JSON faceting now suggested even if column has blank strings, closes #1246

datasette/facets.py

@@ -279,6 +279,7 @@ class ArrayFacet(Facet):
             suggested_facet_sql = """
                 select distinct json_type({column})
                 from ({sql})
+                where {column} is not null and {column} != ''
             """.format(
                 column=escape_sqlite(column), sql=self.sql
             )
@@ -298,9 +299,13 @@ class ArrayFacet(Facet):
                         v[0]
                         for v in await self.ds.execute(
                             self.database,
-                            "select {column} from ({sql}) where {column} is not null and json_array_length({column}) > 0 limit 100".format(
+                            (
-                                column=escape_sqlite(column), sql=self.sql
+                                "select {column} from ({sql}) "
-                            ),
+                                "where {column} is not null "
+                                "and {column} != '' "
+                                "and json_array_length({column}) > 0 "
+                                "limit 100"
+                            ).format(column=escape_sqlite(column), sql=self.sql),
                             self.params,
                             truncate=False,
                             custom_time_limit=self.ds.setting(

tests/test_facets.py

@@ -1,3 +1,5 @@
+from datasette.app import Datasette
+from datasette.database import Database
 from datasette.facets import ColumnFacet, ArrayFacet, DateFacet
 from datasette.utils.asgi import Request
 from datasette.utils import detect_json1
@@ -325,3 +327,23 @@ async def test_date_facet_results(app_client):
             "truncated": False,
         }
     } == buckets
+
+
+@pytest.mark.asyncio
+async def test_json_array_with_blanks_and_nulls():
+    ds = Datasette([], memory=True)
+    db = ds.add_database(Database(ds, memory_name="test_json_array"))
+    await db.execute_write("create table foo(json_column text)", block=True)
+    for value in ('["a", "b", "c"]', '["a", "b"]', "", None):
+        await db.execute_write(
+            "insert into foo (json_column) values (?)", [value], block=True
+        )
+    response = await ds.client.get("/test_json_array/foo.json")
+    data = response.json()
+    assert data["suggested_facets"] == [
+        {
+            "name": "json_column",
+            "type": "array",
+            "toggle_url": "http://localhost/test_json_array/foo.json?_facet_array=json_column",
+        }
+    ]