SERVER-22184 check for the new error format in peekError

(cherry picked from commit 3a5c0f9bcb46f083863622e0d734cf29023e7275)

2 files changed, 27 insertions, 1 deletions

diff --git a/jstests/sharding/error_propagation.js b/jstests/sharding/error_propagation.js
new file mode 100644
index 00000000000..9948da66190
--- /dev/null
+++ b/jstests/sharding/error_propagation.js
@@ -0,0 +1,23 @@
+(function() {
+    // Tests that errors encountered on shards are correctly returned to the client when mongos uses
+    // the legacy DBClientCursor method of executing commands on shards. We use aggregation here
+    // specifically because it is one of the few query paths that still uses the legacy DBClient
+    // classes in mongos.
+    "use strict";
+
+    var st = new ShardingTest({mongos: 1, shards: 1, rs: {nodes: 3}});
+
+    var db = st.getDB('test');
+    db.setSlaveOk(true);
+
+    assert.writeOK(db.foo.insert({a:1}, {writeConcern: {w:3}}));
+    assert.commandWorked(db.runCommand({aggregate: 'foo',
+                                        pipeline: [{$project: {total: {'$add': ['$a', 1]}}}]}));
+
+    assert.writeOK(db.foo.insert({a: [1, 2]}, {writeConcern: {w:3}}));
+
+    var res = db.runCommand({aggregate: 'foo',
+                             pipeline: [{$project: {total: {'$add': ['$a', 1]}}}]});
+    assert.commandFailed(res);
+    assert.eq("$add only supports numeric or date types, not Array", res.errmsg, printjson(res));
+}());
diff --git a/src/mongo/client/dbclientcursor.cpp b/src/mongo/client/dbclientcursor.cpp
index 861aa905547..2e0a5bdade3 100644
--- a/src/mongo/client/dbclientcursor.cpp
+++ b/src/mongo/client/dbclientcursor.cpp
@@ -417,7 +417,10 @@ bool DBClientCursor::peekError(BSONObj* error) {
     peek(v, 1);
 
     verify(v.size() == 1);
-    verify(hasErrField(v[0]));
+    // We check both the legacy error format, and the new error format. hasErrField checks for
+    // $err, and getStatusFromCommandResult checks for modern errors of the form '{ok: 0.0, code:
+    // <...>, errmsg: ...}'.
+    verify(hasErrField(v[0]) || !getStatusFromCommandResult(v[0]).isOK());
 
     if (error)
         *error = v[0].getOwned();