Update according to first review

Better documentation and more readable function structrue
review: aboutcode-org#443 (review)

Signed-off-by: Hritik Vijay <hritikxx8@gmail.com>

vulnerabilities/helpers.py

@@ -167,10 +167,10 @@ def __lt__(self, other):
     return affected_package_with_patched_package_objects
 
 
-def split_markdown_front_matter(lines: str) -> Tuple[str, str]:
+def split_markdown_front_matter(text: str) -> Tuple[str, str]:
     r"""
-    Split text into markdown front matter and the markdown body
-    Return ("", text) for text with non existing front matter
+    Return a tuple of (front matter, markdown body) strings split from ``text``.
+    Each can be an empty string.
 
     >>> text='''---
     ... title: DUMMY-SECURITY-2019-001
@@ -180,19 +180,13 @@ def split_markdown_front_matter(lines: str) -> Tuple[str, str]:
     ... # Markdown starts here
     ... '''
     >>> split_markdown_front_matter(text)
-    ('title: DUMMY-SECURITY-2019-001\ndescription: Incorrect access control.\ncves: [CVE-2042-1337]', '# Markdown starts here\n')
+    ('title: DUMMY-SECURITY-2019-001\ndescription: Incorrect access control.\ncves: [CVE-2042-1337]', '# Markdown starts here')
     """
-    fmlines = []
-    mdlines = []
-    splitter = mdlines
-
-    lines = lines.replace("\r\n", "\n")
-    for index, line in enumerate(lines.split("\n")):
-        if index == 0 and line.strip().startswith("---"):
-            splitter = fmlines
-        elif line.strip().startswith("---"):
-            splitter = mdlines
-        else:
-            splitter.append(line)
-
-    return "\n".join(fmlines), "\n".join(mdlines)
+    lines = text.splitlines()
+    if lines[0] == "---":
+        lines = lines[1:]
+        text = "\n".join(lines)
+        frontmatter, _, markdown = text.partition("\n---\n")
+        return frontmatter, markdown
+
+    return "", text

vulnerabilities/importers/istio.py

@@ -174,10 +174,8 @@ def process_file(self, path):
         return advisories
 
     def get_data_from_md(self, path):
-        """Return a mapping of vulnerability data from istio. The data is
-        in the form of yaml objects found inside front matter of the .md file.
-        """
+        """Return a mapping of vulnerability data extracted from an advisory."""
 
         with open(path) as f:
-            yaml_lines, _ = split_markdown_front_matter(f.read())
-            return saneyaml.load(yaml_lines)
+            front_matter, _ = split_markdown_front_matter(f.read())
+            return saneyaml.load(front_matter)