base_url configuration setting, closes #394

* base_url configuration setting
* base_url works for static assets as well

tests/test_html.py

@@ -1157,3 +1157,46 @@ def test_metadata_sort_desc(app_client):
     table = Soup(response.body, "html.parser").find("table")
     rows = [[str(td) for td in tr.select("td")] for tr in table.select("tbody tr")]
     assert list(reversed(expected)) == rows
+
+
+@pytest.mark.parametrize("base_url", ["/prefix/", "https://example.com/"])
+@pytest.mark.parametrize(
+    "path",
+    [
+        "/",
+        "/fixtures",
+        "/fixtures/compound_three_primary_keys",
+        "/fixtures/compound_three_primary_keys/a,a,a",
+        "/fixtures/paginated_view",
+    ],
+)
+def test_base_url_config(base_url, path):
+    for client in make_app_client(config={"base_url": base_url}):
+        response = client.get(base_url + path.lstrip("/"))
+        soup = Soup(response.body, "html.parser")
+        for el in soup.findAll(["a", "link", "script"]):
+            if "href" in el.attrs:
+                href = el["href"]
+            elif "src" in el.attrs:
+                href = el["src"]
+            else:
+                continue  # Could be a <script>...</script>
+            if (
+                not href.startswith("#")
+                and href
+                not in {
+                    "https://github.com/simonw/datasette",
+                    "https://github.com/simonw/datasette/blob/master/LICENSE",
+                    "https://github.com/simonw/datasette/blob/master/tests/fixtures.py",
+                }
+                and not href.startswith("https://plugin-example.com/")
+            ):
+                # If this has been made absolute it may start http://localhost/
+                if href.startswith("http://localhost/"):
+                    href = href[len("http://localost/") :]
+                assert href.startswith(base_url), {
+                    "base_url": base_url,
+                    "path": path,
+                    "href_or_src": href,
+                    "element_parent": str(el.parent),
+                }