refactor: remove SKIP_SESSION aspect

Now that we have disambiguated `maybePromise` from
`executeOperation`, there is no need to signal that an operation
should skip impliict sessions.

lib/operations/count.js

@@ -1,8 +1,6 @@
 'use strict';
 
-const Aspect = require('./operation').Aspect;
 const buildCountCommand = require('./common_functions').buildCountCommand;
-const defineAspects = require('./operation').defineAspects;
 const OperationBase = require('./operation').OperationBase;
 
 class CountOperation extends OperationBase {
@@ -67,6 +65,4 @@ class CountOperation extends OperationBase {
   }
 }
 
-defineAspects(CountOperation, Aspect.SKIP_SESSION);
-
 module.exports = CountOperation;

lib/operations/execute_operation.js

@@ -30,11 +30,7 @@ function executeOperation(topology, operation, callback) {
     throw new TypeError('This method requires a valid operation instance');
   }
 
-  if (
-    isUnifiedTopology(topology) &&
-    !operation.hasAspect(Aspect.SKIP_SESSION) &&
-    topology.shouldCheckForSessionSupport()
-  ) {
+  if (isUnifiedTopology(topology) && topology.shouldCheckForSessionSupport()) {
     return selectServerForSessionSupport(topology, operation, callback);
   }
 
@@ -43,7 +39,7 @@ function executeOperation(topology, operation, callback) {
   // The driver sessions spec mandates that we implicitly create sessions for operations
   // that are not explicitly provided with a session.
   let session, owner;
-  if (!operation.hasAspect(Aspect.SKIP_SESSION) && topology.hasSessionSupport()) {
+  if (topology.hasSessionSupport()) {
     if (operation.session == null) {
       owner = Symbol();
       session = topology.startSession({ owner });

lib/operations/find.js

@@ -28,8 +28,7 @@ class FindOperation extends OperationBase {
 defineAspects(FindOperation, [
   Aspect.READ_OPERATION,
   Aspect.RETRYABLE,
-  Aspect.EXECUTE_WITH_SELECTION,
-  Aspect.SKIP_SESSION
+  Aspect.EXECUTE_WITH_SELECTION
 ]);
 
 module.exports = FindOperation;

lib/operations/operation.js

@@ -2,7 +2,6 @@
 
 const Aspect = {
   READ_OPERATION: Symbol('READ_OPERATION'),
-  SKIP_SESSION: Symbol('SKIP_SESSION'),
   WRITE_OPERATION: Symbol('WRITE_OPERATION'),
   RETRYABLE: Symbol('RETRYABLE'),
   EXECUTE_WITH_SELECTION: Symbol('EXECUTE_WITH_SELECTION')
@@ -12,8 +11,7 @@ const Aspect = {
  * This class acts as a parent class for any operation and is responsible for setting this.options,
  * as well as setting and getting a session.
  * Additionally, this class implements `hasAspect`, which determines whether an operation has
- * a specific aspect, including `SKIP_SESSION` and other aspects to encode retryability
- * and other functionality.
+ * a specific aspect.
  */
 class OperationBase {
   constructor(options) {

lib/operations/remove_user.js

@@ -47,6 +47,6 @@ class RemoveUserOperation extends CommandOperation {
   }
 }
 
-defineAspects(RemoveUserOperation, [Aspect.WRITE_OPERATION, Aspect.SKIP_SESSIONS]);
+defineAspects(RemoveUserOperation, Aspect.WRITE_OPERATION);
 
 module.exports = RemoveUserOperation;