Support loading plugins with config.

blag/blag.py

@@ -15,7 +15,12 @@
 
 import blag
 from blag.devserver import serve
-from blag.markdown import convert_markdown, markdown_factory
+from blag.markdown import (
+    MarkdownExtensionLoadError,
+    check_extensions,
+    convert_markdown,
+    markdown_factory,
+)
 from blag.quickstart import quickstart
 from blag.version import __VERSION__
 
@@ -242,6 +247,12 @@ def build(args: argparse.Namespace) -> None:
         shutil.copytree(args.static_dir, args.output_dir, dirs_exist_ok=True)
 
     config = get_config("config.ini")
+    extra_extensions = get_extra_extensions(config)
+    try:
+        check_extensions(extra_extensions)
+    except MarkdownExtensionLoadError:
+        logger.error(f"Problem loading extensions: {extra_extensions}")
+        sys.exit(1)
 
     env = environment_factory(args.template_dir, dict(site=config))
 
@@ -268,6 +279,7 @@ def build(args: argparse.Namespace) -> None:
         args.output_dir,
         page_template,
         article_template,
+        extra_extensions,
     )
 
     generate_feed(
@@ -283,12 +295,21 @@ def build(args: argparse.Namespace) -> None:
     generate_tags(articles, tags_template, tag_template, args.output_dir)
 
 
+def get_extra_extensions(config: configparser.SectionProxy) -> list[str]:
+    """Parse named extensions from config and return a list."""
+    if extensions := config.get("extensions"):
+        return list(set(extensions.split(",")))
+    else:
+        return []
+
+
 def process_markdown(
     convertibles: list[tuple[str, str]],
     input_dir: str,
     output_dir: str,
     page_template: Template,
     article_template: Template,
+    extra_extensions: list[str] = [],
 ) -> tuple[list[tuple[str, dict[str, Any]]], list[tuple[str, dict[str, Any]]]]:
     """Process markdown files.
 
@@ -308,6 +329,9 @@ def process_markdown(
     output_dir
     page_template, archive_template
         templates for pages and articles
+    extra_extensions
+        additional supported markdown extensions.
+        see: https://python-markdown.github.io/extensions/
 
     Returns
     -------
@@ -316,7 +340,7 @@ def process_markdown(
 
     """
     logger.info("Converting Markdown files...")
-    md = markdown_factory()
+    md = markdown_factory(extra_extensions)
 
     articles = []
     pages = []
@@ -396,7 +420,7 @@ def generate_feed(
         )
 
     with open(f"{output_dir}/atom.xml", "w") as fh:
-        feed.write(fh, encoding='utf-8')
+        feed.write(fh, encoding="utf-8")
 
 
 def generate_index(

blag/devserver.py

@@ -54,7 +54,7 @@ def get_last_modified(dirs: list[str]) -> float:
     return last_mtime
 
 
-def autoreload(args: argparse.Namespace, wait: int=1) -> NoReturn:
+def autoreload(args: argparse.Namespace, wait: int = 1) -> NoReturn:
     """Start the autoreloader.
 
     This method monitors the given directories for changes (i.e. the

blag/markdown.py

@@ -17,7 +17,13 @@
 logger = logging.getLogger(__name__)
 
 
-def markdown_factory() -> Markdown:
+class MarkdownExtensionLoadError(Exception):
+    """An error thrown when extensions cannot be loaded."""
+
+    pass
+
+
+def markdown_factory(extra_extensions: list[str] = []) -> Markdown:
     """Create a Markdown instance.
 
     This method exists only to ensure we use the same Markdown instance
@@ -28,14 +34,20 @@ def markdown_factory() -> Markdown:
     markdown.Markdown
 
     """
+    default_extensions = [
+        "codehilite",
+        "fenced_code",
+        "footnotes",
+        "meta",
+        "smarty",
+    ]
+    # Ensure the extra don't duplicate the default
+    all_extensions = list(set(default_extensions + extra_extensions))
+
     md = Markdown(
         extensions=[
-            "meta",
-            "fenced_code",
-            "codehilite",
-            "smarty",
-            "footnotes",
             MarkdownLinkExtension(),
+            *all_extensions,
         ],
         output_format="html",
     )
@@ -132,3 +144,11 @@ def extendMarkdown(self, md: Markdown) -> None:
             "mdlink",
             0,
         )
+
+
+def check_extensions(extensions: list[str]) -> None:
+    """Attempt to load the named extensions."""
+    try:
+        Markdown(extensions=extensions)
+    except ModuleNotFoundError:
+        raise MarkdownExtensionLoadError

docs/manual.md

@@ -251,6 +251,23 @@ freely in you templates. However, some metadata elements are treated special:
   header and in the atom feed.
 
 
+### Markdown Extensions
+
+`blag` loads several Markdown extensions by default, including `meta`,
+`fenced_code`, `codehilite`, and `smarty`.  If you wish to use additional
+extensions, you may add a line to your configuration file as a comma-separated
+list, like this:
+
+```
+extensions = footnotes,tables
+```
+
+You can view the full list of officially supported extensions for the
+Python-Markdown libary here:
+
+<https://python-markdown.github.io/extensions/#officially-supported-extensions>
+
+
 ## Devserver
 
 blag provides a devserver which you can use for local web-development. The

tests/conftest.py

@@ -92,5 +92,6 @@ def args(cleandir: Callable[[], Iterator[str]]) -> Iterator[Namespace]:
         output_dir="build",
         static_dir="static",
         template_dir="templates",
+        extensions=["footnotes"],
     )
     yield args

tests/test_blag.py

@@ -192,6 +192,45 @@ def test_get_config() -> None:
         assert config_parsed["base_url"] == "https://example.com/"
 
 
+def test_get_extra_extensions() -> None:
+    """Test parsing extensions string from config."""
+    # No extensions in config
+    config = """
+[main]
+base_url = https://example.com/
+title = title
+description = description
+author = a. u. thor
+    """
+    with TemporaryDirectory() as dir:
+        configfile = f"{dir}/config.ini"
+        with open(configfile, "w") as fh:
+            fh.write(config)
+
+        config_parsed = blag.get_config(configfile)
+        extra_extensions = blag.get_extra_extensions(config_parsed)
+        assert isinstance(extra_extensions, list)
+        assert len(extra_extensions) == 0
+
+    # Some extensions in the config
+    config = """
+[main]
+base_url = https://example.com/
+title = title
+description = description
+author = a. u. thor
+extensions = footnotes,tables
+    """
+    with TemporaryDirectory() as dir:
+        configfile = f"{dir}/config.ini"
+        with open(configfile, "w") as fh:
+            fh.write(config)
+        config_parsed = blag.get_config(configfile)
+        extra_extensions = blag.get_extra_extensions(config_parsed)
+        assert "footnotes" in extra_extensions
+        assert "tables" in extra_extensions
+
+
 def test_environment_factory(cleandir: str) -> None:
     """Test environment_factory."""
     globals_: dict[str, object] = {"foo": "bar", "test": "me"}

tests/test_markdown.py

@@ -6,7 +6,12 @@
 import markdown
 import pytest
 
-from blag.markdown import convert_markdown, markdown_factory
+from blag.markdown import (
+    MarkdownExtensionLoadError,
+    check_extensions,
+    convert_markdown,
+    markdown_factory,
+)
 
 
 @pytest.mark.parametrize(
@@ -125,3 +130,12 @@ def test_footnotes() -> None:
     assert "<hr>" in html
     assert "<ol>" in html
     assert "footnotetext" in html
+
+def test_check_extensions() -> None:
+    """Test that bad extensions throw an error, good extensions don't."""
+    ok_extensions = ["footnotes", "toc"]
+    check_extensions(ok_extensions)
+
+    bad_extensions = ["foobar", "bazbom"]
+    with pytest.raises(MarkdownExtensionLoadError):
+        check_extensions(bad_extensions)