From 13ebbefc0460522b90df6954892546e692684731 Mon Sep 17 00:00:00 2001
From: "github-actions[bot]" <github-actions[bot]@users.noreply.github.com>
Date: Mon, 23 Mar 2026 04:20:24 +0000
Subject: [PATCH] test: add coverage for parser error paths (5 new tests)

No existing test ever called parse() with malformed input and asserted
Err was returned. This adds five tests that cover the two highest-value
error categories: lexer errors (unclosed strings) and parser errors
(invalid grammar such as topic without a name, bare top-level expressions).

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
---
 tests/test_reasoning_minimal.rs | 78 +++++++++++++++++++++++++++++++++
 1 file changed, 78 insertions(+)

diff --git a/tests/test_reasoning_minimal.rs b/tests/test_reasoning_minimal.rs
index 3c9b7d4..55cf519 100644
--- a/tests/test_reasoning_minimal.rs
+++ b/tests/test_reasoning_minimal.rs
@@ -756,3 +756,81 @@ topic main:
         }
     }
 }
+
+// ============================================================================
+// Parser error-path tests
+//
+// The tests above exclusively exercise the happy path (valid input → Ok).
+// Nothing previously verified that parse() returns Err for malformed input.
+// These tests cover the four highest-value error cases.
+// ============================================================================
+
+#[test]
+fn test_parse_fails_on_unclosed_string_literal() {
+    // A string literal whose closing double-quote is missing is a lexer error.
+    // parse() must return Err and include at least one error message.
+    let src = "config:\n   agent_name: \"unclosed";
+    let result = parser::parse(src);
+    assert!(result.is_err(), "Expected Err for unclosed string literal, got Ok");
+    let errors = result.unwrap_err();
+    assert!(!errors.is_empty(), "Error list must be non-empty for unclosed string");
+}
+
+#[test]
+fn test_parse_fails_when_topic_has_no_name() {
+    // `topic:` without a following identifier violates the grammar — the parser
+    // expects `topic <ident>:` but finds a bare colon.  parse() must return Err.
+    let src = "config:\n   agent_name: \"Test\"\n\ntopic:\n   description: \"Nameless\"\n";
+    let result = parser::parse(src);
+    assert!(result.is_err(), "Expected Err when topic keyword has no identifier name");
+}
+
+#[test]
+fn test_parse_with_errors_returns_partial_ast_and_errors_on_invalid_block() {
+    // parse_with_errors() is the error-tolerant API.  When the input contains a
+    // recoverable parse error sandwiched between two valid blocks, it should return
+    // both a non-empty error list AND a partial AST that includes the valid blocks.
+    let src = r#"config:
+   agent_name: "Test"
+
+!!!invalid_block!!!
+
+topic main:
+   description: "Main"
+"#;
+    let (partial, errors) = parser::parse_with_errors(src);
+    assert!(!errors.is_empty(), "Expected parse errors for invalid top-level content");
+    // The valid config and topic blocks should be recovered by the error-recovery pass.
+    let ast = partial.expect("Expected a partial AST even in the presence of errors");
+    assert!(ast.config.is_some(), "config block should be present after error recovery");
+}
+
+#[test]
+fn test_parse_with_errors_reports_errors_for_bare_reference_at_top_level() {
+    // A bare `@variables.x = 5` expression at the top level is not a valid block.
+    // parse_with_errors() must surface at least one error and must not panic.
+    let src = "config:\n   agent_name: \"Test\"\n\n@variables.x = 5\n";
+    let (_, errors) = parser::parse_with_errors(src);
+    assert!(!errors.is_empty(), "Expected errors for bare reference assignment at top level");
+}
+
+#[test]
+fn test_parse_with_structured_errors_returns_message_for_invalid_input() {
+    // parse_with_structured_errors() must return Err with structured ParseErrorInfo
+    // for malformed input.  Each error must carry a non-empty human-readable message
+    // (used by IDEs and language servers).
+    use busbar_sf_agentscript::parse_with_structured_errors;
+
+    let src = "config:\n   agent_name: \"unclosed";
+    let result = parse_with_structured_errors(src);
+    assert!(result.is_err(), "Expected Err from parse_with_structured_errors for malformed input");
+    let errors = result.unwrap_err();
+    assert!(!errors.is_empty(), "Expected at least one structured error");
+    for err in &errors {
+        assert!(
+            !err.message.is_empty(),
+            "ParseErrorInfo.message must not be empty, got: {:?}",
+            err
+        );
+    }
+}