solidlsp: recognize Arduino .ino files as C++

src/solidlsp/ls_config.py

@@ -350,6 +350,11 @@ def get_source_fn_matcher(self) -> FilenameMatcher:
                     # OpenCL
                     ".cl",
                     ".clcpp",
+                    # Arduino sketch: not in clang's extension table, but it is C++.
+                    # Routing it here lets clangd serve symbols; the project must
+                    # tell clangd it is C++ (a .clangd with CompileFlags Add: [-xc++],
+                    # or a compile DB), since the clang driver can't infer a job from .ino.
+                    ".ino",
                     case_sensitive=False,
                 )
             case self.CPP_CCLS:
@@ -375,6 +380,8 @@ def get_source_fn_matcher(self) -> FilenameMatcher:
                     # Objective-C
                     ".m",
                     ".mm",
+                    # Arduino sketch (C++); see note in the CPP case above.
+                    ".ino",
                     case_sensitive=False,
                 )
             case self.KOTLIN:

test/solidlsp/cpp/test_cpp_basic.py

@@ -24,6 +24,20 @@
     _cpp_servers.append(Language.CPP_CCLS)
 
 
+@pytest.mark.parametrize("language", [Language.CPP, Language.CPP_CCLS])
+def test_source_fn_matcher_includes_ino(language: Language) -> None:
+    """Arduino .ino sketches are C++ and must route to the C++ language server.
+
+    This is a pure matcher check; it needs no running language server.
+    """
+    matcher = language.get_source_fn_matcher()
+    assert matcher.is_relevant_filename("sketch.ino")
+    assert matcher.is_relevant_filename("BLINK.INO")  # case-insensitive
+    assert matcher.is_relevant_filename("/path/to/s3_camera.ino")
+    assert matcher.is_relevant_filename("main.cpp")  # regression: ordinary C++ still matches
+    assert not matcher.is_relevant_filename("notes.md")
+
+
 @pytest.mark.cpp
 @pytest.mark.skipif(not _cpp_servers, reason="No C++ language server (clangd or ccls) available")
 class TestCppLanguageServer: