Improve cpp log level classification (#1422)

src/solidlsp/language_servers/clangd_language_server.py

@@ -34,6 +34,39 @@ class ClangdLanguageServer(SolidLanguageServer):
           (default: the bundled Serena version).
     """
 
+    @staticmethod
+    def _determine_log_level(line: str) -> int:
+        """
+        Classify a clangd stderr line using clangd's explicit level prefix.
+
+        See `clang::clangd::Logger::indicator` for details:
+        https://clang.llvm.org/extra/doxygen/classclang_1_1clangd_1_1Logger.html
+
+        Clangd emits each log record prefixed by a single indicator character
+        followed by a timestamp in square brackets, e.g. ``I[12:27:16.234]``.
+
+        The indicators are ``D`` (Debug), ``I`` (Info), ``E`` (Error) and
+        ``F`` (Fatal). Continuation lines of multi-line records carry no
+        prefix and are treated as informational.
+
+        Without this override, the base implementation scans the line for
+        the substrings ``error`` and ``exception``, which produces false
+        positives on clangd's reconstructed compile commands in some cases
+        (e.g. ``-DNO_EXCEPTIONS``, ``-fno-exceptions``).
+        """
+        # classify by clangd's level indicator character
+        if len(line) >= 2 and line[1] == "[":
+            indicator = line[0]
+            if indicator in ("E", "F"):
+                return logging.ERROR
+            if indicator == "I":
+                return logging.INFO
+            if indicator == "D":
+                return logging.DEBUG
+
+        # continuation line or non-prefixed output: default to INFO, do not keyword-scan
+        return logging.INFO
+
     def __init__(self, config: LanguageServerConfig, repository_root_path: str, solidlsp_settings: SolidLSPSettings):
         """
         Creates a ClangdLanguageServer instance. This class is not meant to be instantiated directly. Use LanguageServer.create() instead.

test/solidlsp/cpp/test_clangd_logging.py

@@ -0,0 +1,43 @@
+import logging
+
+import pytest
+
+from solidlsp import SolidLanguageServer
+from solidlsp.language_servers.clangd_language_server import ClangdLanguageServer
+
+
+@pytest.mark.cpp
+class TestClangdLogging:
+    @pytest.mark.parametrize(
+        "expected, line",
+        [
+            # Parametrize names instead of codes for human-readable output in test logs.
+            (logging.getLevelName(logging.INFO), "I[12:00:00.000] clangd version 22.1.3"),
+            (logging.getLevelName(logging.INFO), "V[12:00:00.000] verbose detail"),
+            (logging.getLevelName(logging.DEBUG), "D[12:00:00.000] debug detail"),
+            (logging.getLevelName(logging.ERROR), "E[12:00:00.000] something bad"),
+            (logging.getLevelName(logging.ERROR), "F[12:00:00.000] fatal"),
+        ],
+    )
+    def test_log_record_detection(self, expected: str, line: str) -> None:
+        """
+        Verifies clangd's stderr log classifier maps each level prefix to the
+        expected Python logging level and avoids misclassifying compile-command
+        payloads as ERROR.
+        """
+        assert ClangdLanguageServer._determine_log_level(line) == logging.getLevelNamesMapping()[expected]
+
+    def test_log_record_info_payload_mentions_fno_exceptions(self) -> None:
+        line = """clang++ -fno-exceptions -c no_exceptions.cpp"""
+        # Basic classifier incorrectly detects line as an error log.
+        assert SolidLanguageServer._determine_log_level(line) == logging.ERROR
+        # Clangd classifier correctly detects line as an info log.
+        assert ClangdLanguageServer._determine_log_level(line) == logging.INFO
+
+    def test_log_record_info_payload_without_prefix(self) -> None:
+        # Multi-line records: first line carries the I[...] prefix, subsequent
+        # lines do not. Treat lack of prefix as continuation.
+        assert ClangdLanguageServer._determine_log_level("[/home/user/project/build]") == logging.INFO
+
+    def test_log_record_info_payload_empty(self) -> None:
+        assert ClangdLanguageServer._determine_log_level("") == logging.INFO