$match: {_id: 17}}, array_to_object_expr], 40397);
 
-    assert.writeOK(coll.insert({_id: 18, expanded: [{k: "missing"}]}));
-    assertErrorCode(coll, [{$match: {_id: 18}}, array_to_object_expr], 40392);
+    assert.writeOK(coll.insert({_id: 18, expanded: {y: []}}));
+    assertErrorCode(coll, [{$match: {_id: 18}}, array_to_object_expr], 40386);
 
-    assert.writeOK(coll.insert({_id: 19, expanded: [{k: 24, v: "string"}]}));
-    assertErrorCode(coll, [{$match: {_id: 19}}, array_to_object_expr], 40394);
+    assert.writeOK(coll.insert({_id: 19, expanded: [{y: "x", x: "y"}]}));
+    assertErrorCode(coll, [{$match: {_id: 19}}, array_to_object_expr], 40393);
 
-    assert.writeOK(coll.insert({_id: 20, expanded: [{y: "ignored", k: "item", v: "pear"}]}));
+    assert.writeOK(coll.insert({_id: 20, expanded: [{k: "missing"}]}));
     assertErrorCode(coll, [{$match: {_id: 20}}, array_to_object_expr], 40392);
 
-    assert.writeOK(coll.insert({_id: 21, expanded: NaN}));
-    assertErrorCode(coll, [{$match: {_id: 21}}, array_to_object_expr], 40386);
+    assert.writeOK(coll.insert({_id: 21, expanded: [{k: 24, v: "string"}]}));
+    assertErrorCode(coll, [{$match: {_id: 21}}, array_to_object_expr], 40394);
+
+    assert.writeOK(coll.insert({_id: 22, expanded: [{k: null, v: "nullKey"}]}));
+    assertErrorCode(coll, [{$match: {_id: 22}}, array_to_object_expr], 40394);
+
+    assert.writeOK(coll.insert({_id: 23, expanded: [{k: undefined, v: "undefinedKey"}]}));
+    assertErrorCode(coll, [{$match: {_id: 23}}, array_to_object_expr], 40394);
+
+    assert.writeOK(coll.insert({_id: 24, expanded: [{y: "ignored", k: "item", v: "pear"}]}));
+    assertErrorCode(coll, [{$match: {_id: 24}}, array_to_object_expr], 40392);
+
+    assert.writeOK(coll.insert({_id: 25, expanded: NaN}));
+    assertErrorCode(coll, [{$match: {_id: 25}}, array_to_object_expr], 40386);
 }());
diff --git a/src/mongo/db/pipeline/expression.cpp b/src/mongo/db/pipeline/expression.cpp
index a562144382b..7406e2ccaea 100644
--- a/src/mongo/db/pipeline/expression.cpp
+++ b/src/mongo/db/pipeline/expression.cpp
@@ -711,7 +711,7 @@ Value ExpressionArrayToObject::evaluateInternal(Variables* vars) const {
                     str::stream() << "$arrayToObject requires an object with keys 'k' and 'v'. "
                                      "Missing either or both keys from: "
                                   << elem.toString(),
-                    (!key.nullish() && !value.nullish()));
+                    (!key.missing() && !value.missing()));
 
             uassert(
                 40394,