Error on startup if invalid setting types

datasette/app.py

@@ -394,10 +394,37 @@ class Datasette:
         config = config or {}
         config_settings = config.get("settings") or {}
 
-        # validate "settings" keys in datasette.json
+        # Validate settings from config file
-        for key in config_settings:
+        for key, value in config_settings.items():
             if key not in DEFAULT_SETTINGS:
-                raise StartupError("Invalid setting '{}' in datasette.json".format(key))
+                raise StartupError(f"Invalid setting '{key}' in config file")
+            # Validate type matches expected type from DEFAULT_SETTINGS
+            if value is not None:  # Allow None/null values
+                expected_type = type(DEFAULT_SETTINGS[key])
+                actual_type = type(value)
+                if actual_type != expected_type:
+                    raise StartupError(
+                        f"Setting '{key}' in config file has incorrect type. "
+                        f"Expected {expected_type.__name__}, got {actual_type.__name__}. "
+                        f"Value: {value!r}. "
+                        f"Hint: In YAML/JSON config files, remove quotes from boolean and integer values."
+                    )
+
+        # Validate settings from constructor parameter
+        if settings:
+            for key, value in settings.items():
+                if key not in DEFAULT_SETTINGS:
+                    raise StartupError(f"Invalid setting '{key}' in settings parameter")
+                if value is not None:
+                    expected_type = type(DEFAULT_SETTINGS[key])
+                    actual_type = type(value)
+                    if actual_type != expected_type:
+                        raise StartupError(
+                            f"Setting '{key}' in settings parameter has incorrect type. "
+                            f"Expected {expected_type.__name__}, got {actual_type.__name__}. "
+                            f"Value: {value!r}"
+                        )
+
         self.config = config
         # CLI settings should overwrite datasette.json settings
         self._settings = dict(DEFAULT_SETTINGS, **(config_settings), **(settings or {}))

datasette/default_permissions.py

@@ -179,9 +179,7 @@ def permission_allowed_default_allow_sql(datasette, actor, action, resource):
     This runs before other permission checks to ensure the setting is respected.
     """
     if action == "execute-sql":
-        default_allow_sql_setting = datasette.setting("default_allow_sql")
+        if not datasette.setting("default_allow_sql"):
-        # Handle both boolean False and string "false" (from CLI)
-        if default_allow_sql_setting in (False, "false"):
             return False
     return None
 
@@ -227,9 +225,7 @@ async def permission_resources_sql(datasette, actor, action):
     rules.extend(config_rules)
 
     # Check default_allow_sql setting for execute-sql action
-    default_allow_sql_setting = datasette.setting("default_allow_sql")
+    if action == "execute-sql" and not datasette.setting("default_allow_sql"):
-    # Handle both boolean False and string "false" (from CLI)
-    if action == "execute-sql" and default_allow_sql_setting in (False, "false"):
         # Return a deny rule for all databases
         sql = "SELECT NULL AS parent, NULL AS child, 0 AS allow, 'default_allow_sql is false' AS reason"
         rules.append(

tests/test_cli.py

@@ -307,7 +307,57 @@ def test_setting_type_validation():
     runner = CliRunner()
     result = runner.invoke(cli, ["--setting", "default_page_size", "dog"])
     assert result.exit_code == 2
-    assert '"settings.default_page_size" should be an integer' in result.stderr
+    assert '"settings.default_page_size" should be an integer' in result.output
+
+
+def test_setting_boolean_validation_invalid():
+    """Test that invalid boolean values are rejected"""
+    runner = CliRunner()
+    result = runner.invoke(
+        cli, ["--setting", "default_allow_sql", "invalid", "--get", "/-/settings.json"]
+    )
+    assert result.exit_code == 2
+    assert (
+        '"settings.default_allow_sql" should be on/off/true/false/1/0' in result.output
+    )
+
+
+@pytest.mark.parametrize("value", ("off", "false", "0"))
+def test_setting_boolean_validation_false_values(value):
+    """Test that 'off', 'false', '0' work for boolean settings"""
+    runner = CliRunner()
+    result = runner.invoke(
+        cli,
+        [
+            "--setting",
+            "default_allow_sql",
+            value,
+            "--get",
+            "/_memory/-/query.json?sql=select+1",
+        ],
+    )
+    # Should be forbidden (setting is false)
+    assert result.exit_code == 1, result.output
+    assert "Forbidden" in result.output
+
+
+@pytest.mark.parametrize("value", ("on", "true", "1"))
+def test_setting_boolean_validation_true_values(value):
+    """Test that 'on', 'true', '1' work for boolean settings"""
+    runner = CliRunner()
+    result = runner.invoke(
+        cli,
+        [
+            "--setting",
+            "default_allow_sql",
+            value,
+            "--get",
+            "/_memory/-/query.json?sql=select+1&_shape=objects",
+        ],
+    )
+    # Should succeed (setting is true)
+    assert result.exit_code == 0, result.output
+    assert json.loads(result.output)["rows"][0] == {"1": 1}
 
 
 @pytest.mark.parametrize("default_allow_sql", (True, False))

tests/test_config_dir.py

@@ -88,7 +88,7 @@ def test_invalid_settings(config_dir):
     try:
         with pytest.raises(StartupError) as ex:
             ds = Datasette([], config_dir=config_dir)
-        assert ex.value.args[0] == "Invalid setting 'invalid' in datasette.json"
+        assert ex.value.args[0] == "Invalid setting 'invalid' in config file"
     finally:
         (config_dir / "datasette.json").write_text(previous, "utf-8")
 

tests/test_utils_permissions.py

@@ -37,7 +37,9 @@ def plugin_allow_all_for_user(user: str) -> Callable[[str], PermissionSQL]:
     return provider
 
 
-def plugin_deny_specific_table(user: str, parent: str, child: str) -> Callable[[str], PermissionSQL]:
+def plugin_deny_specific_table(
+    user: str, parent: str, child: str
+) -> Callable[[str], PermissionSQL]:
     def provider(action: str) -> PermissionSQL:
         return PermissionSQL(
             "deny_specific_table",
@@ -66,7 +68,9 @@ def plugin_org_policy_deny_parent(parent: str) -> Callable[[str], PermissionSQL]
     return provider
 
 
-def plugin_allow_parent_for_user(user: str, parent: str) -> Callable[[str], PermissionSQL]:
+def plugin_allow_parent_for_user(
+    user: str, parent: str
+) -> Callable[[str], PermissionSQL]:
     def provider(action: str) -> PermissionSQL:
         return PermissionSQL(
             "allow_parent",
@@ -81,7 +85,9 @@ def plugin_allow_parent_for_user(user: str, parent: str) -> Callable[[str], Perm
     return provider
 
 
-def plugin_child_allow_for_user(user: str, parent: str, child: str) -> Callable[[str], PermissionSQL]:
+def plugin_child_allow_for_user(
+    user: str, parent: str, child: str
+) -> Callable[[str], PermissionSQL]:
     def provider(action: str) -> PermissionSQL:
         return PermissionSQL(
             "allow_child",
@@ -137,7 +143,9 @@ def plugin_conflicting_same_child_rules(
     return [allow_provider, deny_provider]
 
 
-def plugin_allow_all_for_action(user: str, allowed_action: str) -> Callable[[str], PermissionSQL]:
+def plugin_allow_all_for_action(
+    user: str, allowed_action: str
+) -> Callable[[str], PermissionSQL]:
     def provider(action: str) -> PermissionSQL:
         if action != allowed_action:
             return PermissionSQL(