feat: add proper handling of query/path/body parameters for rest transport

gapic/schema/wrappers.py

@@ -769,13 +769,13 @@ def http_opt(self) -> Optional[Dict[str, str]]:
 
     @property
     def path_params(self) -> Sequence[str]:
-        """Return the path parameters found in the http annotation url"""
+        """Return the path parameters found in the http annotation path template"""
         # TODO(yon-mg): fully implement grpc transcoding (currently only handles basic case)
         if self.http_opt is None:
             return []
-        pattern = r'\{\w+\}'
 
-        return [x[1:-1] for x in re.findall(pattern, self.http_opt['url'])]
+        pattern = r'\{(\w+)\}'
+        return re.findall(pattern, self.http_opt['url'])
 
     @property
     def query_params(self) -> Set[str]:

gapic/templates/%namespace/%name_%version/%sub/services/%service/transports/rest.py.j2

@@ -168,13 +168,16 @@ class {{ service.name }}RestTransport({{ service.name }}Transport):
         #}
         # TODO(yon-mg): handle nested fields corerctly rather than using only top level fields
         #               not required for GCE
-        potentialParams = {
+        query_params = {
             {%- for field in method.query_params %}
             '{{ field|camel_case }}': request.{{ field }},
             {%- endfor %}
         }
-        potentialParams = ((k, v) for k, v in potentialParams.items() if v)
-        for i, (param_name, param_value) in enumerate(potentialParams):
+        # TODO(yon-mg): further discussion needed whether 'python truthiness' is appropriate here
+        #               discards default values
+        # TODO(yon-mg): add test for proper url encoded strings
+        query_params = ((k, v) for k, v in query_params.items() if v)
+        for i, (param_name, param_value) in enumerate(query_params):
             q = '?' if i == 0 else '&'
             url += "{q}{name}={value}".format(q=q, name=param_name, value=param_value.replace(' ', '+'))