Flip --incompatible_enable_cc_toolchain_resolution

src/main/java/com/google/devtools/build/lib/rules/cpp/CppOptions.java

@@ -911,7 +911,7 @@ public Label getMemProfProfileLabel() {
 
   @Option(
       name = "incompatible_enable_cc_toolchain_resolution",
-      defaultValue = "false",
+      defaultValue = "true",
       documentationCategory = OptionDocumentationCategory.UNDOCUMENTED,
       effectTags = {OptionEffectTag.LOADING_AND_ANALYSIS},
       metadataTags = {OptionMetadataTag.INCOMPATIBLE_CHANGE},

src/test/java/com/google/devtools/build/lib/analysis/AutoExecGroupsTest.java

@@ -1811,7 +1811,7 @@ public void ccCommonLink_cppLTOActionExecutesOnFirstPlatform() throws Exception
         "  srcs = ['custom.cc'],",
         "  deps = ['dep'],",
         ")");
-    useConfiguration("--incompatible_auto_exec_groups", "--features=thin_lto");
+    useConfiguration("--incompatible_auto_exec_groups", "--features=thin_lto", "--noincompatible_enable_cc_toolchain_resolution");
     AnalysisMock.get()
         .ccSupport()
         .setupCcToolchainConfig(
@@ -1991,7 +1991,7 @@ public void ccCommonCompile_moduleActionsExecuteOnFirstPlatform() throws Excepti
         "  srcs = ['custom.cc'],",
         "  hdrs = ['custom.h'],",
         ")");
-    useConfiguration("--incompatible_auto_exec_groups", "--features=header_modules");
+    useConfiguration("--incompatible_auto_exec_groups", "--features=header_modules", "--noincompatible_enable_cc_toolchain_resolution");
     AnalysisMock.get()
         .ccSupport()
         .setupCcToolchainConfig(
@@ -2061,7 +2061,8 @@ public void ccCommonCompile_codeGenModuleActionExecutesOnFirstPlatform() throws
     useConfiguration(
         "--incompatible_auto_exec_groups",
         "--features=header_modules",
-        "--features=header_module_codegen");
+        "--features=header_module_codegen",
+        "--noincompatible_enable_cc_toolchain_resolution");
     AnalysisMock.get()
         .ccSupport()
         .setupCcToolchainConfig(
@@ -2126,7 +2127,7 @@ public void ccCommonCompile_compileHeaderActionExecutesOnFirstPlatform() throws
         "  srcs = ['custom.cc'],",
         "  hdrs = ['custom.h'],",
         ")");
-    useConfiguration("--incompatible_auto_exec_groups", "--features=parse_headers");
+    useConfiguration("--incompatible_auto_exec_groups", "--features=parse_headers", "--noincompatible_enable_cc_toolchain_resolution");
     AnalysisMock.get()
         .ccSupport()
         .setupCcToolchainConfig(

src/test/java/com/google/devtools/build/lib/rules/cpp/CcToolchainSuiteTest.java

@@ -29,7 +29,7 @@ public class CcToolchainSuiteTest extends BuildViewTestCase {
   @Test
   public void testInvalidCpu() throws Exception {
     reporter.removeHandler(failFastHandler);
-    useConfiguration("--cpu=bogus");
+    useConfiguration("--cpu=bogus", "--noincompatible_enable_cc_toolchain_resolution");
     getConfiguredTarget(
         ruleClassProvider.getToolsRepository() + "//tools/cpp:current_cc_toolchain");
     assertContainsEvent("does not contain a toolchain for cpu 'bogus'");

src/test/java/com/google/devtools/build/lib/rules/cpp/StarlarkCcCommonTest.java

@@ -5763,7 +5763,10 @@ private static void createFiles(
         bzlFilePath + "/extension.bzl",
         "load('//myinfo:myinfo.bzl', 'MyInfo')",
         "def _cc_aspect_impl(target, ctx):",
-        "    toolchain = ctx.attr._cc_toolchain[cc_common.CcToolchainInfo]",
+        "    if ctx.attr._cc_toolchain:",
+        "      toolchain = ctx.attr._cc_toolchain[cc_common.CcToolchainInfo]",
+        "    else:",
+        "      toolchain = ctx.toolchains['@bazel_tools//tools/cpp:toolchain_type'].cc",
         "    feature_configuration = cc_common.configure_features(",
         "        ctx = ctx,",
         "        cc_toolchain = toolchain,",
@@ -5795,14 +5798,18 @@ private static void createFiles(
             + " '@bazel_tools//tools/cpp:current_cc_toolchain'),",
         "    },",
         fragments,
+        "    toolchains = ['@bazel_tools//tools/cpp:toolchain_type']",
         ")",
         "def _cc_starlark_library_impl(ctx):",
         "    dep_compilation_contexts = []",
         "    dep_linking_contexts = []",
         "    for dep in ctx.attr._deps:",
         "        dep_compilation_contexts.append(dep[CcInfo].compilation_context)",
         "        dep_linking_contexts.append(dep[CcInfo].linking_context)",
-        "    toolchain = ctx.attr._my_cc_toolchain[cc_common.CcToolchainInfo]",
+        "    if ctx.attr._my_cc_toolchain:",
+        "      toolchain = ctx.attr._my_cc_toolchain[cc_common.CcToolchainInfo]",
+        "    else:",
+        "      toolchain = ctx.toolchains['@bazel_tools//tools/cpp:toolchain_type'].cc",
         "    feature_configuration = cc_common.configure_features(",
         "        ctx = ctx,",
         "        cc_toolchain=toolchain,",
@@ -5866,6 +5873,7 @@ private static void createFiles(
         "          configuration_field(fragment = 'cpp', name = 'cc_toolchain'))",
         "    },",
         fragments,
+        "    toolchains = ['@bazel_tools//tools/cpp:toolchain_type']",
         ")");
     scratch.file(
         "foo/BUILD",
@@ -6369,7 +6377,10 @@ private static void createCcBinRule(
         extensionDirectory + "/extension.bzl",
         "load('//myinfo:myinfo.bzl', 'MyInfo')",
         "def _cc_bin_impl(ctx):",
-        "    toolchain = ctx.attr._cc_toolchain[cc_common.CcToolchainInfo]",
+        "    if ctx.attr._cc_toolchain:",
+        "      toolchain = ctx.attr._cc_toolchain[cc_common.CcToolchainInfo]",
+        "    else:",
+        "      toolchain = ctx.toolchains['@bazel_tools//tools/cpp:toolchain_type'].cc",
         "    feature_configuration = cc_common.configure_features(",
         "      ctx = ctx,",
         "      cc_toolchain = toolchain,",
@@ -6406,6 +6417,7 @@ private static void createCcBinRule(
         "      'additional_outputs': attr.output_list(),",
         "    },",
         fragments,
+        "    toolchains = ['@bazel_tools//tools/cpp:toolchain_type']",
         ")");
   }
 
@@ -8175,14 +8187,19 @@ public void testGrepIncludesIsSetToNullInsideCcToolchain() throws Exception {
     scratch.file(
         "foo/extension.bzl",
         "def _cc_skylark_library_impl(ctx):",
-        "    return [ctx.attr._cc_toolchain[cc_common.CcToolchainInfo]]",
+        "    if ctx.attr._cc_toolchain:",
+        "      toolchain = ctx.attr._cc_toolchain[cc_common.CcToolchainInfo]",
+        "    else:",
+        "      toolchain = ctx.toolchains['@bazel_tools//tools/cpp:toolchain_type'].cc",
+         "    return [toolchain]",
         "cc_skylark_library = rule(",
         "    implementation = _cc_skylark_library_impl,",
         "    attrs = {",
         "      '_cc_toolchain': attr.label(default =",
         "          configuration_field(fragment = 'cpp', name = 'cc_toolchain')),",
         "    },",
         "    fragments = ['cpp'],",
+        "    toolchains = ['@bazel_tools//tools/cpp:toolchain_type']",
         ")");
 
     ConfiguredTarget target = getConfiguredTarget("//foo:skylark_lib");

src/test/java/com/google/devtools/build/lib/starlark/StarlarkDefinedAspectsTest.java

@@ -352,7 +352,7 @@ public void aspectsPropagatingForDefaultAndImplicit() throws Exception {
 
     assertThat(names).containsAtLeast("xxx", "yyy");
     // 3-4 is the C++ toolchain and alias; its name changes between Blaze and Bazel.
-    assertThat(names).hasSize(4);
+    assertThat(names).hasSize(3);
   }
 
   @Test

src/test/java/com/google/devtools/build/lib/view/java/JavaConfigurationTest.java

@@ -48,13 +48,13 @@ public void testJavaLauncherConfiguration() throws Exception {
 
   @Test
   public void testHostCrosstoolTop() throws Exception {
-    BuildConfigurationValue config = createConfiguration();
+    BuildConfigurationValue config = createConfiguration("--noincompatible_enable_cc_toolchain_resolution");
     assertThat(config.getFragment(CppConfiguration.class).getRuleProvidingCcToolchainProvider())
         .isEqualTo(
             Label.parseCanonicalUnchecked(
                 TestConstants.TOOLS_REPOSITORY + "//tools/cpp:toolchain"));
 
-    BuildConfigurationValue execConfig = createExec();
+    BuildConfigurationValue execConfig = createExec("--noincompatible_enable_cc_toolchain_resolution");
     assertThat(execConfig.getFragment(CppConfiguration.class).getRuleProvidingCcToolchainProvider())
         .isEqualTo(
             Label.parseCanonicalUnchecked(