[Test] Break massive ios_test function into factory

Add the ability to override stuff.

Test rules were impossible to extend and difficult reasoning about how
it worked with rules_apple - which led to issues implementing new
features like shard by class.

Test rules simply accept a `test_suite_factory`. On the default one,
which you can override parts if necesary. _The default one could be much
generic - but at some point, I expect people to just make their own
`test_suite_factory` VS adding too many abstractions to it_

Last: normalize all into a single bundle - otherwise it would duplicate
tons of data and be un-useable at scale.

rules/test.bzl

@@ -1,4 +1,4 @@
-load("@build_bazel_rules_apple//apple:ios.bzl", rules_apple_ios_ui_test = "ios_ui_test", rules_apple_ios_ui_test_suite = "ios_ui_test_suite", rules_apple_ios_unit_test = "ios_unit_test", rules_apple_ios_unit_test_suite = "ios_unit_test_suite")
+load("@build_bazel_rules_apple//apple/internal/testing:ios_rules.bzl", _ios_internal_ui_test_bundle = "ios_internal_ui_test_bundle", _ios_internal_unit_test_bundle = "ios_internal_unit_test_bundle", _ios_ui_test = "ios_ui_test", _ios_unit_test = "ios_unit_test",)
 load("@bazel_skylib//lib:types.bzl", "types")
 load("//rules:library.bzl", "apple_library")
 load("//rules:plists.bzl", "process_infoplists")
@@ -25,14 +25,95 @@ _IOS_TEST_KWARGS = [
     "visibility",
 ]
 
-def _ios_test(name, test_rule, test_suite_rule, apple_library, infoplists_by_build_setting = {}, split_name_to_kwargs = {}, internal_test_deps = [], **kwargs):
+_APPLE_BUNDLE_ATTRS = {
+    x: None
+    for x in [
+        "additional_contents",
+        "deps",
+        "bundle_id",
+        "bundle_name",
+        "families",
+        "frameworks",
+        "infoplists",
+        "linkopts",
+        "minimum_os_version",
+        "provisioning_profile",
+        "resources",
+        "test_host",
+    ]
+}
+
+_DEFAULT_APPLE_TEST_RUNNER = "@build_bazel_rules_apple//apple/testing/default_runner:ios_default_runner"
+
+def _make_runner_split(name, runner, **in_split):
+    split = {}
+    split.update(in_split)
+    split["runner"] = runner
+    return split
+
+def _make_named_split(name, split_kwargs, **in_split):
+    split = {}
+    split.update(in_split)
+    split.update(split_kwargs)
+    return split
+
+def _make_test_suite_splits(factory, name, **in_kwargs):
+    """
+    Helper function to split up a test for named splits and runners splits
+  
+    At the end of the day, we need to able to control how many tests / bundles
+    there are for sharding by class, otherwise it would recompile many times.
+
+    Finally - you can set the splits to be whatever you want.
+    """
+    if "runners" in in_kwargs and "runner" in in_kwargs:
+        fail("cannot use runner/s attribute in both split and top level kwargs for %s" % test_name)
+
+    split_name_to_kwargs = in_kwargs.get("split_name_to_kwargs", {})
+    splits = {}
+    if split_name_to_kwargs and len(split_name_to_kwargs) > 0:
+        for suffix, split_kwargs in split_name_to_kwargs.items():
+            test_name = "{}_{}".format(name, suffix)
+            splits[test_name] = factory.make_named_split(name, split_kwargs, **in_kwargs)
+
+    runners = in_kwargs.get("runners", [])
+    if runners and len(runners) > 0:
+        splits_by_runners = {}
+        if len(splits) == 0:
+            splits[name] = in_kwargs
+        for runner in runners:
+            runner_name = runner.rsplit(":", 1)[-1]
+            for in_test_name, in_split in splits:
+                test_name = "{}_{}".format(in_test_name, runner_name)
+                splits_by_runners[test_name] = factory.make_runner_split(name, runner, **in_split)
+        splits = splits_by_runners
+    return splits
+
+def _make_test_suite(factory, name, test_rule, **test_kwargs):
+    splits = factory.make_test_suite_splits(factory, name, test_kwargs)
+    tests = []
+    for split_name, split in splits.items():
+        tests.append(split_name)
+        test_rule(split_name, split)
+    test_suite_visibility = test_kwargs.get("visibility", None)
+    test_suite_tags = test_kwargs.get("tags", [])
+    native.test_suite(name = name, tests = tests, visibility = test_suite_visibility, tags = test_suite_tags)
+
+default_test_suite_factory = struct(
+    make_test_suite = _make_test_suite,
+    make_test_suite_splits = _make_test_suite_splits,
+    make_runner_split = _make_runner_split,
+    make_named_split = _make_named_split
+)
+
+def _ios_test(name,  bundle_rule, test_rule, test_suite_factory, apple_library, infoplists_by_build_setting = {}, split_name_to_kwargs = {}, internal_test_deps = [], **kwargs):
     """
     Builds and packages iOS Unit/UI Tests.
 
     Args:
         name: The name of the unit test.
         test_rule: The underlying rules_apple test rule.
-        test_suite_rule: The underlying rules_apple test suite rule.
+        bundle_rule: The underlying rules_apple test suite rule.
         apple_library: The macro used to package sources into a library.
         infoplists_by_build_setting: A dictionary of infoplists grouped by bazel build setting.
 
@@ -84,61 +165,37 @@ def _ios_test(name, test_rule, test_suite_rule, apple_library, infoplists_by_bui
         xcconfig_by_build_setting = kwargs.get("xcconfig_by_build_setting", {}),
     )
 
-    if split_name_to_kwargs and len(split_name_to_kwargs) > 0:
-        tests = []
-        for suffix, split_kwargs in split_name_to_kwargs.items():
-            test_name = "{}_{}".format(name, suffix)
+    # Set this to a single __internal__ test bundle.
+    test_bundle_name = name + ".__internal__.__test_bundle"
+    bundle_attrs = {k: v for (k, v) in ios_test_kwargs.items() if k in _APPLE_BUNDLE_ATTRS}
+    bundle_rule(
+        name = test_bundle_name,
+        bundle_name = name,
+        test_bundle_output = "{}.zip".format(name),
+        testonly = True,
+        frameworks = frameworks,
+        infoplists = select(infoplists),
+        deps = [dep_name] + internal_test_deps,
+        **bundle_attrs
+    )
 
-            all_kwargs = {}
-            all_kwargs.update(ios_test_kwargs)
-            all_kwargs.update(split_kwargs)
-
-            if runner and ("runner" in all_kwargs or "runners" in all_kwargs):
-                fail("cannot use runner/s attribute in both split and top level kwargs for %s" % test_name)
-
-            if not runner:
-                split_runner = all_kwargs.pop("runner", all_kwargs.pop("runners", None))
-            else:
-                split_runner = runner
-
-            split_rule = test_rule
-            if split_runner:
-                if types.is_list(runner):
-                    all_kwargs["runners"] = split_runner
-                    split_rule = test_suite_rule
-                else:
-                    all_kwargs["runner"] = split_runner
-
-            tests.append(test_name)
-            split_rule(
-                name = test_name,
-                deps = [dep_name] + internal_test_deps,
-                frameworks = frameworks,
-                testonly = testonly,
-                infoplists = select(infoplists),
-                **all_kwargs
-            )
-        test_suite_visibility = ios_test_kwargs.get("visibility", None)
-        test_suite_tags = ios_test_kwargs.get("tags", [])
-        native.test_suite(name = name, tests = tests, visibility = test_suite_visibility, tags = test_suite_tags)
-    else:
-        rule = test_rule
-        if runner:
-            if types.is_list(runner):
-                ios_test_kwargs["runners"] = runner
-                rule = test_suite_rule
-            else:
-                ios_test_kwargs["runner"] = runner
-
-        rule(
-            name = name,
-            deps = [dep_name] + internal_test_deps,
-            frameworks = frameworks,
-            infoplists = select(infoplists),
-            **ios_test_kwargs
+    def _make_test(test_name, **kwargs):
+        runner = kwargs.pop("runner", None) or _DEFAULT_APPLE_TEST_RUNNER
+        test_attrs = {k: v for (k, v) in kwargs.items() if k not in _APPLE_BUNDLE_ATTRS}
+        test_rule(
+            name = test_name,
+            runner = runner,
+            deps = [":{}".format(test_bundle_name)],
+            testonly = testonly,
+            **test_attrs
         )
 
-def ios_unit_test(name, apple_library = apple_library, **kwargs):
+    if "runners" in ios_test_kwargs or "split_name_to_kwargs" in ios_test_kwargs:
+        test_suite_factory.make_test_suite(test_suite_factory, name, _make_test, **ios_test_kwargs)
+    else:
+        _make_test(name, **ios_test_kwargs)
+
+def ios_unit_test(name, apple_library = apple_library, test_suite_factory = default_test_suite_factory, **kwargs):
     """
     Builds and packages iOS Unit Tests.
 
@@ -147,9 +204,9 @@ def ios_unit_test(name, apple_library = apple_library, **kwargs):
         apple_library: The macro used to package sources into a library.
         **kwargs: Arguments passed to the apple_library and ios_unit_test rules as appropriate.
     """
-    _ios_test(name, rules_apple_ios_unit_test, rules_apple_ios_unit_test_suite, apple_library, **kwargs)
+    _ios_test(name, _ios_internal_unit_test_bundle, _ios_unit_test, test_suite_factory, apple_library, **kwargs)
 
-def ios_ui_test(name, apple_library = apple_library, **kwargs):
+def ios_ui_test(name, apple_library = apple_library, test_suite_factory = default_test_suite_factory, **kwargs):
     """
     Builds and packages iOS UI Tests.
 
@@ -160,9 +217,9 @@ def ios_ui_test(name, apple_library = apple_library, **kwargs):
     """
     if not kwargs.get("test_host", None):
         fail("test_host is required for ios_ui_test.")
-    _ios_test(name, rules_apple_ios_ui_test, rules_apple_ios_ui_test_suite, apple_library, **kwargs)
+    _ios_test(name, _ios_internal_ui_test_bundle, _ios_ui_test, test_suite_factory, apple_library, **kwargs)
 
-def ios_unit_snapshot_test(name, apple_library = apple_library, **kwargs):
+def ios_unit_snapshot_test(name, apple_library = apple_library, test_suite_factory = default_test_suite_factory, **kwargs):
     """
     Builds and packages iOS Unit Snapshot Tests.
 
@@ -171,4 +228,4 @@ def ios_unit_snapshot_test(name, apple_library = apple_library, **kwargs):
         apple_library: The macro used to package sources into a library.
         **kwargs: Arguments passed to the apple_library and ios_unit_test rules as appropriate.
     """
-    _ios_test(name, rules_apple_ios_unit_test, rules_apple_ios_unit_test_suite, apple_library, internal_test_deps = ["@bazel_tools//tools/cpp/runfiles"], **kwargs)
+    _ios_test(name, _ios_internal_unit_test_bundle, _ios_unit_test, test_suite_factory, apple_library, internal_test_deps = ["@bazel_tools//tools/cpp/runfiles"], **kwargs)