SERVER-31630 getParameter for featureCompatibilityVersion must expose targetVersion

8 files changed, 149 insertions, 94 deletions

diff --git a/jstests/libs/feature_compatibility_version.js b/jstests/libs/feature_compatibility_version.js
new file mode 100644
index 00000000000..116706eaf27
--- /dev/null
+++ b/jstests/libs/feature_compatibility_version.js
@@ -0,0 +1,33 @@
+// Contains helpers for checking the featureCompatibilityVersion.
+
+/**
+ * Checks the featureCompatibilityVersion document and server parameter. The
+ * featureCompatibilityVersion document is of the form {_id: "featureCompatibilityVersion", version:
+ * <required>, targetVersion: <optional>}. The getParameter result is of the form
+ * {featureCompatibilityVersion: {version: <required>, targetVersion: <optional>}, ok: 1}.
+ */
+function checkFCV(adminDB, version, targetVersion) {
+    let res = adminDB.runCommand({getParameter: 1, featureCompatibilityVersion: 1});
+    assert.commandWorked(res);
+    assert.eq(res.featureCompatibilityVersion.version, version, tojson(res));
+    assert.eq(res.featureCompatibilityVersion.targetVersion, targetVersion, tojson(res));
+
+    let doc = adminDB.system.version.findOne({_id: "featureCompatibilityVersion"});
+    assert.eq(doc.version, version, tojson(doc));
+    assert.eq(doc.targetVersion, targetVersion, tojson(doc));
+}
+
+/**
+ * Checks the featureCompatibilityVersion document and server parameter for a 3.4 binary. In 3.4,
+ * the featureCompatibilityVersion document is of the form {_id: "featureCompatibilityVersion",
+ * version: <value>}. The getParameter result is of the form {featureCompatibilityVersion: <value>,
+ * ok: 1}.
+ */
+function checkFCV34(adminDB, version) {
+    let res = adminDB.runCommand({getParameter: 1, featureCompatibilityVersion: 1});
+    assert.commandWorked(res);
+    assert.eq(res.featureCompatibilityVersion, version, tojson(res));
+
+    let doc = adminDB.system.version.findOne({_id: "featureCompatibilityVersion"});
+    assert.eq(doc.version, version, tojson(doc));
+}
\ No newline at end of file
diff --git a/jstests/multiVersion/incomplete_upgrade_downgrade.js b/jstests/multiVersion/incomplete_upgrade_downgrade.js
index a46d9e7993c..f03533d3324 100644
--- a/jstests/multiVersion/incomplete_upgrade_downgrade.js
+++ b/jstests/multiVersion/incomplete_upgrade_downgrade.js
@@ -5,14 +5,7 @@
 (function() {
     "use strict";
 
-    let checkFCV = function(adminDB, version, targetVersion) {
-        let res = adminDB.runCommand({getParameter: 1, featureCompatibilityVersion: 1});
-        assert.commandWorked(res);
-        assert.eq(res.featureCompatibilityVersion, version);
-        let doc = adminDB.system.version.findOne({_id: "featureCompatibilityVersion"});
-        assert.eq(doc.version, version);
-        assert.eq(doc.targetVersion, targetVersion);
-    };
+    load("jstests/libs/feature_compatibility_version.js");
 
     let setFCV = function(adminDB, version) {
         assert.commandWorked(adminDB.runCommand({setFeatureCompatibilityVersion: version}));
diff --git a/jstests/multiVersion/set_feature_compatibility_version.js b/jstests/multiVersion/set_feature_compatibility_version.js
index d17eee1f235..c9917fee3d0 100644
--- a/jstests/multiVersion/set_feature_compatibility_version.js
+++ b/jstests/multiVersion/set_feature_compatibility_version.js
@@ -7,25 +7,9 @@ TestData.skipCheckingUUIDsConsistentAcrossCluster = true;
     "use strict";
 
     load("jstests/replsets/rslib.js");
+    load("jstests/libs/feature_compatibility_version.js");
     load("jstests/libs/get_index_helpers.js");
 
-    let checkFCV = function(adminDB, version, targetVersion) {
-        let res = adminDB.runCommand({getParameter: 1, featureCompatibilityVersion: 1});
-        assert.commandWorked(res);
-        assert.eq(res.featureCompatibilityVersion, version);
-
-        let doc = adminDB.system.version.findOne({_id: "featureCompatibilityVersion"});
-        assert.eq(doc.version, version);
-
-        // The 'targetVersion' field only exists on v3.6+ binaries, and is only present while an
-        // upgrade or downgrade is in progress.
-        if (targetVersion) {
-            assert.eq(doc.targetVersion, targetVersion);
-        } else {
-            assert.eq(null, doc.targetVersion);
-        }
-    };
-
     let res;
     const latest = "latest";
     const downgrade = "3.4";
@@ -204,7 +188,7 @@ TestData.skipCheckingUUIDsConsistentAcrossCluster = true;
         null, conn, "mongod was unable to start up with version=" + latest + " and no data files");
     assert.writeOK(conn.getDB("test").coll.insert({a: 5}));
     adminDB = conn.getDB("admin");
-    checkFCV(adminDB, "3.4");
+    checkFCV34(adminDB, "3.4");
     MongoRunner.stopMongod(conn);
 
     conn = MongoRunner.runMongod({dbpath: dbpath, binVersion: latest, noCleanData: true});
@@ -399,7 +383,8 @@ TestData.skipCheckingUUIDsConsistentAcrossCluster = true;
     assert.eq(res.featureCompatibilityVersion, "3.2");
     res = secondaryAdminDB.runCommand({getParameter: 1, featureCompatibilityVersion: 1});
     assert.commandWorked(res);
-    assert.eq(res.featureCompatibilityVersion, "3.4");
+    assert.eq(res.featureCompatibilityVersion.version, "3.4", tojson(res));
+    assert.eq(res.featureCompatibilityVersion.targetVersion, null, tojson(res));
     rst.stopSet();
 
     //
@@ -560,7 +545,7 @@ TestData.skipCheckingUUIDsConsistentAcrossCluster = true;
     downgradeShard.startSet();
     downgradeShard.initiate();
     assert.commandWorked(mongosAdminDB.runCommand({addShard: downgradeShard.getURL()}));
-    checkFCV(downgradeShard.getPrimary().getDB("admin"), "3.4");
+    checkFCV34(downgradeShard.getPrimary().getDB("admin"), "3.4");
 
     // call ShardingTest.stop before shutting down downgradeShard, so that the UUID check in
     // ShardingTest.stop can talk to downgradeShard.
diff --git a/jstests/multiVersion/set_schema_version.js b/jstests/multiVersion/set_schema_version.js
index e7ee9079230..3290cf53ce0 100644
--- a/jstests/multiVersion/set_schema_version.js
+++ b/jstests/multiVersion/set_schema_version.js
@@ -3,6 +3,7 @@
     "use strict";
 
     load("jstests/replsets/rslib.js");
+    load("jstests/libs/feature_compatibility_version.js");
     load("jstests/libs/get_index_helpers.js");
 
     const latest = "latest";
@@ -30,16 +31,6 @@
         });
     };
 
-    let checkFCV = function(adminDB, version, is34) {
-        if (!is34) {
-            let res = adminDB.runCommand({getParameter: 1, featureCompatibilityVersion: 1});
-            assert.commandWorked(res);
-            assert.eq(res.featureCompatibilityVersion, version);
-        }
-        assert.eq(adminDB.system.version.findOne({_id: "featureCompatibilityVersion"}).version,
-                  version);
-    };
-
     let setFCV = function(adminDB, version) {
         assert.commandWorked(adminDB.runCommand({setFeatureCompatibilityVersion: version}));
         checkFCV(adminDB, version);
@@ -102,7 +93,7 @@
         let downgradeAdminDB = downgradeConn.getDB("admin");
 
         // Check FCV document
-        checkFCV(downgradeAdminDB, "3.4", true);
+        checkFCV34(downgradeAdminDB, "3.4");
 
         // Ensure there are no UUIDs
         checkCollectionUUIDs(downgradeAdminDB, true);
@@ -185,10 +176,10 @@
 
         // Initially featureCompatibilityVersion document is 3.4 on primary and secondaries.
         checkCollectionUUIDs(downgradePrimaryAdminDB, true);
-        checkFCV(downgradePrimaryAdminDB, "3.4", true);
+        checkFCV34(downgradePrimaryAdminDB, "3.4");
         for (let j = 0; j < downgradeSecondaries.length; j++) {
             let secondaryAdminDB = downgradeSecondaries[j].getDB("admin");
-            checkFCV(secondaryAdminDB, "3.4", true);
+            checkFCV34(secondaryAdminDB, "3.4");
 
             // Ensure no collections have UUIDs
             checkCollectionUUIDs(secondaryAdminDB, true);
diff --git a/jstests/noPassthrough/arrayFilters_feature_compatibility_version.js b/jstests/noPassthrough/arrayFilters_feature_compatibility_version.js
index 6877bc12c30..940ea71b762 100644
--- a/jstests/noPassthrough/arrayFilters_feature_compatibility_version.js
+++ b/jstests/noPassthrough/arrayFilters_feature_compatibility_version.js
@@ -19,9 +19,6 @@
     //
 
     assert.commandWorked(adminDB.runCommand({setFeatureCompatibilityVersion: "3.4"}));
-    res = adminDB.runCommand({getParameter: 1, featureCompatibilityVersion: 1});
-    assert.commandWorked(res);
-    assert.eq("3.4", res.featureCompatibilityVersion);
 
     // Update.
     res = coll.update({_id: 0}, {$set: {"a.$[i]": 5}}, {arrayFilters: [{i: 0}]});
@@ -54,9 +51,6 @@
     //
 
     assert.commandWorked(adminDB.runCommand({setFeatureCompatibilityVersion: "3.6"}));
-    res = adminDB.runCommand({getParameter: 1, featureCompatibilityVersion: 1});
-    assert.commandWorked(res);
-    assert.eq("3.6", res.featureCompatibilityVersion);
 
     // Update.
     assert.writeOK(coll.update({_id: 0}, {$set: {"a.$[i]": 5}}, {arrayFilters: [{i: 0}]}));
diff --git a/jstests/noPassthrough/drop_collections_two_phase_feature_compatibility_version.js b/jstests/noPassthrough/drop_collections_two_phase_feature_compatibility_version.js
index cfaa25407e7..1dc34206575 100644
--- a/jstests/noPassthrough/drop_collections_two_phase_feature_compatibility_version.js
+++ b/jstests/noPassthrough/drop_collections_two_phase_feature_compatibility_version.js
@@ -10,6 +10,7 @@
 (function() {
     "use strict";
 
+    load("jstests/libs/feature_compatibility_version.js");
     load("jstests/replsets/libs/two_phase_drops.js");  // For TwoPhaseDropCollectionTest.
 
     // Set feature compatibility version on the given node. Note that setting FCV requires a
@@ -17,10 +18,7 @@
     function setFCV(node, featureCompatibilityVersion) {
         assert.commandWorked(
             node.adminCommand({setFeatureCompatibilityVersion: featureCompatibilityVersion}));
-        let res = node.adminCommand({getParameter: 1, featureCompatibilityVersion: 1});
-        assert.commandWorked(
-            res, "failed to set feature compatibility version to " + featureCompatibilityVersion);
-        assert.eq(featureCompatibilityVersion, res.featureCompatibilityVersion);
+        checkFCV(node.getDB("admin"), featureCompatibilityVersion);
     }
 
     // Restart the primary of the given ReplSetTest.
diff --git a/jstests/noPassthrough/feature_compatibility_version.js b/jstests/noPassthrough/feature_compatibility_version.js
index 9645ed79163..de37a2a29a2 100644
--- a/jstests/noPassthrough/feature_compatibility_version.js
+++ b/jstests/noPassthrough/feature_compatibility_version.js
@@ -4,84 +4,124 @@
 (function() {
     "use strict";
 
+    load("jstests/libs/feature_compatibility_version.js");
+
+    /**
+     * Checks that the featureCompatibilityVersion document is missing, and the
+     * featureCompatibilityVersion server parameter is "3.4".
+     */
+    let checkFCVDocumentMissing = function(adminDB) {
+        assert.eq(null, adminDB.system.version.findOne({_id: "featureCompatibilityVersion"}));
+
+        let res = adminDB.runCommand({getParameter: 1, featureCompatibilityVersion: 1});
+        assert.commandWorked(res);
+        assert.eq("3.4", res.featureCompatibilityVersion.version, tojson(res));
+        assert.eq(null, res.featureCompatibilityVersion.targetVersion, tojson(res));
+    };
+
     const conn = MongoRunner.runMongod({});
     assert.neq(null, conn, "mongod was unable to start up");
 
     let adminDB = conn.getDB("admin");
 
     // Initially the featureCompatibilityVersion is 3.6.
-    let res = adminDB.runCommand({getParameter: 1, featureCompatibilityVersion: 1});
-    assert.commandWorked(res);
-    assert.eq("3.6", res.featureCompatibilityVersion);
+    checkFCV(adminDB, "3.6");
 
     // Updating the featureCompatibilityVersion document changes the featureCompatibilityVersion
     // server parameter.
     assert.writeOK(adminDB.system.version.update({_id: "featureCompatibilityVersion"},
                                                  {$set: {version: "3.4"}}));
-    res = adminDB.runCommand({getParameter: 1, featureCompatibilityVersion: 1});
-    assert.commandWorked(res);
-    assert.eq("3.4", res.featureCompatibilityVersion);
+    checkFCV(adminDB, "3.4");
 
     assert.writeOK(adminDB.system.version.update({_id: "featureCompatibilityVersion"},
-                                                 {$set: {version: "3.6"}}));
-    res = adminDB.runCommand({getParameter: 1, featureCompatibilityVersion: 1});
-    assert.commandWorked(res);
-    assert.eq("3.6", res.featureCompatibilityVersion);
+                                                 {$set: {version: "3.4", targetVersion: "3.6"}}));
+    checkFCV(adminDB, "3.4", "3.6");
+
+    assert.writeOK(adminDB.system.version.update({_id: "featureCompatibilityVersion"},
+                                                 {$set: {version: "3.4", targetVersion: "3.4"}}));
+    checkFCV(adminDB, "3.4", "3.4");
+
+    assert.writeOK(
+        adminDB.system.version.update({_id: "featureCompatibilityVersion"},
+                                      {$set: {version: "3.6"}, $unset: {targetVersion: true}}));
+    checkFCV(adminDB, "3.6");
 
     // Updating the featureCompatibilityVersion document with an invalid version fails.
     assert.writeErrorWithCode(adminDB.system.version.update({_id: "featureCompatibilityVersion"},
                                                             {$set: {version: "3.2"}}),
                               ErrorCodes.BadValue);
-    res = adminDB.runCommand({getParameter: 1, featureCompatibilityVersion: 1});
-    assert.commandWorked(res);
-    assert.eq("3.6", res.featureCompatibilityVersion);
+    checkFCV(adminDB, "3.6");
+
+    // Updating the featureCompatibilityVersion document with an invalid targetVersion fails.
+    assert.writeErrorWithCode(adminDB.system.version.update({_id: "featureCompatibilityVersion"},
+                                                            {$set: {targetVersion: "3.4"}}),
+                              ErrorCodes.BadValue);
+    checkFCV(adminDB, "3.6");
+
+    assert.writeErrorWithCode(adminDB.system.version.update({_id: "featureCompatibilityVersion"},
+                                                            {$set: {targetVersion: "3.6"}}),
+                              ErrorCodes.BadValue);
+    checkFCV(adminDB, "3.6");
 
     // Deleting the featureCompatibilityVersion document changes the featureCompatibilityVersion
     // server parameter to 3.4.
     assert.writeOK(adminDB.system.version.remove({_id: "featureCompatibilityVersion"}));
-    res = adminDB.runCommand({getParameter: 1, featureCompatibilityVersion: 1});
-    assert.commandWorked(res);
-    assert.eq("3.4", res.featureCompatibilityVersion);
+    checkFCVDocumentMissing(adminDB);
 
     // Inserting a featureCompatibilityVersion document with an invalid version fails.
     assert.writeErrorWithCode(
         adminDB.system.version.insert({_id: "featureCompatibilityVersion", version: "3.2"}),
         ErrorCodes.BadValue);
-    res = adminDB.runCommand({getParameter: 1, featureCompatibilityVersion: 1});
-    assert.commandWorked(res);
-    assert.eq("3.4", res.featureCompatibilityVersion);
+    checkFCVDocumentMissing(adminDB);
 
     assert.writeErrorWithCode(
         adminDB.system.version.insert({_id: "featureCompatibilityVersion", version: "3.8"}),
         ErrorCodes.BadValue);
-    res = adminDB.runCommand({getParameter: 1, featureCompatibilityVersion: 1});
-    assert.commandWorked(res);
-    assert.eq("3.4", res.featureCompatibilityVersion);
+    checkFCVDocumentMissing(adminDB);
+
+    // Inserting a featureCompatibilityVersion document with an invalid targetVersion fails.
+    assert.writeErrorWithCode(
+        adminDB.system.version.insert(
+            {_id: "featureCompatibilityVersion", version: "3.6", targetVersion: "3.4"}),
+        ErrorCodes.BadValue);
+    checkFCVDocumentMissing(adminDB);
+
+    assert.writeErrorWithCode(
+        adminDB.system.version.insert(
+            {_id: "featureCompatibilityVersion", version: "3.6", targetVersion: "3.6"}),
+        ErrorCodes.BadValue);
+    checkFCVDocumentMissing(adminDB);
 
     // Inserting the featureCompatibilityVersion document changes the featureCompatibilityVersion
     // server parameter.
     assert.writeOK(
         adminDB.system.version.insert({_id: "featureCompatibilityVersion", version: "3.4"}));
-    res = adminDB.runCommand({getParameter: 1, featureCompatibilityVersion: 1});
-    assert.commandWorked(res);
-    assert.eq("3.4", res.featureCompatibilityVersion);
+    checkFCV(adminDB, "3.4");
+
+    assert.writeOK(adminDB.system.version.remove({_id: "featureCompatibilityVersion"}));
+    checkFCVDocumentMissing(adminDB);
+
+    assert.writeOK(adminDB.system.version.insert(
+        {_id: "featureCompatibilityVersion", version: "3.4", targetVersion: "3.6"}));
+    checkFCV(adminDB, "3.4", "3.6");
+
+    assert.writeOK(adminDB.system.version.remove({_id: "featureCompatibilityVersion"}));
+    checkFCVDocumentMissing(adminDB);
+
+    assert.writeOK(adminDB.system.version.insert(
+        {_id: "featureCompatibilityVersion", version: "3.4", targetVersion: "3.4"}));
+    checkFCV(adminDB, "3.4", "3.4");
 
     assert.writeOK(adminDB.system.version.remove({_id: "featureCompatibilityVersion"}));
-    res = adminDB.runCommand({getParameter: 1, featureCompatibilityVersion: 1});
-    assert.commandWorked(res);
-    assert.eq("3.4", res.featureCompatibilityVersion);
+    checkFCVDocumentMissing(adminDB);
 
     assert.writeOK(
         adminDB.system.version.insert({_id: "featureCompatibilityVersion", version: "3.6"}));
-    res = adminDB.runCommand({getParameter: 1, featureCompatibilityVersion: 1});
-    assert.commandWorked(res);
-    assert.eq("3.6", res.featureCompatibilityVersion);
+    checkFCV(adminDB, "3.6");
 
     // Dropping the admin database changes the featureCompatibilityVersion server parameter to 3.4.
     adminDB.dropDatabase();
-    res = adminDB.runCommand({getParameter: 1, featureCompatibilityVersion: 1});
-    assert.commandWorked(res);
-    assert.eq("3.4", res.featureCompatibilityVersion);
+    checkFCVDocumentMissing(adminDB);
 
     MongoRunner.stopMongod(conn);
 }());
diff --git a/src/mongo/db/commands/feature_compatibility_version.cpp b/src/mongo/db/commands/feature_compatibility_version.cpp
index 10444bea57c..c4b3053d4ce 100644
--- a/src/mongo/db/commands/feature_compatibility_version.cpp
+++ b/src/mongo/db/commands/feature_compatibility_version.cpp
@@ -448,15 +448,36 @@ public:
                           ) {}
 
     virtual void append(OperationContext* opCtx, BSONObjBuilder& b, const std::string& name) {
-        std::string version;
-        if (serverGlobalParams.featureCompatibility.isFullyUpgradedTo36()) {
-            b.append(name,
-                     FeatureCompatibilityVersion::toString(
-                         ServerGlobalParams::FeatureCompatibility::Version::kFullyUpgradedTo36));
-        } else {
-            b.append(name,
-                     FeatureCompatibilityVersion::toString(
-                         ServerGlobalParams::FeatureCompatibility::Version::kFullyDowngradedTo34));
+        BSONObjBuilder featureCompatibilityVersionBuilder(b.subobjStart(name));
+        switch (serverGlobalParams.featureCompatibility.getVersion()) {
+            case ServerGlobalParams::FeatureCompatibility::Version::kFullyUpgradedTo36:
+                featureCompatibilityVersionBuilder.append(
+                    FeatureCompatibilityVersion::kVersionField,
+                    FeatureCompatibilityVersionCommandParser::kVersion36);
+                return;
+            case ServerGlobalParams::FeatureCompatibility::Version::kFullyDowngradedTo34:
+                featureCompatibilityVersionBuilder.append(
+                    FeatureCompatibilityVersion::kVersionField,
+                    FeatureCompatibilityVersionCommandParser::kVersion34);
+                return;
+            case ServerGlobalParams::FeatureCompatibility::Version::kUpgradingTo36:
+                featureCompatibilityVersionBuilder.append(
+                    FeatureCompatibilityVersion::kVersionField,
+                    FeatureCompatibilityVersionCommandParser::kVersion34);
+                featureCompatibilityVersionBuilder.append(
+                    FeatureCompatibilityVersion::kTargetVersionField,
+                    FeatureCompatibilityVersionCommandParser::kVersion36);
+                return;
+            case ServerGlobalParams::FeatureCompatibility::Version::kDowngradingTo34:
+                featureCompatibilityVersionBuilder.append(
+                    FeatureCompatibilityVersion::kVersionField,
+                    FeatureCompatibilityVersionCommandParser::kVersion34);
+                featureCompatibilityVersionBuilder.append(
+                    FeatureCompatibilityVersion::kTargetVersionField,
+                    FeatureCompatibilityVersionCommandParser::kVersion34);
+                return;
+            default:
+                MONGO_UNREACHABLE;
         }
     }