add method to from resource path to request path

incorporealcms/pages.py

@@ -2,6 +2,7 @@
 import datetime
 import logging
 import os
+import re
 
 from flask import Blueprint, Markup, abort
 from flask import current_app as app
@@ -110,6 +111,15 @@ def request_path_to_instance_resource_path(path):
     return absolute_resource.replace(f'{app.instance_path}{os.path.sep}', '')
 
 
+def instance_resource_path_to_request_path(path):
+    """Reverse a (presumed to exist) disk path to the canonical path that would show up in a Flask route.
+
+    This does not include the leading /, so aside from the root index case, this should be
+    bidirectional.
+    """
+    return re.sub(r'^pages/', '', re.sub(r'.md$', '', re.sub(r'index.md$', '', path)))
+
+
 def resolve_page_file(path):
     """Manipulate the request path to find appropriate page file.
 

tests/test_pages.py

@@ -2,8 +2,8 @@
 import pytest
 from werkzeug.http import dump_cookie
 
-from incorporealcms.pages import (generate_parent_navs, render, request_path_to_instance_resource_path,
-                                  resolve_page_file)
+from incorporealcms.pages import (generate_parent_navs, instance_resource_path_to_request_path, render,
+                                  request_path_to_instance_resource_path, resolve_page_file)
 
 
 def test_resolve_page_file_dir_to_index():
@@ -146,3 +146,39 @@ def test_request_path_to_instance_resource_path_absolute_file_errors(app):
     with app.test_request_context():
         with pytest.raises(PermissionError):
             assert request_path_to_instance_resource_path('/etc/hosts')
+
+
+def test_instance_resource_path_to_request_path_on_index(app):
+    """Test index.md -> /."""
+    with app.test_request_context():
+        assert instance_resource_path_to_request_path('index.md') == ''
+
+
+def test_instance_resource_path_to_request_path_on_page(app):
+    """Test no-title.md -> no-title."""
+    with app.test_request_context():
+        assert instance_resource_path_to_request_path('no-title.md') == 'no-title'
+
+
+def test_instance_resource_path_to_request_path_on_subdir(app):
+    """Test subdir/index.md -> subdir/."""
+    with app.test_request_context():
+        assert instance_resource_path_to_request_path('subdir/index.md') == 'subdir/'
+
+
+def test_instance_resource_path_to_request_path_on_subdir_and_page(app):
+    """Test subdir/page.md -> subdir/page."""
+    with app.test_request_context():
+        assert instance_resource_path_to_request_path('subdir/page.md') == 'subdir/page'
+
+
+def test_request_resource_request_root(app):
+    """Test that a request can resolve to a resource and back to a request."""
+    with app.test_request_context():
+        instance_resource_path_to_request_path(request_path_to_instance_resource_path('index')) == ''
+
+
+def test_request_resource_request_page(app):
+    """Test that a request can resolve to a resource and back to a request."""
+    with app.test_request_context():
+        instance_resource_path_to_request_path(request_path_to_instance_resource_path('no-title')) == 'no-title'