fix: Gzip comment with header checksum produces corrupt streams (#2288)

src/core/operations/Gzip.mjs

@@ -74,13 +74,11 @@ class Gzip extends Operation {
         }
         if (comment.length) {
             options.flags.comment = true;
+            options.flags.fcomment = true;
             options.comment = comment;
         }
         const gzipObj = new Zlib.Gzip(new Uint8Array(input), options);
         const compressed = new Uint8Array(gzipObj.compress());
-        if (options.flags.comment && !(compressed[3] & 0x10)) {
-            compressed[3] |= 0x10;
-        }
         return compressed.buffer;
     }
 

tests/operations/tests/Gzip.mjs

@@ -86,4 +86,64 @@ TestRegister.addTests([
             }
         ]
     },
+    {
+        name: "Gzip: Comment with checksum round-trips through Gunzip",
+        input: "hello hello hello",
+        expectedOutput: "hello hello hello",
+        recipeConfig: [
+            {
+                op: "Gzip",
+                args: ["Dynamic Huffman Coding", "", "test", true]
+            },
+            {
+                op: "Gunzip",
+                args: []
+            }
+        ]
+    },
+    {
+        name: "Gzip: Filename and comment with checksum round-trips through Gunzip",
+        input: "The quick brown fox jumped over the slow dog",
+        expectedOutput: "The quick brown fox jumped over the slow dog",
+        recipeConfig: [
+            {
+                op: "Gzip",
+                args: ["Dynamic Huffman Coding", "file.txt", "a comment", true]
+            },
+            {
+                op: "Gunzip",
+                args: []
+            }
+        ]
+    },
+    {
+        name: "Gzip: No comment, with checksum round-trips through Gunzip",
+        input: "The quick brown fox jumped over the slow dog",
+        expectedOutput: "The quick brown fox jumped over the slow dog",
+        recipeConfig: [
+            {
+                op: "Gzip",
+                args: ["Dynamic Huffman Coding", "", "", true]
+            },
+            {
+                op: "Gunzip",
+                args: []
+            }
+        ]
+    },
+    {
+        name: "Gzip: No options round-trips through Gunzip",
+        input: "The quick brown fox jumped over the slow dog",
+        expectedOutput: "The quick brown fox jumped over the slow dog",
+        recipeConfig: [
+            {
+                op: "Gzip",
+                args: ["Dynamic Huffman Coding", "", "", false]
+            },
+            {
+                op: "Gunzip",
+                args: []
+            }
+        ]
+    },
 ]);