SERVER-49117 Remove storage validation of '$' and '.' in field names for insert and update

31 files changed, 184 insertions, 290 deletions

diff --git a/buildscripts/build/eslint b/buildscripts/build/eslint
new file mode 100755
index 00000000000..3ea705c1289
--- /dev/null
+++ b/buildscripts/build/eslint
diff --git a/buildscripts/resmokeconfig/suites/replica_sets_kill_primary_jscore_passthrough.yml b/buildscripts/resmokeconfig/suites/replica_sets_kill_primary_jscore_passthrough.yml
index ee21efb3f14..f1677f377cc 100644
--- a/buildscripts/resmokeconfig/suites/replica_sets_kill_primary_jscore_passthrough.yml
+++ b/buildscripts/resmokeconfig/suites/replica_sets_kill_primary_jscore_passthrough.yml
@@ -59,7 +59,6 @@ selector:
   - jstests/core/benchrun_pipeline_updates.js # benchRun() used for writes
   - jstests/core/connection_string_validation.js # Does not expect a replica set connection string.
   - jstests/core/explain_large_bounds.js # Stepdown can timeout waiting for global lock.
-  - jstests/core/insert2.js # Creates new mongo connection.
   - jstests/core/list_collections_filter.js # Temporary collections are dropped on failover.
   - jstests/core/startup_log.js # Checks pid, which is different on each server.
   - jstests/core/validate_cmd_ns.js # Calls _exec() directly, not retryable.
diff --git a/buildscripts/resmokeconfig/suites/replica_sets_multi_stmt_txn_kill_primary_jscore_passthrough.yml b/buildscripts/resmokeconfig/suites/replica_sets_multi_stmt_txn_kill_primary_jscore_passthrough.yml
index 6f535d3d154..df0ac0d1b09 100644
--- a/buildscripts/resmokeconfig/suites/replica_sets_multi_stmt_txn_kill_primary_jscore_passthrough.yml
+++ b/buildscripts/resmokeconfig/suites/replica_sets_multi_stmt_txn_kill_primary_jscore_passthrough.yml
@@ -245,7 +245,6 @@ selector:
   - jstests/core/benchrun_pipeline_updates.js # benchRun() used for writes
   - jstests/core/connection_string_validation.js # Does not expect a replica set connection string.
   - jstests/core/explain_large_bounds.js # Stepdown can timeout waiting for global lock.
-  - jstests/core/insert2.js # Creates new mongo connection.
   - jstests/core/list_collections_filter.js # Temporary collections are dropped on failover.
   - jstests/core/startup_log.js # Checks pid, which is different on each server.
 
diff --git a/buildscripts/resmokeconfig/suites/replica_sets_multi_stmt_txn_stepdown_jscore_passthrough.yml b/buildscripts/resmokeconfig/suites/replica_sets_multi_stmt_txn_stepdown_jscore_passthrough.yml
index c6b41120c4f..49f6c37275a 100644
--- a/buildscripts/resmokeconfig/suites/replica_sets_multi_stmt_txn_stepdown_jscore_passthrough.yml
+++ b/buildscripts/resmokeconfig/suites/replica_sets_multi_stmt_txn_stepdown_jscore_passthrough.yml
@@ -246,7 +246,6 @@ selector:
   - jstests/core/benchrun_pipeline_updates.js # benchRun() used for writes
   - jstests/core/connection_string_validation.js # Does not expect a replica set connection string.
   - jstests/core/explain_large_bounds.js # Stepdown can timeout waiting for global lock.
-  - jstests/core/insert2.js # Creates new mongo connection.
   - jstests/core/list_collections_filter.js # Temporary collections are dropped on failover.
   - jstests/core/startup_log.js # Checks pid, which is different on each server.
 
diff --git a/buildscripts/resmokeconfig/suites/replica_sets_multi_stmt_txn_terminate_primary_jscore_passthrough.yml b/buildscripts/resmokeconfig/suites/replica_sets_multi_stmt_txn_terminate_primary_jscore_passthrough.yml
index 6a74ccd058c..efb2e96e7e0 100644
--- a/buildscripts/resmokeconfig/suites/replica_sets_multi_stmt_txn_terminate_primary_jscore_passthrough.yml
+++ b/buildscripts/resmokeconfig/suites/replica_sets_multi_stmt_txn_terminate_primary_jscore_passthrough.yml
@@ -243,7 +243,6 @@ selector:
   - jstests/core/benchrun_pipeline_updates.js # benchRun() used for writes
   - jstests/core/connection_string_validation.js # Does not expect a replica set connection string.
   - jstests/core/explain_large_bounds.js # Stepdown can timeout waiting for global lock.
-  - jstests/core/insert2.js # Creates new mongo connection.
   - jstests/core/list_collections_filter.js # Temporary collections are dropped on failover.
   - jstests/core/startup_log.js # Checks pid, which is different on each server.
 
diff --git a/buildscripts/resmokeconfig/suites/replica_sets_terminate_primary_jscore_passthrough.yml b/buildscripts/resmokeconfig/suites/replica_sets_terminate_primary_jscore_passthrough.yml
index 0228ac4f220..e1379646dca 100644
--- a/buildscripts/resmokeconfig/suites/replica_sets_terminate_primary_jscore_passthrough.yml
+++ b/buildscripts/resmokeconfig/suites/replica_sets_terminate_primary_jscore_passthrough.yml
@@ -59,7 +59,6 @@ selector:
   - jstests/core/benchrun_pipeline_updates.js # benchRun() used for writes
   - jstests/core/connection_string_validation.js # Does not expect a replica set connection string.
   - jstests/core/explain_large_bounds.js # Stepdown can timeout waiting for global lock.
-  - jstests/core/insert2.js # Creates new mongo connection.
   - jstests/core/list_collections_filter.js # Temporary collections are dropped on failover.
   - jstests/core/startup_log.js # Checks pid, which is different on each server.
   - jstests/core/validate_cmd_ns.js # Calls _exec() directly, not retryable.
diff --git a/buildscripts/resmokeconfig/suites/retryable_writes_jscore_stepdown_passthrough.yml b/buildscripts/resmokeconfig/suites/retryable_writes_jscore_stepdown_passthrough.yml
index d0cb71d09c4..07d0f62743a 100644
--- a/buildscripts/resmokeconfig/suites/retryable_writes_jscore_stepdown_passthrough.yml
+++ b/buildscripts/resmokeconfig/suites/retryable_writes_jscore_stepdown_passthrough.yml
@@ -63,7 +63,6 @@ selector:
   - jstests/core/benchrun_pipeline_updates.js # benchRun() used for writes
   - jstests/core/connection_string_validation.js # Does not expect a replica set connection string.
   - jstests/core/explain_large_bounds.js # Stepdown can timeout waiting for global lock.
-  - jstests/core/insert2.js # Creates new mongo connection.
   - jstests/core/list_collections_filter.js # Temporary collections are dropped on failover.
   - jstests/core/startup_log.js # Checks pid, which is different on each server.
   - jstests/core/validate_cmd_ns.js # Calls _exec() directly, not retryable.
diff --git a/jstests/core/batch_write_command_insert.js b/jstests/core/batch_write_command_insert.js
index e63632e3c5a..70acafe3d34 100644
--- a/jstests/core/batch_write_command_insert.js
+++ b/jstests/core/batch_write_command_insert.js
@@ -98,22 +98,6 @@ assert.eq(1, result.n);
 assert.eq(coll.count(), 1);
 
 //
-// Document with illegal key should fail
-coll.drop();
-request = {
-    insert: coll.getName(),
-    documents: [{$set: {a: 1}}],
-    writeConcern: {w: 1},
-    ordered: false
-};
-result = coll.runCommand(request);
-assert(result.ok, tojson(result));
-assert(result.writeErrors != null);
-assert.eq(1, result.writeErrors.length);
-assert.eq(0, result.n);
-assert.eq(coll.count(), 0);
-
-//
 // Document with valid nested key should insert (op log format)
 coll.drop();
 request = {
diff --git a/jstests/core/field_name_validation.js b/jstests/core/field_name_validation.js
index 3568103e768..e1c8f390f72 100644
--- a/jstests/core/field_name_validation.js
+++ b/jstests/core/field_name_validation.js
@@ -7,7 +7,7 @@
  *
  * contained in a top-level element, embedded element, and within _id.
  *
- * @tags: [assumes_unsharded_collection]
+ * @tags: [assumes_unsharded_collection, requires_fcv_46]
  */
 (function() {
 "use strict";
@@ -31,15 +31,14 @@ assert.writeError(coll.insert({_id: /a/}));
 // Test that _id cannot be an array.
 assert.writeError(coll.insert({_id: [9]}));
 
-// Test that $-prefixed field names are allowed in embedded objects.
+// Test that $-prefixed field names are allowed.
 assert.commandWorked(coll.insert({a: {$b: 1}}));
 assert.eq(1, coll.find({"a.$b": 1}).itcount());
+assert.commandWorked(coll.insert({$a: 1}));
+assert.commandWorked(coll.insert({valid: 1, $a: 1}));
+assert.commandWorked(coll.insert({$a: {$b: 1}}));
 
-// Test that $-prefixed field names are not allowed at the top level.
-assert.writeErrorWithCode(coll.insert({$a: 1}), ErrorCodes.BadValue);
-assert.writeErrorWithCode(coll.insert({valid: 1, $a: 1}), ErrorCodes.BadValue);
-
-// Test that reserved $-prefixed field names are also not allowed.
+// Test that reserved $-prefixed field names are not allowed.
 assert.writeErrorWithCode(coll.insert({$ref: 1}), ErrorCodes.BadValue);
 assert.writeErrorWithCode(coll.insert({$id: 1}), ErrorCodes.BadValue);
 assert.writeErrorWithCode(coll.insert({$db: 1}), ErrorCodes.BadValue);
@@ -53,6 +52,15 @@ assert.commandWorked(coll.insert({a: {_id: [9]}}));
 assert.commandWorked(coll.insert({a: {_id: /a/}}));
 assert.commandWorked(coll.insert({a: {_id: {$b: 1}}}));
 
+// Test that inserting an object with a $-prefixed field name is properly validated.
+assert.commandWorked(coll.insert({_id: 0, $valid: 1, "a": 1}));
+assert.eq([{_id: 0, $valid: 1, "a": 1}], coll.find({_id: 0}).toArray());
+
+assert.writeErrorWithCode(coll.insert({_id: 0, $valid: 1, $id: 1}), ErrorCodes.BadValue);
+assert.writeErrorWithCode(coll.insert({_id: 0, $valid: 1, $db: 1}), ErrorCodes.BadValue);
+assert.writeErrorWithCode(coll.insert({_id: 0, $valid: 1, $ref: 1}), ErrorCodes.BadValue);
+assert.commandWorked(coll.insert({_id: 1, $valid: 1, $alsoValid: 1}));
+
 //
 // Update command field name validation.
 //
@@ -75,18 +83,37 @@ assert.eq(1, coll.find({a: {b: 2}}).itcount());
 assert.commandWorked(coll.update({"a.b": 2}, {"a.b": 3}));
 assert.eq(0, coll.find({"a.b": 3}).itcount());
 
-// $-prefixed field names are not allowed.
-assert.writeErrorWithCode(coll.update({"a.b": 1}, {$c: 1}, {upsert: true}),
+// $-prefixed field names are allowed.
+assert.commandWorked(coll.update({"a.b": 1}, {$c: 1}, {upsert: true}));
+assert.commandWorked(coll.update({"a.b": 1}, {$set: {$c: 1}}, {upsert: true}));
+assert.commandWorked(coll.update({"a.b": 1}, {$set: {c: {$d: 1}}}, {upsert: true}));
+
+// Reserved $-prefixed field names are not allowed.
+assert.writeErrorWithCode(coll.update({"a.b": 1}, {$ref: 1}), ErrorCodes.InvalidDBRef);
+assert.writeErrorWithCode(coll.update({"a.b": 1}, {$id: 1}), ErrorCodes.InvalidDBRef);
+assert.writeErrorWithCode(coll.update({"a.b": 1}, {$db: 1}), ErrorCodes.InvalidDBRef);
+
+// Test that update docs with recognized operators are treated as modifier-style docs while update
+// docs with non-operator field names are treated as replacement-style docs.
+
+// Test that update documents with non-operators as field names are treated as replacement-style
+// updates.
+coll.update({_id: 1}, {$nonOp: 1}, {upsert: true});
+assert.eq([{_id: 1, $nonOp: 1}], coll.find({_id: 1}).toArray());
+
+// Test that update documents with recognized operators as field names are treated as modifier-style
+// updates.
+coll.update({_id: 2}, {$inc: {x: 1}}, {upsert: true});
+assert.eq([{_id: 2, x: 1}], coll.find({_id: 2}).toArray());
+
+// Test that update documents with a non-operator after an operator will not parse (expects all
+// operators).
+assert.writeErrorWithCode(coll.update({_id: 3}, {$set: {x: 12}, $hello: 1}, {upsert: true}),
                           ErrorCodes.FailedToParse);
-assert.writeErrorWithCode(coll.update({"a.b": 1}, {$set: {$c: 1}}, {upsert: true}),
-                          ErrorCodes.DollarPrefixedFieldName);
-assert.writeErrorWithCode(coll.update({"a.b": 1}, {$set: {c: {$d: 1}}}, {upsert: true}),
-                          ErrorCodes.DollarPrefixedFieldName);
 
-// Reserved $-prefixed field names are also not allowed.
-assert.writeErrorWithCode(coll.update({"a.b": 1}, {$ref: 1}), ErrorCodes.FailedToParse);
-assert.writeErrorWithCode(coll.update({"a.b": 1}, {$id: 1}), ErrorCodes.FailedToParse);
-assert.writeErrorWithCode(coll.update({"a.b": 1}, {$db: 1}), ErrorCodes.FailedToParse);
+// Test that update documents with a non-operator before an operator will expect only non-operators.
+assert.writeErrorWithCode(coll.update({_id: 4}, {$hello: 1, $set: {x: 12}}, {upsert: true}),
+                          ErrorCodes.BadValue);
 
 //
 // FindAndModify field name validation.
@@ -108,13 +135,15 @@ assert.eq([{_id: 0, "a.b": 1}], coll.find({_id: 0}).toArray());
 coll.findAndModify({query: {_id: 1, "a.b": 1}, update: {$set: {_id: 1, "a.b": 2}}});
 assert.eq([{_id: 1, a: {b: 2}}], coll.find({_id: 1}).toArray());
 
-// $-prefixed field names are not allowed.
-assert.throws(function() {
-    coll.findAndModify({query: {_id: 1}, update: {_id: 1, $invalid: 1}});
-});
-assert.throws(function() {
-    coll.findAndModify({query: {_id: 1}, update: {$set: {_id: 1, $invalid: 1}}});
-});
+// Test that $-prefixed fields are allowed.
+coll.findAndModify({query: {_id: 1}, update: {_id: 1, $valid: 1}});
+assert.eq([{_id: 1, $valid: 1}], coll.find({_id: 1}).toArray());
+
+coll.findAndModify({query: {_id: 1}, update: {_id: 1, $embed: {$a: 1, "b": 2}}});
+assert([{_id: 1, $embed: {$a: 1, "b": 2}}], coll.find({_id: 1}).toArray());
+
+coll.findAndModify({query: {_id: 2}, update: {_id: 2, out: {$in: 1, "x": 2}, upsert: true}});
+assert([{_id: 2, out: {$in: 1, "x": 2}}], coll.find({_id: 2}).toArray());
 
 // Reserved $-prefixed field names are also not allowed.
 assert.throws(function() {
diff --git a/jstests/core/insert2.js b/jstests/core/insert2.js
deleted file mode 100644
index 6052f1eeb8d..00000000000
--- a/jstests/core/insert2.js
+++ /dev/null
@@ -1,21 +0,0 @@
-// Cannot implicitly shard accessed collections because of collection existing when none
-// expected.
-// @tags: [
-//   assumes_no_implicit_collection_creation_after_drop,
-//   requires_collstats,
-//   uses_multiple_connections,
-// ]
-
-// Create a new connection object so it won't affect the global connection when we modify
-// it's settings.
-var conn = new Mongo(db.getMongo().host);
-conn.forceWriteMode(db.getMongo().writeMode());
-
-t = conn.getDB(db.getName()).insert2;
-t.drop();
-
-assert.isnull(t.findOne(), "A");
-assert.writeError(t.insert({z: 1, $inc: {x: 1}}, 0, true));
-assert.isnull(t.findOne(), "B");
-// Collection should not exist
-assert.isnull(t.exists());
diff --git a/jstests/core/push_sort.js b/jstests/core/push_sort.js
index 347f230a93d..05a64b88f12 100644
--- a/jstests/core/push_sort.js
+++ b/jstests/core/push_sort.js
@@ -1,4 +1,4 @@
-// @tags: [requires_non_retryable_writes]
+// @tags: [requires_non_retryable_writes, requires_fcv_46]
 
 //
 //  $push acquired the possibility of sorting the resulting array as part of SERVER-8008. This
@@ -54,12 +54,13 @@ assert.eq([{a: {b: 2}}, {a: {b: 3}}], t.findOne({_id: 7}).x);
 // Invalid Cases
 //
 
-// $push with $sort should not push a "$sort" field
+// Test that when given a document with a $sort field that matches the form of a plain document
+// (instead of a $sort modifier document), $push will add that field to the specified array.
 var doc8 = {_id: 8, x: [{a: 1}, {a: 2}]};
 t.save(doc8);
 var res = t.update({_id: 8}, {$push: {x: {$sort: {a: -1}}}});
-assert.writeErrorWithCode(res, ErrorCodes.DollarPrefixedFieldName);
-assert.docEq(t.findOne({_id: 8}), doc8);  // ensure doc was not changed
+assert.commandWorked(res);
+assert.docEq(t.findOne({_id: 8}), {_id: 8, x: [{a: 1}, {a: 2}, {$sort: {a: -1}}]});
 
 t.save({_id: 100, x: [{a: 1}]});
 
diff --git a/jstests/core/update_addToSet.js b/jstests/core/update_addToSet.js
index 5927dd882f8..7e9b262591c 100644
--- a/jstests/core/update_addToSet.js
+++ b/jstests/core/update_addToSet.js
@@ -71,28 +71,6 @@ t.update({_id: 1}, {$addToSet: {a: {$each: [3, 2, 2, 3, 3]}}});
 o.a.push(3);
 assert.eq(o, t.findOne(), "D4");
 
-// Test that dotted and '$' prefixed field names fail.
-t.drop();
-o = {
-    _id: 1,
-    a: [1, 2]
-};
-assert.commandWorked(t.insert(o));
-
-assert.commandWorked(t.update({}, {$addToSet: {a: {'x.$.y': 'bad'}}}));
-assert.commandWorked(t.update({}, {$addToSet: {a: {b: {'x.$.y': 'bad'}}}}));
-
-assert.writeError(t.update({}, {$addToSet: {a: {"$bad": "bad"}}}));
-assert.writeError(t.update({}, {$addToSet: {a: {b: {"$bad": "bad"}}}}));
-
-assert.commandWorked(t.update({}, {$addToSet: {a: {_id: {"x.y": 2}}}}));
-
-assert.commandWorked(t.update({}, {$addToSet: {a: {$each: [{'x.$.y': 'bad'}]}}}));
-assert.commandWorked(t.update({}, {$addToSet: {a: {$each: [{b: {'x.$.y': 'bad'}}]}}}));
-
-assert.writeError(t.update({}, {$addToSet: {a: {$each: [{'$bad': 'bad'}]}}}));
-assert.writeError(t.update({}, {$addToSet: {a: {$each: [{b: {'$bad': 'bad'}}]}}}));
-
 // Test that nested _id fields are allowed.
 t.drop();
 o = {
diff --git a/jstests/core/update_with_pipeline.js b/jstests/core/update_with_pipeline.js
index 4f044a19352..891d9feb83e 100644
--- a/jstests/core/update_with_pipeline.js
+++ b/jstests/core/update_with_pipeline.js
@@ -4,7 +4,7 @@
  * 'requires_find_command' needed to prevent this test from running with 'compatibility' write mode
  * as pipeline-style update is not supported by OP_UPDATE.
  *
- * @tags: [requires_find_command, requires_non_retryable_writes]
+ * @tags: [requires_find_command, requires_non_retryable_writes, requires_fcv_46]
  */
 (function() {
 "use strict";
@@ -195,8 +195,9 @@ assert.commandFailedWithCode(
         }]),
     ErrorCodes.InvalidOptions);
 
-// Update fails when supported agg stage is specified outside of pipeline.
-assert.commandFailedWithCode(coll.update({_id: 1}, {$addFields: {x: 1}}), ErrorCodes.FailedToParse);
+// Update uses replacement document when supported agg stage is specified outside of pipeline.
+coll.update({_id: 1}, {$addFields: {x: 1}});
+assert.eq([{_id: 1, $addFields: {x: 1}}], coll.find({_id: 1}).toArray());
 
 // The 'arrayFilters' option is not valid for pipeline updates.
 assert.commandFailedWithCode(
@@ -254,12 +255,12 @@ testUpdate({
     nModified: 1
 });
 
-// Cannot use expressions in constants.
-assert.commandFailedWithCode(db.runCommand({
+// Test that expressions within constants are treated as field names instead of expressions.
+db.runCommand({
     update: collName,
     updates: [{q: {_id: 1}, u: [{$set: {x: "$$foo"}}], c: {foo: {$add: [1, 2]}}}]
-}),
-                             ErrorCodes.DollarPrefixedFieldName);
+});
+assert.eq([{_id: 1, x: {$add: [1, 2]}, foo: "$x"}], coll.find({_id: 1}).toArray());
 
 // Cannot use constants with regular updates.
 assert.commandFailedWithCode(
diff --git a/jstests/core/updateh.js b/jstests/core/updateh.js
index 1fd3d62750d..e647fb4bfb8 100644
--- a/jstests/core/updateh.js
+++ b/jstests/core/updateh.js
@@ -1,9 +1,9 @@
 // Cannot implicitly shard accessed collections because of following errmsg: A single
 // update/delete on a sharded collection must contain an exact match on _id or contain the shard
 // key.
-// @tags: [assumes_unsharded_collection]
+// @tags: [assumes_unsharded_collection, requires_fcv_46]
 
-// Disallow $ in field names
+// Allow $ in field names (as of SERVER-49117)
 var res;
 
 t = db.jstest_updateh;
@@ -11,39 +11,39 @@ t.drop();
 
 t.insert({x: 1});
 
-res = t.update({x: 1}, {$set: {y: 1}});  // ok
+res = t.update({x: 1}, {$set: {y: 1}});
 assert.commandWorked(res);
 
-res = t.update({x: 1}, {$set: {$z: 1}});  // not ok
-assert.writeError(res);
+res = t.update({x: 1}, {$set: {$z: 1}});
+assert.commandWorked(res);
 
-res = t.update({x: 1}, {$set: {'a.$b': 1}});  // not ok
-assert.writeError(res);
+res = t.update({x: 1}, {$set: {'a.$b': 1}});
+assert.commandWorked(res);
 
-res = t.update({x: 1}, {$inc: {$z: 1}});  // not ok
-assert.writeError(res);
+res = t.update({x: 1}, {$inc: {$z: 1}});
+assert.commandWorked(res);
 
 // Second section
 t.drop();
 
 t.save({_id: 0, n: 0});
 
-// Test that '$' cannot be the first character in a field.
-// SERVER-7150
+// Test that '$' can be the first character in a field.
+// (as of SERVER-49117)
 res = t.update({n: 0}, {$set: {$x: 1}});
-assert.writeError(res);
+assert.commandWorked(res);
 
 res = t.update({n: 0}, {$set: {$$$: 1}});
-assert.writeError(res);
+assert.commandWorked(res);
 
 res = t.update({n: 0}, {$set: {"sneaky.$x": 1}});
-assert.writeError(res);
+assert.commandWorked(res);
 
 res = t.update({n: 0}, {$set: {"secret.agent$.$x": 1}});
-assert.writeError(res);
+assert.commandWorked(res);
 
 res = t.update({n: 0}, {$set: {"$secret.agent.x": 1}});
-assert.writeError(res);
+assert.commandWorked(res);
 
 res = t.update({n: 0}, {$set: {"secret.agent$": 1}});
 assert.commandWorked(res);
@@ -60,14 +60,16 @@ t.save({_id: 0, n: 0});
 
 // SERVER-11241: Validation used to allow any DBRef field name as a prefix
 // thus allowing things like $idXXX
+// SERVER-49117: $-prefixed field names are allowed, as long as they are
+// not equal to reserved $-prefixed field names (i.e. $ref/$id/$db)
 res = t.update({n: 0}, {$set: {$reffoo: 1}});
-assert.writeError(res);
+assert.commandWorked(res);
 
 res = t.update({n: 0}, {$set: {$idbar: 1}});
-assert.writeError(res);
+assert.commandWorked(res);
 
 res = t.update({n: 0}, {$set: {$dbbaz: 1}});
-assert.writeError(res);
+assert.commandWorked(res);
 
 // Test that '$id', '$db', and '$ref' are acceptable field names in
 // the correct case ( subdoc)
diff --git a/jstests/core/write_result.js b/jstests/core/write_result.js
index 49735bee7d6..100322a00e4 100644
--- a/jstests/core/write_result.js
+++ b/jstests/core/write_result.js
@@ -119,7 +119,7 @@ assert.eq(coll.count(), 1);
 // Update with error
 coll.remove({});
 coll.insert({foo: "bar"});
-printjson(result = coll.update({foo: "bar"}, {$invalid: "expr"}));
+result = coll.update({foo: "bar"}, {_id: /a/});
 assert.eq(result.nUpserted, 0);
 assert.eq(result.nMatched, 0);
 if (coll.getMongo().writeMode() == "commands")
diff --git a/jstests/gle/gle_sharded_write.js b/jstests/gle/gle_sharded_write.js
index 21a42381c96..38ce0f839de 100644
--- a/jstests/gle/gle_sharded_write.js
+++ b/jstests/gle/gle_sharded_write.js
@@ -111,7 +111,7 @@ assert.eq(coll.count(), 0);
 //
 // Error on one host during update
 coll.remove({});
-coll.update({_id: 1}, {$invalid: "xxx"}, true);
+coll.update({_id: 1}, {$set: {x: 12}, $hello: 1}, true);
 printjson(gle = coll.getDB().runCommand({getLastError: 1}));
 assert(gle.ok);
 assert(gle.err);
@@ -135,7 +135,7 @@ assert.eq(coll.count(), 0);
 //
 // Repeated calls to GLE should work
 coll.remove({});
-coll.update({_id: 1}, {$invalid: "xxx"}, true);
+coll.update({_id: 1}, {$set: {x: 12}, $hello: 1}, true);
 printjson(gle = coll.getDB().runCommand({getLastError: 1}));
 assert(gle.ok);
 assert(gle.err);
diff --git a/jstests/sharding/server_status_crud_metrics.js b/jstests/sharding/server_status_crud_metrics.js
index 62a513242ca..4f83d7e4b6e 100644
--- a/jstests/sharding/server_status_crud_metrics.js
+++ b/jstests/sharding/server_status_crud_metrics.js
@@ -33,8 +33,8 @@ assert.commandWorked(testDB.coll.update({_id: 1}, {$set: {a: 2}}, {multi: false}
 // fails on the individual shard.
 assert.commandFailedWithCode(testDB.coll.update({_id: 1}, {$set: {x: 2}}, {multi: false}), 31025);
 assert.commandFailedWithCode(
-    testDB.coll.update({_id: 1}, {$set: {x: 2, $invalidField: 4}}, {multi: false}),
-    ErrorCodes.DollarPrefixedFieldName);
+    testDB.coll.update({_id: 1}, {$set: {x: 12}, $hello: 1}, {multi: false}),
+    ErrorCodes.FailedToParse);
 
 let mongosServerStatus = testDB.adminCommand({serverStatus: 1});
 
diff --git a/src/mongo/db/matcher/expression_parser.cpp b/src/mongo/db/matcher/expression_parser.cpp
index c4013697ebe..1ef996ffed0 100644
--- a/src/mongo/db/matcher/expression_parser.cpp
+++ b/src/mongo/db/matcher/expression_parser.cpp
@@ -66,6 +66,7 @@
 #include "mongo/db/matcher/schema/expression_internal_schema_xor.h"
 #include "mongo/db/matcher/schema/json_schema_parser.h"
 #include "mongo/db/namespace_string.h"
+#include "mongo/db/query/dbref.h"
 #include "mongo/db/query/query_knobs_gen.h"
 #include "mongo/util/str.h"
 #include "mongo/util/string_map.h"
@@ -214,15 +215,15 @@ bool isDBRefDocument(const BSONObj& obj, bool allowIncompleteDBRef) {
         auto element = i.next();
         auto fieldName = element.fieldNameStringData();
         // $ref
-        if (!hasRef && "$ref"_sd == fieldName) {
+        if (!hasRef && dbref::kRefFieldName == fieldName) {
             hasRef = true;
         }
         // $id
-        else if (!hasID && "$id"_sd == fieldName) {
+        else if (!hasID && dbref::kIdFieldName == fieldName) {
             hasID = true;
         }
         // $db
-        else if (!hasDB && "$db"_sd == fieldName) {
+        else if (!hasDB && dbref::kDbFieldName == fieldName) {
             hasDB = true;
         }
     }
diff --git a/src/mongo/db/ops/insert.cpp b/src/mongo/db/ops/insert.cpp
index 383536913e1..07663838aec 100644
--- a/src/mongo/db/ops/insert.cpp
+++ b/src/mongo/db/ops/insert.cpp
@@ -34,6 +34,7 @@
 
 #include "mongo/bson/bson_depth.h"
 #include "mongo/db/commands/feature_compatibility_version_parser.h"
+#include "mongo/db/query/dbref.h"
 #include "mongo/db/vector_clock_mutable.h"
 #include "mongo/db/views/durable_view_catalog.h"
 #include "mongo/util/str.h"
@@ -74,6 +75,11 @@ Status validateDepth(const BSONObj& obj) {
 }
 }  // namespace
 
+bool isReservedDollarPrefixedWord(StringData fieldName) {
+    return (std::find(dbref::kDbRefFieldNames.begin(), dbref::kDbRefFieldNames.end(), fieldName) !=
+            std::end(dbref::kDbRefFieldNames));
+}
+
 StatusWith<BSONObj> fixDocumentForInsert(ServiceContext* service, const BSONObj& doc) {
     if (doc.objsize() > BSONObjMaxUserSize)
         return StatusWith<BSONObj>(ErrorCodes::BadValue,
@@ -102,10 +108,13 @@ StatusWith<BSONObj> fixDocumentForInsert(ServiceContext* service, const BSONObj&
 
             auto fieldName = e.fieldNameStringData();
 
-            if (fieldName[0] == '$') {
-                return StatusWith<BSONObj>(
-                    ErrorCodes::BadValue,
-                    str::stream() << "Document can't have $ prefixed field names: " << fieldName);
+            // Ensure that fieldName is not a reserved $-prefixed field name.
+            if (isReservedDollarPrefixedWord(fieldName)) {
+
+                return StatusWith<BSONObj>(ErrorCodes::BadValue,
+                                           str::stream() << fieldName << " is a reserved fieldName"
+                                                         << " and cannot be used. Please"
+                                                         << " try another field name.");
             }
 
             // check no regexp for _id (SERVER-9502)
diff --git a/src/mongo/db/ops/insert.h b/src/mongo/db/ops/insert.h
index d21e74ceb1c..a0b24f4a271 100644
--- a/src/mongo/db/ops/insert.h
+++ b/src/mongo/db/ops/insert.h
@@ -34,6 +34,12 @@ namespace mongo {
 
 class ServiceContext;
 
+/*
+ * Returns true if fieldName is one of the reserved $-prefixed words
+ * and false if it isn't.
+ */
+bool isReservedDollarPrefixedWord(StringData fieldName);
+
 /**
  * Validates that 'doc' is legal for insertion, possibly with some modifications.
  *
diff --git a/src/mongo/db/query/dbref.h b/src/mongo/db/query/dbref.h
new file mode 100644
index 00000000000..ffa4be06b26
--- /dev/null
+++ b/src/mongo/db/query/dbref.h
@@ -0,0 +1,47 @@
+/**
+ *    Copyright (C) 2018-present MongoDB, Inc.
+ *
+ *    This program is free software: you can redistribute it and/or modify
+ *    it under the terms of the Server Side Public License, version 1,
+ *    as published by MongoDB, Inc.
+ *
+ *    This program is distributed in the hope that it will be useful,
+ *    but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *    Server Side Public License for more details.
+ *
+ *    You should have received a copy of the Server Side Public License
+ *    along with this program. If not, see
+ *    <http://www.mongodb.com/licensing/server-side-public-license>.
+ *
+ *    As a special exception, the copyright holders give permission to link the
+ *    code of portions of this program with the OpenSSL library under certain
+ *    conditions as described in each individual source file and distribute
+ *    linked combinations including the program with the OpenSSL library. You
+ *    must comply with the Server Side Public License in all respects for
+ *    all of the code used other than as permitted herein. If you modify file(s)
+ *    with this exception, you may extend this exception to your version of the
+ *    file(s), but you are not obligated to do so. If you do not wish to do so,
+ *    delete this exception statement from your version. If you delete this
+ *    exception statement from all source files in the program, then also delete
+ *    it in the license file.
+ */
+
+#pragma once
+
+#include <set>
+
+#include "mongo/base/string_data.h"
+
+namespace mongo {
+namespace dbref {
+
+constexpr StringData kDbFieldName = "$db"_sd;
+constexpr StringData kIdFieldName = "$id"_sd;
+constexpr StringData kRefFieldName = "$ref"_sd;
+
+// A list containing all the reserved $-prefixed field names.
+constexpr std::array<StringData, 3> kDbRefFieldNames = {kDbFieldName, kIdFieldName, kRefFieldName};
+
+}  // namespace dbref
+}  // namespace mongo
\ No newline at end of file
diff --git a/src/mongo/db/repl/storage_interface_impl_test.cpp b/src/mongo/db/repl/storage_interface_impl_test.cpp
index 9a121099170..8abf0c66405 100644
--- a/src/mongo/db/repl/storage_interface_impl_test.cpp
+++ b/src/mongo/db/repl/storage_interface_impl_test.cpp
@@ -2220,31 +2220,6 @@ TEST_F(StorageInterfaceImplTest,
               ErrorCodes::IndexNotFound);
 }
 
-TEST_F(StorageInterfaceImplTest,
-       UpsertSingleDocumentReturnsFailedToParseWhenUpdateDocumentContainsUnknownOperator) {
-    auto opCtx = getOperationContext();
-    auto nss = makeNamespace(_agent);
-    auto options = generateOptionsWithUuid();
-
-    StorageInterfaceImpl storage;
-    ASSERT_OK(storage.createCollection(opCtx, nss, options));
-
-    auto unknownUpdateOp = BSON("$unknownUpdateOp" << BSON("x" << 1000));
-    ASSERT_THROWS_CODE_AND_WHAT(
-        storage.upsertById(opCtx, nss, BSON("" << 1).firstElement(), unknownUpdateOp),
-        AssertionException,
-        ErrorCodes::FailedToParse,
-        "Unknown modifier: $unknownUpdateOp. Expected a valid update modifier or pipeline-style "
-        "update specified as an array");
-
-    ASSERT_THROWS_CODE(storage.upsertById(opCtx,
-                                          {nss.db().toString(), *options.uuid},
-                                          BSON("" << 1).firstElement(),
-                                          unknownUpdateOp),
-                       DBException,
-                       ErrorCodes::FailedToParse);
-}
-
 TEST_F(StorageInterfaceImplTest, DeleteByFilterReturnsNamespaceNotFoundWhenDatabaseDoesNotExist) {
     auto opCtx = getOperationContext();
     StorageInterfaceImpl storage;
diff --git a/src/mongo/db/update/SConscript b/src/mongo/db/update/SConscript
index 9a93690dd21..dec70a64686 100644
--- a/src/mongo/db/update/SConscript
+++ b/src/mongo/db/update/SConscript
@@ -9,8 +9,7 @@ env.Library(
     source=[
         'field_checker.cpp',
         'log_builder.cpp',
-        'path_support.cpp',
-        'storage_validation.cpp',
+        'path_support.cpp'
     ],
     LIBDEPS=[
         '$BUILD_DIR/mongo/base',
@@ -37,6 +36,7 @@ env.Library(
         'push_node.cpp',
         'rename_node.cpp',
         'set_node.cpp',
+        'storage_validation.cpp',
         'unset_node.cpp',
         'update_array_node.cpp',
         'update_internal_node.cpp',
diff --git a/src/mongo/db/update/object_replace_executor_test.cpp b/src/mongo/db/update/object_replace_executor_test.cpp
index 0f7adf40df5..284c74639d5 100644
--- a/src/mongo/db/update/object_replace_executor_test.cpp
+++ b/src/mongo/db/update/object_replace_executor_test.cpp
@@ -258,18 +258,6 @@ TEST_F(ObjectReplaceExecutorTest, CanAddImmutableId) {
     ASSERT_BSONOBJ_BINARY_EQ(fromjson("{_id: 0}"), result.oplogEntry);
 }
 
-TEST_F(ObjectReplaceExecutorTest, CannotCreateDollarPrefixedNameWhenValidateForStorageIsTrue) {
-    auto obj = fromjson("{a: {b: 1, $bad: 1}}");
-    ObjectReplaceExecutor node(obj);
-
-    mutablebson::Document doc(fromjson("{}"));
-    ASSERT_THROWS_CODE_AND_WHAT(
-        node.applyUpdate(getApplyParams(doc.root())),
-        AssertionException,
-        ErrorCodes::DollarPrefixedFieldName,
-        "The dollar ($) prefixed field '$bad' in 'a.$bad' is not valid for storage.");
-}
-
 TEST_F(ObjectReplaceExecutorTest, CanCreateDollarPrefixedNameWhenValidateForStorageIsFalse) {
     auto obj = fromjson("{a: {b: 1, $bad: 1}}");
     ObjectReplaceExecutor node(obj);
diff --git a/src/mongo/db/update/rename_node_test.cpp b/src/mongo/db/update/rename_node_test.cpp
index 6eec4d8f498..f263204f708 100644
--- a/src/mongo/db/update/rename_node_test.cpp
+++ b/src/mongo/db/update/rename_node_test.cpp
@@ -550,21 +550,6 @@ TEST_F(RenameNodeTest, ApplyCanRemoveImmutablePathIfNoop) {
     ASSERT_EQUALS(getModifiedPaths(), "{a.b.c, d}");
 }
 
-TEST_F(RenameNodeTest, ApplyCannotCreateDollarPrefixedField) {
-    auto update = fromjson("{$rename: {a: '$bad'}}");
-    boost::intrusive_ptr<ExpressionContextForTest> expCtx(new ExpressionContextForTest());
-    RenameNode node;
-    ASSERT_OK(node.init(update["$rename"]["a"], expCtx));
-
-    mutablebson::Document doc(fromjson("{a: 0}"));
-    setPathToCreate("$bad");
-    ASSERT_THROWS_CODE_AND_WHAT(
-        node.apply(getApplyParams(doc.root()), getUpdateNodeApplyParams()),
-        AssertionException,
-        ErrorCodes::DollarPrefixedFieldName,
-        "The dollar ($) prefixed field '$bad' in '$bad' is not valid for storage.");
-}
-
 TEST_F(RenameNodeTest, ApplyCannotOverwriteImmutablePath) {
     auto update = fromjson("{$rename: {a: 'b'}}");
     boost::intrusive_ptr<ExpressionContextForTest> expCtx(new ExpressionContextForTest());
diff --git a/src/mongo/db/update/set_node_test.cpp b/src/mongo/db/update/set_node_test.cpp
index 8cd2b60243e..e31edf0b6a6 100644
--- a/src/mongo/db/update/set_node_test.cpp
+++ b/src/mongo/db/update/set_node_test.cpp
@@ -1018,66 +1018,6 @@ TEST_F(SetNodeTest, ApplySetModToEphemeralDocument) {
     ASSERT_FALSE(doc.isInPlaceModeEnabled());
 }
 
-TEST_F(SetNodeTest, ApplyCannotCreateDollarPrefixedFieldInsideSetElement) {
-    auto update = fromjson("{$set: {a: {$bad: 1}}}");
-    boost::intrusive_ptr<ExpressionContextForTest> expCtx(new ExpressionContextForTest());
-    SetNode node;
-    ASSERT_OK(node.init(update["$set"]["a"], expCtx));
-
-    mutablebson::Document doc(fromjson("{a: 5}"));
-    setPathTaken("a");
-    ASSERT_THROWS_CODE_AND_WHAT(
-        node.apply(getApplyParams(doc.root()["a"]), getUpdateNodeApplyParams()),
-        AssertionException,
-        ErrorCodes::DollarPrefixedFieldName,
-        "The dollar ($) prefixed field '$bad' in 'a.$bad' is not valid for storage.");
-}
-
-TEST_F(SetNodeTest, ApplyCannotCreateDollarPrefixedFieldAtStartOfPath) {
-    auto update = fromjson("{$set: {'$bad.a': 1}}");
-    boost::intrusive_ptr<ExpressionContextForTest> expCtx(new ExpressionContextForTest());
-    SetNode node;
-    ASSERT_OK(node.init(update["$set"]["$bad.a"], expCtx));
-
-    mutablebson::Document doc(fromjson("{}"));
-    setPathToCreate("$bad.a");
-    ASSERT_THROWS_CODE_AND_WHAT(
-        node.apply(getApplyParams(doc.root()), getUpdateNodeApplyParams()),
-        AssertionException,
-        ErrorCodes::DollarPrefixedFieldName,
-        "The dollar ($) prefixed field '$bad' in '$bad' is not valid for storage.");
-}
-
-TEST_F(SetNodeTest, ApplyCannotCreateDollarPrefixedFieldInMiddleOfPath) {
-    auto update = fromjson("{$set: {'a.$bad.b': 1}}");
-    boost::intrusive_ptr<ExpressionContextForTest> expCtx(new ExpressionContextForTest());
-    SetNode node;
-    ASSERT_OK(node.init(update["$set"]["a.$bad.b"], expCtx));
-
-    mutablebson::Document doc(fromjson("{}"));
-    setPathToCreate("a.$bad.b");
-    ASSERT_THROWS_CODE_AND_WHAT(
-        node.apply(getApplyParams(doc.root()), getUpdateNodeApplyParams()),
-        AssertionException,
-        ErrorCodes::DollarPrefixedFieldName,
-        "The dollar ($) prefixed field '$bad' in 'a.$bad' is not valid for storage.");
-}
-
-TEST_F(SetNodeTest, ApplyCannotCreateDollarPrefixedFieldAtEndOfPath) {
-    auto update = fromjson("{$set: {'a.$bad': 1}}");
-    boost::intrusive_ptr<ExpressionContextForTest> expCtx(new ExpressionContextForTest());
-    SetNode node;
-    ASSERT_OK(node.init(update["$set"]["a.$bad"], expCtx));
-
-    mutablebson::Document doc(fromjson("{}"));
-    setPathToCreate("a.$bad");
-    ASSERT_THROWS_CODE_AND_WHAT(
-        node.apply(getApplyParams(doc.root()), getUpdateNodeApplyParams()),
-        AssertionException,
-        ErrorCodes::DollarPrefixedFieldName,
-        "The dollar ($) prefixed field '$bad' in 'a.$bad' is not valid for storage.");
-}
-
 TEST_F(SetNodeTest, ApplyCanCreateDollarPrefixedFieldNameWhenValidateForStorageIsFalse) {
     auto update = fromjson("{$set: {$bad: 1}}");
     boost::intrusive_ptr<ExpressionContextForTest> expCtx(new ExpressionContextForTest());
diff --git a/src/mongo/db/update/storage_validation.cpp b/src/mongo/db/update/storage_validation.cpp
index 009343776f0..6f2d1e9298b 100644
--- a/src/mongo/db/update/storage_validation.cpp
+++ b/src/mongo/db/update/storage_validation.cpp
@@ -32,6 +32,8 @@
 #include "mongo/bson/bson_depth.h"
 #include "mongo/bson/mutable/algorithm.h"
 #include "mongo/bson/mutable/document.h"
+#include "mongo/db/query/dbref.h"
+#include "mongo/db/update/modifier_table.h"
 
 namespace mongo {
 
@@ -58,14 +60,15 @@ void storageValidChildren(mutablebson::ConstElement elem,
 /**
  * Validates an element that has a field name which starts with a dollar sign ($).
  * In the case of a DBRef field ($id, $ref, [$db]) these fields may be valid in
- * the correct order/context only.
+ * the correct order/context only. In other cases, $-prefixed field names are
+ * now allowed (SERVER-49117).
  */
 void validateDollarPrefixElement(mutablebson::ConstElement elem) {
     auto curr = elem;
     auto currName = elem.getFieldName();
 
     // Found a $db field.
-    if (currName == "$db") {
+    if (currName == dbref::kDbFieldName) {
         uassert(ErrorCodes::InvalidDBRef,
                 str::stream() << "The DBRef $db field must be a String, not a "
                               << typeName(curr.getType()),
@@ -80,7 +83,7 @@ void validateDollarPrefixElement(mutablebson::ConstElement elem) {
     }
 
     // Found a $id field.
-    if (currName == "$id") {
+    if (currName == dbref::kIdFieldName) {
         curr = curr.leftSibling();
         uassert(ErrorCodes::InvalidDBRef,
                 "Found $id field without a $ref before it, which is invalid.",
@@ -90,7 +93,7 @@ void validateDollarPrefixElement(mutablebson::ConstElement elem) {
     }
 
     // Found a $ref field.
-    if (currName == "$ref") {
+    if (currName == dbref::kRefFieldName) {
         uassert(ErrorCodes::InvalidDBRef,
                 str::stream() << "The DBRef $ref field must be a String, not a "
                               << typeName(curr.getType()),
@@ -99,14 +102,13 @@ void validateDollarPrefixElement(mutablebson::ConstElement elem) {
         uassert(ErrorCodes::InvalidDBRef,
                 "The DBRef $ref field must be followed by a $id field",
                 curr.rightSibling().ok() && curr.rightSibling().getFieldName() == "$id");
-    } else {
-
-        // Not an okay, $ prefixed field name.
-        uasserted(ErrorCodes::DollarPrefixedFieldName,
-                  str::stream() << "The dollar ($) prefixed field '" << elem.getFieldName()
-                                << "' in '" << mutablebson::getFullName(elem)
-                                << "' is not valid for storage.");
     }
+
+    // Found a non-reserved $-prefixed field.
+    uassert(ErrorCodes::BadValue,
+            str::stream() << "Field " << currName << " is invalid. "
+                          << "Please use a field name that is not an update modifier",
+            modifiertable::getType(currName) == modifiertable::MOD_UNKNOWN);
 }
 }  // namespace
 
diff --git a/src/mongo/db/update/update_driver.cpp b/src/mongo/db/update/update_driver.cpp
index e0cf8dafb4c..91b625ee3ef 100644
--- a/src/mongo/db/update/update_driver.cpp
+++ b/src/mongo/db/update/update_driver.cpp
@@ -312,7 +312,10 @@ void UpdateDriver::setCollator(const CollatorInterface* collator) {
 
 bool UpdateDriver::isDocReplacement(const write_ops::UpdateModification& updateMod) {
     return (updateMod.type() == write_ops::UpdateModification::Type::kClassic &&
-            *updateMod.getUpdateClassic().firstElementFieldName() != '$') ||
+            (modifiertable::getType(
+                 updateMod.getUpdateClassic().firstElementFieldNameStringData()) ==
+                 modifiertable::MOD_UNKNOWN &&
+             updateMod.getUpdateClassic().firstElementFieldNameStringData() != "$v"_sd)) ||
         updateMod.type() == write_ops::UpdateModification::Type::kPipeline;
 }
 
diff --git a/src/mongo/db/update/update_driver_test.cpp b/src/mongo/db/update/update_driver_test.cpp
index 5c736122c65..c9610841d80 100644
--- a/src/mongo/db/update/update_driver_test.cpp
+++ b/src/mongo/db/update/update_driver_test.cpp
@@ -128,15 +128,12 @@ TEST(Parse, EmptyMod) {
         "'$set' is empty. You must specify a field like so: {$set: {<field>: ...}}");
 }
 
-TEST(Parse, WrongMod) {
+TEST(Parse, UnknownMod) {
     boost::intrusive_ptr<ExpressionContextForTest> expCtx(new ExpressionContextForTest());
     UpdateDriver driver(expCtx);
     std::map<StringData, std::unique_ptr<ExpressionWithPlaceholder>> arrayFilters;
-    ASSERT_THROWS_CODE_AND_WHAT(driver.parse(fromjson("{$xyz:{a:1}}"), arrayFilters),
-                                AssertionException,
-                                ErrorCodes::FailedToParse,
-                                "Unknown modifier: $xyz. Expected a valid update modifier or "
-                                "pipeline-style update specified as an array");
+    ASSERT_DOES_NOT_THROW(driver.parse(fromjson("{$xyz:{a:1}}"), arrayFilters));
+    ASSERT_TRUE(driver.type() == UpdateDriver::UpdateType::kReplacement);
 }
 
 TEST(Parse, WrongType) {
diff --git a/src/mongo/dbtests/updatetests.cpp b/src/mongo/dbtests/updatetests.cpp
index f37dc9adb9b..cfb0ba85311 100644
--- a/src/mongo/dbtests/updatetests.cpp
+++ b/src/mongo/dbtests/updatetests.cpp
@@ -112,12 +112,6 @@ class ModNonmodMix : public Fail {
     }
 };
 
-class InvalidMod : public Fail {
-    void doIt() {
-        update(ns(), BSONObj(), fromjson("{$awk:{a:4}}"));
-    }
-};
-
 class ModNotFirst : public Fail {
     void doIt() {
         update(ns(), BSONObj(), fromjson("{z:3,$set:{a:4}}"));
@@ -136,20 +130,6 @@ class IncNonNumber : public Fail {
     }
 };
 
-class PushAllNonArray : public Fail {
-    void doIt() {
-        insert(ns(), fromjson("{a:[1]}"));
-        update(ns(), BSONObj(), fromjson("{$pushAll:{a:'d'}}"));
-    }
-};
-
-class PullAllNonArray : public Fail {
-    void doIt() {
-        insert(ns(), fromjson("{a:[1]}"));
-        update(ns(), BSONObj(), fromjson("{$pullAll:{a:'d'}}"));
-    }
-};
-
 class IncTargetNonNumber : public Fail {
     void doIt() {
         insert(ns(),
@@ -2004,12 +1984,9 @@ public:
     void setupTests() {
         add<ModId>();
         add<ModNonmodMix>();
-        add<InvalidMod>();
         add<ModNotFirst>();
         add<ModDuplicateFieldSpec>();
         add<IncNonNumber>();
-        add<PushAllNonArray>();
-        add<PullAllNonArray>();
         add<IncTargetNonNumber>();
         add<SetNum>();
         add<SetString>();
diff --git a/src/mongo/embedded/stitch_support/stitch_support_test.cpp b/src/mongo/embedded/stitch_support/stitch_support_test.cpp
index d8984f43367..7c6dc94cb62 100644
--- a/src/mongo/embedded/stitch_support/stitch_support_test.cpp
+++ b/src/mongo/embedded/stitch_support/stitch_support_test.cpp
@@ -575,10 +575,6 @@ TEST_F(StitchSupportTest, TestUpdateWithSetOnInsert) {
 }
 
 TEST_F(StitchSupportTest, TestUpdateProducesProperStatus) {
-    ASSERT_EQ(
-        "Unknown modifier: $bogus. Expected a valid update modifier or pipeline-style update "
-        "specified as an array",
-        checkUpdateStatus("{$bogus: {a: 2}}", "{a: 1}"));
     ASSERT_EQ("Updating the path 'a' would create a conflict at 'a'",
               checkUpdateStatus("{$set: {a: 2, a: 3}}", "{a: 1}"));
     ASSERT_EQ("No array filter found for identifier 'i' in path 'a.$[i]'",