Cleanup

node_modules/mongodb/lib/operations/execute_operation.js

@@ -1,5 +1,6 @@
 'use strict';
 
+const maybePromise = require('../utils').maybePromise;
 const MongoError = require('../core/error').MongoError;
 const Aspect = require('./operation').Aspect;
 const OperationBase = require('./operation').OperationBase;
@@ -21,7 +22,7 @@ const isUnifiedTopology = require('../core/utils').isUnifiedTopology;
  * @param {Operation} operation The operation to execute
  * @param {function} callback The command result callback
  */
-function executeOperation(topology, operation, callback) {
+function executeOperation(topology, operation, cb) {
   if (topology == null) {
     throw new TypeError('This method requires a valid topology instance');
   }
@@ -30,64 +31,57 @@ function executeOperation(topology, operation, callback) {
     throw new TypeError('This method requires a valid operation instance');
   }
 
-  if (isUnifiedTopology(topology) && topology.shouldCheckForSessionSupport()) {
-    return selectServerForSessionSupport(topology, operation, callback);
-  }
-
-  const Promise = topology.s.promiseLibrary;
-
-  // The driver sessions spec mandates that we implicitly create sessions for operations
-  // that are not explicitly provided with a session.
-  let session, owner;
-  if (topology.hasSessionSupport()) {
-    if (operation.session == null) {
-      owner = Symbol();
-      session = topology.startSession({ owner });
-      operation.session = session;
-    } else if (operation.session.hasEnded) {
-      throw new MongoError('Use of expired sessions is not permitted');
+  return maybePromise(topology, cb, callback => {
+    if (isUnifiedTopology(topology) && topology.shouldCheckForSessionSupport()) {
+      // Recursive call to executeOperation after a server selection
+      return selectServerForSessionSupport(topology, operation, callback);
     }
-  }
 
-  let result;
-  if (typeof callback !== 'function') {
-    result = new Promise((resolve, reject) => {
-      callback = (err, res) => {
-        if (err) return reject(err);
-        resolve(res);
-      };
-    });
-  }
-
-  function executeCallback(err, result) {
-    if (session && session.owner === owner) {
-      session.endSession();
-      if (operation.session === session) {
-        operation.clearSession();
+    // The driver sessions spec mandates that we implicitly create sessions for operations
+    // that are not explicitly provided with a session.
+    let session, owner;
+    if (topology.hasSessionSupport()) {
+      if (operation.session == null) {
+        owner = Symbol();
+        session = topology.startSession({ owner });
+        operation.session = session;
+      } else if (operation.session.hasEnded) {
+        return callback(new MongoError('Use of expired sessions is not permitted'));
       }
+    } else if (operation.session) {
+      // If the user passed an explicit session and we are still, after server selection,
+      // trying to run against a topology that doesn't support sessions we error out.
+      return callback(new MongoError('Current topology does not support sessions'));
     }
 
-    callback(err, result);
-  }
-
-  try {
-    if (operation.hasAspect(Aspect.EXECUTE_WITH_SELECTION)) {
-      executeWithServerSelection(topology, operation, executeCallback);
-    } else {
-      operation.execute(executeCallback);
-    }
-  } catch (e) {
-    if (session && session.owner === owner) {
-      session.endSession();
-      if (operation.session === session) {
-        operation.clearSession();
+    function executeCallback(err, result) {
+      if (session && session.owner === owner) {
+        session.endSession();
+        if (operation.session === session) {
+          operation.clearSession();
+        }
       }
+
+      callback(err, result);
     }
 
-    throw e;
-  }
+    try {
+      if (operation.hasAspect(Aspect.EXECUTE_WITH_SELECTION)) {
+        executeWithServerSelection(topology, operation, executeCallback);
+      } else {
+        operation.execute(executeCallback);
+      }
+    } catch (error) {
+      if (session && session.owner === owner) {
+        session.endSession();
+        if (operation.session === session) {
+          operation.clearSession();
+        }
+      }
 
-  return result;
+      callback(error);
+    }
+  });
 }
 
 function supportsRetryableReads(server) {
@@ -139,7 +133,6 @@ function executeWithServerSelection(topology, operation, callback) {
       callback(err, null);
       return;
     }
-
     const shouldRetryReads =
       topology.s.options.retryReads !== false &&
       operation.session &&
@@ -156,31 +149,16 @@ function executeWithServerSelection(topology, operation, callback) {
   });
 }
 
-// TODO: This is only supported for unified topology, it should go away once
-//       we remove support for legacy topology types.
+// The Unified Topology runs serverSelection before executing every operation
+// Session support is determined by the result of a monitoring check triggered by this selection
 function selectServerForSessionSupport(topology, operation, callback) {
-  const Promise = topology.s.promiseLibrary;
-
-  let result;
-  if (typeof callback !== 'function') {
-    result = new Promise((resolve, reject) => {
-      callback = (err, result) => {
-        if (err) return reject(err);
-        resolve(result);
-      };
-    });
-  }
-
   topology.selectServer(ReadPreference.primaryPreferred, err => {
     if (err) {
-      callback(err);
-      return;
+      return callback(err);
     }
 
     executeOperation(topology, operation, callback);
   });
-
-  return result;
 }
 
 module.exports = executeOperation;