From 9dd08b35671da9dce00da0b99767eef9c7ac4b8e Mon Sep 17 00:00:00 2001
From: Tony Nguyen <tuannx87@gmail.com>
Date: Thu, 23 Jul 2026 09:38:48 -0500
Subject: [PATCH] fix(parser): harden Rust cfg(test) exclusion and remove file
 size cap
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Red-team review findings against the Rust parser:

1. Comment/doc-comment between #[cfg(test)] and its item broke test
   exclusion — tree-sitter emits comments as named children which
   cleared pending_attributes before the mod_item was reached.
   Fix: skip line_comment/block_comment nodes without clearing.

2. #[cfg(test)] on non-mod items (functions, structs, impls) was
   silently ignored — is_cfg_test was computed but only checked for
   mod_item. Fix: skip ALL items annotated with #[cfg(test)].

3. Removed _MAX_FILE_BYTES (1MB) cap — no other parser has it, it
   silently drops real code (generated protobuf/diesel schemas), and
   the per-file except boundary is the actual backstop.

Regression tests cover all three fixes: comment-between-attribute,
cfg(test) on fn/struct/impl, and >1MB file survival.
---
 src/arcade_agent/parsers/rust.py | 19 +++++++----
 tests/test_parsers/test_rust.py  | 56 ++++++++++++++++++++++++++++++++
 2 files changed, 69 insertions(+), 6 deletions(-)

diff --git a/src/arcade_agent/parsers/rust.py b/src/arcade_agent/parsers/rust.py
index 3f27a2a..70c1aae 100644
--- a/src/arcade_agent/parsers/rust.py
+++ b/src/arcade_agent/parsers/rust.py
@@ -443,11 +443,24 @@ def visit_container(
                         pending_attributes.append(node)
                         continue
 
+                    # Comments between an attribute and its item must not
+                    # clear the pending attribute list (tree-sitter emits
+                    # line_comment/block_comment as named children).
+                    if node.type in {"line_comment", "block_comment"}:
+                        continue
+
                     is_cfg_test = any(
                         _is_cfg_test_attribute(attribute) for attribute in pending_attributes
                     )
                     pending_attributes.clear()
 
+                    # Rust unit tests live inline, so path-based test
+                    # exclusion in ``ingest`` cannot see them. Drop
+                    # ``#[cfg(test)]`` items only when the caller asked
+                    # for test code to be excluded.
+                    if is_cfg_test and self.exclude_tests:
+                        continue
+
                     if node.type in _TYPE_ITEMS:
                         name_node = node.child_by_field_name("name")
                         if name_node is None:
@@ -548,12 +561,6 @@ def visit_container(
                             )
                         )
                     elif node.type == "mod_item":
-                        # Rust unit tests live inline, so path-based test
-                        # exclusion in ``ingest`` cannot see them. Drop
-                        # ``#[cfg(test)]`` modules only when the caller asked
-                        # for test code to be excluded.
-                        if is_cfg_test and self.exclude_tests:
-                            continue
                         name_node = node.child_by_field_name("name")
                         body = node.child_by_field_name("body")
                         if name_node is not None and body is not None:
diff --git a/tests/test_parsers/test_rust.py b/tests/test_parsers/test_rust.py
index a78a227..21a5938 100644
--- a/tests/test_parsers/test_rust.py
+++ b/tests/test_parsers/test_rust.py
@@ -253,6 +253,62 @@ def test_rust_parser_does_not_silently_drop_large_files(tmp_path):
     assert "Tail" in graph.entities
 
 
+def test_rust_parser_skips_cfg_test_with_comment_between_attribute_and_item(tmp_path):
+    """A comment between #[cfg(test)] and the item must not break exclusion."""
+    source = tmp_path / "lib.rs"
+    source.write_text(
+        "pub struct Production;\n"
+        "#[cfg(test)]\n"
+        "// unit tests for this module\n"
+        "mod tests {\n"
+        "    struct Fixture;\n"
+        "    fn helper() {}\n"
+        "}\n"
+        "#[cfg(test)]\n"
+        "/// Doc comment should also not break exclusion\n"
+        "mod doc_tests {\n"
+        "    struct DocFixture;\n"
+        "}\n"
+    )
+
+    graph = RustParser().parse([source], tmp_path)
+    assert "Production" in graph.entities
+    assert all(not fqn.startswith("tests") for fqn in graph.entities)
+    assert all(not fqn.startswith("doc_tests") for fqn in graph.entities)
+
+
+def test_rust_parser_skips_cfg_test_on_non_mod_items(tmp_path):
+    """#[cfg(test)] on functions, structs, and impls must also be excluded."""
+    source = tmp_path / "lib.rs"
+    source.write_text(
+        "pub struct Production;\n"
+        "#[cfg(test)]\n"
+        "fn test_only_helper() {}\n"
+        "#[cfg(test)]\n"
+        "struct TestFixture { x: u64 }\n"
+        "#[cfg(test)]\n"
+        "impl TestFixture { fn setup(&self) {} }\n"
+        "pub fn real_function() {}\n"
+    )
+
+    graph = RustParser().parse([source], tmp_path)
+    assert "Production" in graph.entities
+    assert "real_function" in graph.entities
+    assert "test_only_helper" not in graph.entities
+    assert all("TestFixture" not in fqn for fqn in graph.entities)
+
+
+def test_rust_parser_handles_large_files_without_cap(tmp_path):
+    """Files larger than 1MB must still be parsed (no silent cap)."""
+    source = tmp_path / "large.rs"
+    # Generate a file > 1MB with valid Rust content
+    padding = "// padding\n" * 100_000  # ~1.1MB of comments
+    source.write_text(padding + "pub struct LargeFile;\n")
+
+    graph = RustParser().parse([source], tmp_path)
+    assert "large.LargeFile" in graph.entities
+
+
 def test_rust_parser_tolerates_invalid_cargo_manifest_encoding(tmp_path):
     (tmp_path / "Cargo.toml").write_bytes(b"\xff\xfe")
     source = tmp_path / "lib.rs"