[Python-checkins] peps: [PEP 451] Changes related to the find_spec() target module.

[eric.snow]

http://hg.python.org/peps/rev/63595acfe51d
changeset:   5246:63595acfe51d
user:        Eric Snow <ericsnowcurrently at gmail.com>
date:        Sat Nov 02 15:08:19 2013 -0600
summary:
  [PEP 451] Changes related to the find_spec() target module.

files:
  pep-0451.txt |  51 ++++++++++++++-------------------------
  1 files changed, 19 insertions(+), 32 deletions(-)


diff --git a/pep-0451.txt b/pep-0451.txt
--- a/pep-0451.txt
+++ b/pep-0451.txt
@@ -278,7 +278,7 @@
 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 @@
             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 @@
 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 @@
 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 @@
 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 @@
 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 @@
 * 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 @@
 .. [#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
 
 Copyright

-- 
Repository URL: http://hg.python.org/peps