SERVER-31437 Fix parsing of host/db connect string

2 files changed, 36 insertions, 3 deletions

diff --git a/jstests/core/shell_connection_strings.js b/jstests/core/shell_connection_strings.js
new file mode 100644
index 00000000000..22861e6ce25
--- /dev/null
+++ b/jstests/core/shell_connection_strings.js
@@ -0,0 +1,33 @@
+// Test mongo shell connect strings.
+(function() {
+    'use strict';
+
+    const mongod = new MongoURI(db.getMongo().host).servers[0];
+    const host = mongod.host;
+    const port = mongod.port;
+
+    function testConnect(ok, ...args) {
+        const exitCode = runMongoProgram('mongo', '--eval', ';', ...args);
+        if (ok) {
+            assert.eq(exitCode, 0, "failed to connect with `" + args.join(' ') + "`");
+        } else {
+            assert.neq(
+                exitCode, 0, "unexpectedly succeeded connecting with `" + args.join(' ') + "`");
+        }
+    }
+
+    testConnect(true, `${host}:${port}`);
+    testConnect(true, `${host}:${port}/test`);
+    testConnect(true, `${host}:${port}/admin`);
+    testConnect(true, host, '--port', port);
+    testConnect(true, '--host', host, '--port', port, 'test');
+    testConnect(true, '--host', host, '--port', port, 'admin');
+    testConnect(true, `mongodb://${host}:${port}/test`);
+    testConnect(true, `mongodb://${host}:${port}/test?connectTimeoutMS=10000`);
+
+    // if a full URI is provided, you cannot also specify host or port
+    testConnect(false, `${host}/test`, '--port', port);
+    testConnect(false, `mongodb://${host}:${port}/test`, '--port', port);
+    testConnect(false, `mongodb://${host}:${port}/test`, '--host', host);
+    testConnect(false, `mongodb://${host}:${port}/test`, '--host', host, '--port', port);
+})();
diff --git a/src/mongo/shell/dbshell.cpp b/src/mongo/shell/dbshell.cpp
index 9273e7b6f25..34cdbed3d9e 100644
--- a/src/mongo/shell/dbshell.cpp
+++ b/src/mongo/shell/dbshell.cpp
@@ -332,11 +332,11 @@ string getURIFromArgs(const std::string& arg, const std::string& host, const std
         // --host provided, treat it as the connect string and get db from positional arg.
         return parseDbHost(arg, host);
     } else if (arg.size()) {
-        // --host missing, but we have a potential db/host positional arg.
+        // --host missing, but we have a potential host/db positional arg.
         const auto slashPos = arg.find('/');
         if (slashPos != std::string::npos) {
-            // db/host pair.
-            return parseDbHost(arg.substr(0, slashPos), arg.substr(slashPos + 1));
+            // host/db pair.
+            return parseDbHost(arg.substr(slashPos + 1), arg.substr(0, slashPos));
         }
 
         // Compatability formats.