Close #65: do a safer/better job of parsing dependency versions

shinywidgets/_dependencies.py

@@ -157,4 +157,15 @@ def widget_pkg(w: object) -> str:
 
 
 def as_version(v: str) -> str:
-    return re.sub("\\D*", "", str(packaging.version.parse(v)))
+    try:
+        # version could be in node-semver format
+        # which is not compatible with packaging.version.parse
+        # so we strip out the leading non-numeric characters
+        # e.g., ^1.2.3 -> 1.2.3
+        v = re.sub("^\\D+", "", v)
+        return str(packaging.version.parse(v))
+    except Exception:
+        # parsing could still fail if the version is something like
+        # "*", but get the _actual_ version doesn't seem that important
+        # since I don't think it'll be possible
+        return "0.0"