Add type support for scanStream

Closes #1279

README.md

@@ -583,12 +583,15 @@ stream.on("end", () => {
 });
 ```
 
-`scanStream` accepts an option, with which you can specify the `MATCH` pattern and the `COUNT` argument:
+`scanStream` accepts an option, with which you can specify the `MATCH` pattern, the `TYPE` filter, and the `COUNT` argument:
 
 ```javascript
 const stream = redis.scanStream({
   // only returns keys following the pattern of `user:*`
   match: "user:*",
+  // only return objects that match a given type,
+  // (requires Redis >= 6.0)
+  type: "zset",
   // returns approximately 100 elements per call
   count: 100,
 });

lib/ScanStream.ts

@@ -9,6 +9,7 @@ import { Readable, ReadableOptions } from "stream";
 export interface IScanStreamOptions extends ReadableOptions {
   key?: string;
   match?: string;
+  type?: string;
   command: string;
   redis: any;
   count?: string | number;
@@ -42,6 +43,9 @@ export default class ScanStream extends Readable {
     if (this.opt.match) {
       args.push("MATCH", this.opt.match);
     }
+    if (this.opt.type) {
+      args.push("TYPE", this.opt.type);
+    }
     if (this.opt.count) {
       args.push("COUNT", String(this.opt.count));
     }

test/functional/scan_stream.ts

@@ -77,6 +77,28 @@ describe("*scanStream", function () {
       );
     });
 
+    it("should recognize `TYPE`", function (done) {
+      let keys = [];
+      const redis = new Redis();
+      redis.set("foo1", "bar");
+      redis.set("foo2", "bar");
+      redis.set("foo3", "bar");
+      redis.lpush("loo1", "1");
+      redis.lpush("loo2", "1");
+      redis.lpush("loo3", "1");
+      const stream = redis.scanStream({
+        type: "list",
+      });
+      stream.on("data", function (data) {
+        keys = keys.concat(data);
+      });
+      stream.on("end", function () {
+        expect(keys.sort()).to.eql(["loo1", "loo2", "loo3"]);
+        redis.disconnect();
+        done();
+      });
+    });
+
     it("should recognize `COUNT`", function (done) {
       let keys = [];
       const redis = new Redis();