Correct errors associated with build process.

Signed-off-by: Chris Butler <chris@thebutlers.me>

README.md

@@ -4,16 +4,32 @@
 [![codecov.io][cov-badge]][cov-link]
 [![PyPI version][pypi-badge]][pypi-link]
 
-An [mdformat](https://github.com/executablebooks/mdformat) plugin for ensuring that yaml frontmatter is respected. As we are unable
-to tell the intent of a user if the yaml is incorrectly formatted it will trigger an exception.
+An [mdformat](https://github.com/executablebooks/mdformat) plugin for ensuring that yaml `front-matter` is respected.
+Many tools (such as [jekyll](https://github.com/jekyll/jekyll)) use yaml front matter for automation purposes.
+`mdformat-frontmatter` only supports yaml. For example:
 
-This package was built from the [template](https://github.com/executablebooks/mdformat-plugin) provided by [executable books](https://github.com/executablebooks) and customized (specifically to separate content PR's from the release cycle).
+```markdown
 
+---
+test: yaml
+---
+# This looks okay
+For some markdown code.
+```
 
+Frontmatter can only be at the first line or two of the code.
+```markdown
+# This is not
+---
+test: yaml
+---
+```
+Note: that at this stage this plugin is not that sophisticated. The principle objective is to allow properly formed yaml header blocks to pass through.
+Incorrectly formed blocks may result in strange behaviour.
 
 ## Development
-
-This package dirver [flit](https://flit.readthedocs.io) as the build engine, and [tox](https://tox.readthedocs.io) for test automation.
+This package was built from the [template](https://github.com/executablebooks/mdformat-plugin) provided by [executable books](https://github.com/executablebooks) and customized (specifically to separate content PR's from the release cycle).
+This package driver [flit](https://flit.readthedocs.io) as the build engine, and [tox](https://tox.readthedocs.io) for test automation.
 
 To install these development dependencies:
 

mdformat_frontmatter/__init__.py

@@ -3,4 +3,4 @@
 
 from .plugin import render_token, update_mdit  # noqa: F401
 
-__version__ = "0.1.1"
+__version__ = "0.1.3"

mdformat_frontmatter/plugin.py

@@ -2,9 +2,10 @@
 
 from markdown_it import MarkdownIt
 from markdown_it.token import Token
+import mdformat.renderer
 from mdformat.renderer import MDRenderer
 from mdit_py_plugins.front_matter import front_matter_plugin
-from yaml import dump, load
+from yaml import YAMLError, dump, load
 
 try:
     from yaml import CDumper as Dumper
@@ -32,9 +33,14 @@ def render_token(
     token = tokens[index]
     if token.type != "front_matter":
         return None
-    index
     # Safety check - parse and dump yaml to ensure it is correctly formatted
-    yamled = load(token.content, Loader=Loader)
-    serialized = dump(yamled, Dumper=Dumper)
-    content = token.markup + "\n" + serialized + token.markup + "\n"
+    try:
+        yamled = load(token.content, Loader=Loader)
+        serialized = dump(yamled, Dumper=Dumper)
+        content = token.markup + "\n" + serialized + token.markup + "\n"
+    except YAMLError:
+        mdformat.renderer.LOGGER.warning("Invalid YAML in a front matter block")
+
+        content = token.markup + "\n" + token.content + token.markup + "\n"
+
     return content, index

tests/fixtures.md

@@ -22,3 +22,36 @@ Some *markdown*
 
 * c
 .
+
+Test yaml header
+.
+---
+some: yaml
+---
+# Now some markdown
+And some more.
+.
+---
+some: yaml
+---
+# Now some markdown
+
+And some more.
+.
+
+Test yaml reformat
+.
+---
+some: yaml
+
+---
+# Now some markdown
+And some more.
+.
+---
+some: yaml
+---
+# Now some markdown
+
+And some more.
+.

tests/pre-commit-test.md

@@ -1,3 +1,6 @@
+---
+test: yaml
+---
 # Test file
 
-add your syntax here
+This file