repl: Render iterators and generators

Evaluating an expression that yields a generator or other iterator object
printed an empty object, since such objects have no own enumerable keys.
Encode them as a new tagged value by pulling up to 100 items, marking when
more remain, and label them by their toStringTag so a generator shows as
Generator[...] and a Map iterator as Map Iterator[...]. The iterator is
consumed by the display, as it would be by any other means of looking at
its items.

agents/repl/value.ts

@@ -8,6 +8,7 @@ export interface EncodeOptions {
 }
 
 const DEFAULT_MAX_DEPTH = 3;
+const MAX_ITERATOR_ITEMS = 100;
 
 export type PackedValue = [EncodedValueTree, ArrayBuffer | null];
 
@@ -40,6 +41,7 @@ const enum ValueTag {
     WeakSet = 19,
     DepthLimit = 20,
     Circular = 21,
+    Iterator = 22,
 }
 
 type TypedArrayName =
@@ -145,6 +147,7 @@ function collectTree(
         const isArray = Array.isArray(obj);
         const isMap = obj instanceof Map;
         const isSet = obj instanceof Set;
+        const isIterator = typeof obj.next === "function" && typeof obj[Symbol.iterator] === "function";
 
         const existingId = state.seen.get(obj);
         if (existingId !== undefined) {
@@ -161,6 +164,9 @@ function collectTree(
             if (isSet) {
                 return [ValueTag.DepthLimit, ValueTag.Set];
             }
+            if (isIterator) {
+                return [ValueTag.DepthLimit, ValueTag.Iterator];
+            }
             return [ValueTag.DepthLimit, ValueTag.Object];
         }
 
@@ -194,6 +200,20 @@ function collectTree(
             return [ValueTag.Array, id, elements];
         }
 
+        if (isIterator) {
+            const label = obj[Symbol.toStringTag] ?? "Iterator";
+            const items: EncodedValueTree[] = [];
+            let truncated = false;
+            for (const v of obj as Iterable<unknown>) {
+                if (items.length === MAX_ITERATOR_ITEMS) {
+                    truncated = true;
+                    break;
+                }
+                items.push(collectTree(v, chunks, maxDepth, depth + 1, state));
+            }
+            return [ValueTag.Iterator, id, label, items, truncated];
+        }
+
         try {
             const maybeToJSON = obj.toJSON;
             if (typeof maybeToJSON === "function") {
@@ -349,6 +369,15 @@ function patchTree(
             return [ValueTag.Set, id, patchedItems];
         }
 
+        case ValueTag.Iterator: {
+            const id = rest[0] as number;
+            const label = rest[1] as string;
+            const items = rest[2] as EncodedValueTree[];
+            const truncated = rest[3] as boolean;
+            const patchedItems = items.map(child => patchTree(child, offsets));
+            return [ValueTag.Iterator, id, label, patchedItems, truncated];
+        }
+
         default:
             return tree;
     }

frida_tools/repl_inspect.py

@@ -33,6 +33,7 @@ WEAKMAP = 18
 WEAKSET = 19
 DEPTH_LIMIT = 20
 CIRCULAR = 21
+ITERATOR = 22
 
 _CYAN = "fg:#64d2ff"
 _MINT = "fg:#66d4cf"
@@ -47,7 +48,7 @@ _MAX_ITEMS = 100
 
 _HEX_BYTES_PER_ROW = 16
 
-_CONTAINER_NAMES = {OBJECT: "Object", ARRAY: "Array", MAP: "Map", SET: "Set"}
+_CONTAINER_NAMES = {OBJECT: "Object", ARRAY: "Array", MAP: "Map", SET: "Set", ITERATOR: "Iterator"}
 
 Node = Sequence[Any]
 Fragment = Tuple[str, str]
@@ -147,6 +148,9 @@ def _append(node: Node, level: int, out: List[Fragment], blob: Sequence[int]) ->
     elif tag == CIRCULAR:
         out.append((_ORANGE, "⟳ circular *%d" % node[1]))
 
+    elif tag == ITERATOR:
+        _append_iterator(node, level, out, blob)
+
 
 def _append_object(node: Node, level: int, out: List[Fragment], blob: Sequence[int]) -> None:
     properties = node[2]
@@ -263,6 +267,28 @@ def _append_set(node: Node, level: int, out: List[Fragment], blob: Sequence[int]
     out.append((_CYAN, "]"))
 
 
+def _append_iterator(node: Node, level: int, out: List[Fragment], blob: Sequence[int]) -> None:
+    label, elements, truncated = node[2], node[3], node[4]
+    if not elements:
+        out.append((_CYAN, "%s[]" % label))
+        return
+
+    out.append((_CYAN, "%s[" % label))
+    out.append(("", "\n"))
+    for index, element in enumerate(elements):
+        _indent(level + 1, out)
+        _append(element, level + 1, out, blob)
+        if _has_more(index, elements, truncated):
+            out.append(("", ","))
+        out.append(("", "\n"))
+    if truncated:
+        _indent(level + 1, out)
+        out.append((_ORANGE, "… more"))
+        out.append(("", "\n"))
+    _indent(level, out)
+    out.append((_CYAN, "]"))
+
+
 def _capped(items: Sequence[Any]) -> Tuple[Sequence[Any], int]:
     shown = items[:_MAX_ITEMS]
     return shown, len(items) - len(shown)