Fix double-prefixed export links with base_url

Use the router-stripped route_path when building request-derived export
URLs, so table, row, and query JSON/CSV links do not apply base_url twice.

Keep urls.path() behavior unchanged, and add coverage for both /prefix/
exports and a /data/ base_url with a data database.

Closes #2759

datasette/utils/__init__.py

@@ -837,7 +837,8 @@ def path_with_format(
     *, request=None, path=None, format=None, extra_qs=None, replace_format=None
 ):
     qs = extra_qs or {}
-    path = request.path if request else path
+    if path is None and request:
+        path = request.path
     if replace_format and path.endswith(f".{replace_format}"):
         path = path[: -(1 + len(replace_format))]
     if "." in path:

datasette/views/base.py

@@ -153,7 +153,13 @@ class BaseView:
         if self.has_json_alternate:
             alternate_url_json = self.ds.absolute_url(
                 request,
-                self.ds.urls.path(path_with_format(request=request, format="json")),
+                self.ds.urls.path(
+                    path_with_format(
+                        request=request,
+                        path=request.scope.get("route_path"),
+                        format="json",
+                    )
+                ),
             )
             template_context["alternate_url_json"] = alternate_url_json
             headers.update(
@@ -347,13 +353,21 @@ class DataView(BaseView):
                 if it_can_render:
                     renderers[key] = self.ds.urls.path(
                         path_with_format(
-                            request=request, format=key, extra_qs={**url_labels_extra}
+                            request=request,
+                            path=request.scope.get("route_path"),
+                            format=key,
+                            extra_qs={**url_labels_extra},
                         )
                     )
 
             url_csv_args = {"_size": "max", **url_labels_extra}
             url_csv = self.ds.urls.path(
-                path_with_format(request=request, format="csv", extra_qs=url_csv_args)
+                path_with_format(
+                    request=request,
+                    path=request.scope.get("route_path"),
+                    format="csv",
+                    extra_qs=url_csv_args,
+                )
             )
             url_csv_path = url_csv.split("?")[0]
             context = {

datasette/views/database.py

@@ -157,7 +157,13 @@ class DatabaseView(View):
         assert format_ == "html"
         alternate_url_json = datasette.absolute_url(
             request,
-            datasette.urls.path(path_with_format(request=request, format="json")),
+            datasette.urls.path(
+                path_with_format(
+                    request=request,
+                    path=request.scope.get("route_path"),
+                    format="json",
+                )
+            ),
         )
         templates = (f"database-{to_css_class(database)}.html", "database.html")
         environment = datasette.get_jinja_environment(request)
@@ -744,7 +750,13 @@ class QueryView(View):
             template = environment.select_template(templates)
             alternate_url_json = datasette.absolute_url(
                 request,
-                datasette.urls.path(path_with_format(request=request, format="json")),
+                datasette.urls.path(
+                    path_with_format(
+                        request=request,
+                        path=request.scope.get("route_path"),
+                        format="json",
+                    )
+                ),
             )
             data = {}
             headers.update(
@@ -776,7 +788,11 @@ class QueryView(View):
                 it_can_render = await await_me_maybe(it_can_render)
                 if it_can_render:
                     renderers[key] = datasette.urls.path(
-                        path_with_format(request=request, format=key)
+                        path_with_format(
+                            request=request,
+                            path=request.scope.get("route_path"),
+                            format=key,
+                        )
                     )
 
             allow_execute_sql = await datasette.allowed(
@@ -905,7 +921,10 @@ class QueryView(View):
                         renderers=renderers,
                         url_csv=datasette.urls.path(
                             path_with_format(
-                                request=request, format="csv", extra_qs={"_size": "max"}
+                                request=request,
+                                path=request.scope.get("route_path"),
+                                format="csv",
+                                extra_qs={"_size": "max"},
                             )
                         ),
                         show_hide_hidden=markupsafe.Markup(show_hide_hidden),

datasette/views/table.py

@@ -1072,7 +1072,13 @@ async def table_view_traced(datasette, request):
         template = environment.select_template(templates)
         alternate_url_json = datasette.absolute_url(
             request,
-            datasette.urls.path(path_with_format(request=request, format="json")),
+            datasette.urls.path(
+                path_with_format(
+                    request=request,
+                    path=request.scope.get("route_path"),
+                    format="json",
+                )
+            ),
         )
         headers.update(
             {
@@ -1878,7 +1884,10 @@ async def table_view_data(
             if it_can_render:
                 renderers[key] = datasette.urls.path(
                     path_with_format(
-                        request=request, format=key, extra_qs={**url_labels_extra}
+                        request=request,
+                        path=request.scope.get("route_path"),
+                        format=key,
+                        extra_qs={**url_labels_extra},
                     )
                 )
         return renderers
@@ -2042,7 +2051,12 @@ async def table_view_data(
             url_labels_extra = {"_labels": "on"}
         url_csv_args = {"_size": "max", **url_labels_extra}
         url_csv = datasette.urls.path(
-            path_with_format(request=request, format="csv", extra_qs=url_csv_args)
+            path_with_format(
+                request=request,
+                path=request.scope.get("route_path"),
+                format="csv",
+                extra_qs=url_csv_args,
+            )
         )
         url_csv_path = url_csv.split("?")[0]
         data.update(