refactor!: remove deprecated Collection.group helper

The group command was deprecated in MongoDB 3.4 and removed in
MongoDB 3.6, this PR removes it from the driver.

NODE-1487

Author: emadum

src/collection.ts

@@ -77,7 +77,6 @@ import { RenameOperation, RenameOptions } from './operations/rename';
 import { ReplaceOneOperation, ReplaceOptions } from './operations/replace_one';
 import { CollStatsOperation, CollStatsOptions } from './operations/stats';
 import { executeOperation } from './operations/execute_operation';
-import { EvalGroupOperation, GroupOperation } from './operations/group';
 import type { Db } from './db';
 import type { OperationOptions, Hint } from './operations/operation';
 import type { IndexInformationOptions } from './operations/common_functions';
@@ -1510,76 +1509,6 @@ export class Collection implements OperationParent {
     );
   }
 
-  /**
-   * Run a group command across a collection
-   *
-   * @deprecated MongoDB 3.6 or higher no longer supports the group command. We recommend rewriting using the aggregation framework.
-   * @param keys - An object, array or function expressing the keys to group by.
-   * @param condition - An optional condition that must be true for a row to be considered.
-   * @param initial - Initial value of the aggregation counter object.
-   * @param reduce - The reduce function aggregates (reduces) the objects iterated
-   * @param finalize - An optional function to be run on each item in the result set just before the item is returned.
-   * @param command - Specify if you wish to run using the internal group command or using eval, default is true.
-   * @param options - Optional settings for the command
-   * @param callback - An optional callback, a Promise will be returned if none is provided
-   */
-  group(
-    // eslint-disable-next-line @typescript-eslint/explicit-module-boundary-types
-    keys: any,
-    condition: Document,
-    initial: Document,
-    // TODO: Use labeled tuples when api-extractor supports TS 4.0
-    ...args: [/*reduce?:*/ any, /*finalize?:*/ any, /*command?:*/ any, /*callback?:*/ Callback]
-  ): Promise<Document> | void {
-    const callback = typeof args[args.length - 1] === 'function' ? args.pop() : undefined;
-    let reduce = args.length ? args.shift() : undefined;
-    let finalize = args.length ? args.shift() : undefined;
-    let command = args.length ? args.shift() : undefined;
-    let options = args.length ? args.shift() || {} : {};
-
-    // Make sure we are backward compatible
-    if (!(typeof finalize === 'function')) {
-      command = finalize;
-      finalize = undefined;
-    }
-
-    if (
-      !Array.isArray(keys) &&
-      keys instanceof Object &&
-      typeof keys !== 'function' &&
-      !(keys._bsontype === 'Code')
-    ) {
-      keys = Object.keys(keys);
-    }
-
-    if (typeof reduce === 'function') {
-      reduce = reduce.toString();
-    }
-
-    if (typeof finalize === 'function') {
-      finalize = finalize.toString();
-    }
-
-    // Set up the command as default
-    command = command == null ? true : command;
-
-    options = resolveOptions(this, options);
-
-    if (command == null) {
-      return executeOperation(
-        getTopology(this),
-        new EvalGroupOperation(this, keys, condition, initial, reduce, finalize, options),
-        callback
-      );
-    }
-
-    return executeOperation(
-      getTopology(this),
-      new GroupOperation(this, keys, condition, initial, reduce, finalize, options),
-      callback
-    );
-  }
-
   /**
    * Find and modify a document.
    *
@@ -1694,8 +1623,3 @@ Collection.prototype.findAndRemove = deprecate(
   Collection.prototype.findAndRemove,
   'collection.findAndRemove is deprecated. Use findOneAndDelete instead.'
 );
-
-Collection.prototype.group = deprecate(
-  Collection.prototype.group,
-  'MongoDB 3.6 or higher no longer supports the group command. We recommend rewriting using the aggregation framework.'
-);

src/operations/group.ts

@@ -717,14 +717,7 @@ class ServerSessionPool {
 // TODO: this should be codified in command construction
 // @see https://github.com/mongodb/specifications/blob/master/source/read-write-concern/read-write-concern.rst#read-concern
 function commandSupportsReadConcern(command: Document, options?: Document): boolean {
-  if (
-    command.aggregate ||
-    command.count ||
-    command.distinct ||
-    command.find ||
-    command.geoNear ||
-    command.group
-  ) {
+  if (command.aggregate || command.count || command.distinct || command.find || command.geoNear) {
     return true;
   }
 

src/sessions.ts

@@ -166,50 +166,6 @@ describe('Collation', function () {
     }
   });
 
-  it('Successfully pass through collation to group command', {
-    metadata: { requires: { generators: true, topology: 'single', mongodb: '<=4.1.0' } },
-
-    test: function () {
-      const configuration = this.configuration;
-      const client = configuration.newClient(`mongodb://${testContext.server.uri()}/test`);
-      const primary = [Object.assign({}, mock.DEFAULT_ISMASTER)];
-
-      let commandResult;
-      testContext.server.setMessageHandler(request => {
-        var doc = request.document;
-        if (doc.ismaster) {
-          request.reply(primary[0]);
-        } else if (doc.group) {
-          commandResult = doc;
-          request.reply({ ok: 1 });
-        } else if (doc.endSessions) {
-          request.reply({ ok: 1 });
-        }
-      });
-
-      return client.connect().then(() => {
-        const db = client.db(configuration.db);
-
-        return db
-          .collection('test')
-          .group(
-            [],
-            { a: { $gt: 1 } },
-            { count: 0 },
-            'function (obj, prev) { prev.count++; }',
-            'function (obj, prev) { prev.count++; }',
-            true,
-            { collation: { caseLevel: true } }
-          )
-          .then(() => {
-            expect(commandResult).to.have.property('collation');
-            expect(commandResult.collation).to.eql({ caseLevel: true });
-            return client.close();
-          });
-      });
-    }
-  });
-
   it('Successfully pass through collation to mapReduce command', {
     metadata: { requires: { generators: true, topology: 'single' } },
 

test/functional/collations.test.js

@@ -9,62 +9,6 @@ describe('MapReduce', function () {
     return setupDatabase(this.configuration, ['outputCollectionDb']);
   });
 
-  it('shouldCorrectlyExecuteGroupFunctionWithFinalizeFunction', {
-    metadata: {
-      requires: {
-        mongodb: '<=4.1.0',
-        topology: ['single', 'replicaset', 'sharded', 'ssl', 'heap', 'wiredtiger']
-      }
-    },
-
-    test: function (done) {
-      var configuration = this.configuration;
-      var client = configuration.newClient(configuration.writeConcernMax(), { poolSize: 1 });
-      client.connect(function (err, client) {
-        var db = client.db(configuration.db);
-        db.createCollection('test_group2', function (err, collection) {
-          collection.group(
-            [],
-            {},
-            { count: 0 },
-            'function (obj, prev) { prev.count++; }',
-            true,
-            function (err, results) {
-              test.deepEqual([], results);
-
-              // Trigger some inserts
-              collection.insert(
-                [{ a: 2 }, { b: 5, a: 0 }, { a: 1 }, { c: 2, a: 0 }],
-                configuration.writeConcernMax(),
-                function (err) {
-                  expect(err).to.not.exist;
-                  collection.group(
-                    [],
-                    {},
-                    { count: 0, running_average: 0 },
-                    function (doc, out) {
-                      out.count++;
-                      out.running_average += doc.a;
-                    },
-                    function (out) {
-                      out.average = out.running_average / out.count;
-                    },
-                    true,
-                    function (err, results) {
-                      test.equal(3, results[0].running_average);
-                      test.equal(0.75, results[0].average);
-                      client.close(done);
-                    }
-                  );
-                }
-              );
-            }
-          );
-        });
-      });
-    }
-  });
-
   /**
    * Mapreduce tests
    */
@@ -386,68 +330,6 @@ describe('MapReduce', function () {
     }
   });
 
-  it('shouldCorrectlyReturnNestedKeys', {
-    metadata: {
-      requires: {
-        mongodb: '<=4.1.0', // Because of use of `group` command
-        topology: ['single', 'replicaset', 'sharded', 'ssl', 'heap', 'wiredtiger']
-      }
-    },
-
-    test: function (done) {
-      var configuration = this.configuration;
-      var client = configuration.newClient(configuration.writeConcernMax(), { poolSize: 1 });
-      client.connect(function (err, client) {
-        var db = client.db(configuration.db);
-        var start = new Date().setTime(new Date().getTime() - 10000);
-        var end = new Date().setTime(new Date().getTime() + 10000);
-
-        var keys = {
-          'data.lastname': true
-        };
-
-        var condition = {
-          'data.date': {
-            $gte: start,
-            $lte: end
-          }
-        };
-
-        condition = {};
-
-        var initial = {
-          count: 0
-        };
-
-        var reduce = function (doc, output) {
-          output.count++;
-        };
-
-        // Execute the group
-        db.createCollection('data', function (err, collection) {
-          collection.insert(
-            {
-              data: {
-                lastname: 'smith',
-                date: new Date()
-              }
-            },
-            configuration.writeConcernMax(),
-            function (err) {
-              expect(err).to.not.exist;
-              // Execute the group
-              collection.group(keys, condition, initial, reduce, true, function (err, r) {
-                test.equal(1, r[0].count);
-                test.equal('smith', r[0]['data.lastname']);
-                client.close(done);
-              });
-            }
-          );
-        });
-      });
-    }
-  });
-
   /**
    * Mapreduce tests
    */