Deprecate string style base for env.doc2path()

CHANGES

@@ -16,6 +16,7 @@ Deprecated
 ----------
 
 * The ``suffix`` argument of ``env.doc2path()`` is deprecated.
+* The string style ``base`` argument of ``env.doc2path()`` is deprecated.
 * ``sphinx.ext.doctest.doctest_encode()``
 * ``sphinx.testing.util.remove_unicode_literal()``
 

doc/extdev/index.rst

@@ -121,6 +121,11 @@ The following is a list of deprecated interface.
      - 4.0
      - N/A
 
+   * - string style ``base`` argument of ``BuildEnvironment.doc2path()``
+     - 2.0
+     - 4.0
+     - ``os.path.join()``
+
    * - ``sphinx.ext.doctest.doctest_encode()``
      - 2.0
      - 4.0

sphinx/environment/__init__.py

@@ -342,6 +342,9 @@ class BuildEnvironment(object):
         if suffix:
             warnings.warn('The suffix argument for doc2path() is deprecated.',
                           RemovedInSphinx40Warning)
+        if base not in (True, None):
+            warnings.warn('The string style base argument for doc2path() is deprecated.',
+                          RemovedInSphinx40Warning)
 
         docname = docname.replace(SEP, path.sep)
         if suffix is None: