From 99d6ffba7c8931c50d948c4f8dc489010ac4ab0a Mon Sep 17 00:00:00 2001
From: Sean N <sean@isean.co.za>
Date: Thu, 16 Apr 2026 12:10:16 +0200
Subject: [PATCH] Fix fingerprint stacking on incremental builds (#11)

---
 pyproject.toml            |  4 +--
 src/nitro/core/bundler.py |  6 +++++
 tests/test_bundler.py     | 51 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 59 insertions(+), 2 deletions(-)

diff --git a/pyproject.toml b/pyproject.toml
index 6929c69..e9275a3 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "nitro-cli"
-version = "1.0.12"
+version = "1.0.13"
 description = "Build static sites with Python code instead of template engines"
 authors = [
     {name = "Sean Nieuwoudt", email = "sean@nitro.sh"}
@@ -49,13 +49,13 @@ dependencies = [
     "nitro-datastore>=1.0.2",
     "nitro-dispatch>=1.0.0",
     "beautifulsoup4>=4.12.0",
+    "html5lib>=1.1",
 ]
 
 [project.optional-dependencies]
 dev = [
     "pytest>=8.0.0",
     "pytest-cov>=5.0.0",
-    "html5lib>=1.1",
     "black>=24.0.0",
     "flake8>=7.0.0",
 ]
diff --git a/src/nitro/core/bundler.py b/src/nitro/core/bundler.py
index 9eeb9be..5138320 100644
--- a/src/nitro/core/bundler.py
+++ b/src/nitro/core/bundler.py
@@ -233,6 +233,9 @@ def create_asset_manifest(self, output_path: Path) -> None:
         except (IOError, OSError) as e:
             error(f"Failed to write asset manifest: {e}")
 
+    # Matches stems that already end with an 8-char hex fingerprint (e.g. "nav.36da3320")
+    _FINGERPRINT_RE = re.compile(r"\.[0-9a-f]{8}$")
+
     def fingerprint_assets(self) -> Dict[str, str]:
         """Add content hashes to CSS and JS filenames for cache busting."""
         asset_files = []
@@ -245,6 +248,9 @@ def fingerprint_assets(self) -> Dict[str, str]:
         path_mapping = {}
 
         for asset_path in asset_files:
+            # Skip files already fingerprinted from a previous build
+            if self._FINGERPRINT_RE.search(asset_path.stem):
+                continue
             content = asset_path.read_bytes()
             hasher = hashlib.sha256()
             hasher.update(content)
diff --git a/tests/test_bundler.py b/tests/test_bundler.py
index 129e148..755f2cf 100644
--- a/tests/test_bundler.py
+++ b/tests/test_bundler.py
@@ -262,6 +262,57 @@ def test_updates_html_references(self):
             new_css_name = Path(mapping["style.css"]).name
             assert new_css_name in html_content
 
+    def test_skips_already_fingerprinted_files(self):
+        """Should not re-fingerprint files from a previous build (issue #11)."""
+        with tempfile.TemporaryDirectory() as tmpdir:
+            build_dir = Path(tmpdir)
+
+            # Simulate state after a previous build: both the fresh source
+            # file and the old fingerprinted copy exist in build/
+            js_content = "console.log('nav');"
+            (build_dir / "nav.js").write_text(js_content)
+            (build_dir / "nav.36da3320.js").write_text(js_content)
+
+            bundler = Bundler(build_dir)
+            mapping = bundler.fingerprint_assets()
+
+            # Only the fresh file should be fingerprinted
+            assert "nav.js" in mapping
+            assert "nav.36da3320.js" not in mapping
+
+            # No double-hashed files should exist
+            for f in build_dir.iterdir():
+                # Count dots in stem — a stacked hash would have 2+ dots
+                assert f.stem.count(".") <= 1, f"Stacked fingerprint: {f.name}"
+
+    def test_incremental_build_no_hash_stacking(self):
+        """Running fingerprint_assets twice should not stack hashes."""
+        with tempfile.TemporaryDirectory() as tmpdir:
+            build_dir = Path(tmpdir)
+
+            css_content = "body { color: blue; }"
+            (build_dir / "main.css").write_text(css_content)
+
+            bundler = Bundler(build_dir)
+
+            # First fingerprint
+            mapping1 = bundler.fingerprint_assets()
+            first_result = mapping1["main.css"]
+
+            # Simulate incremental build: fresh source file reappears
+            (build_dir / "main.css").write_text(css_content)
+
+            # Second fingerprint
+            mapping2 = bundler.fingerprint_assets()
+
+            assert "main.css" in mapping2
+            assert mapping2["main.css"] == first_result
+
+            # Only fingerprinted files and the newly renamed file should exist
+            css_files = list(build_dir.glob("*.css"))
+            # Should not have more than 1 CSS file (the fingerprinted one)
+            assert len(css_files) <= 1, f"Expected 1 CSS file, got: {[f.name for f in css_files]}"
+
 
 class TestSitemapCleanUrls:
     """Tests for clean_urls option in generate_sitemap."""