Force local_config_platform to redirect to the bundled platforms repo

Similar to 77469e0, we redirect the redirects/aliases generated by `local_config_plaform` to the bundled platforms repo (`@internal_platforms_do_not_use`) if Bzlmod is not enabled. Same for the `@bazel_tools//tools:host_platform` alias.

Fixes #21877.

Closes #22021.

PiperOrigin-RevId: 625613724
Change-Id: I17940e5d4fbd8a7690d9199f80b80ceb62b53d1a

src/main/java/com/google/devtools/build/lib/bazel/repository/BUILD

@@ -36,15 +36,16 @@ java_library(
  "//src/main/java/com/google/devtools/build/lib/concurrent",
  "//src/main/java/com/google/devtools/build/lib/events",
  "//src/main/java/com/google/devtools/build/lib/packages",
+ "//src/main/java/com/google/devtools/build/lib/packages/semantics",
  "//src/main/java/com/google/devtools/build/lib/repository:repository_events",
  "//src/main/java/com/google/devtools/build/lib/rules:repository/repo_recorded_input",
  "//src/main/java/com/google/devtools/build/lib/rules:repository/repository_directory_value",
  "//src/main/java/com/google/devtools/build/lib/rules:repository/repository_function",
  "//src/main/java/com/google/devtools/build/lib/rules:repository/resolved_file_value",
  "//src/main/java/com/google/devtools/build/lib/rules:repository/workspace_base_rule",
  "//src/main/java/com/google/devtools/build/lib/rules:repository/workspace_configured_target_factory",
+ "//src/main/java/com/google/devtools/build/lib/skyframe:precomputed_value",
  "//src/main/java/com/google/devtools/build/lib/util",
- "//src/main/java/com/google/devtools/build/lib/util:os",
  "//src/main/java/com/google/devtools/build/lib/vfs",
  "//src/main/java/com/google/devtools/build/lib/vfs:pathfragment",
  "//src/main/java/com/google/devtools/build/skyframe",

src/main/java/com/google/devtools/build/lib/bazel/repository/LocalConfigPlatformFunction.java

@@ -14,25 +14,25 @@
 
 package com.google.devtools.build.lib.bazel.repository;
 
-import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableMap;
 import com.google.devtools.build.lib.analysis.BlazeDirectories;
 import com.google.devtools.build.lib.analysis.RuleDefinition;
 import com.google.devtools.build.lib.bazel.ResolvedEvent;
 import com.google.devtools.build.lib.packages.Rule;
+import com.google.devtools.build.lib.packages.semantics.BuildLanguageOptions;
 import com.google.devtools.build.lib.rules.repository.RepoRecordedInput;
 import com.google.devtools.build.lib.rules.repository.RepositoryDirectoryValue;
 import com.google.devtools.build.lib.rules.repository.RepositoryFunction;
 import com.google.devtools.build.lib.rules.repository.ResolvedFileValue;
+import com.google.devtools.build.lib.skyframe.PrecomputedValue;
 import com.google.devtools.build.lib.vfs.Path;
 import com.google.devtools.build.lib.vfs.XattrProvider;
 import com.google.devtools.build.skyframe.SkyFunction.Environment;
 import com.google.devtools.build.skyframe.SkyFunctionException.Transience;
 import com.google.devtools.build.skyframe.SkyKey;
 import java.io.IOException;
-import java.util.List;
 import java.util.Map;
-import java.util.stream.Collectors;
+import net.starlark.java.eval.StarlarkSemantics;
 
 /** Create a local repository that describes the auto-detected host platform. */
 public class LocalConfigPlatformFunction extends RepositoryFunction {
@@ -55,14 +55,25 @@ public RepositoryDirectoryValue.Builder fetch(
  Environment env,
  Map<RepoRecordedInput, String> recordedInputValues,
  SkyKey key)
- throws RepositoryFunctionException {
+ throws RepositoryFunctionException, InterruptedException {
+ StarlarkSemantics starlarkSemantics = PrecomputedValue.STARLARK_SEMANTICS.get(env);
+ if (starlarkSemantics == null) {
+ return null;
+ }
+ boolean enableBzlmod = starlarkSemantics.getBool(BuildLanguageOptions.ENABLE_BZLMOD);
+ // If Bzlmod is enabled, @platforms is definitely new enough to contain the new host platform
+ // and constraints bzl file. Otherwise, @platforms might be an older version, so we use the
+ // bundled @internal_platforms_do_not_use repo instead (see local_config_platform.WORKSPACE).
+ String platformsRepoName = enableBzlmod ? "@platforms" : "@internal_platforms_do_not_use";
  String name = rule.getName();
  try {
  outputDirectory.createDirectoryAndParents();
  RepositoryFunction.writeFile(outputDirectory, "WORKSPACE", workspaceFileContent(name));
  RepositoryFunction.writeFile(outputDirectory, "MODULE.bazel", moduleFileContent(name));
- RepositoryFunction.writeFile(outputDirectory, "BUILD.bazel", buildFileContent());
- RepositoryFunction.writeFile(outputDirectory, "constraints.bzl", constraintFileContent());
+ RepositoryFunction.writeFile(
+ outputDirectory, "BUILD.bazel", buildFileContent(platformsRepoName));
+ RepositoryFunction.writeFile(
+ outputDirectory, "constraints.bzl", constraintFileContent(platformsRepoName));
  } catch (IOException e) {
  throw new RepositoryFunctionException(
  new IOException("Could not create content for " + name + ": " + e.getMessage()),
@@ -96,47 +107,45 @@ public Object getResolvedInformation(XattrProvider xattrProvider) {
  }
 
  private static String workspaceFileContent(String repositoryName) {
- return format(
- ImmutableList.of(
- "# DO NOT EDIT: automatically generated WORKSPACE file for local_config_platform",
- "workspace(name = \"%s\")"),
+ return String.format(
+ """
+ # DO NOT EDIT: automatically generated WORKSPACE file for local_config_platform
+ workspace(name = "%s")
+ """,
  repositoryName);
  }
 
  private static String moduleFileContent(String repositoryName) {
- return format(
- ImmutableList.of(
- "# DO NOT EDIT: automatically generated MODULE file for local_config_platform",
- "module(name = \"%s\")",
- // Try to keep this updated with the src/MODULE.tools file. (Due to MVS, even if this is
- // not kept up to date, we'll use the latest version anyhow)
- "bazel_dep(name = \"platforms\", version = \"0.0.7\")"),
+ return String.format(
+ """
+ # DO NOT EDIT: automatically generated MODULE file for local_config_platform
+ module(name = "%s")
+ bazel_dep(name = "platforms", version = "0.0.7")
+ """,
  repositoryName);
  }
 
- private static String buildFileContent() {
- return format(
- ImmutableList.of(
- "# DO NOT EDIT: automatically generated BUILD file for local_config_platform",
- "package(default_visibility = ['//visibility:public'])",
- "alias(name = 'host', actual = '@platforms//host')",
- "exports_files([",
- " # Export constraints.bzl for use in downstream bzl_library targets.",
- " 'constraints.bzl',",
- "])"));
- }
-
- private static String constraintFileContent() {
- return format(
- ImmutableList.of(
- "# DO NOT EDIT: automatically generated constraints list for local_config_platform",
- "load('@platforms//host:constraints.bzl', _HOST_CONSTRAINTS='HOST_CONSTRAINTS')",
- "HOST_CONSTRAINTS = _HOST_CONSTRAINTS"));
+ private static String buildFileContent(String platformsRepoName) {
+ return String.format(
+ """
+ # DO NOT EDIT: automatically generated BUILD file for local_config_platform
+ package(default_visibility = ['//visibility:public'])
+ alias(name = 'host', actual = '%s//host')
+ exports_files([
+ # Export constraints.bzl for use in downstream bzl_library targets.
+ 'constraints.bzl',
+ ])
+ """,
+ platformsRepoName);
  }
 
- private static String format(List<String> lines, Object... params) {
- // Add a newline between each line, and also after the final line.
- String content = lines.stream().collect(Collectors.joining("\n", "", "\n"));
- return String.format(content, params);
+ private static String constraintFileContent(String platformsRepoName) {
+ return String.format(
+ """
+ # DO NOT EDIT: automatically generated constraints list for local_config_platform
+ load('%s//host:constraints.bzl', _HOST_CONSTRAINTS='HOST_CONSTRAINTS')
+ HOST_CONSTRAINTS = _HOST_CONSTRAINTS
+ """,
+ platformsRepoName);
  }
 }

tools/BUILD

@@ -1,3 +1,5 @@
+load(":build_defs.bzl", "BZLMOD_ENABLED")
+
 package(default_visibility = ["//visibility:public"])
 
 filegroup(
@@ -94,5 +96,5 @@ sh_binary(
 
 alias(
  name = "host_platform",
- actual = "@platforms//host",
+ actual = "@platforms//host" if BZLMOD_ENABLED else "@internal_platforms_do_not_use//host",
 )

tools/build_defs.bzl

@@ -46,3 +46,5 @@ def transition_java_language_8_filegroup(name, files, visibility):
  files = files,
  visibility = visibility,
  )
+
+BZLMOD_ENABLED = str(Label("@bazel_tools//:foo")).startswith("@@")