From 3631fce5cf7e449bb570c27a3710fa01c57642c2 Mon Sep 17 00:00:00 2001
From: Sergei Zharinov <zharinov@users.noreply.github.com>
Date: Sat, 3 Jan 2026 10:32:24 -0300
Subject: [PATCH] fix: recursion depth tracking and sequence quantifier
 navigation

---
 crates/plotnik-lib/src/compile/navigation.rs  |  1 +
 crates/plotnik-lib/src/emit/codegen_tests.rs  | 11 +++
 ...odegen_tests__captures_wrapper_struct.snap |  2 +-
 ...emit__codegen_tests__quantifiers_plus.snap |  2 +-
 ...gen_tests__quantifiers_plus_nongreedy.snap |  2 +-
 ...s__quantifiers_sequence_in_called_def.snap | 80 +++++++++++++++++++
 ...emit__codegen_tests__quantifiers_star.snap |  2 +-
 ...gen_tests__quantifiers_star_nongreedy.snap |  2 +-
 crates/plotnik-lib/src/engine/checkpoint.rs   |  2 +
 crates/plotnik-lib/src/engine/vm.rs           | 11 ++-
 10 files changed, 108 insertions(+), 7 deletions(-)
 create mode 100644 crates/plotnik-lib/src/emit/snapshots/plotnik_lib__emit__codegen_tests__quantifiers_sequence_in_called_def.snap

diff --git a/crates/plotnik-lib/src/compile/navigation.rs b/crates/plotnik-lib/src/compile/navigation.rs
index eb29f387..cdd4bd9f 100644
--- a/crates/plotnik-lib/src/compile/navigation.rs
+++ b/crates/plotnik-lib/src/compile/navigation.rs
@@ -91,6 +91,7 @@ pub fn repeat_nav_for(first_nav: Option<Nav>) -> Option<Nav> {
         Some(Nav::DownSkip) => Some(Nav::NextSkip),
         Some(Nav::DownExact) => Some(Nav::NextExact),
         Some(nav @ (Nav::Next | Nav::NextSkip | Nav::NextExact)) => Some(nav),
+        None | Some(Nav::Stay) => Some(Nav::Next),
         _ => None,
     }
 }
diff --git a/crates/plotnik-lib/src/emit/codegen_tests.rs b/crates/plotnik-lib/src/emit/codegen_tests.rs
index 05a883e5..e25675f8 100644
--- a/crates/plotnik-lib/src/emit/codegen_tests.rs
+++ b/crates/plotnik-lib/src/emit/codegen_tests.rs
@@ -235,6 +235,17 @@ fn quantifiers_repeat_navigation() {
     "#});
 }
 
+/// Regression test: sequence quantifiers in called definitions need sibling navigation.
+/// Previously, `{...}*` compiled without navigation, causing infinite loops.
+#[test]
+fn quantifiers_sequence_in_called_def() {
+    snap!(indoc! {r#"
+        Item = (identifier) @name
+        Collect = {(Item) @item}* @items
+        Test = (parent (Collect))
+    "#});
+}
+
 // ============================================================================
 // 5. SEQUENCES
 // ============================================================================
diff --git a/crates/plotnik-lib/src/emit/snapshots/plotnik_lib__emit__codegen_tests__captures_wrapper_struct.snap b/crates/plotnik-lib/src/emit/snapshots/plotnik_lib__emit__codegen_tests__captures_wrapper_struct.snap
index ebf84e56..400f0a50 100644
--- a/crates/plotnik-lib/src/emit/snapshots/plotnik_lib__emit__codegen_tests__captures_wrapper_struct.snap
+++ b/crates/plotnik-lib/src/emit/snapshots/plotnik_lib__emit__codegen_tests__captures_wrapper_struct.snap
@@ -59,7 +59,7 @@ Test:
   25   ε   [EndObj Push]                    37
   27   ε   [EndObj Set(M2)]                 25
   29   ▷   (number) [Node Set(M1)]          27
-  31       (identifier) [Node Set(M0)]      29
+  31   ▷   (identifier) [Node Set(M0)]      29
   33   ε   [Obj]                            31
   35   ε   [Obj]                            33
   37   ε                                    35, 11
diff --git a/crates/plotnik-lib/src/emit/snapshots/plotnik_lib__emit__codegen_tests__quantifiers_plus.snap b/crates/plotnik-lib/src/emit/snapshots/plotnik_lib__emit__codegen_tests__quantifiers_plus.snap
index a7a92118..4739079f 100644
--- a/crates/plotnik-lib/src/emit/snapshots/plotnik_lib__emit__codegen_tests__quantifiers_plus.snap
+++ b/crates/plotnik-lib/src/emit/snapshots/plotnik_lib__emit__codegen_tests__quantifiers_plus.snap
@@ -37,5 +37,5 @@ Test:
   08                                        ▶
   09   ε   [EndObj]                         08
   11   ε   [EndArr Set(M0)]                 09
-  13       (identifier) [Node Push]         15
+  13   ▷   (identifier) [Node Push]         15
   15   ε                                    13, 11
diff --git a/crates/plotnik-lib/src/emit/snapshots/plotnik_lib__emit__codegen_tests__quantifiers_plus_nongreedy.snap b/crates/plotnik-lib/src/emit/snapshots/plotnik_lib__emit__codegen_tests__quantifiers_plus_nongreedy.snap
index b7fa9ccc..b4aa3301 100644
--- a/crates/plotnik-lib/src/emit/snapshots/plotnik_lib__emit__codegen_tests__quantifiers_plus_nongreedy.snap
+++ b/crates/plotnik-lib/src/emit/snapshots/plotnik_lib__emit__codegen_tests__quantifiers_plus_nongreedy.snap
@@ -37,5 +37,5 @@ Test:
   08                                        ▶
   09   ε   [EndObj]                         08
   11   ε   [EndArr Set(M0)]                 09
-  13       (identifier) [Node Push]         15
+  13   ▷   (identifier) [Node Push]         15
   15   ε                                    11, 13
diff --git a/crates/plotnik-lib/src/emit/snapshots/plotnik_lib__emit__codegen_tests__quantifiers_sequence_in_called_def.snap b/crates/plotnik-lib/src/emit/snapshots/plotnik_lib__emit__codegen_tests__quantifiers_sequence_in_called_def.snap
new file mode 100644
index 00000000..8e27ed10
--- /dev/null
+++ b/crates/plotnik-lib/src/emit/snapshots/plotnik_lib__emit__codegen_tests__quantifiers_sequence_in_called_def.snap
@@ -0,0 +1,80 @@
+---
+source: crates/plotnik-lib/src/emit/codegen_tests.rs
+---
+Item = (identifier) @name
+Collect = {(Item) @item}* @items
+Test = (parent (Collect))
+---
+[flags]
+linked = false
+
+[strings]
+S0 "Beauty will save the world"
+S1 "name"
+S2 "item"
+S3 "items"
+S4 "Item"
+S5 "Collect"
+S6 "Test"
+S7 "identifier"
+S8 "parent"
+
+[type_defs]
+T0 = <Node>
+T1 = Struct  M0:1  ; { name }
+T2 = Struct  M1:2  ; { name, item }
+T3 = ArrayStar(T2)  ; T2*
+T4 = Struct  M3:1  ; { items }
+
+[type_members]
+M0: S1 → T0  ; name: <Node>
+M1: S1 → T0  ; name: <Node>
+M2: S2 → T0  ; item: <Node>
+M3: S3 → T3  ; items: T3
+
+[type_names]
+N0: S4 → T1  ; Item
+N1: S5 → T4  ; Collect
+N2: S6 → T4  ; Test
+
+[entrypoints]
+Collect = 09 :: T4
+Item    = 01 :: T1
+Test    = 16 :: T4
+
+[transitions]
+  00   ε                                    ◼
+
+Item:
+  01   ε                                    02
+  02   ε   [Obj]                            04
+  04       (identifier) [Node Set(M0)]      06
+  06   ε   [EndObj]                         08
+  08                                        ▶
+
+Collect:
+  09   ε                                    10
+  10   ε   [Obj]                            12
+  12   ε   [Arr]                            14
+  14   ε                                    35, 28
+
+Test:
+  16   ε                                    17
+  17   ε   [Obj]                            19
+  19       (parent)                         20
+  20   ▽   (Collect)                        21 ⯇
+  21   △                                    22
+  22   ε   [EndObj]                         24
+  24                                        ▶
+  25                                        ▶
+  26   ε   [EndObj]                         25
+  28   ε   [EndArr Set(M3)]                 26
+  30   ε   [EndObj Push]                    44
+  32   ε   [Set(M2)]                        30
+  34       (Item)                           32 ⯇
+  35   ε   [Obj]                            34
+  37   ε   [EndObj Push]                    44
+  39   ε   [Set(M2)]                        37
+  41   ▷   (Item)                           39 ⯇
+  42   ε   [Obj]                            41
+  44   ε                                    42, 28
diff --git a/crates/plotnik-lib/src/emit/snapshots/plotnik_lib__emit__codegen_tests__quantifiers_star.snap b/crates/plotnik-lib/src/emit/snapshots/plotnik_lib__emit__codegen_tests__quantifiers_star.snap
index e3a99a1c..654e3288 100644
--- a/crates/plotnik-lib/src/emit/snapshots/plotnik_lib__emit__codegen_tests__quantifiers_star.snap
+++ b/crates/plotnik-lib/src/emit/snapshots/plotnik_lib__emit__codegen_tests__quantifiers_star.snap
@@ -38,5 +38,5 @@ Test:
   09   ε   [EndObj]                         08
   11   ε   [EndArr Set(M0)]                 09
   13       (identifier) [Node Push]         17
-  15       (identifier) [Node Push]         17
+  15   ▷   (identifier) [Node Push]         17
   17   ε                                    15, 11
diff --git a/crates/plotnik-lib/src/emit/snapshots/plotnik_lib__emit__codegen_tests__quantifiers_star_nongreedy.snap b/crates/plotnik-lib/src/emit/snapshots/plotnik_lib__emit__codegen_tests__quantifiers_star_nongreedy.snap
index 77dc3ea7..6921986c 100644
--- a/crates/plotnik-lib/src/emit/snapshots/plotnik_lib__emit__codegen_tests__quantifiers_star_nongreedy.snap
+++ b/crates/plotnik-lib/src/emit/snapshots/plotnik_lib__emit__codegen_tests__quantifiers_star_nongreedy.snap
@@ -38,5 +38,5 @@ Test:
   09   ε   [EndObj]                         08
   11   ε   [EndArr Set(M0)]                 09
   13       (identifier) [Node Push]         17
-  15       (identifier) [Node Push]         17
+  15   ▷   (identifier) [Node Push]         17
   17   ε                                    11, 15
diff --git a/crates/plotnik-lib/src/engine/checkpoint.rs b/crates/plotnik-lib/src/engine/checkpoint.rs
index 1323d82f..ceca754f 100644
--- a/crates/plotnik-lib/src/engine/checkpoint.rs
+++ b/crates/plotnik-lib/src/engine/checkpoint.rs
@@ -13,6 +13,8 @@ pub struct Checkpoint {
     pub effect_watermark: usize,
     /// Frame arena state at checkpoint.
     pub frame_index: Option<u32>,
+    /// Recursion depth at checkpoint.
+    pub recursion_depth: u32,
     /// Resume point (raw step index).
     pub ip: u16,
 }
diff --git a/crates/plotnik-lib/src/engine/vm.rs b/crates/plotnik-lib/src/engine/vm.rs
index 1da8b3ef..e1c36143 100644
--- a/crates/plotnik-lib/src/engine/vm.rs
+++ b/crates/plotnik-lib/src/engine/vm.rs
@@ -133,9 +133,10 @@ impl<'t> VM<'t> {
             self.emit_effect(effect_op, tracer);
         }
 
-        self.matched_node = None;
-
+        // Only clear matched_node for non-epsilon transitions.
+        // For epsilon, preserve matched_node from previous match or return.
         if !m.is_epsilon() {
+            self.matched_node = None;
             self.navigate_and_match(m, tracer)?;
         }
 
@@ -213,6 +214,7 @@ impl<'t> VM<'t> {
                 descendant_index: self.cursor.descendant_index(),
                 effect_watermark: self.effects.len(),
                 frame_index: self.frames.current(),
+                recursion_depth: self.recursion_depth,
                 ip: m.successor(i).get(),
             });
             tracer.trace_checkpoint_created(self.ip);
@@ -296,6 +298,10 @@ impl<'t> VM<'t> {
         // Prune frames (O(1) amortized)
         self.frames.prune(self.checkpoints.max_frame_ref());
 
+        // Set matched_node to current cursor position so effects after
+        // a Call can capture the node that the callee matched.
+        self.matched_node = Some(self.cursor.node());
+
         self.ip = return_addr;
         Ok(())
     }
@@ -306,6 +312,7 @@ impl<'t> VM<'t> {
         self.cursor.goto_descendant(cp.descendant_index);
         self.effects.truncate(cp.effect_watermark);
         self.frames.restore(cp.frame_index);
+        self.recursion_depth = cp.recursion_depth;
         self.ip = cp.ip;
         Err(RuntimeError::Backtracked)
     }