Implement MERMAID_USE_CDN setting property (GH-21)

Author: ArtyomVancyan

README.md

@@ -76,6 +76,15 @@ the `MERMAID_THEME` variable.
 {% startmermaid "dark" %}graph LR; A--B;{% endmermaid %}
 ```
 
+### Mermaid use CDN
+
+By default, Django Mermaid uses the local copy of mermaid from staticfiles. However, if you want to use the CDN version
+directly, you can set the `MERMAID_USE_CDN` variable in your Django project's **settings.py** file.
+
+```python
+MERMAID_USE_CDN = True
+```
+
 ### Mermaid theme variables
 
 You can define your custom theme by overriding the `MERMAID_THEME_VARIABLES` variable. You will need to use

src/django_mermaid/__init__.py

@@ -1 +1 @@
-__version__ = "0.0.8"
+__version__ = "0.0.9"

src/django_mermaid/apps.py

@@ -5,6 +5,7 @@
 from django.conf import settings
 
 from .templatetags import DEFAULT_VERSION
+from .templatetags import MERMAID_CDN
 
 
 class MermaidConfig(AppConfig):
@@ -13,12 +14,11 @@ class MermaidConfig(AppConfig):
     def ready(self):
         """Download mermaid.js from CDN if not already present"""
         version = getattr(settings, "MERMAID_VERSION", DEFAULT_VERSION)
-        cdn = "https://cdnjs.cloudflare.com/ajax/libs/mermaid/%s/mermaid.min.js" % version
         current_dir = pathlib.Path(__file__).parent
         static_dir = current_dir / "static"
         mermaid_dir = static_dir / "mermaid" / version
         mermaid_js = mermaid_dir / "mermaid.js"
         if not mermaid_js.exists() or \
                mermaid_js.stat().st_size == 0:
             mermaid_dir.mkdir(parents=True, exist_ok=True)
-            urlretrieve(cdn, str(mermaid_js))
+            urlretrieve(MERMAID_CDN % version, str(mermaid_js))

src/django_mermaid/templatetags/__init__.py

@@ -1,7 +1,12 @@
+MERMAID_CDN = "https://cdnjs.cloudflare.com/ajax/libs/mermaid/%s/mermaid.min.js"
+
 DEFAULT_VERSION = "9.4.3"  # default to latest stable version
 DEFAULT_THEME = "default"  # use the mermaid 'default' theme
+DEFAULT_USE_CDN = False  # use local mermaid.js by default
 
 __all__ = [
+    "DEFAULT_USE_CDN",
     "DEFAULT_VERSION",
     "DEFAULT_THEME",
+    "MERMAID_CDN",
 ]

src/django_mermaid/templatetags/mermaid.py

@@ -7,7 +7,9 @@
 from django.utils.safestring import mark_safe
 
 from . import DEFAULT_THEME
+from . import DEFAULT_USE_CDN
 from . import DEFAULT_VERSION
+from . import MERMAID_CDN
 
 register = template.Library()
 
@@ -24,10 +26,11 @@ def mermaid(diagram=None, theme=None):
     """
 
     version = getattr(settings, "MERMAID_VERSION", DEFAULT_VERSION)
+    use_cdn = getattr(settings, "MERMAID_USE_CDN", DEFAULT_USE_CDN)
     theme = theme or getattr(settings, "MERMAID_THEME", DEFAULT_THEME)
     theme_variables = getattr(settings, "MERMAID_THEME_VARIABLES", {}) if theme == "base" else {}
 
-    mermaid_uri = static("mermaid/%s/mermaid.js" % version)
+    mermaid_uri = MERMAID_CDN % version if use_cdn else static("mermaid/%s/mermaid.js" % version)
     html = "<div class=\"mermaid\">%s</div><script src=\"%s\"></script>" % (diagram or "", mermaid_uri)
     init_properties = {"startOnLoad": True, "theme": theme, "themeVariables": theme_variables}
     return html + "<script>mermaid.initialize(%s);</script>" % json.dumps(init_properties)

tests/test_tag.py

@@ -36,6 +36,24 @@ def test_tag_use_in_template(version, template_code):
     )
 
 
+@override_settings(MERMAID_USE_CDN=True)
+@pytest.mark.parametrize(
+    "template_code",
+    [
+        "{% load mermaid %}{% mermaid content %}",
+        "{% load mermaid %}{% startmermaid %}{{ content|safe }}{% endmermaid %}"
+    ]
+)
+def test_tag_use_mermaid_cdn(version, template_code):
+    template = Template(template_code)
+    template = template.render(Context({"content": "graph LR; A-->B;"}))
+    assert template == (
+            "<div class=\"mermaid\">graph LR; A-->B;</div><script src=\"https://cdnjs.cloudflare.com/ajax/libs/mermaid/%s/mermaid.min.js\"></script>"
+            "<script>mermaid.initialize({\"startOnLoad\": true, \"theme\": \"default\", \"themeVariables\""
+            ": {}});</script>" % version
+    )
+
+
 @override_settings(MERMAID_THEME="forest")
 @pytest.mark.parametrize(
     "template_code",