Transition on edges not self

As per bazelbuild/bazel#15157 currently we
can't configure any transition-relevant attributes using select. This is
because we use self-transitions on targets, and when this happens,
configurable attributes aren't passed to the transition, so we make
incorrect transition decisions.

Instead, insert a dummy rule which exists only to transition its
dependencies using an edge transition, which means the appropriate
attributes are resolved before the transition is called.

To achieve this, we symlink the actual built binaries into our
transitioning wrapper rules, and forward any providers needed.

Fixes bazelbuild#3103.

go/private/rules/BUILD.bazel

@@ -43,6 +43,7 @@ bzl_library(
         "//go/private:providers",
         "//go/private:rpath",
         "//go/private/rules:transition",
+        "@bazel_skylib//lib:dicts",
     ],
 )
 
@@ -132,6 +133,7 @@ bzl_library(
         "//go/private:providers",
         "//go/private/rules:binary",
         "//go/private/rules:transition",
+        "@bazel_skylib//lib:dicts",
         "@bazel_skylib//lib:structs",
     ],
 )
@@ -148,6 +150,7 @@ bzl_library(
         "//go/private:mode",
         "//go/private:platforms",
         "//go/private:providers",
+        "//go/private/skylib/lib:dicts",
     ],
 )
 

go/private/rules/binary.bzl

@@ -29,8 +29,11 @@ load(
 )
 load(
     "//go/private/rules:transition.bzl",
-    "go_transition_rule",
     "non_go_transition",
+    "ForwardingPastTransitionProvider",
+    "forward_through_transition_impl",
+    "go_transition",
+    "transition_attrs",
 )
 load(
     "//go/private:mode.bzl",
@@ -44,6 +47,10 @@ load(
     "//go/private:rpath.bzl",
     "rpath",
 )
+load(
+    "@bazel_skylib//lib:dicts.bzl",
+    "dicts",
+)
 
 _EMPTY_DEPSET = depset([])
 
@@ -124,19 +131,14 @@ def _go_binary_impl(ctx):
         executable = executable,
     )
 
-    providers = [
+    providers_to_forward = [
         library,
         source,
         archive,
         OutputGroupInfo(
             cgo_exports = archive.cgo_exports,
             compilation_outputs = [archive.data.file],
         ),
-        DefaultInfo(
-            files = depset([executable]),
-            runfiles = runfiles,
-            executable = executable,
-        ),
     ]
 
     # If the binary's linkmode is c-archive or c-shared, expose CcInfo
@@ -165,11 +167,19 @@ def _go_binary_impl(ctx):
         ccinfo = cc_common.merge_cc_infos(
             cc_infos = [ccinfo] + [d[CcInfo] for d in source.cdeps],
         )
-        providers.append(ccinfo)
+        providers_to_forward.append(ccinfo)
 
-    return providers
+    forwarding_provider = ForwardingPastTransitionProvider(executable = executable, runfiles = runfiles, providers_to_forward = providers_to_forward)
+    return providers_to_forward + [
+        forwarding_provider,
+        DefaultInfo(
+            files = depset([executable]),
+            runfiles = runfiles,
+            executable = executable,
+        ),
+    ]
 
-_go_binary_kwargs = {
+go_binary_kwargs = {
     "implementation": _go_binary_impl,
     "attrs": {
         "srcs": attr.label_list(
@@ -394,9 +404,17 @@ _go_binary_kwargs = {
     """,
 }
 
-go_binary = rule(executable = True, **_go_binary_kwargs)
-go_transition_binary = go_transition_rule(executable = True, **_go_binary_kwargs)
-go_non_executable_transition_binary = go_transition_rule(executable = False, **_go_binary_kwargs)
+go_binary = rule(executable = True, **go_binary_kwargs)
+go_non_executable_transition_binary = rule(executable = False, **go_binary_kwargs)
+
+go_transition_binary = rule(
+    implementation = forward_through_transition_impl,
+    attrs = dicts.add(transition_attrs, {
+        "is_windows": attr.bool(),
+        "transition_dep": attr.label(cfg = go_transition),
+    }),
+    executable = True,
+)
 
 def _go_tool_binary_impl(ctx):
     sdk = ctx.attr.sdk[GoSDK]

go/private/rules/test.bzl

@@ -39,13 +39,20 @@ load(
 )
 load(
     "//go/private/rules:transition.bzl",
-    "go_transition_rule",
     "non_go_transition",
+    "ForwardingPastTransitionProvider",
+    "forward_through_transition_impl",
+    "go_transition",
+    "transition_attrs",
 )
 load(
     "//go/private:mode.bzl",
     "LINKMODE_NORMAL",
 )
+load(
+    "@bazel_skylib//lib:dicts.bzl",
+    "dicts",
+)
 load(
     "@bazel_skylib//lib:structs.bzl",
     "structs",
@@ -54,6 +61,22 @@ load(
 def _testmain_library_to_source(go, attr, source, merge):
     source["deps"] = source["deps"] + [attr.library]
 
+go_transition_test = rule(
+    implementation = forward_through_transition_impl,
+    attrs = dicts.add(transition_attrs, {
+        "transition_dep": attr.label(cfg = go_transition),
+        "is_windows": attr.bool(),
+        # Workaround for bazelbuild/bazel#6293. See comment in lcov_merger.sh.
+        "_lcov_merger": attr.label(
+            executable = True,
+            default = "//go/tools/builders:lcov_merger",
+            cfg = "target",
+        ),
+    }),
+    executable = True,
+    test = True,
+)
+
 def _go_test_impl(ctx):
     """go_test_impl implements go testing.
 
@@ -168,13 +191,8 @@ def _go_test_impl(ctx):
     # source file is present, Bazel will set the COVERAGE_OUTPUT_FILE
     # environment variable during tests and will save that file to the build
     # events + test outputs.
-    return [
+    providers_to_forward = [
         test_archive,
-        DefaultInfo(
-            files = depset([executable]),
-            runfiles = runfiles,
-            executable = executable,
-        ),
         OutputGroupInfo(
             compilation_outputs = [internal_archive.data.file],
         ),
@@ -187,7 +205,22 @@ def _go_test_impl(ctx):
         testing.TestEnvironment(env),
     ]
 
-_go_test_kwargs = {
+    forwarding_provider = ForwardingPastTransitionProvider(
+        executable = executable,
+        runfiles = runfiles,
+        providers_to_forward = providers_to_forward,
+    )
+
+    return providers_to_forward + [
+        forwarding_provider,
+        DefaultInfo(
+            files = depset([executable]),
+            runfiles = runfiles,
+            executable = executable,
+        ),
+    ]
+
+go_test_kwargs = {
     "implementation": _go_test_impl,
     "attrs": {
         "data": attr.label_list(
@@ -448,8 +481,7 @@ _go_test_kwargs = {
     """,
 }
 
-go_test = rule(**_go_test_kwargs)
-go_transition_test = go_transition_rule(**_go_test_kwargs)
+go_test = rule(**go_test_kwargs)
 
 def _recompile_external_deps(go, external_source, internal_archive, library_labels):
     """Recompiles some archives in order to split internal and external tests.