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fix: Bypass Up navigation when Down fails for childless nodes #308

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Merged
zharinov merged 1 commit into from
Jan 7, 2026
Merged

fix: Bypass Up navigation when Down fails for childless nodes #308

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2 changes: 1 addition & 1 deletion crates/plotnik-lib/src/compile/expressions.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -104,7 +104,7 @@ impl Compiler<'_> {
true,
None,
CaptureEffects::default(),
None, // No skip_exit bypass - all paths need Up
Some(final_exit), // Skip exit bypasses Up when Down fails (childless node)
);

self.instructions
Expand Down
21 changes: 17 additions & 4 deletions crates/plotnik-lib/src/compile/quantifier.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -445,12 +445,23 @@ impl Compiler<'_> {
self.emit_null_for_internal_captures(null_exit, inner)
};

// Skip-retry iteration leading to null exit
// Skip-retry iteration:
// For Optional, both skip paths (entry-level and retry-exhaust) need null.
// - Entry-level (Down fails): skip_with_null (bypass Up, has null from caller)
// - Retry exhaust (Down succeeded but pattern fails): need Up, then null
// When needs_split_exits, create a retry exhaust path with null → match_exit.
let first_nav_mode = first_nav.unwrap_or(Nav::Down);
let iterate_exit = if needs_split_exits {
// Retry exhaust needs null injection then goes to match_exit (for Up)
let null_exit = self.emit_null_for_skip_path(match_exit, &element_capture);
self.emit_null_for_internal_captures(null_exit, inner)
} else {
skip_with_null
};
let iterate = self.compile_skip_retry_iteration(
first_nav_mode,
body_entry,
skip_with_null,
iterate_exit,
is_greedy,
);

Expand Down Expand Up @@ -554,10 +565,12 @@ impl Compiler<'_> {
self.compile_expr_inner(inner, loop_entry, Some(Nav::StayExact), capture)
};

// First iteration: skip-retry with skip_exit as fallback
// First iteration: skip-retry with match_exit as internal fallback.
// When retry exhausts (Down succeeded but pattern fails), we need Up via match_exit.
// The entry-level epsilon (below) handles Down failure → skip_exit (bypass Up).
let first_nav_mode = nav_override.unwrap_or(Nav::Down);
let first_iterate =
self.compile_skip_retry_iteration(first_nav_mode, body_entry, skip_exit, is_greedy);
self.compile_skip_retry_iteration(first_nav_mode, body_entry, match_exit, is_greedy);

// Repeat iteration: skip-retry with match_exit as fallback
let repeat_iterate =
Expand Down
31 changes: 16 additions & 15 deletions ...nik-lib/src/emit/snapshots/plotnik_lib__emit__emit_tests__alternations_in_quantifier.snap
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Original file line number Diff line number Diff line change
Expand Up @@ -53,22 +53,23 @@ Test:
06 ε 07
07 ! (object) 08
08 ε [Arr] 10
10 ε 37, 12
10 ε 39, 20
12 ε [EndArr Set(M5)] 14
14 △ _ 19
15 ε [EndObj Push] 17
17 ε 43, 12
17 ε 45, 12
19 ▶
20 ε [Set(M4)] 15
22 ! [Enum(M2)] (pair) [Node Set(M0) EndEnum] 20
25 ! [Enum(M3)] (shorthand_property_identifier) [Node Set(M1) EndEnum] 20
28 ε 22, 25
30 ε [Obj] 28
32 ▷ _ 35
33 ε 32, 12
35 ε 30, 33
37 ▽ _ 35
38 ▷ _ 41
39 ε 38, 12
41 ε 30, 39
43 ▷ _ 41
20 ε [EndArr Set(M5)] 19
22 ε [Set(M4)] 15
24 ! [Enum(M2)] (pair) [Node Set(M0) EndEnum] 22
27 ! [Enum(M3)] (shorthand_property_identifier) [Node Set(M1) EndEnum] 22
30 ε 24, 27
32 ε [Obj] 30
34 ▷ _ 37
35 ε 34, 12
37 ε 32, 35
39 ▽ _ 37
40 ▷ _ 43
41 ε 40, 12
43 ε 32, 41
45 ▷ _ 43
31 changes: 16 additions & 15 deletions ...nik-lib/src/emit/snapshots/plotnik_lib__emit__emit_tests__definitions_nested_capture.snap
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Original file line number Diff line number Diff line change
Expand Up @@ -56,22 +56,23 @@ Outer:
12 ε 13
13 ! (parent) 14
14 ε [Arr] 16
16 ε 40, 18
16 ε 42, 26
18 ε [EndArr Set(M2)] 20
20 △ _ 25
21 ε [EndObj Push] 23
23 ε 46, 18
23 ε 48, 18
25 ▶
26 ε [Set(M1)] 21
28 ε [EndObj] 26
30 ! (Inner) 06 : 28
31 ε [Obj] 30
33 ε [Obj] 31
35 ▷ _ 38
36 ε 35, 18
38 ε 33, 36
40 ▽ _ 38
41 ▷ _ 44
42 ε 41, 18
44 ε 33, 42
46 ▷ _ 44
26 ε [EndArr Set(M2)] 25
28 ε [Set(M1)] 21
30 ε [EndObj] 28
32 ! (Inner) 06 : 30
33 ε [Obj] 32
35 ε [Obj] 33
37 ▷ _ 40
38 ε 37, 18
40 ε 35, 38
42 ▽ _ 40
43 ▷ _ 46
44 ε 43, 18
46 ε 35, 44
48 ▷ _ 46
17 changes: 9 additions & 8 deletions ...s/plotnik-lib/src/emit/snapshots/plotnik_lib__emit__emit_tests__optional_first_child.snap
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Original file line number Diff line number Diff line change
Expand Up @@ -44,14 +44,15 @@ _ObjWrap:
Test:
06 ε 07
07 ! (program) 08
08 ε 24, 15
08 ε 26, 15
10 ▶
11 ▽ (number) [Node Set(M1)] 25
13 ▷ (number) [Node Set(M1)] 25
11 ▽ (number) [Node Set(M1)] 27
13 ▷ (number) [Node Set(M1)] 27
15 ε [Null Set(M0)] 11
17 ! (identifier) [Node Set(M0)] 13
19 ▷ _ 22
20 ε 19, 15
22 ε 17, 20
24 ▽ _ 22
25 △ _ 10
19 ε [Null Set(M0)] 13
21 ▷ _ 24
22 ε 21, 19
24 ε 17, 22
26 ▽ _ 24
27 △ _ 10
17 changes: 9 additions & 8 deletions ...lotnik-lib/src/emit/snapshots/plotnik_lib__emit__emit_tests__optional_null_injection.snap
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Original file line number Diff line number Diff line change
Expand Up @@ -37,12 +37,13 @@ _ObjWrap:
Test:
06 ε 07
07 ! (function_declaration) 08
08 ε 20, 13
08 ε 22, 11
10 ▶
11 ! (decorator) [Node Set(M0)] 21
13 ε [Null Set(M0)] 21
15 ▷ _ 18
16 ε 15, 13
18 ε 11, 16
20 ▽ _ 18
21 △ _ 10
11 ε [Null Set(M0)] 10
13 ! (decorator) [Node Set(M0)] 23
15 ε [Null Set(M0)] 23
17 ▷ _ 20
18 ε 17, 15
20 ε 13, 18
22 ▽ _ 20
23 △ _ 10
2 changes: 1 addition & 1 deletion ...-lib/src/emit/snapshots/plotnik_lib__emit__emit_tests__quantifiers_first_child_array.snap
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Original file line number Diff line number Diff line change
Expand Up @@ -54,7 +54,7 @@ Test:
21 ε [EndArr Set(M0)] 19
23 ε [EndArr Set(M0)] 17
25 ▷ _ 28
26 ε 25, 23
26 ε 25, 21
28 ε 12, 26
30 ▽ _ 28
31 ▷ _ 34
Expand Down
17 changes: 9 additions & 8 deletions ...s/plotnik-lib/src/emit/snapshots/plotnik_lib__emit__emit_tests__quantifiers_optional.snap
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Original file line number Diff line number Diff line change
Expand Up @@ -37,12 +37,13 @@ _ObjWrap:
Test:
06 ε 07
07 ! (function_declaration) 08
08 ε 20, 13
08 ε 22, 11
10 ▶
11 ! (decorator) [Node Set(M0)] 21
13 ε [Null Set(M0)] 21
15 ▷ _ 18
16 ε 15, 13
18 ε 11, 16
20 ▽ _ 18
21 △ _ 10
11 ε [Null Set(M0)] 10
13 ! (decorator) [Node Set(M0)] 23
15 ε [Null Set(M0)] 23
17 ▷ _ 20
18 ε 17, 15
20 ε 13, 18
22 ▽ _ 20
23 △ _ 10
17 changes: 9 additions & 8 deletions ...lib/src/emit/snapshots/plotnik_lib__emit__emit_tests__quantifiers_optional_nongreedy.snap
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Original file line number Diff line number Diff line change
Expand Up @@ -37,12 +37,13 @@ _ObjWrap:
Test:
06 ε 07
07 ! (function_declaration) 08
08 ε 13, 20
08 ε 11, 22
10 ▶
11 ! (decorator) [Node Set(M0)] 21
13 ε [Null Set(M0)] 21
15 ▷ _ 18
16 ε 13, 15
18 ε 16, 11
20 ▽ _ 18
21 △ _ 10
11 ε [Null Set(M0)] 10
13 ! (decorator) [Node Set(M0)] 23
15 ε [Null Set(M0)] 23
17 ▷ _ 20
18 ε 15, 17
20 ε 18, 13
22 ▽ _ 20
23 △ _ 10
21 changes: 11 additions & 10 deletions ...-lib/src/emit/snapshots/plotnik_lib__emit__emit_tests__quantifiers_repeat_navigation.snap
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Original file line number Diff line number Diff line change
Expand Up @@ -38,17 +38,18 @@ Test:
06 ε 07
07 ! (function_declaration) 08
08 ε [Arr] 10
10 ε 25, 12
10 ε 27, 20
12 ε [EndArr Set(M0)] 14
14 △ _ 19
15 ! (decorator) [Node Push] 17
17 ε 31, 12
17 ε 33, 12
19 ▶
20 ▷ _ 23
21 ε 20, 12
23 ε 15, 21
25 ▽ _ 23
26 ▷ _ 29
27 ε 26, 12
29 ε 15, 27
31 ▷ _ 29
20 ε [EndArr Set(M0)] 19
22 ▷ _ 25
23 ε 22, 12
25 ε 15, 23
27 ▽ _ 25
28 ▷ _ 31
29 ε 28, 12
31 ε 15, 29
33 ▷ _ 31
27 changes: 14 additions & 13 deletions ...otnik-lib/src/emit/snapshots/plotnik_lib__emit__emit_tests__quantifiers_struct_array.snap
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Original file line number Diff line number Diff line change
Expand Up @@ -48,20 +48,21 @@ Test:
06 ε 07
07 ! (array) 08
08 ε [Arr] 10
10 ε 31, 12
10 ε 33, 20
12 ε [EndArr Set(M2)] 14
14 △ _ 19
15 ε [EndObj Push] 17
17 ε 37, 12
17 ε 39, 12
19 ▶
20 ▷ (number) [Node Set(M1)] 15
22 ! (identifier) [Node Set(M0)] 20
24 ε [Obj] 22
26 ▷ _ 29
27 ε 26, 12
29 ε 24, 27
31 ▽ _ 29
32 ▷ _ 35
33 ε 32, 12
35 ε 24, 33
37 ▷ _ 35
20 ε [EndArr Set(M2)] 19
22 ▷ (number) [Node Set(M1)] 15
24 ! (identifier) [Node Set(M0)] 22
26 ε [Obj] 24
28 ▷ _ 31
29 ε 28, 12
31 ε 26, 29
33 ▽ _ 31
34 ▷ _ 37
35 ε 34, 12
37 ε 26, 35
39 ▷ _ 37
23 changes: 12 additions & 11 deletions ...lotnik-lib/src/emit/snapshots/plotnik_lib__emit__emit_tests__sequences_in_quantifier.snap
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Original file line number Diff line number Diff line change
Expand Up @@ -39,18 +39,19 @@ Test:
06 ε 07
07 ! (parent) 08
08 ε [Arr] 10
10 ε 26, 12
10 ε 28, 20
12 ε [EndArr Set(M0)] 14
14 △ _ 19
15 ▷ (b) [Node Push] 17
17 ε 32, 12
17 ε 34, 12
19 ▶
20 ! (a) 15
21 ▷ _ 24
22 ε 21, 12
24 ε 20, 22
26 ▽ _ 24
27 ▷ _ 30
28 ε 27, 12
30 ε 20, 28
32 ▷ _ 30
20 ε [EndArr Set(M0)] 19
22 ! (a) 15
23 ▷ _ 26
24 ε 23, 12
26 ε 22, 24
28 ▽ _ 26
29 ▷ _ 32
30 ε 29, 12
32 ε 22, 30
34 ▷ _ 32
38 changes: 38 additions & 0 deletions crates/plotnik-lib/src/engine/engine_tests.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -634,3 +634,41 @@ fn regression_nested_quantifiers_struct_captures_mixed() {
"class Empty { } class One { foo() {} } class Two { bar() {} baz() {} }"
);
}

/// BUG #9: Childless nodes with inner quantifiers caused outer quantifier to miss matches.
///
/// For `(identifier (_)* @items)` inside a star quantifier, if `identifier` has zero
/// children at runtime (tree-sitter identifiers are terminal nodes with no children),
/// the Down navigation fails. The skip path should NOT execute Up since we never
/// descended, but currently it does, causing the cursor to ascend one level too high.
///
/// This breaks the outer quantifier's iteration: after processing the first match,
/// the cursor is at the grandparent level instead of sibling level, so Next fails.
///
/// Fix: When Down fails immediately (childless node), the skip path should bypass
/// the Up instruction. Only execute Up when we actually descended into children.
#[test]
fn regression_childless_node_with_inner_star() {
snap!(
indoc! {r#"
Q = (program {(expression_statement
(identifier (_)* @items) @id
) @stmt}* @stmts)
"#},
"foo; bar; baz"
);
}

/// Same bug with optional quantifier instead of star.
/// `(identifier (_)? @item)` should also handle childless nodes correctly.
#[test]
fn regression_childless_node_with_inner_optional() {
snap!(
indoc! {r#"
Q = (program {(expression_statement
(identifier (_)? @item) @id
) @stmt}* @stmts)
"#},
"foo; bar; baz"
);
}
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