Add path checks to _page_generator.

Author: ayjayt

src/py/kaleido/_page_generator.py

@@ -1,4 +1,5 @@
 from pathlib import Path
+from urllib.parse import urlparse
 
 import logistro
 
@@ -10,6 +11,13 @@
 KJS_PATH = Path(__file__).resolve().parent / "vendor" / "kaleido_scopes.js"
 
 
+def _ensure_path(path: Path):
+    if urlparse(path).scheme:  # is url
+        return
+    if not path.exists():
+        raise ValueError(f"{path} does not seem to be a valid path.")
+
+
 class PageGenerator:
     """
     A page generator can set the versions of the js libraries used to render.
@@ -45,13 +53,14 @@ def __init__(self, *, plotly=None, mathjax=None, others=None, force_cdn=False):
         Create a PageGenerator.
 
         Args:
-            plotly: the url to the plotly script to use. The default is the one
-            plotly.py is using, if not installed, it uses the constant declared.
-            mathjax: the url to the mathjax script. By default is constant above.
-            Can be set to false to turn off.
-            others: a list of other script urls to include. Usually strings, but can be
-            (str, str) where its (url, encoding).
-            force_cdn: (default False) Don't use plotly import, use CDN
+            plotly: The url to the plotly.js to use. Defaults to plotly.js
+                present in plotly.py, if installed. Otherwise fallback to
+                global constant.
+            mathjax: The url to the mathjax script. Defaults to global constant.
+                Can be set to false to turn off.
+            others: A list of other script urls to include. Usually strings, but
+                can be (str, str) where it's (url, encoding).
+            force_cdn: Set True to force CDN use, defaults to False.
 
         """
         self._scripts = []
@@ -81,14 +90,19 @@ def __init__(self, *, plotly=None, mathjax=None, others=None, force_cdn=False):
                 _logger.info("Plotly not installed. Using CDN.")
                 plotly = (DEFAULT_PLOTLY, "utf-8")
         elif isinstance(plotly, str):
+            _ensure_path(plotly)
             plotly = (plotly, "utf-8")
         _logger.debug(f"Plotly script: {plotly}")
         self._scripts.append(plotly)
         if mathjax is not False:
             if not mathjax:
                 mathjax = DEFAULT_MATHJAX
+            else:
+                _ensure_path(mathjax)
             self._scripts.append(mathjax)
         if others:
+            for o in others:
+                _ensure_path(o)
             self._scripts.extend(others)
 
     def generate_index(self, path=None):