From a6ff123de5464806441f6a6f95145c9a83b7f20b Mon Sep 17 00:00:00 2001
From: Simon Willison <swillison@gmail.com>
Date: Sun, 12 Dec 2021 12:01:51 -0800
Subject: [PATCH] keep_blank_values=True when parsing query_string, closes
 #1551

Refs #1518
---
 datasette/utils/asgi.py         |  2 +-
 datasette/views/table.py        | 11 +++--------
 tests/test_internals_request.py | 16 ++++++++++++++++
 3 files changed, 20 insertions(+), 9 deletions(-)

diff --git a/datasette/utils/asgi.py b/datasette/utils/asgi.py
index ad137fa9..cd3ec654 100644
--- a/datasette/utils/asgi.py
+++ b/datasette/utils/asgi.py
@@ -97,7 +97,7 @@ class Request:
 
     @property
     def args(self):
-        return MultiParams(parse_qs(qs=self.query_string))
+        return MultiParams(parse_qs(qs=self.query_string, keep_blank_values=True))
 
     @property
     def actor(self):
diff --git a/datasette/views/table.py b/datasette/views/table.py
index f58b78f5..59010723 100644
--- a/datasette/views/table.py
+++ b/datasette/views/table.py
@@ -393,21 +393,16 @@ class TableView(RowTableShared):
             nocount = True
             nofacet = True
 
-        # Ensure we don't drop anything with an empty value e.g. ?name__exact=
-        args = MultiParams(
-            urllib.parse.parse_qs(request.query_string, keep_blank_values=True)
-        )
-
         # Special args start with _ and do not contain a __
         # That's so if there is a column that starts with _
         # it can still be queried using ?_col__exact=blah
         special_args = {}
         other_args = []
-        for key in args:
+        for key in request.args:
             if key.startswith("_") and "__" not in key:
-                special_args[key] = args[key]
+                special_args[key] = request.args[key]
             else:
-                for v in args.getlist(key):
+                for v in request.args.getlist(key):
                     other_args.append((key, v))
 
         # Handle ?_filter_column and redirect, if present
diff --git a/tests/test_internals_request.py b/tests/test_internals_request.py
index cd956f3f..01c93eec 100644
--- a/tests/test_internals_request.py
+++ b/tests/test_internals_request.py
@@ -121,3 +121,19 @@ def test_request_properties(path, query_string, expected_full_path):
     assert request.path == path
     assert request.query_string == query_string
     assert request.full_path == expected_full_path
+
+
+def test_request_blank_values():
+    query_string = "a=b&foo=bar&foo=bar2&baz="
+    path_with_query_string = "/?" + query_string
+    scope = {
+        "http_version": "1.1",
+        "method": "POST",
+        "path": "/",
+        "raw_path": path_with_query_string.encode("latin-1"),
+        "query_string": query_string.encode("latin-1"),
+        "scheme": "http",
+        "type": "http",
+    }
+    request = Request(scope, None)
+    assert request.args._data == {"a": ["b"], "foo": ["bar", "bar2"], "baz": [""]}