Revert "Add automatic platform detection from inbound crosstool_top and cpu (#2859)" (#3468)

This reverts commit 026db6df5ad760e9002f627bdb4f6b695c04d76a.

Bazel is migrating to platforms and toolchains resolution, but this
logic frequently reset platforms back based on the value of the
legacy `--cpu` and `--crosstool_top` flags. Instead, users of rules that
still rely on these flags should use the `platform_mappings` file.

4 files changed, 0 insertions, 88 deletions

diff --git a/go/platform/BUILD.bazel b/go/platform/BUILD.bazel
index 24311562..5f31f37d 100644
--- a/go/platform/BUILD.bazel
+++ b/go/platform/BUILD.bazel
@@ -36,8 +36,3 @@ bzl_library(
     name = "apple",
     srcs = ["apple.bzl"],
 )
-
-bzl_library(
-    name = "crosstool",
-    srcs = ["crosstool.bzl"],
-)
diff --git a/go/platform/crosstool.bzl b/go/platform/crosstool.bzl
deleted file mode 100644
index 02ec33bf..00000000
--- a/go/platform/crosstool.bzl
+++ /dev/null
@@ -1,60 +0,0 @@
-# Copyright 2020 The Bazel Authors. All rights reserved.
-#
-# Licensed under the Apache License, Version 2.0 (the "License");
-# you may not use this file except in compliance with the License.
-# You may obtain a copy of the License at
-#
-#    http://www.apache.org/licenses/LICENSE-2.0
-#
-# Unless required by applicable law or agreed to in writing, software
-# distributed under the License is distributed on an "AS IS" BASIS,
-# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-# See the License for the specific language governing permissions and
-# limitations under the License.
-
-def _match_apple(_crosstool_top, cpu):
-    """_match_apple will try to detect wether the inbound crosstool/cpu is
-    targeting the Apple ecosystem. Apple crosstool CPUs are prefixed, so
-    matching is easy."""
-    platform = {
-        "darwin": "darwin_amd64",
-        "darwin_x86_64": "darwin_amd64",
-        "darwin_arm64": "darwin_arm64",
-        "ios_arm64": "ios_arm64",
-        "ios_armv7": "ios_arm",
-        "ios_i386": "ios_386",
-        "ios_x86_64": "ios_amd64",
-    }.get(cpu)
-    if platform:
-        return "{}_cgo".format(platform)
-    return None
-
-def _match_android(crosstool_top, cpu):
-    """_match_android will try to detect wether the inbound crosstool is the
-    Android NDK toolchain. It can either be `//external:android/crosstool` or be
-    part of the `@androidndk` workspace. After that, translate Android CPUs to
-    Go CPUs."""
-    if str(crosstool_top) == "//external:android/crosstool" or \
-       crosstool_top.workspace_name == "androidndk":
-        platform_cpu = {
-            "arm64-v8a": "arm64",
-            "armeabi-v7a": "arm",
-            "x86": "386",
-            "x86_64": "amd64",
-        }.get(cpu)
-        if platform_cpu:
-            return "android_{}_cgo".format(platform_cpu)
-    return None
-
-def platform_from_crosstool(crosstool_top, cpu):
-    """platform_from_crosstool runs matchers against the crosstool_top/cpu pair
-    to automatically infer the target platform."""
-    matchers = [
-        _match_apple,
-        _match_android,
-    ]
-    for matcher in matchers:
-        platform = matcher(crosstool_top, cpu)
-        if platform:
-            return "@io_bazel_rules_go//go/toolchain:{}".format(platform)
-    return None
diff --git a/go/private/rules/BUILD.bazel b/go/private/rules/BUILD.bazel
index 2de381d5..50d2c39b 100644
--- a/go/private/rules/BUILD.bazel
+++ b/go/private/rules/BUILD.bazel
@@ -144,7 +144,6 @@ bzl_library(
         "//proto:__pkg__",
     ],
     deps = [
-        "//go/platform:crosstool",
         "//go/private:mode",
         "//go/private:platforms",
         "//go/private:providers",
diff --git a/go/private/rules/transition.bzl b/go/private/rules/transition.bzl
index 2883b982..8ee26ae7 100644
--- a/go/private/rules/transition.bzl
+++ b/go/private/rules/transition.bzl
@@ -32,13 +32,6 @@ load(
     "GoLibrary",
     "GoSource",
 )
-load(
-    "//go/platform:crosstool.bzl",
-    "platform_from_crosstool",
-)
-
-_DEFAULT_PLATFORMS_VALUE = [Label("@local_config_platform//:host")]
-_PLATFORMS_LABEL = "//command_line_option:platforms"
 
 # A list of rules_go settings that are possibly set by go_transition.
 # Keep their package name in sync with the implementation of
@@ -101,8 +94,6 @@ def _go_transition_impl(settings, attr):
 
     goos = getattr(attr, "goos", "auto")
     goarch = getattr(attr, "goarch", "auto")
-    crosstool_top = settings.pop("//command_line_option:crosstool_top")
-    cpu = settings.pop("//command_line_option:cpu")
     _check_ternary("pure", pure)
     if goos != "auto" or goarch != "auto":
         if goos == "auto":
@@ -115,17 +106,6 @@ def _go_transition_impl(settings, attr):
             fail('pure is "off" but cgo is not supported on {} {}'.format(goos, goarch))
         platform = "@io_bazel_rules_go//go/toolchain:{}_{}{}".format(goos, goarch, "_cgo" if cgo else "")
         settings["//command_line_option:platforms"] = platform
-    else:
-        # If the current target platform differs from the default value (the
-        # host platform), then we don't want to override it with a value
-        # inferred from the legacy --cpu and --crosstool_top flags. Otherwise
-        # it would become impossible to "platformize" a Go build without having
-        # a matching platform mappings file.
-        if settings[_PLATFORMS_LABEL] == _DEFAULT_PLATFORMS_VALUE:
-            # Detect the platform the inbound crosstool/cpu.
-            platform = platform_from_crosstool(crosstool_top, cpu)
-            if platform:
-                settings[_PLATFORMS_LABEL] = platform
 
     tags = getattr(attr, "gotags", [])
     if tags:
@@ -181,8 +161,6 @@ request_nogo_transition = transition(
 go_transition = transition(
     implementation = _go_transition_impl,
     inputs = [
-        "//command_line_option:cpu",
-        "//command_line_option:crosstool_top",
         "//command_line_option:platforms",
     ] + TRANSITIONED_GO_SETTING_KEYS,
     outputs = [