Move calls to self.app outside of error handling

On py3, if/when you hit an error, you can get very noisy tracebacks like

  <traceback coming out of split_path()>

  During handling of the above exception, another exception occurred:

  <meaningful traceback>

In general, I like this, but when we've used exception handling for
flow-control, it gets difficult to separate the wheat from the chaff.

Change-Id: I5f3bc6416207cab2c7e3a77ee6689360b55990e7

swift/common/middleware/copy.py

@@ -225,7 +225,10 @@ class ServerSideCopyMiddleware(object):
         req = Request(env)
         try:
             (version, account, container, obj) = req.split_path(4, 4, True)
+            is_obj_req = True
         except ValueError:
+            is_obj_req = False
+        if not is_obj_req:
             # If obj component is not present in req, do not proceed further.
             return self.app(env, start_response)
 

swift/common/middleware/crypto/decrypter.py

@@ -433,7 +433,10 @@ class Decrypter(object):
         req = Request(env)
         try:
             parts = req.split_path(3, 4, True)
+            is_cont_or_obj_req = True
         except ValueError:
+            is_cont_or_obj_req = False
+        if not is_cont_or_obj_req:
             return self.app(env, start_response)
 
         if parts[3] and req.method in ('GET', 'HEAD'):

swift/common/middleware/dlo.py

@@ -420,7 +420,10 @@ class DynamicLargeObject(object):
         req = Request(env)
         try:
             vrs, account, container, obj = req.split_path(4, 4, True)
+            is_obj_req = True
         except ValueError:
+            is_obj_req = False
+        if not is_obj_req:
             return self.app(env, start_response)
 
         if ((req.method == 'GET' or req.method == 'HEAD') and

swift/common/middleware/listing_formats.py

@@ -128,6 +128,10 @@ class ListingFilter(object):
             # account and container only
             version, acct, cont = req.split_path(2, 3)
         except ValueError:
+            is_container_req = False
+        else:
+            is_container_req = True
+        if not is_container_req:
             return self.app(env, start_response)
 
         if not valid_api_version(version) or req.method not in ('GET', 'HEAD'):

swift/common/middleware/s3api/s3api.py

@@ -119,7 +119,11 @@ class ListingEtagMiddleware(object):
             if not valid_api_version(v):
                 raise ValueError
         except ValueError:
-            # not a container request; pass through
+            is_container_req = False
+        else:
+            is_container_req = True
+        if not is_container_req:
+            # pass through
             return self.app(env, start_response)
 
         ctx = WSGIContext(self.app)

swift/common/middleware/slo.py

@@ -1511,7 +1511,10 @@ class StaticLargeObject(object):
         req = Request(env)
         try:
             vrs, account, container, obj = req.split_path(3, 4, True)
+            is_cont_or_obj_req = True
         except ValueError:
+            is_cont_or_obj_req = False
+        if not is_cont_or_obj_req:
             return self.app(env, start_response)
 
         if not obj:

swift/common/middleware/symlink.py

@@ -551,7 +551,10 @@ class SymlinkMiddleware(object):
         req = Request(env)
         try:
             version, acc, cont, obj = req.split_path(3, 4, True)
+            is_cont_or_obj_req = True
         except ValueError:
+            is_cont_or_obj_req = False
+        if not is_cont_or_obj_req:
             return self.app(env, start_response)
 
         try:

swift/common/middleware/versioned_writes.py

@@ -814,7 +814,10 @@ class VersionedWritesMiddleware(object):
         req = Request(env)
         try:
             (api_version, account, container, obj) = req.split_path(3, 4, True)
+            is_cont_or_obj_req = True
         except ValueError:
+            is_cont_or_obj_req = False
+        if not is_cont_or_obj_req:
             return self.app(env, start_response)
 
         # In case allow_versioned_writes is set in the filter configuration,