[PEP 451] Changes related to the find_spec() target module.

pep-0451.txt

@@ -278,7 +278,7 @@ finders.  See the `Factory Functions`_ section below for more detail.
 Other API Additions
 -------------------
 
-* importlib.find_spec(name, path=None, existing=None) will work exactly
+* importlib.find_spec(name, path=None, target=None) will work exactly
   the same as importlib.find_loader() (which it replaces), but return a
   spec instead of a loader.
 
@@ -493,7 +493,7 @@ Here is the corresponding outline for reload()::
             name = module.__spec__.name
         except AttributeError:
             name = module.__name__
-        spec = find_spec(name, existing=module)
+        spec = find_spec(name, target=module)
 
         if sys.modules.get(name) is not module:
             raise ImportError
@@ -521,7 +521,7 @@ see if the module was already in sys.modules.  Now, by the time
 exec_module() is called during load (not reload) the import machinery
 would already have placed the module in sys.modules.  This is part of
 the reason why find_spec() has
-`the "existing" parameter <The "existing" parameter of find_spec()>`_.
+`the "target" parameter <The "target" parameter of find_spec()>`_.
 
 The semantics of reload will remain essentially the same as they exist
 already [#reload-semantics-fix]_.  The impact of this PEP on some kinds
@@ -697,9 +697,9 @@ than returned directly.  As is currently the case without the PEP, if a
 loader would be costly to create, that loader can be designed to defer
 the cost until later.
 
-**MetaPathFinder.find_spec(name, path=None, existing=None)**
+**MetaPathFinder.find_spec(name, path=None, target=None)**
 
-**PathEntryFinder.find_spec(name, existing=None)**
+**PathEntryFinder.find_spec(name, target=None)**
 
 Finders must return ModuleSpec objects when find_spec() is
 called.  This new method replaces find_module() and
@@ -714,8 +714,8 @@ especially considering PathEntryFinder.find_loader() was just
 added in Python 3.3.  However, the extra complexity and a less-than-
 explicit method name aren't worth it.
 
-The "existing" parameter of find_spec()
----------------------------------------
+The "target" parameter of find_spec()
+-------------------------------------
 
 A module object with the same name as the "name" argument (or None, the
 default) should be passed in to "exising".  This argument allows the
@@ -727,26 +727,26 @@ Through find_spec() the finder will always identify the loader it
 will return in the spec.  In the case of reload, at this point the
 finder should also decide whether or not the loader supports loading
 into the module-to-be-reloaded (which was passed in to find_spec() as
-"existing").  This decision may entail consulting with the loader.  If
+"target").  This decision may entail consulting with the loader.  If
 the finder determines that the loader does not support reloading that
-module, it should either find another loader or return None (indicating
-that it could not "find" the module).  This reload decision is important
-since, as noted in `How Reloading Will Work`_, loaders will no longer be
-able to trivially identify a reload situation on their own.
+module, it should either find another loader or raise ImportError
+(completely stopping import of the module).  This reload decision is
+important since, as noted in `How Reloading Will Work`_, loaders will
+no longer be able to trivially identify a reload situation on their own.
 
-Two alternatives were presented to the "existing" parameter:
-Loader.supports_reload() and adding "existing" to Loader.exec_module()
+Two alternatives were presented to the "target" parameter:
+Loader.supports_reload() and adding "target" to Loader.exec_module()
 instead of find_spec().  supports_reload() was the initial approach to
 the reload situation. [#supports_reload]_  However, there was some
 opposition to the loader-specific, reload-centric approach.
 [#supports_reload_considered_harmful]_
 
-As to "existing" on exec_module(), the loader may need other information
-from the existing module (or spec) during reload, more than just "does
+As to "target" on exec_module(), the loader may need other information
+from the target module (or spec) during reload, more than just "does
 this loader support reloading this module", that is no longer available
 with the move away from load_module().  A proposal on the table was to
-add something like "existing" to exec_module().  [#exec_module_existing]_
-However, putting "existing" on find_spec() instead is more in line with
+add something like "target" to exec_module().  [#exec_module_target]_
+However, putting "target" on find_spec() instead is more in line with
 the goals of this PEP.  Furthermore, it obviates the need for
 supports_reload().
 
@@ -835,19 +835,6 @@ Other Changes
 * importlib.reload() will now make use of the per-module import lock.
 
 
-Open Issues
-===========
-
-\* In the `Finders`_ section, the PEP specifies returning None (or using
-a different loader) when the found loader does not support loading into
-an existing module (e.g during reload).  An alternative to returning
-None would be to raise ImportError with a message like "the loader does
-not support reloading the module".  This may actually be a better
-approach since "could not find a loader" and "the found loader won't
-work" are different situations that a single return value (None) may not
-sufficiently represent.
-
-
 Reference Implementation
 ========================
 
@@ -943,7 +930,7 @@ References
 .. [#supports_reload_considered_harmful]
    https://mail.python.org/pipermail/python-dev/2013-October/129971.html
 
-.. [#exec_module_existing]
+.. [#exec_module_target]
    https://mail.python.org/pipermail/python-dev/2013-October/129933.html
 
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