pw_unit_test: Fix googletest backend

With this change, you can use the googletest backend with
simple_printing_main.

The most important changes here are,

1. Making //pw_unit_test directly expose the pw_unit_test/framework.h
   header.
2. Adding the dep on googletest_handler_adapter to the googletest
   target. This was a missing dependency before.

But doing (2) requires removing a bunch of target_compatible_with
attributes that produced a circular dependency. When the backend is set
to googletest, pw_unit_test depends on googletest, which depends on
googletest_handler_adapter. But the googletest_handler_adapter used to
have a dependency on pw_unit_test itself, through the config_setting
that depends on pw_unit_test.

I also remove the target_compatible_with on the "framework_test". This
test should be compatible with all backends, and indeed passes for the
googletest backend.

Internal-only consequences: this change makes is a layering check
violation to #include "gtest/gtest.h" from a pw_cc_test that doesn't
directly depend on googletest. This is good: tests that use pw_unit_test
as a framework should #include "pw_unit_test/framework.h" instead,
which provides only that subset of gtest.h symbols that are actually
supported when building an on-device test.

Test: bazel test --//targets:pw_unit_test_backend=//pw_unit_test:googletest //...
Fixed: b/324116813
Change-Id: I1bd77d936adcfcbcf5122fabd6a9b9f158926188
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/190593
Presubmit-Verified: CQ Bot Account <[email protected]>
Reviewed-by: Armando Montanez <[email protected]>
Commit-Queue: Ted Pudlik <[email protected]>

pw_unit_test/BUILD.bazel

@@ -39,16 +39,12 @@ label_flag(
     build_setting_default = "//pw_build:default_module_config",
 )
 
-alias(
-    name = "pw_unit_test",
-    actual = "@pigweed//targets:pw_unit_test_backend",
-)
-
 cc_library(
-    name = "framework",
+    name = "pw_unit_test",
     testonly = True,
     hdrs = ["public/pw_unit_test/framework.h"],
     includes = ["public"],
+    deps = ["@pigweed//targets:pw_unit_test_backend"],
 )
 
 cc_library(
@@ -71,7 +67,6 @@ cc_library(
     deps = [
         ":config",
         ":event_handler",
-        ":framework",
         "//pw_assert",
         "//pw_polyfill",
         "//pw_preprocessor",
@@ -88,7 +83,7 @@ cc_library(
     ],
     includes = ["googletest_public_overrides"],
     deps = [
-        ":framework",
+        ":googletest_handler_adapter",
         "@com_google_googletest//:gtest",
     ],
 )
@@ -100,6 +95,10 @@ config_setting(
     flag_values = {
         "@pigweed//targets:pw_unit_test_backend": "@pigweed//pw_unit_test:light",
     },
+    # Do not depend on this config_setting outside upstream Pigweed. Config
+    # settings based on label flags are unreliable. See
+    # https://github.com/bazelbuild/bazel/issues/21189.
+    visibility = ["//:__subpackages__"],
 )
 
 config_setting(
@@ -108,6 +107,10 @@ config_setting(
     flag_values = {
         "@pigweed//targets:pw_unit_test_backend": "@pigweed//pw_unit_test:googletest",
     },
+    # Do not depend on this config_setting outside upstream Pigweed. Config
+    # settings based on label flags are unreliable. See
+    # https://github.com/bazelbuild/bazel/issues/21189.
+    visibility = ["//:__subpackages__"],
 )
 
 cc_library(
@@ -132,10 +135,6 @@ cc_library(
     srcs = ["googletest_handler_adapter.cc"],
     hdrs = ["public/pw_unit_test/googletest_handler_adapter.h"],
     includes = ["public"],
-    target_compatible_with = select({
-        ":gtest_setting": [],
-        "//conditions:default": ["@platforms//:incompatible"],
-    }),
     deps = [
         ":event_handler",
         "//pw_preprocessor",
@@ -148,10 +147,6 @@ cc_library(
     testonly = True,
     hdrs = ["public/pw_unit_test/googletest_test_matchers.h"],
     includes = ["public"],
-    target_compatible_with = select({
-        ":gtest_setting": [],
-        "//conditions:default": ["@platforms//:incompatible"],
-    }),
     deps = [
         "//pw_result",
         "//pw_status",
@@ -162,10 +157,6 @@ cc_library(
 pw_cc_test(
     name = "googletest_test_matchers_test",
     srcs = ["googletest_test_matchers_test.cc"],
-    target_compatible_with = select({
-        ":gtest_setting": [],
-        "//conditions:default": ["@platforms//:incompatible"],
-    }),
     deps = [
         ":googletest_test_matchers",
     ],
@@ -221,8 +212,15 @@ cc_library(
     ],
 )
 
-cc_library(
+# TODO: b/324116813 - Remove this alias once no downstream project depends on
+# it.
+alias(
     name = "logging_event_handler",
+    actual = "logging",
+)
+
+cc_library(
+    name = "logging",
     testonly = True,
     srcs = [
         "logging_event_handler.cc",
@@ -239,16 +237,6 @@ cc_library(
     ],
 )
 
-# Provides logging to either the light framework or an external GoogleTest.
-cc_library(
-    name = "logging",
-    testonly = True,
-    deps = [":logging_event_handler"] + select({
-        ":gtest_setting": [":googletest_handler_adapter"],
-        "//conditions:default": [],
-    }),
-)
-
 pw_cc_binary(
     name = "logging_main",
     testonly = True,
@@ -353,7 +341,12 @@ cc_library(
     srcs = ["static_library_support.cc"],
     hdrs = ["public/pw_unit_test/static_library_support.h"],
     includes = ["public"],
-    deps = [":light"],  # This library only works with the light backend
+    # This library only works with the light backend
+    target_compatible_with = select({
+        ":light_setting": [],
+        "//conditions:default": ["@platforms//:incompatible"],
+    }),
+    deps = [":pw_unit_test"],
 )
 
 cc_library(
@@ -371,11 +364,8 @@ cc_library(
 pw_cc_test(
     name = "static_library_support_test",
     srcs = ["static_library_support_test.cc"],
-    target_compatible_with = select({
-        "//pw_unit_test:light_setting": [],
-        "//conditions:default": ["@platforms//:incompatible"],
-    }),
     deps = [
+        ":pw_unit_test",
         ":static_library_support",
         ":tests_in_archive",
         "//pw_assert",
@@ -385,10 +375,6 @@ pw_cc_test(
 pw_cc_test(
     name = "framework_test",
     srcs = ["framework_test.cc"],
-    target_compatible_with = select({
-        "//pw_unit_test:light_setting": [],
-        "//conditions:default": ["@platforms//:incompatible"],
-    }),
     deps = [
         ":pw_unit_test",
         "//pw_assert",
@@ -400,7 +386,7 @@ pw_cc_test(
     name = "framework_light_test",
     srcs = ["framework_light_test.cc"],
     target_compatible_with = select({
-        "//pw_unit_test:light_setting": [],
+        ":light_setting": [],
         "//conditions:default": ["@platforms//:incompatible"],
     }),
     deps = [