Allow local template overrides in the site directory

closes #13

omicron/ssg/cli.py

@@ -149,7 +149,6 @@ def init(args: argparse.Namespace) -> None:
             "items_per_page": int(items_per_page),
         }
     )
-    Site.resolve_template_path(config.template)
 
     config.to_file(config_path)
     (args.site / "content").mkdir(exist_ok=True)

omicron/ssg/site.py

@@ -27,6 +27,7 @@ from pathlib import Path
 from jinja2 import Environment, FileSystemLoader
 
 log = logging.getLogger(__name__)
+builtin_templates = Path(__file__).parent / "templates"
 
 
 class Site:
@@ -43,15 +44,18 @@ class Site:
         self.tags_by_count: list[tuple[str, int]] = []
 
         self.config = SiteConfig.from_file(site / "config.yml")
-        self.template_path: Path = Site.resolve_template_path(self.config.template)
+        self.template_path: Path = self.resolve_template_path(self.config.template)
         self.output_path: Path = self.site_path / "output"
         self.jinja_env = Environment(loader=FileSystemLoader(self.template_path))
 
-    @staticmethod
-    def resolve_template_path(template: str) -> Path:
-        path = Path(__file__).parent / "templates" / template
+    def resolve_template_path(self, template: str) -> Path:
+        path = self.site_path / "templates" / template
+        if path.is_dir():
+            return path
+
+        path = builtin_templates / template
         if not path.is_dir():
-            raise ConfigError(f"template '{template}' not found at {path}")
+            raise ConfigError(f"template '{template}' not found.")
         return path
 
     def add_by_section(self, content: Content) -> None:

tests/unit/test_site.py

@@ -78,9 +78,29 @@ def test_clean_removes_output_directory(make_site):
     assert not site.output_path.exists()
 
 
-def test_resolve_template_path_raises_for_missing_template():
+def test_resolve_template_path_raises_for_missing_template(site_dir):
+    path = site_dir("thin_site")
+    (path / "config.yml").write_text("name: test\ntemplate: does-not-exist\n")
+
     with pytest.raises(ConfigError, match="not found"):
-        Site.resolve_template_path("does-not-exist")
+        Site(path)
+
+
+def test_resolve_template_path_prefers_local_override(site_dir):
+    path = site_dir("thin_site")
+    (path / "config.yml").write_text("name: test\ntemplate: plain\n")
+    local = path / "templates" / "plain"
+    local.mkdir(parents=True)
+
+    assert Site(path).template_path == local
+
+
+def test_resolve_template_path_falls_back_to_builtin(site_dir):
+    path = site_dir("thin_site")
+    (path / "config.yml").write_text("name: test\ntemplate: plain\n")
+
+    assert Site(path).template_path.name == "plain"
+    assert not Site(path).template_path.is_relative_to(path)
 
 
 def test_home_url(site_dir):