fix: fix resource path args for paths with =** (#1089)

Some resources have `=**` in the segment. . A segment with `=**` is not matched by the current regex:

```py
Python 3.9.5 (default, Jul 27 2021, 22:06:04) 
[GCC 10.2.1 20210110] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import re
>>> pattern = re.compile(r"\{([a-zA-Z0-9_-]+)\}")
>>> pattern.search("projects/{project}/metricDescriptors/{metric_descriptor=**}").groups()
('project',)

```

This pattern shows up in the some real APIs ([monitoring protos](https://github.com/googleapis/googleapis/blob/3b9c98eda3bded7bb01e2f5f5c7d20f4a5d3e121/google/monitoring/v3/metric_service.proto#L39-L46), `google/cloud/iap/v1`, `google/cloud/iap/v1beta1`, `google/cloud/recommendationengine/v1beta1`, `google/devtools/remoteworkers/v1test2`, `google/home/graph/v1`, `google/iam/v1`). `**` is mentioned in passing in [Resource Names](https://cloud.google.com/apis/design/resource_names#q_how_should_i_generate_and_parse_resource_names). I was not able to find an explanation of what wildcards are considered valid in https://google.aip.dev/122 or https://google.aip.dev/client-libraries/4231.



Monitoring Proto Example:
```proto
option (google.api.resource_definition) = {
  type: "monitoring.googleapis.com/MetricDescriptor"
  pattern: "projects/{project}/metricDescriptors/{metric_descriptor=**}"
  pattern: "organizations/{organization}/metricDescriptors/{metric_descriptor=**}"
  pattern: "folders/{folder}/metricDescriptors/{metric_descriptor=**}"
  pattern: "*"
  history: ORIGINALLY_SINGLE_PATTERN
};
```

gapic/samplegen/samplegen.py

@@ -110,7 +110,7 @@ class TransformedRequest:
 
     # Resource patterns look something like
     # kingdom/{kingdom}/phylum/{phylum}/class/{class}
-    RESOURCE_RE = re.compile(r"\{([^}/]+)\}")
+    RESOURCE_RE = wrappers.MessageType.PATH_ARG_RE
 
     @classmethod
     def build(
@@ -198,6 +198,11 @@ def build(
                 raise types.NoSuchResourcePattern(
                     f"Resource {resource_typestr} has no pattern with params: {attr_name_str}"
                 )
+            # This re-writes
+            # patterns like: 'projects/{project}/metricDescriptors/{metric_descriptor=**}'
+            # to 'projects/{project}/metricDescriptors/{metric_descriptor}
+            # so it can be used in sample code as an f-string.
+            pattern = cls.RESOURCE_RE.sub(r"{\g<1>}", pattern)
 
             return cls(base=base, body=attrs, single=None, pattern=pattern,)
 

gapic/schema/wrappers.py

@@ -317,7 +317,8 @@ def __getattr__(self, name):
 class MessageType:
     """Description of a message (defined with the ``message`` keyword)."""
     # Class attributes
-    PATH_ARG_RE = re.compile(r'\{([a-zA-Z0-9_-]+)\}')
+    # https://google.aip.dev/122
+    PATH_ARG_RE = re.compile(r'\{([a-zA-Z0-9_\-]+)(?:=\*\*)?\}')
 
     # Instance attributes
     message_pb: descriptor_pb2.DescriptorProto

tests/snippetgen/goldens/mollusca_generated_mollusca_v1_snippets_list_resources_async.py

@@ -38,8 +38,13 @@ async def sample_list_resources():
     part_id = "part_id_value"
     parent = f"items/{item_id}/parts/{part_id}"
 
+    item_id = "item_id_value"
+    part_id = "part_id_value"
+    resource_with_wildcard = f"items/{item_id}/parts/{part_id}"
+
     request = mollusca_v1.ListResourcesRequest(
         parent=parent,
+        resource_with_wildcard=resource_with_wildcard,
     )
 
     # Make the request

tests/snippetgen/goldens/mollusca_generated_mollusca_v1_snippets_list_resources_sync.py

@@ -38,8 +38,13 @@ def sample_list_resources():
     part_id = "part_id_value"
     parent = f"items/{item_id}/parts/{part_id}"
 
+    item_id = "item_id_value"
+    part_id = "part_id_value"
+    resource_with_wildcard = f"items/{item_id}/parts/{part_id}"
+
     request = mollusca_v1.ListResourcesRequest(
         parent=parent,
+        resource_with_wildcard=resource_with_wildcard,
     )
 
     # Make the request

tests/snippetgen/snippets.proto

@@ -67,9 +67,15 @@ message ListResourcesRequest {
     (google.api.resource_reference) = {
       type: "snippets.example.com/Resource"
     }];
+
+  string resource_with_wildcard = 2 [
+    (google.api.field_behavior) = REQUIRED,
+    (google.api.resource_reference) = {
+      type: "snippets.example.com/ResourceWithWildcardSegment"
+    }];
 
-  int32 page_size = 2;
-  string page_token = 3;
+  int32 page_size = 3;
+  string page_token = 4;
 }
 
 message ListResourcesResponse {
@@ -91,10 +97,17 @@ message Resource {
     pattern: "items/{item_id}/parts/{part_id}"
   };
   string name = 1;
+}
 
-
+message ResourceWithWildcardSegment {
+  option (google.api.resource) = {
+    type: "snippets.example.com/ResourceWithWildcardSegment"
+    pattern: "items/{item_id}/parts/{part_id=**}"
+  };
+  string name = 1;
 }
 
+
 message MessageWithNesting {
   message NestedMessage {
     string required_string = 1 [(google.api.field_behavior) = REQUIRED];

tests/unit/schema/wrappers/test_message.py

@@ -201,6 +201,27 @@ def test_resource_path():
     assert message.resource_type == "Class"
 
 
+def test_resource_path_with_wildcard():
+    options = descriptor_pb2.MessageOptions()
+    resource = options.Extensions[resource_pb2.resource]
+    resource.pattern.append(
+        "kingdoms/{kingdom}/phyla/{phylum}/classes/{klass=**}")
+    resource.pattern.append(
+        "kingdoms/{kingdom}/divisions/{division}/classes/{klass}")
+    resource.type = "taxonomy.biology.com/Class"
+    message = make_message('Squid', options=options)
+
+    assert message.resource_path == "kingdoms/{kingdom}/phyla/{phylum}/classes/{klass=**}"
+    assert message.resource_path_args == ["kingdom", "phylum", "klass"]
+    assert message.resource_type == "Class"
+    assert re.match(message.path_regex_str,
+                    "kingdoms/my-kingdom/phyla/my-phylum/classes/my-klass")
+    assert re.match(message.path_regex_str,
+                    "kingdoms/my-kingdom/phyla/my-phylum/classes/my-klass/additional-segment")
+    assert re.match(message.path_regex_str,
+                    "kingdoms/my-kingdom/phyla/my-phylum/classes/") is None
+
+
 def test_parse_resource_path():
     options = descriptor_pb2.MessageOptions()
     resource = options.Extensions[resource_pb2.resource]