Fix facet selection for explicit exact filters

`colname__exact=value` is now treated the same as `colname=value` when determining which facets are selected.

Closes #1695

datasette/facets.py

@@ -264,10 +264,15 @@ class ColumnFacet(Facet):
                     column_qs = column
                     if column.startswith("_"):
                         column_qs = f"{column}__exact"
-                    selected = (column_qs, str(row["value"])) in qs_pairs
+                    selected_args = {
+                        key: str(row["value"])
+                        for key in (column_qs, f"{column}__exact")
+                        if (key, str(row["value"])) in qs_pairs
+                    }
+                    selected = bool(selected_args)
                     if selected:
                         toggle_path = path_with_removed_args(
-                            self.request, {column_qs: str(row["value"])}
+                            self.request, selected_args
                         )
                     else:
                         toggle_path = path_with_added_args(

docs/changelog.rst

@@ -26,6 +26,7 @@ Datasette plugins can now use **background tasks** to run code independent of th
 Bug fixes
 ~~~~~~~~~
 
+- Column facets now show the remove-filter link for filters using ``column__exact=value``, as well as ``column=value``. (:issue:`1695`)
 - The :ref:`alter-table API <TableAlterView>` now rolls back schema changes when a :ref:`write_wrapper <plugin_hook_write_wrapper>` raises after the write. (:issue:`2924`, :pr:`2925`)
 - The :ref:`extra_template_vars() <plugin_hook_extra_template_vars>` plugin hook can now return a function or awaitable that resolves to ``None`` when no extra variables are needed. (:issue:`2005`)
 - :ref:`request.headers <internals_request>` now supports case-insensitive header lookups, so ``request.headers.get("Content-Type")`` works as well as ``request.headers.get("content-type")``. (:issue:`1861`)

tests/test_facets.py

@@ -1,4 +1,5 @@
 import json
+from urllib.parse import parse_qsl, urlsplit
 
 import pytest
 
@@ -151,6 +152,63 @@ async def test_column_facet_results(ds_client):
     ] == buckets
 
 
+@pytest.mark.asyncio
+@pytest.mark.parametrize(
+    "column,filters,remaining",
+    [
+        ("COUNTY", "COUNTY=Lee", []),
+        ("COUNTY", "COUNTY__exact=Lee", []),
+        ("COUNTY", "COUNTY=Lee&COUNTY__exact=Lee", []),
+        ("COUNTY", "COUNTY__exact=Lee&COUNTY__exact=Lee", []),
+        (
+            "COUNTY",
+            "COUNTY__exact=Lee&COUNTY__exact=Polk",
+            [("COUNTY__exact", "Polk")],
+        ),
+        ("_county", "_county__exact=Lee", []),
+        ("_county", "_county__exact=Lee&_county=Lee", [("_county", "Lee")]),
+    ],
+)
+async def test_column_facet_selected_exact_filters(
+    ds_client, column, filters, remaining
+):
+    facet = ColumnFacet(
+        ds_client.ds,
+        Request.fake(f"/?_facet={column}&{filters}&other=keep&_sort={column}"),
+        database="fixtures",
+        sql=f"select 'Lee' as {column}",
+    )
+    buckets, timed_out = await facet.facet_results()
+    assert not timed_out
+    result = buckets[0]["results"][0]
+    assert result["selected"] is True
+    assert parse_qsl(urlsplit(result["toggle_url"]).query) == [
+        ("_facet", column),
+        *remaining,
+        ("other", "keep"),
+        ("_sort", column),
+    ]
+
+
+@pytest.mark.asyncio
+async def test_column_facet_underscore_argument_is_not_a_filter(ds_client):
+    facet = ColumnFacet(
+        ds_client.ds,
+        Request.fake("/?_facet=_county&_county=Lee"),
+        database="fixtures",
+        sql="select 'Lee' as _county",
+    )
+    buckets, timed_out = await facet.facet_results()
+    assert not timed_out
+    result = buckets[0]["results"][0]
+    assert result["selected"] is False
+    assert parse_qsl(urlsplit(result["toggle_url"]).query) == [
+        ("_facet", "_county"),
+        ("_county", "Lee"),
+        ("_county__exact", "Lee"),
+    ]
+
+
 @pytest.mark.asyncio
 async def test_column_facet_results_column_starts_with_underscore(ds_client):
     facet = ColumnFacet(

tests/test_table_html.py

@@ -484,6 +484,31 @@ async def test_facet_display(ds_client):
     ]
 
 
+@pytest.mark.asyncio
+@pytest.mark.parametrize(
+    "filters", ["state=CA", "state__exact=CA", "state=CA&state__exact=CA"]
+)
+async def test_facet_remove_exact_filter(ds_client, filters):
+    response = await ds_client.get(
+        f"/fixtures/facetable?_facet=state&{filters}&on_earth=1"
+    )
+    assert response.status_code == 200
+    soup = Soup(response.text, "html.parser")
+    remove_link = soup.select_one('.facet-info[data-column="state"] li a.cross')
+    assert remove_link is not None
+    url = urllib.parse.urlsplit(remove_link["href"])
+    assert urllib.parse.parse_qsl(url.query) == [
+        ("_facet", "state"),
+        ("on_earth", "1"),
+    ]
+    unfiltered = await ds_client.get(f"{url.path}.json?{url.query}")
+    assert unfiltered.status_code == 200
+    rows = unfiltered.json()["rows"]
+    assert len(rows) == 14
+    assert all(row["on_earth"] == 1 for row in rows)
+    assert {row["state"] for row in rows} == {"CA", "MI"}
+
+
 @pytest.mark.asyncio
 async def test_facets_persist_through_filter_form(ds_client):
     response = await ds_client.get(