From 21db7b387399f8d53c955f1711ab85c787193c11 Mon Sep 17 00:00:00 2001
From: ohmayr <omairn@google.com>
Date: Wed, 22 Apr 2026 21:24:53 +0000
Subject: [PATCH 1/9] feat: add --resource-name-alias flag to resolve namespace
 collisions

---
 packages/gapic-generator/gapic/schema/api.py  |  1 +
 .../gapic-generator/gapic/schema/wrappers.py  | 28 ++++++++++++-
 .../gapic-generator/gapic/utils/options.py    | 39 ++++++++++++++++++-
 3 files changed, 66 insertions(+), 2 deletions(-)

diff --git a/packages/gapic-generator/gapic/schema/api.py b/packages/gapic-generator/gapic/schema/api.py
index bdb8031d147b..d86d4d29ea9a 100644
--- a/packages/gapic-generator/gapic/schema/api.py
+++ b/packages/gapic-generator/gapic/schema/api.py
@@ -1689,6 +1689,7 @@ def _load_message(
                 documentation=self.docs.get(path, self.EMPTY),
             ),
             oneofs=oneofs,
+            resource_name_aliases=self.opts.resource_name_aliases,
         )
         return self.proto_messages[address.proto]
 
diff --git a/packages/gapic-generator/gapic/schema/wrappers.py b/packages/gapic-generator/gapic/schema/wrappers.py
index ce74043798e2..22976abe9c8e 100644
--- a/packages/gapic-generator/gapic/schema/wrappers.py
+++ b/packages/gapic-generator/gapic/schema/wrappers.py
@@ -520,6 +520,7 @@ class MessageType:
         default_factory=metadata.Metadata,
     )
     oneofs: Optional[Mapping[str, "Oneof"]] = None
+    resource_name_aliases: Mapping[str, str] = dataclasses.field(default_factory=dict)
 
     def __getattr__(self, name):
         return getattr(self.message_pb, name)
@@ -688,7 +689,13 @@ def resource_path(self) -> Optional[str]:
     @property
     def resource_type(self) -> Optional[str]:
         resource = self.options.Extensions[resource_pb2.resource]
-        return resource.type[resource.type.find("/") + 1 :] if resource else None
+        if not resource:
+            return None
+            
+        default_type = resource.type[resource.type.find("/") + 1 :]
+        
+        # 2. Safely read from the class's own strictly-typed dictionary!
+        return self.resource_name_aliases.get(resource.type, default_type)
 
     @property
     def resource_type_full_path(self) -> Optional[str]:
@@ -2323,6 +2330,25 @@ def gen_indirect_resources_used(message):
             key=lambda m: m.resource_type_full_path or m.name
         )
 
+        # Fail-fast collision detection
+        seen_types = {}
+        for msg in sorted_messages:
+            res_type = msg.resource_type
+            if not res_type:
+                continue
+                
+            if res_type in seen_types:
+                incumbent = seen_types[res_type]
+                raise ValueError(
+                    f"\n\nFatal: Namespace collision detected for resource type '{res_type}'.\n"
+                    f"Resources '{incumbent.resource_type_full_path}' and '{msg.resource_type_full_path}' "
+                    f"both flatten to the exact same method name.\n"
+                    f"To protect backward compatibility, explicitly alias one of these using "
+                    f"the `--resource-name-alias` CLI parameter.\n"
+                    f"Example: --resource-name-alias={msg.resource_type_full_path}:CustomName\n"
+                )
+            seen_types[res_type] = msg
+
         return tuple(sorted_messages)
 
     @utils.cached_property
diff --git a/packages/gapic-generator/gapic/utils/options.py b/packages/gapic-generator/gapic/utils/options.py
index 30184f12c0a9..0157fce0c266 100644
--- a/packages/gapic-generator/gapic/utils/options.py
+++ b/packages/gapic-generator/gapic/utils/options.py
@@ -51,6 +51,7 @@ class Options:
     rest_numeric_enums: bool = False
     proto_plus_deps: Tuple[str, ...] = dataclasses.field(default=("",))
     gapic_version: str = "0.0.0"
+    resource_name_aliases: Dict[str, str] = dataclasses.field(default_factory=dict)
 
     # Class constants
     PYTHON_GAPIC_PREFIX: str = "python-gapic-"
@@ -72,7 +73,11 @@ class Options:
             # proto plus dependencies delineated by '+'
             # For example, 'google.cloud.api.v1+google.cloud.anotherapi.v2'
             "proto-plus-deps",
-            "gapic-version",  # A version string following https://peps.python.org/pep-0440
+            "gapic-version",  # A version string following https://peps.python.org/pep-0440,
+            # Resolves method name collisions by mapping a fully qualified 
+            # resource path to a custom TitleCase alias.
+            # Format: resource.path/Name:AliasName
+            "resource-name-alias",
         )
     )
 
@@ -188,6 +193,37 @@ def tweak_path(p):
         if len(proto_plus_deps):
             proto_plus_deps = tuple(proto_plus_deps[0].split("+"))
 
+        # Parse the resource name aliases dictionary (Format: "path/to/Resource:AliasName")
+        resource_name_aliases = {}
+        raw_aliases = opts.pop("resource-name-alias", [])
+        
+        # Normalize: protoc can return a string (1 flag) or list (multiple flags)
+        if not isinstance(raw_aliases, list):
+            raw_aliases = [raw_aliases]
+            
+        # Parse explicitly and safely
+        for mapping in raw_aliases:
+            if not mapping or not mapping.strip():
+                continue
+                
+            try:
+                # split(":", 1) ensures we only split on the FIRST colon 
+                res_path, alias_name = mapping.split(":", 1)
+                
+                clean_path = res_path.strip()
+                clean_alias = alias_name.strip()
+                
+                if not clean_path or not clean_alias:
+                    raise ValueError()
+                    
+                resource_name_aliases[clean_path] = clean_alias
+                
+            except ValueError:
+                warnings.warn(
+                    f"Ignored malformed resource-name-alias: '{mapping}'. "
+                    "Expected format is 'resource.path/Name:AliasName'."
+                )
+
         answer = Options(
             name=opts.pop("name", [""]).pop(),
             namespace=tuple(opts.pop("namespace", [])),
@@ -210,6 +246,7 @@ def tweak_path(p):
             rest_numeric_enums=rest_numeric_enums,
             proto_plus_deps=proto_plus_deps,
             gapic_version=opts.pop("gapic-version", ["0.0.0"]).pop(),
+            resource_name_aliases=resource_name_aliases,
         )
 
         # Note: if we ever need to recursively check directories for sample

From 71f71091d844f47bf15316b369d5adc5b4d4eeb3 Mon Sep 17 00:00:00 2001
From: ohmayr <omairn@google.com>
Date: Wed, 22 Apr 2026 22:04:40 +0000
Subject: [PATCH 2/9] add tests

---
 .../tests/unit/generator/test_options.py      | 21 +++++++++++
 .../unit/schema/wrappers/test_message.py      | 22 ++++++++++++
 .../unit/schema/wrappers/test_service.py      | 36 +++++++++++++++++++
 3 files changed, 79 insertions(+)

diff --git a/packages/gapic-generator/tests/unit/generator/test_options.py b/packages/gapic-generator/tests/unit/generator/test_options.py
index 8b17aae911a6..1d2633e5784d 100644
--- a/packages/gapic-generator/tests/unit/generator/test_options.py
+++ b/packages/gapic-generator/tests/unit/generator/test_options.py
@@ -254,3 +254,24 @@ def test_options_proto_plus_deps():
         "google.apps.script.type.slides",
         "google.apps.script.type",
     )
+
+
+def test_options_resource_name_aliases():
+    with mock.patch.object(warnings, "warn") as warn:
+        opts = Options.build(
+            "resource-name-alias=ces.googleapis.com/Tool:CesTool,"
+            "resource-name-alias=workspace.googleapis.com/Tool:WorkspaceTool,"
+            "resource-name-alias=bad_string_without_colon,"
+            "resource-name-alias=:MissingPath"
+        )
+
+        # Verify the dictionary is perfectly formed
+        expected = {
+            "ces.googleapis.com/Tool": "CesTool",
+            "workspace.googleapis.com/Tool": "WorkspaceTool",
+        }
+        assert opts.resource_name_aliases == expected
+        
+        # Verify that warnings were safely emitted for
+        # the two malformed aliases
+        assert warn.call_count == 2
diff --git a/packages/gapic-generator/tests/unit/schema/wrappers/test_message.py b/packages/gapic-generator/tests/unit/schema/wrappers/test_message.py
index a13f62c02b9b..7d2556dcde22 100644
--- a/packages/gapic-generator/tests/unit/schema/wrappers/test_message.py
+++ b/packages/gapic-generator/tests/unit/schema/wrappers/test_message.py
@@ -473,3 +473,25 @@ def test_extended_operation_request_response_fields():
 
     actual = poll_request.extended_operation_response_fields
     assert actual == expected
+
+
+def test_message_type_resource_type_with_alias():
+    # 1. Cleanly mock the options
+    opts = descriptor_pb2.MessageOptions()
+    opts.Extensions[resource_pb2.resource].type = "ces.googleapis.com/Tool"
+    
+    msg_pb = descriptor_pb2.DescriptorProto(name="MyMessage", options=opts)
+    
+    # 2. Explicitly instantiate MessageType here instead
+    # of using `make_message` to inject 'resource_name_aliases' field.
+    message = wrappers.MessageType(
+        message_pb=msg_pb,
+        fields={},
+        nested_enums={},
+        nested_messages={},
+        resource_name_aliases={"ces.googleapis.com/Tool": "CesTool"},
+    )
+    
+    # 3. Verify it intercepted the default Protobuf logic
+    # and returned the alias
+    assert message.resource_type == "CesTool"
diff --git a/packages/gapic-generator/tests/unit/schema/wrappers/test_service.py b/packages/gapic-generator/tests/unit/schema/wrappers/test_service.py
index 04f7ac7308ea..1bb6bacf791b 100644
--- a/packages/gapic-generator/tests/unit/schema/wrappers/test_service.py
+++ b/packages/gapic-generator/tests/unit/schema/wrappers/test_service.py
@@ -14,6 +14,7 @@
 
 import collections
 import itertools
+import pytest
 import typing
 
 from google.api import resource_pb2
@@ -693,3 +694,38 @@ def test_extended_operations_lro_detection():
     # because Service objects can't perform the lookup.
     # Instead we kick that can to the API object and make it do the lookup and verification.
     assert lro.operation_service == "CustomOperations"
+
+
+def test_resource_messages_throws_informative_collision_error():
+    # 1. Create options with explicit colliding resource types AND valid patterns
+    opts_1 = descriptor_pb2.MessageOptions()
+    opts_1.Extensions[resource_pb2.resource].type = "ces.googleapis.com/Tool"
+    opts_1.Extensions[resource_pb2.resource].pattern.append("ces/{ces}/tool")
+    
+    opts_2 = descriptor_pb2.MessageOptions()
+    opts_2.Extensions[resource_pb2.resource].type = "workspace.googleapis.com/Tool"
+    opts_2.Extensions[resource_pb2.resource].pattern.append("workspaces/{workspace}/tool")
+    
+    # 2. Use the test helpers to build the messages
+    msg_1 = make_message("MessageOne", options=opts_1)
+    msg_2 = make_message("MessageTwo", options=opts_2)
+
+    # 3. Build the service with BOTH methods (so the property loops) 
+    # AND visible_resources (so the internal lookups succeed).
+    service = make_service(
+        name="MyService",
+        methods=(
+            make_method("GetToolOne", input_message=msg_1),
+            make_method("GetToolTwo", input_message=msg_2),
+        ),
+        visible_resources={
+            "ces.googleapis.com/Tool": msg_1,
+            "workspace.googleapis.com/Tool": msg_2,
+        }
+    )
+
+    # 4. Assert that asking the service for its resources throws the custom error
+    expected_error_regex = r"(?s)Namespace collision detected.*--resource-name-alias"
+    
+    with pytest.raises(ValueError, match=expected_error_regex):
+        _ = service.resource_messages

From f148bd967fb063b7b24af50393cb5e532d5a39d2 Mon Sep 17 00:00:00 2001
From: ohmayr <omairn@google.com>
Date: Wed, 22 Apr 2026 22:21:34 +0000
Subject: [PATCH 3/9] add coverage

---
 .../gapic-generator/gapic/schema/wrappers.py  |  2 +-
 .../tests/unit/generator/test_options.py      | 36 +++++++++++++++++
 .../unit/schema/wrappers/test_message.py      | 19 +++++++++
 .../unit/schema/wrappers/test_service.py      | 39 +++++++++++++++++++
 4 files changed, 95 insertions(+), 1 deletion(-)

diff --git a/packages/gapic-generator/gapic/schema/wrappers.py b/packages/gapic-generator/gapic/schema/wrappers.py
index 22976abe9c8e..0569b86c4965 100644
--- a/packages/gapic-generator/gapic/schema/wrappers.py
+++ b/packages/gapic-generator/gapic/schema/wrappers.py
@@ -2331,7 +2331,7 @@ def gen_indirect_resources_used(message):
         )
 
         # Fail-fast collision detection
-        seen_types = {}
+        seen_types: Dict[str, "MessageType"] = {}
         for msg in sorted_messages:
             res_type = msg.resource_type
             if not res_type:
diff --git a/packages/gapic-generator/tests/unit/generator/test_options.py b/packages/gapic-generator/tests/unit/generator/test_options.py
index 1d2633e5784d..10e6a447cf3a 100644
--- a/packages/gapic-generator/tests/unit/generator/test_options.py
+++ b/packages/gapic-generator/tests/unit/generator/test_options.py
@@ -275,3 +275,39 @@ def test_options_resource_name_aliases():
         # Verify that warnings were safely emitted for
         # the two malformed aliases
         assert warn.call_count == 2
+
+
+def test_options_resource_name_aliases():
+    with mock.patch.object(warnings, "warn") as warn:
+        opts = Options.build(
+            "resource-name-alias=ces.googleapis.com/Tool:CesTool,"
+            "resource-name-alias=workspace.googleapis.com/Tool:WorkspaceTool,"
+            "resource-name-alias=bad_string_without_colon,"
+            "resource-name-alias=:MissingPath,"
+            "resource-name-alias=MissingAlias:,"  # <-- Covers 'not clean_alias' (Line 207)
+            "resource-name-alias= ,"              # <-- Covers 'not mapping.strip()' (Line 202)
+        )
+
+        # Verify the dictionary is perfectly formed
+        expected = {
+            "ces.googleapis.com/Tool": "CesTool",
+            "workspace.googleapis.com/Tool": "WorkspaceTool",
+        }
+        assert opts.resource_name_aliases == expected
+        
+        # We expect exactly 3 warnings: 
+        # 1. bad_string
+        # 2. :MissingPath 
+        # 3. MissingAlias: 
+        # (The empty ' ' string safely 'continues' without warning, as intended)
+        assert warn.call_count == 3
+
+
+def test_options_resource_name_aliases_single_string():
+    # Because there is only one flag, the parser treats it as a single string 
+    # instead of a list. This forces the `if not isinstance(..., list):` block to execute
+    opts = Options.build("resource-name-alias=single.googleapis.com/Tool:SingleTool")
+    
+    assert opts.resource_name_aliases == {
+        "single.googleapis.com/Tool": "SingleTool"
+    }
diff --git a/packages/gapic-generator/tests/unit/schema/wrappers/test_message.py b/packages/gapic-generator/tests/unit/schema/wrappers/test_message.py
index 7d2556dcde22..0ca724fcf6d2 100644
--- a/packages/gapic-generator/tests/unit/schema/wrappers/test_message.py
+++ b/packages/gapic-generator/tests/unit/schema/wrappers/test_message.py
@@ -495,3 +495,22 @@ def test_message_type_resource_type_with_alias():
     # 3. Verify it intercepted the default Protobuf logic
     # and returned the alias
     assert message.resource_type == "CesTool"
+
+
+def test_message_type_resource_type_without_alias():
+    # 1. Cleanly mock the options
+    opts = descriptor_pb2.MessageOptions()
+    opts.Extensions[resource_pb2.resource].type = "ces.googleapis.com/Tool"
+    msg_pb = descriptor_pb2.DescriptorProto(name="MyMessage", options=opts)
+    
+    # 2. Instantiate WITHOUT any aliases matching this resource
+    message = wrappers.MessageType(
+        message_pb=msg_pb,
+        fields={},
+        nested_enums={},
+        nested_messages={},
+        resource_name_aliases={"some.other/Resource": "OtherAlias"},
+    )
+    
+    # 3. Verify it falls back to the default type ("Tool")
+    assert message.resource_type == "Tool"
diff --git a/packages/gapic-generator/tests/unit/schema/wrappers/test_service.py b/packages/gapic-generator/tests/unit/schema/wrappers/test_service.py
index 1bb6bacf791b..c687f72fce67 100644
--- a/packages/gapic-generator/tests/unit/schema/wrappers/test_service.py
+++ b/packages/gapic-generator/tests/unit/schema/wrappers/test_service.py
@@ -729,3 +729,42 @@ def test_resource_messages_throws_informative_collision_error():
     
     with pytest.raises(ValueError, match=expected_error_regex):
         _ = service.resource_messages
+
+
+def test_resource_messages_collision_resolved_by_alias():
+    # 1. Colliding types, but valid patterns
+    opts_1 = descriptor_pb2.MessageOptions()
+    opts_1.Extensions[resource_pb2.resource].type = "ces.googleapis.com/Tool"
+    opts_1.Extensions[resource_pb2.resource].pattern.append("ces/{ces}/tool")
+    
+    opts_2 = descriptor_pb2.MessageOptions()
+    opts_2.Extensions[resource_pb2.resource].type = "workspace.googleapis.com/Tool"
+    opts_2.Extensions[resource_pb2.resource].pattern.append("workspaces/{workspace}/tool")
+    
+    # 2. Build the messages WITH the alias injected into one of them!
+    msg_1 = wrappers.MessageType(
+        message_pb=descriptor_pb2.DescriptorProto(name="MessageOne", options=opts_1), 
+        fields={}, nested_enums={}, nested_messages={},
+        resource_name_aliases={"ces.googleapis.com/Tool": "CesTool"} # Resolved!
+    )
+    msg_2 = wrappers.MessageType(
+        message_pb=descriptor_pb2.DescriptorProto(name="MessageTwo", options=opts_2), 
+        fields={}, nested_enums={}, nested_messages={}
+    )
+
+    # 3. Build the service
+    service = make_service(
+        name="MyService",
+        methods=(
+            make_method("GetToolOne", input_message=msg_1),
+            make_method("GetToolTwo", input_message=msg_2),
+        ),
+        visible_resources={
+            "ces.googleapis.com/Tool": msg_1,
+            "workspace.googleapis.com/Tool": msg_2,
+        }
+    )
+
+    # 4. Assert that calling the property succeeds and returns BOTH resources safely
+    resources = service.resource_messages
+    assert len(resources) == 2

From 9e82c9a8c80f8961f14c3826a5a401981300491a Mon Sep 17 00:00:00 2001
From: ohmayr <omairn@google.com>
Date: Wed, 22 Apr 2026 22:26:27 +0000
Subject: [PATCH 4/9] cleanup

---
 packages/gapic-generator/tests/unit/generator/test_options.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/packages/gapic-generator/tests/unit/generator/test_options.py b/packages/gapic-generator/tests/unit/generator/test_options.py
index 10e6a447cf3a..766454b6af76 100644
--- a/packages/gapic-generator/tests/unit/generator/test_options.py
+++ b/packages/gapic-generator/tests/unit/generator/test_options.py
@@ -284,8 +284,8 @@ def test_options_resource_name_aliases():
             "resource-name-alias=workspace.googleapis.com/Tool:WorkspaceTool,"
             "resource-name-alias=bad_string_without_colon,"
             "resource-name-alias=:MissingPath,"
-            "resource-name-alias=MissingAlias:,"  # <-- Covers 'not clean_alias' (Line 207)
-            "resource-name-alias= ,"              # <-- Covers 'not mapping.strip()' (Line 202)
+            "resource-name-alias=MissingAlias:,"
+            "resource-name-alias= ,"
         )
 
         # Verify the dictionary is perfectly formed

From fe9184802b127ef1f992ca80857949659d11c551 Mon Sep 17 00:00:00 2001
From: ohmayr <omairn@google.com>
Date: Wed, 22 Apr 2026 22:31:48 +0000
Subject: [PATCH 5/9] fix tests

---
 .../tests/unit/schema/wrappers/test_service.py              | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/packages/gapic-generator/tests/unit/schema/wrappers/test_service.py b/packages/gapic-generator/tests/unit/schema/wrappers/test_service.py
index c687f72fce67..902c5b6b4d40 100644
--- a/packages/gapic-generator/tests/unit/schema/wrappers/test_service.py
+++ b/packages/gapic-generator/tests/unit/schema/wrappers/test_service.py
@@ -22,7 +22,7 @@
 from google.protobuf import descriptor_pb2
 
 from gapic.schema import imp
-from gapic.schema.wrappers import CommonResource
+from gapic.schema.wrappers import CommonResource, MessageType
 
 from test_utils.test_utils import (
     get_method,
@@ -742,12 +742,12 @@ def test_resource_messages_collision_resolved_by_alias():
     opts_2.Extensions[resource_pb2.resource].pattern.append("workspaces/{workspace}/tool")
     
     # 2. Build the messages WITH the alias injected into one of them!
-    msg_1 = wrappers.MessageType(
+    msg_1 = MessageType(
         message_pb=descriptor_pb2.DescriptorProto(name="MessageOne", options=opts_1), 
         fields={}, nested_enums={}, nested_messages={},
         resource_name_aliases={"ces.googleapis.com/Tool": "CesTool"} # Resolved!
     )
-    msg_2 = wrappers.MessageType(
+    msg_2 = MessageType(
         message_pb=descriptor_pb2.DescriptorProto(name="MessageTwo", options=opts_2), 
         fields={}, nested_enums={}, nested_messages={}
     )

From 783cd7c26008cfaea5ffd0296a6c3b1de564567b Mon Sep 17 00:00:00 2001
From: ohmayr <omairn@google.com>
Date: Thu, 23 Apr 2026 20:46:22 +0000
Subject: [PATCH 6/9] fix coverage

---
 .../gapic-generator/gapic/schema/wrappers.py  |  8 +++-
 .../gapic-generator/gapic/utils/options.py    |  4 --
 .../tests/unit/generator/test_options.py      | 31 -------------
 .../unit/schema/wrappers/test_service.py      | 43 ++++++-------------
 4 files changed, 18 insertions(+), 68 deletions(-)

diff --git a/packages/gapic-generator/gapic/schema/wrappers.py b/packages/gapic-generator/gapic/schema/wrappers.py
index 0569b86c4965..5d18d4fe686f 100644
--- a/packages/gapic-generator/gapic/schema/wrappers.py
+++ b/packages/gapic-generator/gapic/schema/wrappers.py
@@ -689,7 +689,7 @@ def resource_path(self) -> Optional[str]:
     @property
     def resource_type(self) -> Optional[str]:
         resource = self.options.Extensions[resource_pb2.resource]
-        if not resource:
+        if not resource.type:
             return None
             
         default_type = resource.type[resource.type.find("/") + 1 :]
@@ -2335,7 +2335,11 @@ def gen_indirect_resources_used(message):
         for msg in sorted_messages:
             res_type = msg.resource_type
             if not res_type:
-                continue
+                # Fail fast if a resource is missing type
+                raise ValueError(
+                    f"\n\nFatal: Message '{msg.name}' defines a resource pattern but is missing a resource type. "
+                    f"This violates AIP-123 (https://google.aip.dev/123). Please define a 'type' in the google.api.resource option."
+                )
                 
             if res_type in seen_types:
                 incumbent = seen_types[res_type]
diff --git a/packages/gapic-generator/gapic/utils/options.py b/packages/gapic-generator/gapic/utils/options.py
index 0157fce0c266..0a4bbd0cfdc9 100644
--- a/packages/gapic-generator/gapic/utils/options.py
+++ b/packages/gapic-generator/gapic/utils/options.py
@@ -196,10 +196,6 @@ def tweak_path(p):
         # Parse the resource name aliases dictionary (Format: "path/to/Resource:AliasName")
         resource_name_aliases = {}
         raw_aliases = opts.pop("resource-name-alias", [])
-        
-        # Normalize: protoc can return a string (1 flag) or list (multiple flags)
-        if not isinstance(raw_aliases, list):
-            raw_aliases = [raw_aliases]
             
         # Parse explicitly and safely
         for mapping in raw_aliases:
diff --git a/packages/gapic-generator/tests/unit/generator/test_options.py b/packages/gapic-generator/tests/unit/generator/test_options.py
index 766454b6af76..a87e2ef89889 100644
--- a/packages/gapic-generator/tests/unit/generator/test_options.py
+++ b/packages/gapic-generator/tests/unit/generator/test_options.py
@@ -256,27 +256,6 @@ def test_options_proto_plus_deps():
     )
 
 
-def test_options_resource_name_aliases():
-    with mock.patch.object(warnings, "warn") as warn:
-        opts = Options.build(
-            "resource-name-alias=ces.googleapis.com/Tool:CesTool,"
-            "resource-name-alias=workspace.googleapis.com/Tool:WorkspaceTool,"
-            "resource-name-alias=bad_string_without_colon,"
-            "resource-name-alias=:MissingPath"
-        )
-
-        # Verify the dictionary is perfectly formed
-        expected = {
-            "ces.googleapis.com/Tool": "CesTool",
-            "workspace.googleapis.com/Tool": "WorkspaceTool",
-        }
-        assert opts.resource_name_aliases == expected
-        
-        # Verify that warnings were safely emitted for
-        # the two malformed aliases
-        assert warn.call_count == 2
-
-
 def test_options_resource_name_aliases():
     with mock.patch.object(warnings, "warn") as warn:
         opts = Options.build(
@@ -301,13 +280,3 @@ def test_options_resource_name_aliases():
         # 3. MissingAlias: 
         # (The empty ' ' string safely 'continues' without warning, as intended)
         assert warn.call_count == 3
-
-
-def test_options_resource_name_aliases_single_string():
-    # Because there is only one flag, the parser treats it as a single string 
-    # instead of a list. This forces the `if not isinstance(..., list):` block to execute
-    opts = Options.build("resource-name-alias=single.googleapis.com/Tool:SingleTool")
-    
-    assert opts.resource_name_aliases == {
-        "single.googleapis.com/Tool": "SingleTool"
-    }
diff --git a/packages/gapic-generator/tests/unit/schema/wrappers/test_service.py b/packages/gapic-generator/tests/unit/schema/wrappers/test_service.py
index 902c5b6b4d40..2a58ab500c7e 100644
--- a/packages/gapic-generator/tests/unit/schema/wrappers/test_service.py
+++ b/packages/gapic-generator/tests/unit/schema/wrappers/test_service.py
@@ -23,6 +23,7 @@
 
 from gapic.schema import imp
 from gapic.schema.wrappers import CommonResource, MessageType
+from gapic.schema import wrappers
 
 from test_utils.test_utils import (
     get_method,
@@ -731,40 +732,20 @@ def test_resource_messages_throws_informative_collision_error():
         _ = service.resource_messages
 
 
-def test_resource_messages_collision_resolved_by_alias():
-    # 1. Colliding types, but valid patterns
-    opts_1 = descriptor_pb2.MessageOptions()
-    opts_1.Extensions[resource_pb2.resource].type = "ces.googleapis.com/Tool"
-    opts_1.Extensions[resource_pb2.resource].pattern.append("ces/{ces}/tool")
+def test_resource_messages_raises_on_malformed_typeless_resource():
+    # 1. Create a malformed resource: it has a pattern, but no type!
+    opts = descriptor_pb2.MessageOptions()
+    opts.Extensions[resource_pb2.resource].pattern.append("workspaces/{workspace}")
     
-    opts_2 = descriptor_pb2.MessageOptions()
-    opts_2.Extensions[resource_pb2.resource].type = "workspace.googleapis.com/Tool"
-    opts_2.Extensions[resource_pb2.resource].pattern.append("workspaces/{workspace}/tool")
+    malformed_msg = make_message("MalformedMessage", options=opts)
     
-    # 2. Build the messages WITH the alias injected into one of them!
-    msg_1 = MessageType(
-        message_pb=descriptor_pb2.DescriptorProto(name="MessageOne", options=opts_1), 
-        fields={}, nested_enums={}, nested_messages={},
-        resource_name_aliases={"ces.googleapis.com/Tool": "CesTool"} # Resolved!
-    )
-    msg_2 = MessageType(
-        message_pb=descriptor_pb2.DescriptorProto(name="MessageTwo", options=opts_2), 
-        fields={}, nested_enums={}, nested_messages={}
-    )
-
-    # 3. Build the service
     service = make_service(
         name="MyService",
         methods=(
-            make_method("GetToolOne", input_message=msg_1),
-            make_method("GetToolTwo", input_message=msg_2),
-        ),
-        visible_resources={
-            "ces.googleapis.com/Tool": msg_1,
-            "workspace.googleapis.com/Tool": msg_2,
-        }
+            make_method("DoThing", input_message=malformed_msg),
+        )
     )
-
-    # 4. Assert that calling the property succeeds and returns BOTH resources safely
-    resources = service.resource_messages
-    assert len(resources) == 2
+    
+    # 2. Trigger the property and expect it to fail fast with the AIP-123 URL
+    with pytest.raises(ValueError, match="https://google.aip.dev/123"):
+        _ = service.resource_messages

From fdfbced14788d64e571c2bef99dc448bb6a68068 Mon Sep 17 00:00:00 2001
From: ohmayr <omairn@google.com>
Date: Thu, 23 Apr 2026 20:54:59 +0000
Subject: [PATCH 7/9] cover empty string coverage

---
 packages/gapic-generator/tests/unit/generator/test_options.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/packages/gapic-generator/tests/unit/generator/test_options.py b/packages/gapic-generator/tests/unit/generator/test_options.py
index a87e2ef89889..691c9e99bdd9 100644
--- a/packages/gapic-generator/tests/unit/generator/test_options.py
+++ b/packages/gapic-generator/tests/unit/generator/test_options.py
@@ -264,7 +264,8 @@ def test_options_resource_name_aliases():
             "resource-name-alias=bad_string_without_colon,"
             "resource-name-alias=:MissingPath,"
             "resource-name-alias=MissingAlias:,"
-            "resource-name-alias= ,"
+            "resource-name-alias= ," # Covers whitespace (" ")
+            "resource-name-alias=" # Covers empty string ("")
         )
 
         # Verify the dictionary is perfectly formed

From aafe845899ae95c8fa3dece9d10b36f8500b50c3 Mon Sep 17 00:00:00 2001
From: ohmayr <omairn@google.com>
Date: Thu, 23 Apr 2026 21:00:20 +0000
Subject: [PATCH 8/9] remove impossible condition

---
 packages/gapic-generator/gapic/utils/options.py               | 4 +++-
 packages/gapic-generator/tests/unit/generator/test_options.py | 1 -
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/packages/gapic-generator/gapic/utils/options.py b/packages/gapic-generator/gapic/utils/options.py
index 0a4bbd0cfdc9..6778471fc534 100644
--- a/packages/gapic-generator/gapic/utils/options.py
+++ b/packages/gapic-generator/gapic/utils/options.py
@@ -199,7 +199,9 @@ def tweak_path(p):
             
         # Parse explicitly and safely
         for mapping in raw_aliases:
-            if not mapping or not mapping.strip():
+            if not mapping:
+                # We only need to check `not mapping` because the top-level 
+                # opt_string parser already stripped trailing whitespaces
                 continue
                 
             try:
diff --git a/packages/gapic-generator/tests/unit/generator/test_options.py b/packages/gapic-generator/tests/unit/generator/test_options.py
index 691c9e99bdd9..df945d68f417 100644
--- a/packages/gapic-generator/tests/unit/generator/test_options.py
+++ b/packages/gapic-generator/tests/unit/generator/test_options.py
@@ -264,7 +264,6 @@ def test_options_resource_name_aliases():
             "resource-name-alias=bad_string_without_colon,"
             "resource-name-alias=:MissingPath,"
             "resource-name-alias=MissingAlias:,"
-            "resource-name-alias= ," # Covers whitespace (" ")
             "resource-name-alias=" # Covers empty string ("")
         )
 

From 2d415d57537a945a0aa34589fef5dfd93ffa1c63 Mon Sep 17 00:00:00 2001
From: ohmayr <omairn@google.com>
Date: Thu, 23 Apr 2026 21:26:21 +0000
Subject: [PATCH 9/9] address PR feedback

---
 packages/gapic-generator/gapic/schema/wrappers.py | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/packages/gapic-generator/gapic/schema/wrappers.py b/packages/gapic-generator/gapic/schema/wrappers.py
index 5d18d4fe686f..5794bfb92b19 100644
--- a/packages/gapic-generator/gapic/schema/wrappers.py
+++ b/packages/gapic-generator/gapic/schema/wrappers.py
@@ -693,8 +693,7 @@ def resource_type(self) -> Optional[str]:
             return None
             
         default_type = resource.type[resource.type.find("/") + 1 :]
-        
-        # 2. Safely read from the class's own strictly-typed dictionary!
+
         return self.resource_name_aliases.get(resource.type, default_type)
 
     @property