Avoid "File name too long" error (#1128)

* Avoid "File name too long" error

Any file error will be ignored and jump straight to treating var as CSS text.
fixes #1127

* Add docstring and update import order

* Add unit test

* Remove trailing whitespace

* Log a warning if var looks like a filename but can't load

The login page calls load_custom_css() twice with an empty var, so this now returns early for that.

* Update code style test

load_custom_css() now returns an empty string for a file that does not exist, so test_get_css_is_code() has been updated to test CSS code.

* Apply black formatting

* Remove unnecessary pass statement

Co-authored-by: Nathan Swain <swainn@users.noreply.github.com>

* Add comment for is_file

Co-authored-by: Nathan Swain <swainn@users.noreply.github.com>

* Add comment about long CSS string causing OSError

Co-authored-by: Nathan Swain <swainn@users.noreply.github.com>

* Add comment about determining if it is a CSS string

Co-authored-by: Nathan Swain <swainn@users.noreply.github.com>

* Apply black/flake8 formatting

---------

Co-authored-by: Nathan Swain <swainn@users.noreply.github.com>

tests/unit_tests/test_tethys_apps/test_templatetags/test_site_settings.py

@@ -42,5 +42,23 @@ def test_get_css_is_code(self, mock_isfile, mock_settings):
         mock_settings.STATIC_ROOT = "test_base_path1"
         mock_settings.STATICFILES_DIRS = ["test_base_path2"]
 
-        ret = ss.load_custom_css("test.css")
-        self.assertEqual(ret, "<style>test.css</style>")
+        ret = ss.load_custom_css(".navbar-brand { background-color: darkred; }")
+        self.assertEqual(
+            ret, "<style>.navbar-brand { background-color: darkred; }</style>"
+        )
+
+    def test_long_css_text(self):
+        long_css_text = """
+            .site-header { margin: 0 50px 0 0; background-color: red; }
+            .site-header .navbar-brand {
+                background-color: darkred;
+                color: black;
+                font-style: italic;
+                font-variant: small-caps;
+                font-family: cursive;
+                font-size: 24px;
+            }
+        """
+
+        ret = ss.load_custom_css(long_css_text)
+        self.assertEqual(ret, f"<style>{long_css_text}</style>")

tethys_apps/templatetags/site_settings.py

@@ -1,28 +1,59 @@
+import logging
+from pathlib import Path
+
 from django import template
 from django.template.defaultfilters import stringfilter
 from django.conf import settings
 
-from pathlib import Path
-
 from ..static_finders import TethysStaticFinder
 
 static_finder = TethysStaticFinder()
 
 register = template.Library()
 
+log = logging.getLogger(f"tethys.{__name__}")
+
 
 @register.filter
 @stringfilter
 def load_custom_css(var):
+    """Load Custom Styles defined in Tethys Portal -> Site Settings
+
+    Args:
+        var: a filename of CSS to load or CSS text to embed into the page
+
+    Returns:
+        a string of HTML that either embeds CSS text or points to a file
+
+    """
+    if not var.strip():
+        return ""
     if var.startswith("/"):
         var = var.lstrip("/")
 
-    if (Path(settings.STATIC_ROOT) / var).is_file() or static_finder.find(var):
-        return f'<link href="/static/{var}" rel="stylesheet" />'
+    try:
+        # Check if var is a path to a file, if so return a link tag to the file
+        if (Path(settings.STATIC_ROOT) / var).is_file() or static_finder.find(var):
+            return f'<link href="/static/{var}" rel="stylesheet" />'
 
-    else:
         for path in settings.STATICFILES_DIRS:
             if (Path(path) / var).is_file():
                 return f'<link href="/static/{var}" rel="stylesheet" />'
+    # If the string is too long for a file path, which could happen if it is CSS,
+    # an OSError will be raised during the file path checks. This could also happen
+    # if a lengthy file path is given or is otherwise invalid.
+    except OSError as e:
+        oserror_exception = ": " + str(e)
+    else:
+        oserror_exception = ""
+
+    # Verify the string is CSS and log warning if it is not
+    common_css_chars = "{};,"
+    if not any(c in var for c in common_css_chars):
+        # This appears to be a filename and not a CSS string
+        log.warning(
+            "Could not load file '%s' for custom styles%s", var, oserror_exception
+        )
+        return ""
 
     return "<style>" + var + "</style>"