From f7638cf027ca3b2af721bbc43fef15d3b547b8e5 Mon Sep 17 00:00:00 2001
From: mulatta <67085791+mulatta@users.noreply.github.com>
Date: Sat, 26 Sep 2026 23:45:28 +0900
Subject: [PATCH] feat: add Nix language support

Nix files are detected by CocoIndex but excluded from default project walks. Include them by default so semantic indexing and structural grep work without per-project pattern overrides.
---
 README.md                      |  1 +
 src/cocoindex_code/settings.py |  1 +
 tests/test_grep.py             | 17 +++++++++++++++++
 tests/test_settings.py         |  4 ++++
 4 files changed, 23 insertions(+)

diff --git a/README.md b/README.md
index 77bae52..77b8df2 100644
--- a/README.md
+++ b/README.md
@@ -857,6 +857,7 @@ embedding:
 | kotlin | | `.kt`, `.kts` |
 | lua | | `.lua` |
 | markdown | md | `.md`, `.mdx` |
+| nix | | `.nix` |
 | pascal | pas, dpr, delphi | `.pas`, `.dpr` |
 | php | | `.php` |
 | python | | `.py` |
diff --git a/src/cocoindex_code/settings.py b/src/cocoindex_code/settings.py
index 0aa1faf..634fff5 100644
--- a/src/cocoindex_code/settings.py
+++ b/src/cocoindex_code/settings.py
@@ -54,6 +54,7 @@
     "**/*.swift",  # Swift
     "**/*.kt",  # Kotlin
     "**/*.kts",  # Kotlin script
+    "**/*.nix",  # Nix
     "**/*.scala",  # Scala
     "**/*.r",  # R
     "**/*.html",  # HTML
diff --git a/tests/test_grep.py b/tests/test_grep.py
index bb7e686..ec62199 100644
--- a/tests/test_grep.py
+++ b/tests/test_grep.py
@@ -137,6 +137,23 @@ def test_grep_language_filter(codebase: Path) -> None:
     assert {fm.path for fm in results} and all(fm.path.endswith(".rs") for fm in results)
 
 
+def test_grep_nix_binding_with_default_patterns(tmp_path: Path) -> None:
+    nix_file = tmp_path / "default.nix"
+    nix_file.write_text("{ pkgs, ... }: { package-name = pkgs.callPackage ./package.nix {}; }\n")
+    req = g.GrepRequest(
+        pattern=r"package-name = \VALUE;",
+        root=tmp_path,
+        languages=frozenset({"nix"}),
+    )
+
+    results = run_grep(req)
+
+    assert len(results) == 1
+    assert results[0].path == nix_file.as_posix()
+    value = results[0].matches[0].captures["VALUE"][0].text
+    assert value == "pkgs.callPackage ./package.nix {}"
+
+
 def test_grep_single_file(codebase: Path) -> None:
     req = g.GrepRequest(pattern=r"def \NAME(\(ARGS*\)):", root=codebase / "a.py")
     results = run_grep(req)
diff --git a/tests/test_settings.py b/tests/test_settings.py
index abce8e2..bd58ead 100644
--- a/tests/test_settings.py
+++ b/tests/test_settings.py
@@ -82,6 +82,10 @@ def test_default_included_patterns_cover_elixir() -> None:
     assert "**/*.exs" in DEFAULT_INCLUDED_PATTERNS
 
 
+def test_default_included_patterns_cover_nix() -> None:
+    assert "**/*.nix" in DEFAULT_INCLUDED_PATTERNS
+
+
 @pytest.mark.usefixtures("_patch_user_dir")
 def test_save_and_load_user_settings(tmp_path: Path) -> None:
     settings = UserSettings(