feat(NODE-7139): remove pre-4.2 logic and deprecate dead code

src/cmap/connection.ts

@@ -284,6 +284,7 @@ export class Connection extends TypedEventEmitter<ConnectionEvents> {
   private get supportsOpMsg(): boolean {
     return (
       this.description != null &&
+      // TODO(NODE-6672,NODE-6287): This guard is primarily for maxWireVersion = 0
       maxWireVersion(this) >= 6 &&
       !this.description.__nodejs_mock_server__
     );
@@ -880,12 +881,6 @@ export class CryptoConnection extends Connection {
       return await super.command<T>(ns, cmd, options, responseType);
     }
 
-    if (serverWireVersion < 8) {
-      throw new MongoCompatibilityError(
-        'Auto-encryption requires a minimum MongoDB version of 4.2'
-      );
-    }
-
     // Save sort or indexKeys based on the command being run
     // the encrypt API serializes our JS objects to BSON to pass to the native code layer
     // and then deserializes the encrypted result, the protocol level components

src/cursor/change_stream_cursor.ts

@@ -93,7 +93,7 @@ export class ChangeStreamCursor<
       } else {
         options.resumeAfter = this.resumeToken;
       }
-    } else if (this.startAtOperationTime != null && maxWireVersion(this.server) >= 7) {
+    } else if (this.startAtOperationTime != null) {
       options.startAtOperationTime = this.startAtOperationTime;
     }
 
@@ -145,8 +145,7 @@ export class ChangeStreamCursor<
     if (
       this.startAtOperationTime == null &&
       this.changeStreamCursorOptions.resumeAfter == null &&
-      this.changeStreamCursorOptions.startAfter == null &&
-      this.maxWireVersion >= 7
+      this.changeStreamCursorOptions.startAfter == null
     ) {
       this.startAtOperationTime = response.operationTime;
     }

src/operations/aggregate.ts

@@ -1,17 +1,15 @@
-import { type Connection } from '..';
 import type { Document } from '../bson';
 import { CursorResponse, ExplainedCursorResponse } from '../cmap/wire_protocol/responses';
 import { type CursorTimeoutMode } from '../cursor/abstract_cursor';
 import { MongoInvalidArgumentError } from '../error';
 import { type ExplainOptions } from '../explain';
-import { maxWireVersion, type MongoDBNamespace } from '../utils';
+import { type MongoDBNamespace } from '../utils';
 import { WriteConcern } from '../write_concern';
 import { type CollationOptions, CommandOperation, type CommandOperationOptions } from './command';
 import { Aspect, defineAspects, type Hint } from './operation';
 
 /** @internal */
 export const DB_AGGREGATE_COLLECTION = 1 as const;
-const MIN_WIRE_VERSION_$OUT_READ_CONCERN_SUPPORT = 8;
 
 /** @public */
 export interface AggregateOptions extends Omit<CommandOperationOptions, 'explain'> {
@@ -107,15 +105,10 @@ export class AggregateOperation extends CommandOperation<CursorResponse> {
     this.pipeline.push(stage);
   }
 
-  override buildCommandDocument(connection: Connection): Document {
+  override buildCommandDocument(): Document {
     const options = this.options;
-    const serverWireVersion = maxWireVersion(connection);
     const command: Document = { aggregate: this.target, pipeline: this.pipeline };
 
-    if (this.hasWriteStage && serverWireVersion < MIN_WIRE_VERSION_$OUT_READ_CONCERN_SUPPORT) {
-      this.readConcern = undefined;
-    }
-
     if (this.hasWriteStage && this.writeConcern) {
       WriteConcern.apply(command, this.writeConcern);
     }

src/operations/find_and_modify.ts

@@ -188,7 +188,7 @@ export class FindAndModifyOperation extends CommandOperation<Document> {
       command.comment = options.comment;
     }
 
-    decorateWithCollation(command, this.collection, options);
+    decorateWithCollation(command, options);
 
     if (options.hint) {
       const unacknowledgedWrite = this.writeConcern?.w === 0;

src/read_preference.ts

@@ -63,6 +63,9 @@ export class ReadPreference {
   tags?: TagSet[];
   hedge?: HedgeOptions;
   maxStalenessSeconds?: number;
+  /**
+   * @deprecated This will be removed as dead code in the next major version.
+   */
   minWireVersion?: number;
 
   public static PRIMARY = ReadPreferenceMode.primary;

src/sdam/server.ts

@@ -414,7 +414,7 @@ export class Server extends TypedEventEmitter<ServerEvents> {
     } else {
       if (isSDAMUnrecoverableError(error)) {
         if (shouldHandleStateChangeError(this, error)) {
-          const shouldClearPool = maxWireVersion(this) <= 7 || isNodeShuttingDownError(error);
+          const shouldClearPool = isNodeShuttingDownError(error);
           if (this.loadBalanced && connection && shouldClearPool) {
             this.pool.clear({ serviceId: connection.serviceId });
           }

src/sdam/server_selection.ts

@@ -1,4 +1,4 @@
-import { MongoCompatibilityError, MongoInvalidArgumentError } from '../error';
+import { MongoInvalidArgumentError } from '../error';
 import { ReadPreference } from '../read_preference';
 import { ServerType, TopologyType } from './common';
 import type { ServerDescription, TagSet } from './server_description';
@@ -273,17 +273,6 @@ export function readPreferenceServerSelector(readPreference: ReadPreference): Se
     servers: ServerDescription[],
     deprioritized: ServerDescription[] = []
   ): ServerDescription[] {
-    const commonWireVersion = topologyDescription.commonWireVersion;
-    if (
-      commonWireVersion &&
-      readPreference.minWireVersion &&
-      readPreference.minWireVersion > commonWireVersion
-    ) {
-      throw new MongoCompatibilityError(
-        `Minimum wire version '${readPreference.minWireVersion}' required, but found '${commonWireVersion}'`
-      );
-    }
-
     if (topologyDescription.type === TopologyType.LoadBalanced) {
       return servers.filter(loadBalancerFilter);
     }

src/sdam/topology.ts

@@ -1104,7 +1104,10 @@ function isStaleServerDescription(
   );
 }
 
-/** @public */
+/**
+ * @public
+ * @deprecated This class will be removed as dead code in the next major version.
+ */
 export class ServerCapabilities {
   maxWireVersion: number;
   minWireVersion: number;
@@ -1115,37 +1118,37 @@ export class ServerCapabilities {
   }
 
   get hasAggregationCursor(): boolean {
-    return this.maxWireVersion >= 1;
+    return true;
   }
 
   get hasWriteCommands(): boolean {
-    return this.maxWireVersion >= 2;
+    return true;
   }
   get hasTextSearch(): boolean {
-    return this.minWireVersion >= 0;
+    return true;
   }
 
   get hasAuthCommands(): boolean {
-    return this.maxWireVersion >= 1;
+    return true;
   }
 
   get hasListCollectionsCommand(): boolean {
-    return this.maxWireVersion >= 3;
+    return true;
   }
 
   get hasListIndexesCommand(): boolean {
-    return this.maxWireVersion >= 3;
+    return true;
   }
 
   get supportsSnapshotReads(): boolean {
     return this.maxWireVersion >= 13;
   }
 
   get commandsTakeWriteConcern(): boolean {
-    return this.maxWireVersion >= 5;
+    return true;
   }
 
   get commandsTakeCollation(): boolean {
-    return this.maxWireVersion >= 5;
+    return true;
   }
 }

src/sessions.ts

@@ -2,7 +2,6 @@ import { Binary, type Document, Long, type Timestamp } from './bson';
 import type { CommandOptions, Connection } from './cmap/connection';
 import { ConnectionPoolMetrics } from './cmap/metrics';
 import { type MongoDBResponse } from './cmap/wire_protocol/responses';
-import { isSharded } from './cmap/wire_protocol/shared';
 import { PINNED, UNPINNED } from './constants';
 import type { AbstractCursor } from './cursor/abstract_cursor';
 import {
@@ -42,7 +41,6 @@ import {
   commandSupportsReadConcern,
   isPromiseLike,
   List,
-  maxWireVersion,
   MongoDBNamespace,
   noop,
   now,
@@ -51,8 +49,6 @@ import {
 } from './utils';
 import { WriteConcern, type WriteConcernOptions, type WriteConcernSettings } from './write_concern';
 
-const minWireVersionForShardedTransactions = 8;
-
 /** @public */
 export interface ClientSessionOptions {
   /** Whether causal consistency should be enabled on this session */
@@ -405,17 +401,6 @@ export class ClientSession
       this.unpin();
     }
 
-    const topologyMaxWireVersion = maxWireVersion(this.client.topology);
-    if (
-      isSharded(this.client.topology) &&
-      topologyMaxWireVersion != null &&
-      topologyMaxWireVersion < minWireVersionForShardedTransactions
-    ) {
-      throw new MongoCompatibilityError(
-        'Transactions are not supported on sharded clusters in MongoDB < 4.2.'
-      );
-    }
-
     this.commitAttempted = false;
     // increment txnNumber
     this.incrementTransactionNumber();

src/utils.ts

@@ -19,7 +19,6 @@ import type { Db } from './db';
 import {
   type AnyError,
   MongoAPIError,
-  MongoCompatibilityError,
   MongoInvalidArgumentError,
   MongoNetworkTimeoutError,
   MongoNotConnectedError,
@@ -206,18 +205,9 @@ export function isPromiseLike<T = unknown>(value?: unknown): value is PromiseLik
  * @param target - target of command
  * @param options - options containing collation settings
  */
-export function decorateWithCollation(
-  command: Document,
-  target: MongoClient | Db | Collection,
-  options: AnyOptions
-): void {
-  const capabilities = getTopology(target).capabilities;
+export function decorateWithCollation(command: Document, options: AnyOptions): void {
   if (options.collation && typeof options.collation === 'object') {
-    if (capabilities && capabilities.commandsTakeCollation) {
-      command.collation = options.collation;
-    } else {
-      throw new MongoCompatibilityError(`Current topology does not support collation`);
-    }
+    command.collation = options.collation;
   }
 }
 

test/unit/change_stream.test.ts

@@ -184,36 +184,6 @@ describe('ChangeStreamCursor', function () {
             expect(cursor.resumeOptions).to.haveOwnProperty('startAtOperationTime');
           });
         });
-
-        context('when the maxWireVersion < 7', function () {
-          let cursor: ChangeStreamCursor;
-          beforeEach(function () {
-            cursor = new ChangeStreamCursor(
-              new MongoClient('mongodb://localhost:27027'),
-              new MongoDBNamespace('db', 'collection'),
-              [],
-              {
-                startAfter: 'start after',
-                resumeAfter: 'resume after',
-                startAtOperationTime: new Timestamp(Long.ZERO)
-              }
-            );
-            cursor.resumeToken = null;
-            sinon.stub(cursor, 'server').get(() => ({ hello: { maxWireVersion: 6 } }));
-          });
-
-          it('does NOT set the resumeAfter option', function () {
-            expect(cursor.resumeOptions).not.to.haveOwnProperty('resumeAfter');
-          });
-
-          it('does NOT set the startAfter option', function () {
-            expect(cursor.resumeOptions).not.to.haveOwnProperty('startAfter');
-          });
-
-          it('does NOT set the startAtOperationTime option', function () {
-            expect(cursor.resumeOptions).not.to.haveOwnProperty('startAtOperationTime');
-          });
-        });
       });
 
       context('when the cursor does NOT have a saved operation time', function () {
@@ -266,36 +236,6 @@ describe('ChangeStreamCursor', function () {
             expect(cursor.resumeOptions).not.to.haveOwnProperty('startAtOperationTime');
           });
         });
-
-        context('when the maxWireVersion < 7', function () {
-          let cursor: ChangeStreamCursor;
-          beforeEach(function () {
-            cursor = new ChangeStreamCursor(
-              new MongoClient('mongodb://localhost:27027'),
-              new MongoDBNamespace('db', 'collection'),
-              [],
-              {
-                startAfter: 'start after',
-                resumeAfter: 'resume after',
-                startAtOperationTime: new Timestamp(Long.ZERO)
-              }
-            );
-            cursor.resumeToken = null;
-            sinon.stub(cursor, 'server').get(() => ({ hello: { maxWireVersion: 6 } }));
-          });
-
-          it('does NOT set the resumeAfter option', function () {
-            expect(cursor.resumeOptions).not.to.haveOwnProperty('resumeAfter');
-          });
-
-          it('does NOT set the startAfter option', function () {
-            expect(cursor.resumeOptions).not.to.haveOwnProperty('startAfter');
-          });
-
-          it('does NOT set the startAtOperationTime option', function () {
-            expect(cursor.resumeOptions).not.to.haveOwnProperty('startAtOperationTime');
-          });
-        });
       });
     });
   });