streams: fix util inspect returning undefined for CompressionStream & DecompressionStream

lib/internal/webstreams/compression.js

@@ -78,7 +78,7 @@ class CompressionStream {
   }
 
   [kInspect](depth, options) {
-    customInspect(depth, options, 'CompressionStream', {
+    return customInspect(depth, options, 'CompressionStream', {
       readable: this.#transform.readable,
       writable: this.#transform.writable,
     });
@@ -128,7 +128,7 @@ class DecompressionStream {
   }
 
   [kInspect](depth, options) {
-    customInspect(depth, options, 'DecompressionStream', {
+    return customInspect(depth, options, 'DecompressionStream', {
       readable: this.#transform.readable,
       writable: this.#transform.writable,
     });

test/parallel/test-compression-decompression-stream.js

@@ -0,0 +1,41 @@
+// Flags: --no-warnings --expose-internals
+'use strict';
+
+require('../common');
+
+const assert = require('node:assert');
+const { describe, it } = require('node:test');
+const {
+  CompressionStream,
+  DecompressionStream,
+} = require('node:stream/web');
+
+const {
+  customInspectSymbol: kInspect,
+} = require('internal/util');
+
+describe('DecompressionStream kInspect method', () => {
+  it('should return a predictable inspection string with DecompressionStream', () => {
+    const decompressionStream = new DecompressionStream('deflate');
+    const depth = 1;
+    const options = {};
+    const actual = decompressionStream[kInspect](depth, options);
+
+    assert(actual.includes('DecompressionStream'));
+    assert(actual.includes('ReadableStream'));
+    assert(actual.includes('WritableStream'));
+  });
+});
+
+describe('CompressionStream kInspect method', () => {
+  it('should return a predictable inspection string with CompressionStream', () => {
+    const compressionStream = new CompressionStream('deflate');
+    const depth = 1;
+    const options = {};
+    const actual = compressionStream[kInspect](depth, options);
+
+    assert(actual.includes('CompressionStream'));
+    assert(actual.includes('ReadableStream'));
+    assert(actual.includes('WritableStream'));
+  });
+});