Accept a provider_name in TargetSubject.provider() and TargetSubject.has_provider()

CHANGELOG.md

@@ -6,7 +6,8 @@
 
 ### Changed
 
-* Nothing yet
+* `TargetSubject.provider()` and `TargetSubject.has_provider()` accept a
+  `provider_name` for better error messaging.
 
 ### Added
 

lib/private/target_subject.bzl

@@ -175,19 +175,20 @@ def _target_subject_failures(self):
         failure_messages = []
     return CollectionSubject.new(failure_messages, meta, container_name = "failure messages")
 
-def _target_subject_has_provider(self, provider):
+def _target_subject_has_provider(self, provider, provider_name = "<Unknown provider>"):
     """Asserts that the target as provider `provider`.
 
     Method: TargetSubject.has_provider
 
     Args:
         self: implicitly added.
         provider: The provider object to check for.
+        provider_name: The display name of the provider
     """
     if self.meta.has_provider(self.target, provider):
         return
     self.meta.add_failure(
-        "expected to have provider: {}".format(_provider_subject_factory(self, provider).name),
+        "expected to have provider: {}".format(_provider_subject_factory(self, provider, provider_name).name),
         "but provider was not found",
     )
 
@@ -221,7 +222,7 @@ def _target_subject_output_group(self, name):
         meta = self.meta.derive("output_group({})".format(name)),
     )
 
-def _target_subject_provider(self, provider_key, factory = None):
+def _target_subject_provider(self, provider_key, factory = None, provider_name = "<Unknown provider>"):
     """Returns a subject for a provider in the target.
 
     Method: TargetSubject.provider
@@ -235,20 +236,22 @@ def _target_subject_provider(self, provider_key, factory = None):
             signature: `def factory(value, /, *, meta)`.
             Additional types of providers can be pre-registered by using the
             `provider_subject_factories` arg of `analysis_test`.
+        provider_name: The display name of the provider. This must be supplied
+            separately because str(provider_key) just returns "<provider>",
+            which isn't helpful. For lack of a better option, this defaults to
+            <Unknown provider>.
 
     Returns:
         A subject wrapper of the provider value.
     """
     if factory:
         provider_subject_factory = struct(
             type = provider_key,
-            # str(provider_key) just returns "<provider>", which isn't helpful.
-            # For lack of a better option, just call it unknown
-            name = "<Unknown provider>",
+            name = provider_name,
             factory = factory,
         )
     else:
-        provider_subject_factory = _provider_subject_factory(self, provider_key)
+        provider_subject_factory = _provider_subject_factory(self, provider_key, provider_name)
 
     if not provider_subject_factory.factory:
         fail("Unsupported provider: {}".format(provider_subject_factory.name))
@@ -392,14 +395,14 @@ def _target_subject_attr(self, name, *, factory = None):
         meta = self.meta.derive("attr({})".format(name)),
     )
 
-def _provider_subject_factory(self, provider):
+def _provider_subject_factory(self, provider, provider_name = "<Unknown provider>"):
     for provider_subject_factory in self.meta.env.provider_subject_factories:
         if provider_subject_factory.type == provider:
             return provider_subject_factory
 
     return struct(
         type = provider,
-        name = "<Unknown provider>",
+        name = provider_name,
         factory = None,
     )
 

tests/truth_tests.bzl

@@ -147,6 +147,62 @@ def _action_subject_test(env, target):
 
 _suite.append(action_subject_test)
 
+def provider_subject_test(name):
+    analysis_test(name = name, impl = _provider_subject_test, target = "truth_tests_helper")
+
+_UnusedInfo = provider("unused testing provider", fields = [])
+
+def _provider_subject_test(env, target):
+    fake_env = _fake_env(env)
+    fake_env.expect.that_target(target).has_provider(_UnusedInfo)
+    _assert_failure(
+        fake_env,
+        ["expected to have provider: <Unknown provider>"],
+        env = env,
+        msg = "check has_provider() failure uses Unknown provider name",
+    )
+
+    fake_env.expect.that_target(target).has_provider(_UnusedInfo, provider_name = "MyInfo")
+    _assert_failure(
+        fake_env,
+        ["expected to have provider: MyInfo"],
+        env = env,
+        msg = "check has_provider() failure uses supplied provider name",
+    )
+
+    def _factory(_unused, meta):
+        return struct(
+            always_fails = lambda: meta.add_failure("Expected error msg", "Actual error msg"),
+        )
+
+    fake_env.expect.that_target(target).provider(_TestHelperInfo, _factory).always_fails()
+    _assert_failure(
+        fake_env,
+        [
+            ".provider(<Unknown provider>)",
+            "Expected error msg",
+            "Actual error msg",
+        ],
+        env = env,
+        msg = "check has_provider() failure uses Unknown provider name",
+    )
+
+    fake_env.expect.that_target(target).provider(_TestHelperInfo, _factory, provider_name = "MyInfo").always_fails()
+    _assert_failure(
+        fake_env,
+        [
+            ".provider(MyInfo)",
+            "Expected error msg",
+            "Actual error msg",
+        ],
+        env = env,
+        msg = "check provider() failure uses supplied provider name",
+    )
+
+    _end(env, fake_env)
+
+_suite.append(provider_subject_test)
+
 def bool_subject_test(name):
     analysis_test(name = name, impl = _bool_subject_test, target = "truth_tests_helper")
 
@@ -1589,6 +1645,8 @@ def _assert_failure(fake_env, expected_strs, *, env, msg = ""):
 
     fake_env.reset()
 
+_TestHelperInfo = provider("empty provider for testing", fields = [])
+
 def _test_helper_impl(ctx):
     action_output = ctx.actions.declare_file("action.txt")
     generated_input = _empty_file(ctx, "input.gen.txt")
@@ -1627,6 +1685,7 @@ def _test_helper_impl(ctx):
         OutputGroupInfo(
             some_group = depset([_empty_file(ctx, "output_group_file.txt")]),
         ),
+        _TestHelperInfo(),
     ]
 
 test_helper = rule(