Test and impl for resource path parsing methods in generated clients (#391)

Given a fully qualified resource path, it is sometimes desirable to
parse out the component segments. This change adds generated methods
to do this parsing to gapic client classes, accompanying generated
unit tests, logic in the wrapper schema to support this feature, and
generator unit tests for the schema logic.

Author: software-dov

packages/gapic-generator/gapic/ads-templates/%namespace/%name/%version/%sub/services/%service/client.py.j2

@@ -120,6 +120,12 @@ class {{ service.client_name }}(metaclass={{ service.client_name }}Meta):
         """Return a fully-qualified {{ message.resource_type|snake_case }} string."""
         return "{{ message.resource_path }}".format({% for arg in message.resource_path_args %}{{ arg }}={{ arg }}, {% endfor %})
 
+
+    @staticmethod
+    def parse_{{ message.resource_type|snake_case }}_path(path: str) -> Dict[str,str]:
+        """Parse a {{ message.resource_type|snake_case }} path into its component segments."""
+        m = re.match(r"{{ message.path_regex_str }}", path)
+        return m.groupdict() if m else {}
     {% endfor %}
 
     def __init__(self, *,

packages/gapic-generator/gapic/ads-templates/tests/unit/%name_%version/%sub/test_%service.py.j2

@@ -693,7 +693,7 @@ def test_{{ service.name|snake_case }}_grpc_lro_client():
 {% endif -%}
 
 {% for message in service.resource_messages -%}
-{% with molluscs = cycler("squid", "clam", "whelk", "octopus", "oyster", "nudibranch", "cuttlefish", "mussel", "winkle") -%}
+{% with molluscs = cycler("squid", "clam", "whelk", "octopus", "oyster", "nudibranch", "cuttlefish", "mussel", "winkle", "nautilus", "scallop", "abalone") -%}
 def test_{{ message.resource_type|snake_case }}_path():
   {% for arg in message.resource_path_args -%}
   {{ arg }} = "{{ molluscs.next() }}"
@@ -702,6 +702,19 @@ def test_{{ message.resource_type|snake_case }}_path():
   actual = {{ service.client_name }}.{{ message.resource_type|snake_case }}_path({{message.resource_path_args|join(", ") }})
   assert expected == actual
 
+
+def test_parse_{{ message.resource_type|snake_case }}_path():
+    expected = {
+    {% for arg in message.resource_path_args -%}
+        "{{ arg }}": "{{ molluscs.next() }}",
+    {% endfor %}
+    }
+    path = {{ service.client_name }}.{{ message.resource_type|snake_case }}_path(**expected)
+
+    # Check that the path construction is reversible.
+    actual = {{ service.client_name }}.parse_{{ message.resource_type|snake_case }}_path(path)
+    assert expected == actual
+
 {% endwith -%}
 {% endfor -%}
 

packages/gapic-generator/gapic/schema/wrappers.py

@@ -209,6 +209,10 @@ def with_context(self, *, collisions: FrozenSet[str]) -> 'Field':
 @dataclasses.dataclass(frozen=True)
 class MessageType:
     """Description of a message (defined with the ``message`` keyword)."""
+    # Class attributes
+    PATH_ARG_RE = re.compile(r'\{([a-zA-Z0-9_-]+)\}')
+
+    # Instance attributes
     message_pb: descriptor_pb2.DescriptorProto
     fields: Mapping[str, Field]
     nested_enums: Mapping[str, 'EnumType']
@@ -278,8 +282,32 @@ def resource_type(self) -> Optional[str]:
 
     @property
     def resource_path_args(self) -> Sequence[str]:
-        path_arg_re = re.compile(r'\{([a-zA-Z0-9_-]+)\}')
-        return path_arg_re.findall(self.resource_path or '')
+        return self.PATH_ARG_RE.findall(self.resource_path or '')
+
+    @utils.cached_property
+    def path_regex_str(self) -> str:
+        # The indirection here is a little confusing:
+        # we're using the resource path template as the base of a regex,
+        # with each resource ID segment being captured by a regex.
+        # E.g., the path schema
+        # kingdoms/{kingdom}/phyla/{phylum}
+        # becomes the regex
+        # ^kingdoms/(?P<kingdom>.+?)/phyla/(?P<phylum>.+?)$
+        parsing_regex_str = (
+            "^" +
+            self.PATH_ARG_RE.sub(
+                # We can't just use (?P<name>[^/]+) because segments may be
+                # separated by delimiters other than '/'.
+                # Multiple delimiter characters within one schema are allowed,
+                # e.g.
+                # as/{a}-{b}/cs/{c}%{d}_{e}
+                # This is discouraged but permitted by AIP4231
+                lambda m: "(?P<{name}>.+?)".format(name=m.groups()[0]),
+                self.resource_path or ''
+            ) +
+            "$"
+        )
+        return parsing_regex_str
 
     def get_field(self, *field_path: str,
                   collisions: FrozenSet[str] = frozenset()) -> Field:

packages/gapic-generator/gapic/templates/%namespace/%name_%version/%sub/services/%service/client.py.j2

@@ -120,6 +120,12 @@ class {{ service.client_name }}(metaclass={{ service.client_name }}Meta):
         """Return a fully-qualified {{ message.resource_type|snake_case }} string."""
         return "{{ message.resource_path }}".format({% for arg in message.resource_path_args %}{{ arg }}={{ arg }}, {% endfor %})
 
+
+    @staticmethod
+    def parse_{{ message.resource_type|snake_case }}_path(path: str) -> Dict[str,str]:
+        """Parse a {{ message.resource_type|snake_case }} path into its component segments."""
+        m = re.match(r"{{ message.path_regex_str }}", path)
+        return m.groupdict() if m else {}
     {% endfor %}
 
     def __init__(self, *,

packages/gapic-generator/gapic/templates/tests/unit/%name_%version/%sub/test_%service.py.j2

@@ -692,14 +692,27 @@ def test_{{ service.name|snake_case }}_grpc_lro_client():
 {% endif -%}
 
 {% for message in service.resource_messages -%}
-{% with molluscs = cycler("squid", "clam", "whelk", "octopus", "oyster", "nudibranch", "cuttlefish", "mussel", "winkle") -%}
+{% with molluscs = cycler("squid", "clam", "whelk", "octopus", "oyster", "nudibranch", "cuttlefish", "mussel", "winkle", "nautilus", "scallop", "abalone") -%}
 def test_{{ message.resource_type|snake_case }}_path():
-  {% for arg in message.resource_path_args -%}
-  {{ arg }} = "{{ molluscs.next() }}"
-  {% endfor %}
-  expected = "{{ message.resource_path }}".format({% for arg in message.resource_path_args %}{{ arg }}={{ arg }}, {% endfor %})
-  actual = {{ service.client_name }}.{{ message.resource_type|snake_case }}_path({{message.resource_path_args|join(", ") }})
-  assert expected == actual
+    {% for arg in message.resource_path_args -%}
+    {{ arg }} = "{{ molluscs.next() }}"
+    {% endfor %}
+    expected = "{{ message.resource_path }}".format({% for arg in message.resource_path_args %}{{ arg }}={{ arg }}, {% endfor %})
+    actual = {{ service.client_name }}.{{ message.resource_type|snake_case }}_path({{message.resource_path_args|join(", ") }})
+    assert expected == actual
+
+
+def test_parse_{{ message.resource_type|snake_case }}_path():
+    expected = {
+    {% for arg in message.resource_path_args -%}
+        "{{ arg }}": "{{ molluscs.next() }}",
+    {% endfor %}
+    }
+    path = {{ service.client_name }}.{{ message.resource_type|snake_case }}_path(**expected)
+
+    # Check that the path construction is reversible.
+    actual = {{ service.client_name }}.parse_{{ message.resource_type|snake_case }}_path(path)
+    assert expected == actual
 
 {% endwith -%}
 {% endfor -%}

packages/gapic-generator/tests/unit/schema/wrappers/test_message.py

@@ -13,6 +13,7 @@
 # limitations under the License.
 
 import collections
+import re
 from typing import Sequence, Tuple
 
 import pytest
@@ -181,6 +182,46 @@ def test_resource_path():
     assert message.resource_type == "Class"
 
 
+def test_parse_resource_path():
+    options = descriptor_pb2.MessageOptions()
+    resource = options.Extensions[resource_pb2.resource]
+    resource.pattern.append(
+        "kingdoms/{kingdom}/phyla/{phylum}/classes/{klass}"
+    )
+    resource.type = "taxonomy.biology.com/Klass"
+    message = make_message('Klass', options=options)
+
+    # Plausible resource ID path
+    path = "kingdoms/animalia/phyla/mollusca/classes/cephalopoda"
+    expected = {
+        'kingdom': 'animalia',
+        'phylum': 'mollusca',
+        'klass': 'cephalopoda',
+    }
+    actual = re.match(message.path_regex_str, path).groupdict()
+
+    assert expected == actual
+
+    options2 = descriptor_pb2.MessageOptions()
+    resource2 = options2.Extensions[resource_pb2.resource]
+    resource2.pattern.append(
+        "kingdoms-{kingdom}_{phylum}#classes%{klass}"
+    )
+    resource2.type = "taxonomy.biology.com/Klass"
+    message2 = make_message('Klass', options=options2)
+
+    # Plausible resource ID path from a non-standard schema
+    path2 = "kingdoms-Animalia/_Mollusca~#classes%Cephalopoda"
+    expected2 = {
+        'kingdom': 'Animalia/',
+        'phylum': 'Mollusca~',
+        'klass': 'Cephalopoda',
+    }
+    actual2 = re.match(message2.path_regex_str, path2).groupdict()
+
+    assert expected2 == actual2
+
+
 def test_field_map():
     # Create an Entry message.
     entry_msg = make_message(