🎨 Test empty CGI params as None in iemapp

Author: akrherz

CHANGELOG.md

@@ -14,6 +14,7 @@ All notable changes to this library are documented in this file.
   fix a false positive and fix a bug. No data quality impacts (#1167).
 - Refactor `util.get_autoplot_context` into `autoplot.get_autoplot_context`.
 - Require python 3.11+
+- Treat inbound empty CGI parameters as effective `None`.
 - Update TAF storage to include an `issue` and `expire` timestamp, which
   explicitly stores the time domain.  This change modified the storage of
   the observation to not include these timestamp values.

src/pyiem/webutil.py

@@ -517,7 +517,7 @@ def _handle_exp(errormsg, routine=False, code=500):
                     form = {
                         k: v
                         for k, v in _debracket(form).items()
-                        if k in kwargs["schema"].model_fields
+                        if k in kwargs["schema"].model_fields and v != ""
                     }
                     # Retain a reference to the Schema instance as it may have
                     # private / computed attributes that are needed

tests/test_webutil.py

@@ -67,6 +67,25 @@ def application(_environ, start_response):
     assert resp.status_code == 422
 
 
+def test_empty_string():
+    """Test that emptry strings are not passed through..."""
+
+    class MyModel(CGIModel):
+        bogus: Annotated[float | None, Field("Float")] = None
+
+    @iemapp(schema=MyModel)
+    def application(environ, start_response):
+        """Test."""
+        assert environ["bogus"] is None
+        start_response("200 OK", [("Content-type", "text/plain")])
+        return environ.get("unused", "OK")
+
+    c = Client(application)
+    resp = c.get("/?bogus=")
+    assert resp.status_code == 200
+    assert resp.text == "OK"
+
+
 def test_gh1174_self():
     """Test what happens with CGI self= is processed."""