add .NET project file support (.sln, .csproj, .fsproj, .vbproj, .razor, .cshtml)

Adds extract_sln, extract_csproj, and extract_razor extractors. Captures NuGet
package refs, project-to-project dependencies, target frameworks, SDK attribute,
@using/@inject/@inherits/@model directives, Blazor component refs, and @code
methods. Resolves relative project paths to absolute paths so sln/csproj nodes
link correctly when the graph is assembled. Closes #515.

Co-Authored-By: aksrathore <aksrathore@users.noreply.github.com>
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

tests/test_dotnet.py

@@ -0,0 +1,125 @@
+"""Tests for .NET project file extraction (.sln, .csproj, .razor)."""
+from pathlib import Path
+import tempfile
+import pytest
+from graphify.extract import extract_sln, extract_csproj, extract_razor
+
+FIXTURES = Path(__file__).parent / "fixtures"
+
+
+def _labels(r):
+    return [n["label"] for n in r["nodes"]]
+
+
+def _relations(r):
+    return {e["relation"] for e in r["edges"]}
+
+
+# ── .sln ─────────────────────────────────────────────────────────────────────
+
+def test_sln_extracts_projects():
+    r = extract_sln(FIXTURES / "sample.sln")
+    assert "error" not in r
+    labels = set(_labels(r))
+    assert "WebApi" in labels
+    assert "Domain" in labels
+    assert "Tests" in labels
+
+
+def test_sln_contains_edges():
+    r = extract_sln(FIXTURES / "sample.sln")
+    contains = [e for e in r["edges"] if e["relation"] == "contains"]
+    assert len(contains) == 3
+
+
+def test_sln_project_dependency():
+    r = extract_sln(FIXTURES / "sample.sln")
+    assert "imports" in _relations(r)
+
+
+# ── .csproj ──────────────────────────────────────────────────────────────────
+
+def test_csproj_packages():
+    r = extract_csproj(FIXTURES / "sample.csproj")
+    assert "error" not in r
+    labels = _labels(r)
+    assert any("MediatR" in l for l in labels)
+    assert any("FluentValidation" in l for l in labels)
+    assert any("Swashbuckle" in l for l in labels)
+
+
+def test_csproj_project_references():
+    r = extract_csproj(FIXTURES / "sample.csproj")
+    imports = [e for e in r["edges"] if e["relation"] == "imports"]
+    assert len(imports) == 6  # 4 packages + 2 project refs
+
+
+def test_csproj_target_framework():
+    r = extract_csproj(FIXTURES / "sample.csproj")
+    assert "net8.0" in _labels(r)
+
+
+def test_csproj_sdk():
+    r = extract_csproj(FIXTURES / "sample.csproj")
+    assert "Microsoft.NET.Sdk.Web" in _labels(r)
+
+
+def test_csproj_invalid_xml():
+    with tempfile.NamedTemporaryFile(suffix=".csproj", mode="w", delete=False) as f:
+        f.write("<Project><Invalid></Project>")
+        f.flush()
+        r = extract_csproj(Path(f.name))
+    assert "error" in r
+
+
+# ── .razor ───────────────────────────────────────────────────────────────────
+
+def test_razor_using_and_inject():
+    r = extract_razor(FIXTURES / "sample.razor")
+    assert "error" not in r
+    targets = {e["target"] for e in r["edges"] if e["relation"] == "imports"}
+    assert any("microsoft" in t for t in targets)
+    assert any("counterservice" in t.lower() for t in targets)
+
+
+def test_razor_components():
+    r = extract_razor(FIXTURES / "sample.razor")
+    targets = {e["target"] for e in r["edges"] if e["relation"] == "calls"}
+    assert any("weatherdisplay" in t for t in targets)
+    assert any("datagrid" in t for t in targets)
+
+
+def test_razor_page_route():
+    r = extract_razor(FIXTURES / "sample.razor")
+    assert any("/counter" in l for l in _labels(r))
+
+
+def test_razor_inherits():
+    r = extract_razor(FIXTURES / "sample.razor")
+    assert "inherits" in _relations(r)
+
+
+def test_razor_code_methods():
+    r = extract_razor(FIXTURES / "sample.razor")
+    labels = _labels(r)
+    assert "IncrementCount" in labels
+    assert "LoadData" in labels
+
+
+def test_razor_missing_file():
+    r = extract_razor(Path("/nonexistent/file.razor"))
+    assert "error" in r
+
+
+# ── dispatch & detect integration ────────────────────────────────────────────
+
+def test_dispatch_table():
+    from graphify.extract import _get_extractor
+    for ext in (".sln", ".csproj", ".fsproj", ".vbproj", ".razor", ".cshtml"):
+        assert _get_extractor(Path(f"foo{ext}")) is not None, f"{ext} not in dispatch"
+
+
+def test_code_extensions():
+    from graphify.detect import CODE_EXTENSIONS
+    for ext in (".sln", ".csproj", ".fsproj", ".vbproj", ".razor", ".cshtml"):
+        assert ext in CODE_EXTENSIONS, f"{ext} missing"