Fixed bug with metadata config of array/date facets, closes #1552

Thanks @davidbgk for spotting the fix for the bug.

datasette/facets.py

@@ -30,7 +30,7 @@ def load_facet_configs(request, table_metadata):
             assert (
                 len(metadata_config.values()) == 1
             ), "Metadata config dicts should be {type: config}"
-            type, metadata_config = metadata_config.items()[0]
+            type, metadata_config = list(metadata_config.items())[0]
             if isinstance(metadata_config, str):
                 metadata_config = {"simple": metadata_config}
         facet_configs.setdefault(type, []).append(

docs/facets.rst

@@ -16,7 +16,9 @@ To turn on faceting for specific columns on a Datasette table view, add one or m
 
     /dbname/tablename?_facet=state&_facet=city_id
 
-This works for both the HTML interface and the ``.json`` view. When enabled, facets will cause a ``facet_results`` block to be added to the JSON output, looking something like this::
+This works for both the HTML interface and the ``.json`` view. When enabled, facets will cause a ``facet_results`` block to be added to the JSON output, looking something like this:
+
+.. code-block:: json
 
     {
       "state": {
@@ -93,7 +95,9 @@ Facets in metadata.json
 
 You can turn facets on by default for specific tables by adding them to a ``"facets"`` key in a Datasette :ref:`metadata` file.
 
-Here's an example that turns on faceting by default for the ``qLegalStatus`` column in the ``Street_Tree_List`` table in the ``sf-trees`` database::
+Here's an example that turns on faceting by default for the ``qLegalStatus`` column in the ``Street_Tree_List`` table in the ``sf-trees`` database:
+
+.. code-block:: json
 
     {
       "databases": {
@@ -109,6 +113,18 @@ Here's an example that turns on faceting by default for the ``qLegalStatus`` col
 
 Facets defined in this way will always be shown in the interface and returned in the API, regardless of the ``_facet`` arguments passed to the view.
 
+You can specify :ref:`array <facet_by_json_array>` or :ref:`date <facet_by_date>` facets in metadata using JSON objects with a single key of ``array`` or ``date`` and a value specifying the column, like this:
+
+.. code-block:: json
+
+  {
+    "facets": [
+      {"array": "tags"},
+      {"date": "created"}
+    ]
+  }
+
+
 Suggested facets
 ----------------
 

tests/test_facets.py

@@ -3,7 +3,7 @@ from datasette.database import Database
 from datasette.facets import ColumnFacet, ArrayFacet, DateFacet
 from datasette.utils.asgi import Request
 from datasette.utils import detect_json1
-from .fixtures import app_client  # noqa
+from .fixtures import app_client, make_app_client  # noqa
 import json
 import pytest
 
@@ -588,3 +588,26 @@ async def test_facet_size():
     )
     data5 = response5.json()
     assert len(data5["facet_results"]["city"]["results"]) == 20
+
+
+def test_other_types_of_facet_in_metadata():
+    with make_app_client(
+        metadata={
+            "databases": {
+                "fixtures": {
+                    "tables": {
+                        "facetable": {
+                            "facets": ["state", {"array": "tags"}, {"date": "created"}]
+                        }
+                    }
+                }
+            }
+        }
+    ) as client:
+        response = client.get("/fixtures/facetable")
+        for fragment in (
+            "<strong>created (date)\n",
+            "<strong>tags (array)\n",
+            "<strong>state\n",
+        ):
+            assert fragment in response.text