revert(collection): reverting collection-mapping features

Reverts #1698. With mongodb/js-bson#253 and other approaches to
document-class mapping on the table, we'd like to have further
discussion before committing to any one API approach.

Reopens NODE-1450

Author: daprahamian

lib/collection.js

@@ -422,11 +422,6 @@ Collection.prototype.find = function(query, options, callback) {
 
   const cursor = this.s.topology.cursor(this.s.namespace, findCommand, newOptions);
 
-  // automatically call map on the cursor if the map option is set
-  if (typeof this.s.options.map === 'function') {
-    cursor.map(this.s.options.map);
-  }
-
   return typeof callback === 'function' ? handleCallback(callback, null, cursor) : cursor;
 };
 
@@ -756,10 +751,6 @@ Collection.prototype.replaceOne = function(filter, doc, options, callback) {
     options.ignoreUndefined = this.s.options.ignoreUndefined;
   }
 
-  if (typeof this.s.options.unmap === 'function') {
-    doc = this.s.options.unmap(doc);
-  }
-
   return executeOperation(this.s.topology, replaceOne, [this, filter, doc, options, callback]);
 };
 

lib/db.js

@@ -305,8 +305,6 @@ const collectionKeys = [
  * @param {(ReadPreference|string)} [options.readPreference=null] The preferred read preference (ReadPreference.PRIMARY, ReadPreference.PRIMARY_PREFERRED, ReadPreference.SECONDARY, ReadPreference.SECONDARY_PREFERRED, ReadPreference.NEAREST).
  * @param {boolean} [options.serializeFunctions=false] Serialize functions on any object.
  * @param {boolean} [options.strict=false] Returns an error if the collection does not exist
- * @param {function} [options.map] Function to map documents returned in find, findOne, and findAndModify commands.
- * @param {function} [options.unmap] Function to unmap documents passed to insertOne, insertMany, and replaceOne commands.
  * @param {object} [options.readConcern=null] Specify a read concern for the collection. (only MongoDB 3.2 or higher supported)
  * @param {object} [options.readConcern.level='local'] Specify a read concern level for the collection operations, one of [local|majority]. (only MongoDB 3.2 or higher supported)
  * @param {Db~collectionResultCallback} [callback] The collection result callback

lib/operations/collection_ops.js

@@ -502,10 +502,6 @@ function findAndModify(coll, query, sort, doc, options, callback) {
   executeCommand(coll.s.db, queryObject, finalOptions, (err, result) => {
     if (err) return handleCallback(callback, err, null);
 
-    if (result && result.value && typeof coll.s.options.map === 'function') {
-      result.value = coll.s.options.map(result.value);
-    }
-
     return handleCallback(callback, null, result);
   });
 }
@@ -1046,11 +1042,8 @@ function prepareDocs(coll, docs, options) {
       ? options.forceServerObjectId
       : coll.s.db.options.forceServerObjectId;
 
-  const unmap = typeof coll.s.options.unmap === 'function' ? coll.s.options.unmap : false;
-
   // no need to modify the docs if server sets the ObjectId
-  // and unmap collection option is unset
-  if (forceServerObjectId === true && !unmap) {
+  if (forceServerObjectId === true) {
     return docs;
   }
 
@@ -1059,7 +1052,7 @@ function prepareDocs(coll, docs, options) {
       doc._id = coll.s.pkFactory.createPk();
     }
 
-    return unmap ? unmap(doc) : doc;
+    return doc;
   });
 }