Allow transform to return a stream

src/options.ts

@@ -1,5 +1,6 @@
 // turn tar(1) style args like `C` into the more verbose things like `cwd`
 
+import type { Minipass } from 'minipass'
 import { type GzipOptions, type ZlibOptions } from 'minizlib'
 import { type Stats } from 'node:fs'
 import { type ReadEntry } from './read-entry.js'
@@ -248,7 +249,7 @@ export interface TarOptions {
    */
   transform?: (
     entry: ReadEntry,
-  ) => ReadEntry | null | undefined | false | 0 | ''
+  ) => ReadEntry | Minipass | null | undefined | false | 0 | ''
 
   /**
    * Call `chmod()` to ensure that extracted files match the entry's mode

test/transform-type-check.ts

@@ -0,0 +1,16 @@
+import { Minipass } from 'minipass'
+import { extract } from '../src/extract.js'
+import { Unpack } from '../src/unpack.js'
+
+// MiniPass stream return (issue #462)
+const streamTransform = () => new Minipass({ async: true })
+extract({ transform: streamTransform }, [])
+new Unpack({ transform: streamTransform })
+
+// entry / falsey return remains valid (issue #459)
+extract({ transform: entry => entry }, [])
+extract({ transform: () => undefined }, [])
+extract({ transform: () => false }, [])
+
+import { pass } from 'tap'
+pass(`transform may return a stream or a falsey value`)