Mechanism for creating custom pages using templates

Closes #648

tests/test_custom_pages.py

@@ -0,0 +1,90 @@
+import pytest
+from .fixtures import make_app_client
+
+VIEW_NAME_PLUGIN = """
+from datasette import hookimpl
+
+@hookimpl
+def extra_template_vars(view_name):
+    return {
+        "view_name": view_name,
+    }
+"""
+
+
+@pytest.fixture(scope="session")
+def custom_pages_client(tmp_path_factory):
+    template_dir = tmp_path_factory.mktemp("page-templates")
+    extra_plugins = {"view_name.py": VIEW_NAME_PLUGIN}
+    pages_dir = template_dir / "pages"
+    pages_dir.mkdir()
+    (pages_dir / "about.html").write_text("ABOUT! view_name:{{ view_name }}", "utf-8")
+    (pages_dir / "202.html").write_text("{{ custom_status(202) }}202!", "utf-8")
+    (pages_dir / "headers.html").write_text(
+        '{{ custom_header("x-this-is-foo", "foo") }}FOO'
+        '{{ custom_header("x-this-is-bar", "bar") }}BAR',
+        "utf-8",
+    )
+    (pages_dir / "atom.html").write_text(
+        '{{ custom_header("content-type", "application/xml") }}<?xml ...>', "utf-8",
+    )
+    (pages_dir / "redirect.html").write_text(
+        '{{ custom_redirect("/example") }}', "utf-8"
+    )
+    (pages_dir / "redirect2.html").write_text(
+        '{{ custom_redirect("/example", 301) }}', "utf-8"
+    )
+    nested_dir = pages_dir / "nested"
+    nested_dir.mkdir()
+    (nested_dir / "nest.html").write_text("Nest!", "utf-8")
+    for client in make_app_client(
+        template_dir=str(template_dir), extra_plugins=extra_plugins
+    ):
+        yield client
+
+
+def test_custom_pages_view_name(custom_pages_client):
+    response = custom_pages_client.get("/about")
+    assert 200 == response.status
+    assert "ABOUT! view_name:page" == response.text
+
+
+def test_custom_pages_nested(custom_pages_client):
+    response = custom_pages_client.get("/nested/nest")
+    assert 200 == response.status
+    assert "Nest!" == response.text
+    response = custom_pages_client.get("/nested/nest2")
+    assert 404 == response.status
+
+
+def test_custom_status(custom_pages_client):
+    response = custom_pages_client.get("/202")
+    assert 202 == response.status
+    assert "202!" == response.text
+
+
+def test_custom_headers(custom_pages_client):
+    response = custom_pages_client.get("/headers")
+    assert 200 == response.status
+    assert "foo" == response.headers["x-this-is-foo"]
+    assert "bar" == response.headers["x-this-is-bar"]
+    assert "FOOBAR" == response.text
+
+
+def test_custom_content_type(custom_pages_client):
+    response = custom_pages_client.get("/atom")
+    assert 200 == response.status
+    assert response.headers["content-type"] == "application/xml"
+    assert "<?xml ...>" == response.text
+
+
+def test_redirect(custom_pages_client):
+    response = custom_pages_client.get("/redirect", allow_redirects=False)
+    assert 302 == response.status
+    assert "/example" == response.headers["Location"]
+
+
+def test_redirect2(custom_pages_client):
+    response = custom_pages_client.get("/redirect2", allow_redirects=False)
+    assert 301 == response.status
+    assert "/example" == response.headers["Location"]