Support the NOVALUES option of HSCAN

Issue #2705

The NOVALUES option instructs HSCAN to only return keys, without their
values. This is materialized as a new command, `hScanNoValues`, given
that the return type is different from the usual return type of `hScan`.
Also a new iterator is provided, `hScanNoValuesIterator`, for the same
reason.

Author: gerzse

Diff for: packages/client/lib/client/index.spec.ts

@@ -788,6 +788,28 @@ describe('Client', () => {
         assert.deepEqual(hash, results);
     }, GLOBAL.SERVERS.OPEN);
 
+    testUtils.testWithClient('hScanNoValuesIterator', async client => {
+        const hash: Record<string, string> = {};
+        const expectedKeys: Array<string> = [];
+        for (let i = 0; i < 100; i++) {
+            hash[i.toString()] = i.toString();
+            expectedKeys.push(i.toString());
+        }
+
+        await client.hSet('key', hash);
+
+        const keys: Array<string> = [];
+        for await (const key of client.hScanNoValuesIterator('key')) {
+            keys.push(key);
+        }
+
+        function sort(a: string, b: string) {
+            return Number(a) - Number(b);
+        }
+
+        assert.deepEqual(keys.sort(sort), expectedKeys);
+    }, GLOBAL.SERVERS.OPEN);
+
     testUtils.testWithClient('sScanIterator', async client => {
         const members = new Set<string>();
         for (let i = 0; i < 100; i++) {

Diff for: packages/client/lib/client/index.ts

@@ -1,5 +1,5 @@
 import COMMANDS from './commands';
-import { RedisCommand, RedisCommandArguments, RedisCommandRawReply, RedisCommandReply, RedisFunctions, RedisModules, RedisExtensions, RedisScript, RedisScripts, RedisCommandSignature, ConvertArgumentType, RedisFunction, ExcludeMappedString, RedisCommands } from '../commands';
+import { RedisCommand, RedisCommandArgument, RedisCommandArguments, RedisCommandRawReply, RedisCommandReply, RedisFunctions, RedisModules, RedisExtensions, RedisScript, RedisScripts, RedisCommandSignature, ConvertArgumentType, RedisFunction, ExcludeMappedString, RedisCommands } from '../commands';
 import RedisSocket, { RedisSocketOptions, RedisTlsSocketOptions } from './socket';
 import RedisCommandsQueue, { QueueCommandOptions } from './commands-queue';
 import RedisClientMultiCommand, { RedisClientMultiCommandType } from './multi-command';
@@ -820,6 +820,17 @@ export default class RedisClient<
         } while (cursor !== 0);
     }
 
+    async* hScanNoValuesIterator(key: string, options?: ScanOptions): AsyncIterable<ConvertArgumentType<RedisCommandArgument, string>> {
+        let cursor = 0;
+        do {
+            const reply = await (this as any).hScanNoValues(key, cursor, options);
+            cursor = reply.cursor;
+            for (const k of reply.keys) {
+                yield k;
+            }
+        } while (cursor !== 0);
+    }
+
     async* sScanIterator(key: string, options?: ScanOptions): AsyncIterable<string> {
         let cursor = 0;
         do {

Diff for: packages/client/lib/cluster/commands.ts

@@ -64,6 +64,7 @@ import * as HRANDFIELD_COUNT_WITHVALUES from '../commands/HRANDFIELD_COUNT_WITHV
 import * as HRANDFIELD_COUNT from '../commands/HRANDFIELD_COUNT';
 import * as HRANDFIELD from '../commands/HRANDFIELD';
 import * as HSCAN from '../commands/HSCAN';
+import * as HSCAN_NOVALUES from '../commands/HSCAN_NOVALUES';
 import * as HSET from '../commands/HSET';
 import * as HSETNX from '../commands/HSETNX';
 import * as HSTRLEN from '../commands/HSTRLEN';
@@ -343,6 +344,8 @@ export default {
     hRandField: HRANDFIELD,
     HSCAN,
     hScan: HSCAN,
+    HSCAN_NOVALUES,
+    hScanNoValues: HSCAN_NOVALUES,
     HSET,
     hSet: HSET,
     HSETNX,

Diff for: packages/client/lib/commands/HSCAN.spec.ts

@@ -73,5 +73,18 @@ describe('HSCAN', () => {
                 tuples: []
             }
         );
+
+        await Promise.all([
+            client.hSet('key', 'a', '1'),
+            client.hSet('key', 'b', '2')
+        ]);
+
+        assert.deepEqual(
+            await client.hScan('key', 0),
+            {
+                cursor: 0,
+                tuples: [{field: 'a', value: '1'}, {field: 'b', value: '2'}]
+            }
+        );
     }, GLOBAL.SERVERS.OPEN);
 });

Diff for: packages/client/lib/commands/HSCAN.ts

@@ -16,7 +16,7 @@ export function transformArguments(
     ], cursor, options);
 }
 
-type HScanRawReply = [RedisCommandArgument, Array<RedisCommandArgument>];
+export type HScanRawReply = [RedisCommandArgument, Array<RedisCommandArgument>];
 
 export interface HScanTuple {
     field: RedisCommandArgument;

Diff for: packages/client/lib/commands/HSCAN_NOVALUES.spec.ts

@@ -0,0 +1,77 @@
+import { strict as assert } from 'assert';
+import testUtils, { GLOBAL } from '../test-utils';
+import { transformArguments, transformReply } from './HSCAN_NOVALUES';
+
+describe('HSCAN_NOVALUES', () => {
+    describe('transformArguments', () => {
+        it('cusror only', () => {
+            assert.deepEqual(
+                transformArguments('key', 0),
+                ['HSCAN', 'key', '0', 'NOVALUES']
+            );
+        });
+
+        it('with MATCH', () => {
+            assert.deepEqual(
+                transformArguments('key', 0, {
+                    MATCH: 'pattern'
+                }),
+                ['HSCAN', 'key', '0', 'MATCH', 'pattern', 'NOVALUES']
+            );
+        });
+
+        it('with COUNT', () => {
+            assert.deepEqual(
+                transformArguments('key', 0, {
+                    COUNT: 1
+                }),
+                ['HSCAN', 'key', '0', 'COUNT', '1', 'NOVALUES']
+            );
+        });
+    });
+
+    describe('transformReply', () => {
+        it('without keys', () => {
+            assert.deepEqual(
+                transformReply(['0', []]),
+                {
+                    cursor: 0,
+                    keys: []
+                }
+            );
+        });
+
+        it('with keys', () => {
+            assert.deepEqual(
+                transformReply(['0', ['key1', 'key2']]),
+                {
+                    cursor: 0,
+                    keys: ['key1', 'key2']
+                }
+            );
+        });
+    });
+
+    testUtils.testWithClient('client.hScanNoValues', async client => {
+        assert.deepEqual(
+            await client.hScanNoValues('key', 0),
+            {
+                cursor: 0,
+                keys: []
+            }
+        );
+
+        await Promise.all([
+            client.hSet('key', 'a', '1'),
+            client.hSet('key', 'b', '2')
+        ]);
+
+        assert.deepEqual(
+            await client.hScanNoValues('key', 0),
+            {
+                cursor: 0,
+                keys: ['a', 'b']
+            }
+        );
+    }, GLOBAL.SERVERS.OPEN);
+});

Diff for: packages/client/lib/commands/HSCAN_NOVALUES.ts

@@ -0,0 +1,27 @@
+import { RedisCommandArgument, RedisCommandArguments } from '.';
+import { ScanOptions } from './generic-transformers';
+import { HScanRawReply, transformArguments as transformHScanArguments } from './HSCAN';
+
+export {FIRST_KEY_INDEX, IS_READ_ONLY} from './HSCAN';
+
+export function transformArguments(
+    key: RedisCommandArgument,
+    cursor: number,
+    options?: ScanOptions
+): RedisCommandArguments {
+    const args = transformHScanArguments(key, cursor, options);
+    args.push('NOVALUES');
+    return args;
+}
+
+interface HScanNoValuesReply {
+    cursor: number;
+    keys: Array<RedisCommandArgument>;
+}
+
+export function transformReply([cursor, rawData]: HScanRawReply): HScanNoValuesReply {
+    return {
+        cursor: Number(cursor),
+        keys: [...rawData]
+    };
+}