Add new flag --enable_workspace that allows us to disable WORKSPACE…

… handling

* This flag defaults to true
* When turned off (`--noenable_workspace`), no WORKSPACE file reading is ever done (including `WORKSPACE.bzlmod`, `WORKSPACE.resolved`, prefixes, suffixes, etc). No `//external` package is created or used.
* Bzlmod and WORKSPACE can't both be turned off.
* We no longer mandate that a WORKSPACE file has to be at the root of a repo; that is now replaced by `REPO.bazel`. But it's still okay to have a `WORKSPACE` file and no `REPO.bazel` file at the root of a `local_repository`, for example.
* All Bzlmod integration tests now have `--noenable_workspace` set.

Fixes #20185.

RELNOTES: Added a flag `--enable_workspace` (defaults to True) that allows the user to completely disable WORKSPACE logic when turned off.
PiperOrigin-RevId: 589978780
Change-Id: I07a1b8674aaad2758ded57c3a48dba2a19c91e04

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

@@ -26,6 +26,7 @@
 import com.google.devtools.build.lib.bazel.repository.downloader.DownloadManager;
 import com.google.devtools.build.lib.bazel.repository.starlark.RepoFetchingSkyKeyComputeState.Signal;
 import com.google.devtools.build.lib.cmdline.Label;
+import com.google.devtools.build.lib.cmdline.LabelConstants;
 import com.google.devtools.build.lib.cmdline.RepositoryName;
 import com.google.devtools.build.lib.events.Event;
 import com.google.devtools.build.lib.packages.BazelStarlarkContext;
@@ -44,6 +45,7 @@
 import com.google.devtools.build.lib.skyframe.IgnoredPackagePrefixesValue;
 import com.google.devtools.build.lib.skyframe.PrecomputedValue;
 import com.google.devtools.build.lib.util.CPU;
+import com.google.devtools.build.lib.vfs.FileSystemUtils;
 import com.google.devtools.build.lib.vfs.Path;
 import com.google.devtools.build.lib.vfs.PathFragment;
 import com.google.devtools.build.lib.vfs.SyscallCache;
@@ -337,8 +339,12 @@ private RepositoryDirectoryValue.Builder fetchInternal(
           new IOException(rule + " must create a directory"), Transience.TRANSIENT);
     }
 
-    if (!WorkspaceFileHelper.doesWorkspaceFileExistUnder(outputDirectory)) {
-      createWorkspaceFile(outputDirectory, rule.getTargetKind(), rule.getName());
+    if (!WorkspaceFileHelper.isValidRepoRoot(outputDirectory)) {
+      try {
+        FileSystemUtils.createEmptyFile(outputDirectory.getRelative(LabelConstants.REPO_FILE_NAME));
+      } catch (IOException e) {
+        throw new RepositoryFunctionException(e, Transience.TRANSIENT);
+      }
     }
 
     return RepositoryDirectoryValue.builder().setPath(outputDirectory);

src/main/java/com/google/devtools/build/lib/bazel/rules/android/AndroidNdkRepositoryFunction.java

@@ -33,6 +33,7 @@
 import com.google.devtools.build.lib.bazel.rules.android.ndkcrosstools.StlImpls;
 import com.google.devtools.build.lib.bazel.rules.android.ndkcrosstools.StlImpls.GnuLibStdCppStlImpl;
 import com.google.devtools.build.lib.bazel.rules.android.ndkcrosstools.StlImpls.LibCppStlImpl;
+import com.google.devtools.build.lib.cmdline.LabelConstants;
 import com.google.devtools.build.lib.events.Event;
 import com.google.devtools.build.lib.packages.Rule;
 import com.google.devtools.build.lib.packages.Type;
@@ -281,7 +282,12 @@ public RepositoryDirectoryValue.Builder fetch(
     if (environ == null) {
       return null;
     }
-    prepareLocalRepositorySymlinkTree(rule, outputDirectory);
+    try {
+      outputDirectory.createDirectoryAndParents();
+      FileSystemUtils.createEmptyFile(outputDirectory.getRelative(LabelConstants.REPO_FILE_NAME));
+    } catch (IOException e) {
+      throw new RepositoryFunctionException(e, Transience.TRANSIENT);
+    }
     WorkspaceAttributeMapper attributes = WorkspaceAttributeMapper.of(rule);
     PathFragment pathFragment;
     String userDefinedPath = null;

src/main/java/com/google/devtools/build/lib/bazel/rules/android/AndroidSdkRepositoryFunction.java

@@ -27,6 +27,7 @@
 import com.google.devtools.build.lib.analysis.BlazeDirectories;
 import com.google.devtools.build.lib.analysis.RuleDefinition;
 import com.google.devtools.build.lib.bugreport.BugReport;
+import com.google.devtools.build.lib.cmdline.LabelConstants;
 import com.google.devtools.build.lib.io.InconsistentFilesystemException;
 import com.google.devtools.build.lib.packages.Rule;
 import com.google.devtools.build.lib.packages.Type;
@@ -37,6 +38,7 @@
 import com.google.devtools.build.lib.util.ResourceFileLoader;
 import com.google.devtools.build.lib.vfs.Dirent;
 import com.google.devtools.build.lib.vfs.FileSystem;
+import com.google.devtools.build.lib.vfs.FileSystemUtils;
 import com.google.devtools.build.lib.vfs.Path;
 import com.google.devtools.build.lib.vfs.PathFragment;
 import com.google.devtools.build.lib.vfs.Root;
@@ -199,7 +201,12 @@ public RepositoryDirectoryValue.Builder fetch(
     if (environ == null) {
       return null;
     }
-    prepareLocalRepositorySymlinkTree(rule, outputDirectory);
+    try {
+      outputDirectory.createDirectoryAndParents();
+      FileSystemUtils.createEmptyFile(outputDirectory.getRelative(LabelConstants.REPO_FILE_NAME));
+    } catch (IOException e) {
+      throw new RepositoryFunctionException(e, Transience.TRANSIENT);
+    }
     WorkspaceAttributeMapper attributes = WorkspaceAttributeMapper.of(rule);
     FileSystem fs = directories.getOutputBase().getFileSystem();
     Path androidSdkPath;

src/main/java/com/google/devtools/build/lib/packages/semantics/BuildLanguageOptions.java

@@ -205,6 +205,16 @@ public final class BuildLanguageOptions extends OptionsBase {
               + " WORKSPACE. See https://bazel.build/docs/bzlmod for more information.")
   public boolean enableBzlmod;
 
+  @Option(
+      name = "enable_workspace",
+      defaultValue = "true",
+      documentationCategory = OptionDocumentationCategory.STARLARK_SEMANTICS,
+      effectTags = OptionEffectTag.LOADING_AND_ANALYSIS,
+      help =
+          "If true, enables the legacy WORKSPACE system for external dependencies. See"
+              + " https://bazel.build/external/overview for more information.")
+  public boolean enableWorkspace;
+
   @Option(
       name = "experimental_isolated_extension_usages",
       defaultValue = "false",
@@ -739,6 +749,7 @@ public StarlarkSemantics toStarlarkSemantics() {
                 EXPERIMENTAL_ENABLE_ANDROID_MIGRATION_APIS, experimentalEnableAndroidMigrationApis)
             .setBool(EXPERIMENTAL_ENABLE_SCL_DIALECT, experimentalEnableSclDialect)
             .setBool(ENABLE_BZLMOD, enableBzlmod)
+            .setBool(ENABLE_WORKSPACE, enableWorkspace)
             .setBool(EXPERIMENTAL_ISOLATED_EXTENSION_USAGES, experimentalIsolatedExtensionUsages)
             .setBool(
                 INCOMPATIBLE_EXISTING_RULES_IMMUTABLE_VIEW, incompatibleExistingRulesImmutableView)
@@ -846,6 +857,7 @@ public StarlarkSemantics toStarlarkSemantics() {
       "-experimental_enable_android_migration_apis";
   public static final String EXPERIMENTAL_ENABLE_SCL_DIALECT = "-experimental_enable_scl_dialect";
   public static final String ENABLE_BZLMOD = "+enable_bzlmod";
+  public static final String ENABLE_WORKSPACE = "+enable_workspace";
   public static final String EXPERIMENTAL_ISOLATED_EXTENSION_USAGES =
       "-experimental_isolated_extension_usages";
   public static final String INCOMPATIBLE_EXISTING_RULES_IMMUTABLE_VIEW =

src/main/java/com/google/devtools/build/lib/rules/repository/RepositoryDelegatorFunction.java

@@ -237,12 +237,16 @@ private Rule getRepositoryRule(
       }
     }
 
-    // fallback to look up the repository in the WORKSPACE file.
-    try {
-      return getRepoRuleFromWorkspace(repositoryName, env);
-    } catch (NoSuchRepositoryException e) {
-      return null;
+    if (starlarkSemantics.getBool(BuildLanguageOptions.ENABLE_WORKSPACE)) {
+      // fallback to look up the repository in the WORKSPACE file.
+      try {
+        return getRepoRuleFromWorkspace(repositoryName, env);
+      } catch (NoSuchRepositoryException e) {
+        return null;
+      }
     }
+
+    return null;
   }
 
   @Nullable
@@ -428,47 +432,15 @@ public static RepositoryDirectoryValue.Builder symlinkRepoRoot(
           Transience.PERSISTENT);
     }
 
-    // Check that the repository contains a WORKSPACE file.
-    // Note that we need to do this here since we're not creating a WORKSPACE file ourselves, but
-    // entrusting the entire contents of the repo root to this target directory.
-    FileValue workspaceFileValue = getWorkspaceFile(targetDirRootedPath, env);
-    if (workspaceFileValue == null) {
-      return null;
-    }
-
-    if (!workspaceFileValue.exists()) {
-      throw new RepositoryFunctionException(
-          new IOException("No WORKSPACE file found in " + source), Transience.PERSISTENT);
-    }
-    return RepositoryDirectoryValue.builder().setPath(source);
-  }
-
-  @Nullable
-  private static FileValue getWorkspaceFile(RootedPath directory, Environment env)
-      throws RepositoryFunctionException, InterruptedException {
-    RootedPath workspaceRootedFile;
-    try {
-      workspaceRootedFile = WorkspaceFileHelper.getWorkspaceRootedFile(directory, env);
-      if (workspaceRootedFile == null) {
-        return null;
-      }
-    } catch (IOException e) {
+    // Check that the directory contains a repo boundary file.
+    // Note that we need to do this here since we're not creating a repo boundary file ourselves,
+    // but entrusting the entire contents of the repo root to this target directory.
+    if (!WorkspaceFileHelper.isValidRepoRoot(destination)) {
       throw new RepositoryFunctionException(
-          new IOException(
-              "Could not determine workspace file (\"WORKSPACE.bazel\" or \"WORKSPACE\"): "
-                  + e.getMessage()),
+          new IOException("No MODULE.bazel, REPO.bazel, or WORKSPACE file found in " + destination),
           Transience.PERSISTENT);
     }
-    SkyKey workspaceFileKey = FileValue.key(workspaceRootedFile);
-    FileValue value;
-    try {
-      value = (FileValue) env.getValueOrThrow(workspaceFileKey, IOException.class);
-    } catch (IOException e) {
-      throw new RepositoryFunctionException(
-          new IOException("Could not access " + workspaceRootedFile + ": " + e.getMessage()),
-          Transience.PERSISTENT);
-    }
-    return value;
+    return RepositoryDirectoryValue.builder().setPath(source);
   }
 
   // Escape a value for the marker file

src/main/java/com/google/devtools/build/lib/rules/repository/RepositoryFunction.java

@@ -15,7 +15,6 @@
 package com.google.devtools.build.lib.rules.repository;
 
 import static com.google.common.base.Preconditions.checkState;
-import static java.nio.charset.StandardCharsets.UTF_8;
 
 import com.google.common.annotations.VisibleForTesting;
 import com.google.common.base.Preconditions;
@@ -402,35 +401,6 @@ protected boolean isConfigure(Rule rule) {
     return false;
   }
 
-  protected Path prepareLocalRepositorySymlinkTree(Rule rule, Path repositoryDirectory)
-      throws RepositoryFunctionException {
-    try {
-      repositoryDirectory.createDirectoryAndParents();
-    } catch (IOException e) {
-      throw new RepositoryFunctionException(e, Transience.TRANSIENT);
-    }
-
-    // Add x/WORKSPACE.
-    createWorkspaceFile(repositoryDirectory, rule.getTargetKind(), rule.getName());
-    return repositoryDirectory;
-  }
-
-  public static void createWorkspaceFile(Path repositoryDirectory, String ruleKind, String ruleName)
-      throws RepositoryFunctionException {
-    try {
-      Path workspaceFile = repositoryDirectory.getRelative(LabelConstants.WORKSPACE_FILE_NAME);
-      FileSystemUtils.writeContent(
-          workspaceFile,
-          UTF_8,
-          String.format(
-              "# DO NOT EDIT: automatically generated WORKSPACE file for %s\n"
-                  + "workspace(name = \"%s\")\n",
-              ruleKind, ruleName));
-    } catch (IOException e) {
-      throw new RepositoryFunctionException(e, Transience.TRANSIENT);
-    }
-  }
-
   protected static RepositoryDirectoryValue.Builder writeFile(
       Path repositoryDirectory, String filename, String contents)
       throws RepositoryFunctionException {

src/main/java/com/google/devtools/build/lib/rules/repository/WorkspaceFileHelper.java

@@ -17,7 +17,6 @@
 import com.google.devtools.build.lib.cmdline.LabelConstants;
 import com.google.devtools.build.lib.vfs.Path;
 import com.google.devtools.build.lib.vfs.PathFragment;
-import com.google.devtools.build.lib.vfs.Root;
 import com.google.devtools.build.lib.vfs.RootedPath;
 import com.google.devtools.build.skyframe.SkyFunction.Environment;
 import com.google.devtools.build.skyframe.SkyKey;
@@ -27,12 +26,6 @@
 /** A class to help dealing with WORKSPACE.bazel and WORKSAPCE file */
 public class WorkspaceFileHelper {
 
-  public static RootedPath getWorkspaceRootedFile(Root directory, Environment env)
-      throws IOException, InterruptedException {
-    return getWorkspaceRootedFile(
-        RootedPath.toRootedPath(directory, PathFragment.EMPTY_FRAGMENT), env);
-  }
-
   /**
    * Get a RootedPath of the WORKSPACE file we should use for a given directory. This function
    * returns a RootedPath to <directory>/WORKSPACE.bazel file if it exists and it's a regular file
@@ -70,24 +63,18 @@ public static RootedPath getWorkspaceRootedFile(RootedPath directory, Environmen
         directory.getRootRelativePath().getRelative(LabelConstants.WORKSPACE_FILE_NAME));
   }
 
-  public static boolean doesWorkspaceFileExistUnder(Path directory) {
+  public static boolean isValidRepoRoot(Path directory) {
+    // Keep in sync with //src/main/cpp/workspace_layout.h
     return directory.getRelative(LabelConstants.WORKSPACE_DOT_BAZEL_FILE_NAME).exists()
-        || directory.getRelative(LabelConstants.WORKSPACE_FILE_NAME).exists();
-  }
-
-  public static boolean matchWorkspaceFileName(String name) {
-    return matchWorkspaceFileName(PathFragment.create(name));
+        || directory.getRelative(LabelConstants.WORKSPACE_FILE_NAME).exists()
+        || directory.getRelative(LabelConstants.MODULE_DOT_BAZEL_FILE_NAME).exists()
+        || directory.getRelative(LabelConstants.REPO_FILE_NAME).exists();
   }
 
   public static boolean matchWorkspaceFileName(PathFragment name) {
     return name.equals(LabelConstants.WORKSPACE_DOT_BAZEL_FILE_NAME)
         || name.equals(LabelConstants.WORKSPACE_FILE_NAME);
   }
 
-  public static boolean endsWithWorkspaceFileName(PathFragment pathFragment) {
-    return pathFragment.endsWith(LabelConstants.WORKSPACE_DOT_BAZEL_FILE_NAME)
-        || pathFragment.endsWith(LabelConstants.WORKSPACE_FILE_NAME);
-  }
-
   private WorkspaceFileHelper() {}
 }

src/main/java/com/google/devtools/build/lib/skyframe/PackageFunction.java

@@ -333,6 +333,15 @@ private SkyValue getExternalPackage(Environment env)
     if (env.valuesMissing()) {
       return null;
     }
+    if (!starlarkSemantics.getBool(BuildLanguageOptions.ENABLE_WORKSPACE)) {
+      throw PackageFunctionException.builder()
+          .setType(PackageFunctionException.Type.NO_SUCH_PACKAGE)
+          .setTransience(Transience.PERSISTENT)
+          .setPackageIdentifier(LabelConstants.EXTERNAL_PACKAGE_IDENTIFIER)
+          .setMessage("the WORKSPACE file is disabled via --noenable_workspace")
+          .setPackageLoadingCode(PackageLoading.Code.WORKSPACE_FILE_ERROR)
+          .build();
+    }
 
     SkyKey workspaceKey = ExternalPackageFunction.key();
     PackageValue workspace = null;

src/main/java/com/google/devtools/build/lib/skyframe/PackageLookupFunction.java

@@ -116,6 +116,7 @@ public SkyValue compute(SkyKey skyKey, Environment env)
 
     if (packageKey.equals(LabelConstants.EXTERNAL_PACKAGE_IDENTIFIER)) {
       return semantics.getBool(BuildLanguageOptions.EXPERIMENTAL_DISABLE_EXTERNAL_PACKAGE)
+              || !semantics.getBool(BuildLanguageOptions.ENABLE_WORKSPACE)
           ? PackageLookupValue.NO_BUILD_FILE_VALUE
           : computeWorkspacePackageLookupValue(env);
     }

src/main/java/com/google/devtools/build/lib/skyframe/RepositoryMappingFunction.java

@@ -57,6 +57,7 @@ public SkyValue compute(SkyKey skyKey, Environment env)
     }
     RepositoryName repositoryName = ((RepositoryMappingValue.Key) skyKey).repoName();
     boolean enableBzlmod = starlarkSemantics.getBool(BuildLanguageOptions.ENABLE_BZLMOD);
+    boolean enableWorkspace = starlarkSemantics.getBool(BuildLanguageOptions.ENABLE_WORKSPACE);
 
     if (enableBzlmod) {
       if (StarlarkBuiltinsValue.isBuiltinsRepo(repositoryName)) {
@@ -102,7 +103,8 @@ public SkyValue compute(SkyKey skyKey, Environment env)
       }
 
       if (repositoryName.isMain()
-          && ((RepositoryMappingValue.Key) skyKey).rootModuleShouldSeeWorkspaceRepos()) {
+          && ((RepositoryMappingValue.Key) skyKey).rootModuleShouldSeeWorkspaceRepos()
+          && enableWorkspace) {
         // The root module should be able to see repos defined in WORKSPACE. Therefore, we find all
         // workspace repos and add them as extra visible repos in root module's repo mappings.
         PackageValue externalPackageValue =
@@ -157,22 +159,26 @@ public SkyValue compute(SkyKey skyKey, Environment env)
       }
     }
 
-    PackageValue externalPackageValue =
-        (PackageValue) env.getValue(LabelConstants.EXTERNAL_PACKAGE_IDENTIFIER);
-    RepositoryMappingValue rootModuleRepoMappingValue =
-        enableBzlmod
-            ? (RepositoryMappingValue)
-                env.getValue(RepositoryMappingValue.KEY_FOR_ROOT_MODULE_WITHOUT_WORKSPACE_REPOS)
-            : null;
-    if (env.valuesMissing()) {
-      return null;
+    if (enableWorkspace) {
+      PackageValue externalPackageValue =
+          (PackageValue) env.getValue(LabelConstants.EXTERNAL_PACKAGE_IDENTIFIER);
+      RepositoryMappingValue rootModuleRepoMappingValue =
+          enableBzlmod
+              ? (RepositoryMappingValue)
+                  env.getValue(RepositoryMappingValue.KEY_FOR_ROOT_MODULE_WITHOUT_WORKSPACE_REPOS)
+              : null;
+      if (env.valuesMissing()) {
+        return null;
+      }
+
+      RepositoryMapping rootModuleRepoMapping =
+          rootModuleRepoMappingValue == null
+              ? null
+              : rootModuleRepoMappingValue.getRepositoryMapping();
+      return computeFromWorkspace(repositoryName, externalPackageValue, rootModuleRepoMapping);
     }
 
-    RepositoryMapping rootModuleRepoMapping =
-        rootModuleRepoMappingValue == null
-            ? null
-            : rootModuleRepoMappingValue.getRepositoryMapping();
-    return computeFromWorkspace(repositoryName, externalPackageValue, rootModuleRepoMapping);
+    throw new RepositoryMappingFunctionException();
   }
 
   /**

src/main/java/com/google/devtools/build/lib/skyframe/WorkspaceNameFunction.java

@@ -59,16 +59,19 @@ public SkyValue compute(SkyKey skyKey, Environment env)
       // danger (i.e. going through repo mapping is idempotent).
       return WorkspaceNameValue.withName(ruleClassProvider.getRunfilesPrefix());
     }
-    PackageValue externalPackageValue =
-        (PackageValue) env.getValue(LabelConstants.EXTERNAL_PACKAGE_IDENTIFIER);
-    if (externalPackageValue == null) {
-      return null;
-    }
-    Package externalPackage = externalPackageValue.getPackage();
-    if (externalPackage.containsErrors()) {
-      throw new WorkspaceNameFunctionException();
+    if (starlarkSemantics.getBool(BuildLanguageOptions.ENABLE_WORKSPACE)) {
+      PackageValue externalPackageValue =
+          (PackageValue) env.getValue(LabelConstants.EXTERNAL_PACKAGE_IDENTIFIER);
+      if (externalPackageValue == null) {
+        return null;
+      }
+      Package externalPackage = externalPackageValue.getPackage();
+      if (externalPackage.containsErrors()) {
+        throw new WorkspaceNameFunctionException();
+      }
+      return WorkspaceNameValue.withName(externalPackage.getWorkspaceName());
     }
-    return WorkspaceNameValue.withName(externalPackage.getWorkspaceName());
+    throw new WorkspaceNameFunctionException();
   }
 
   private static class WorkspaceNameFunctionException extends SkyFunctionException {