bzlmod: add BzlmodRepoRuleFunction and friends

- BzlmodRepoRuleHelper: calculates the RepoSpec for a given repository. The actual calculation will be implemented in following changes.

- BzlmodRepoRuleFunction: Take a given repository name, look up its RepoSpec via BzlmodRepoRuleHelper, and then create a repository rule out of it. The result will be used in RepositoryDelegatorFunction.

Related: #13316

RELNOTES: None.
PiperOrigin-RevId: 382745079

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

@@ -85,3 +85,39 @@ java_library(
         "//third_party:jsr305",
     ],
 )
+
+java_library(
+    name = "repo_rule_value",
+    srcs = [
+        "BzlmodRepoRuleValue.java",
+    ],
+    deps = [
+        "//src/main/java/com/google/devtools/build/lib/concurrent",
+        "//src/main/java/com/google/devtools/build/lib/packages",
+        "//src/main/java/com/google/devtools/build/lib/skyframe/serialization/autocodec",
+        "//src/main/java/com/google/devtools/build/skyframe:skyframe-objects",
+        "//third_party:guava",
+    ],
+)
+
+java_library(
+    name = "repo_rule_helper",
+    srcs = [
+        "BzlmodRepoRuleHelper.java",
+        "BzlmodRepoRuleHelperImpl.java",
+    ],
+    deps = [
+        "//src/main/java/com/google/devtools/build/lib/bazel/bzlmod:common",
+        "//src/main/java/com/google/devtools/build/skyframe",
+    ],
+)
+
+java_library(
+    name = "repo_rule_creator",
+    srcs = ["BzlmodRepoRuleCreator.java"],
+    deps = [
+        "//src/main/java/com/google/devtools/build/lib/events",
+        "//src/main/java/com/google/devtools/build/lib/packages",
+        "//src/main/java/net/starlark/java/eval",
+    ],
+)

src/main/java/com/google/devtools/build/lib/bazel/bzlmod/BzlmodRepoRuleCreator.java

@@ -0,0 +1,35 @@
+// Copyright 2021 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.
+
+package com.google.devtools.build.lib.bazel.bzlmod;
+
+import com.google.devtools.build.lib.events.EventHandler;
+import com.google.devtools.build.lib.packages.Package;
+import com.google.devtools.build.lib.packages.Rule;
+import com.google.devtools.build.lib.packages.RuleFactory.InvalidRuleException;
+import java.util.Map;
+import net.starlark.java.eval.StarlarkSemantics;
+
+/**
+ * An interface for {@link RepositoryRuleFunction} to create a repository rule instance with given
+ * parameters.
+ */
+public interface BzlmodRepoRuleCreator {
+  Rule createRule(
+      Package.Builder packageBuilder,
+      StarlarkSemantics semantics,
+      Map<String, Object> kwargs,
+      EventHandler handler)
+      throws InterruptedException, InvalidRuleException;
+}

src/main/java/com/google/devtools/build/lib/bazel/bzlmod/BzlmodRepoRuleHelper.java

@@ -0,0 +1,23 @@
+// Copyright 2021 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.
+
+package com.google.devtools.build.lib.bazel.bzlmod;
+
+import com.google.devtools.build.skyframe.SkyFunction.Environment;
+import java.util.Optional;
+
+/** A helper to get {@link RepoSpec} for Bzlmod generated repositories. */
+public interface BzlmodRepoRuleHelper {
+  Optional<RepoSpec> getRepoSpec(Environment env, String repositoryName);
+}

src/main/java/com/google/devtools/build/lib/bazel/bzlmod/BzlmodRepoRuleHelperImpl.java

@@ -0,0 +1,28 @@
+// Copyright 2021 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.
+
+package com.google.devtools.build.lib.bazel.bzlmod;
+
+import com.google.devtools.build.skyframe.SkyFunction.Environment;
+import java.util.Optional;
+
+/** A helper class to get {@link RepoSpec} for Bzlmod generated repositories. */
+public final class BzlmodRepoRuleHelperImpl implements BzlmodRepoRuleHelper {
+
+  @Override
+  public Optional<RepoSpec> getRepoSpec(Environment env, String repositoryName) {
+    // TODO(pcloudy): Implement calculating RepoSpec.
+    return Optional.empty();
+  }
+}

src/main/java/com/google/devtools/build/lib/bazel/bzlmod/BzlmodRepoRuleValue.java

@@ -0,0 +1,78 @@
+// Copyright 2021 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.
+
+package com.google.devtools.build.lib.bazel.bzlmod;
+
+import com.google.common.collect.Interner;
+import com.google.devtools.build.lib.concurrent.BlazeInterners;
+import com.google.devtools.build.lib.packages.Rule;
+import com.google.devtools.build.lib.skyframe.serialization.autocodec.AutoCodec;
+import com.google.devtools.build.skyframe.AbstractSkyKey;
+import com.google.devtools.build.skyframe.SkyFunctionName;
+import com.google.devtools.build.skyframe.SkyValue;
+
+/** The result of {@link BzlmodRepoRuleFunction}, holding a repository rule instance. */
+public class BzlmodRepoRuleValue implements SkyValue {
+  public static final SkyFunctionName BZLMOD_REPO_RULE =
+      SkyFunctionName.createHermetic("BZLMOD_REPO_RULE");
+
+  private final Rule rule;
+
+  public BzlmodRepoRuleValue(Rule rule) {
+    this.rule = rule;
+  }
+
+  public Rule getRule() {
+    return rule;
+  }
+
+  public static Key key(String repositoryName) {
+    return Key.create(repositoryName);
+  }
+
+  /** Represents an unsuccessful repository lookup. */
+  public static final class RepoRuleNotFoundValue extends BzlmodRepoRuleValue {
+    private RepoRuleNotFoundValue() {
+      super(/* rule= */ null);
+    }
+
+    @Override
+    public Rule getRule() {
+      throw new IllegalStateException();
+    }
+  }
+
+  public static final RepoRuleNotFoundValue REPO_RULE_NOT_FOUND_VALUE = new RepoRuleNotFoundValue();
+
+  /** Argument for the SkyKey to request a BzlmodRepoRuleValue. */
+  @AutoCodec
+  public static class Key extends AbstractSkyKey<String> {
+    private static final Interner<Key> interner = BlazeInterners.newWeakInterner();
+
+    private Key(String arg) {
+      super(arg);
+    }
+
+    @AutoCodec.VisibleForSerialization
+    @AutoCodec.Instantiator
+    static Key create(String arg) {
+      return interner.intern(new Key(arg));
+    }
+
+    @Override
+    public SkyFunctionName functionName() {
+      return BZLMOD_REPO_RULE;
+    }
+  }
+}

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

@@ -17,6 +17,7 @@ java_library(
         "//src/main/java/com/google/devtools/build/lib/actions:file_metadata",
         "//src/main/java/com/google/devtools/build/lib/analysis:analysis_cluster",
         "//src/main/java/com/google/devtools/build/lib/analysis:blaze_directories",
+        "//src/main/java/com/google/devtools/build/lib/bazel/bzlmod:repo_rule_creator",
         "//src/main/java/com/google/devtools/build/lib/bazel/debug:workspace-rule-event",
         "//src/main/java/com/google/devtools/build/lib/bazel/repository",
         "//src/main/java/com/google/devtools/build/lib/bazel/repository/cache",

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

@@ -23,6 +23,7 @@
 import com.google.devtools.build.docgen.annot.DocCategory;
 import com.google.devtools.build.lib.analysis.BaseRuleClasses;
 import com.google.devtools.build.lib.analysis.starlark.StarlarkAttrModule.Descriptor;
+import com.google.devtools.build.lib.bazel.bzlmod.BzlmodRepoRuleCreator;
 import com.google.devtools.build.lib.cmdline.Label;
 import com.google.devtools.build.lib.cmdline.LabelSyntaxException;
 import com.google.devtools.build.lib.events.EventHandler;
@@ -36,6 +37,8 @@
 import com.google.devtools.build.lib.packages.Rule;
 import com.google.devtools.build.lib.packages.RuleClass;
 import com.google.devtools.build.lib.packages.RuleClass.Builder.RuleClassType;
+import com.google.devtools.build.lib.packages.RuleFactory;
+import com.google.devtools.build.lib.packages.RuleFactory.BuildLangTypedAttributeValuesMap;
 import com.google.devtools.build.lib.packages.RuleFactory.InvalidRuleException;
 import com.google.devtools.build.lib.packages.StarlarkExportable;
 import com.google.devtools.build.lib.packages.WorkspaceFactoryHelper;
@@ -50,8 +53,11 @@
 import net.starlark.java.eval.Sequence;
 import net.starlark.java.eval.Starlark;
 import net.starlark.java.eval.StarlarkCallable;
+import net.starlark.java.eval.StarlarkSemantics;
 import net.starlark.java.eval.StarlarkThread;
+import net.starlark.java.eval.StarlarkThread.CallStackEntry;
 import net.starlark.java.eval.Tuple;
+import net.starlark.java.syntax.Location;
 
 /**
  * The Starlark module containing the definition of {@code repository_rule} function to define a
@@ -119,7 +125,7 @@ public StarlarkCallable repositoryRule(
           "A callable value that may be invoked during evaluation of the WORKSPACE file to"
               + " instantiate and return a repository rule.")
   private static final class RepositoryRuleFunction
-      implements StarlarkCallable, StarlarkExportable {
+      implements StarlarkCallable, StarlarkExportable, BzlmodRepoRuleCreator {
     private final RuleClass.Builder builder;
     private final StarlarkCallable implementation;
     private Label extensionLabel;
@@ -213,6 +219,23 @@ public Object call(StarlarkThread thread, Tuple args, Dict<String, Object> kwarg
         throw Starlark.errorf("%s", e.getMessage());
       }
     }
+
+    @Override
+    public Rule createRule(
+        Package.Builder packageBuilder,
+        StarlarkSemantics semantics,
+        Map<String, Object> kwargs,
+        EventHandler handler)
+        throws InterruptedException, InvalidRuleException {
+      RuleClass ruleClass = builder.build(exportedName, exportedName);
+      BuildLangTypedAttributeValuesMap attributeValues =
+          new BuildLangTypedAttributeValuesMap(kwargs);
+      ImmutableList.Builder<CallStackEntry> callStack = ImmutableList.builder();
+      // TODO(pcloudy): Optimize the callstack
+      callStack.add(new CallStackEntry("RepositoryRuleFunction.createRule", Location.BUILTIN));
+      return RuleFactory.createRule(
+          packageBuilder, ruleClass, attributeValues, handler, semantics, callStack.build());
+    }
   }
 
   @Override

src/main/java/com/google/devtools/build/lib/cmdline/LabelConstants.java

@@ -36,6 +36,7 @@ public class LabelConstants {
   public static final PathFragment WORKSPACE_FILE_NAME = PathFragment.create("WORKSPACE");
   public static final PathFragment WORKSPACE_DOT_BAZEL_FILE_NAME =
       PathFragment.create("WORKSPACE.bazel");
+  public static final PathFragment MODULE_DOT_BAZEL_FILE_NAME = PathFragment.create("MODULE.bazel");
   public static final String DEFAULT_REPOSITORY_DIRECTORY = "__main__";
 
   // With this prefix, non-main repositories are symlinked under

src/main/java/com/google/devtools/build/lib/packages/BazelStarlarkEnvironment.java

@@ -57,6 +57,8 @@ public final class BazelStarlarkEnvironment {
   private final ImmutableMap<String, Object> workspaceBzlEnv;
   /** The top-level predeclared symbols for a bzl module in the {@code @_builtins} pseudo-repo. */
   private final ImmutableMap<String, Object> builtinsBzlEnv;
+  /** The top-level predeclared symbols for a bzl module in the Bzlmod system. */
+  private final ImmutableMap<String, Object> bzlmodBzlEnv;
 
   BazelStarlarkEnvironment(
       RuleClassProvider ruleClassProvider,
@@ -73,6 +75,9 @@ public final class BazelStarlarkEnvironment {
     this.uninjectedBuildBzlEnv =
         createUninjectedBuildBzlEnv(ruleClassProvider, uninjectedBuildBzlNativeBindings);
     this.workspaceBzlEnv = createWorkspaceBzlEnv(ruleClassProvider, workspaceBzlNativeBindings);
+    // TODO(pcloudy): this should be a bzlmod specific environment, but keep using the workspace
+    // envirnment until we implement module rules.
+    this.bzlmodBzlEnv = createWorkspaceBzlEnv(ruleClassProvider, workspaceBzlNativeBindings);
     this.builtinsBzlEnv =
         createBuiltinsBzlEnv(
             ruleClassProvider, uninjectedBuildBzlNativeBindings, uninjectedBuildBzlEnv);
@@ -126,6 +131,11 @@ public ImmutableMap<String, Object> getBuiltinsBzlEnv() {
     return builtinsBzlEnv;
   }
 
+  /** Returns the environment for Bzlmod-loaded bzl files. */
+  public ImmutableMap<String, Object> getBzlmodBzlEnv() {
+    return bzlmodBzlEnv;
+  }
+
   /**
    * Produces everything that would be in the "native" object for BUILD-loaded bzl files if builtins
    * injection didn't happen.

src/main/java/com/google/devtools/build/lib/packages/Package.java

@@ -420,7 +420,7 @@ private void finishInit(Builder builder) {
     this.packageDirectory = filename.asPath().getParentDirectory();
     String baseName = filename.getRootRelativePath().getBaseName();
 
-    if (isWorkspaceFile(baseName)) {
+    if (isWorkspaceFile(baseName) || isModuleDotBazelFile(baseName)) {
       Preconditions.checkState(
           packageIdentifier.equals(LabelConstants.EXTERNAL_PACKAGE_IDENTIFIER));
       this.sourceRoot = Optional.empty();
@@ -485,6 +485,10 @@ private static boolean isWorkspaceFile(String baseFileName) {
         || baseFileName.equals(LabelConstants.WORKSPACE_FILE_NAME.getPathString());
   }
 
+  private static boolean isModuleDotBazelFile(String baseFileName) {
+    return baseFileName.equals(LabelConstants.MODULE_DOT_BAZEL_FILE_NAME.getPathString());
+  }
+
   /** Returns the list of transitive closure of the Starlark file dependencies of this package. */
   public ImmutableList<Label> getStarlarkFileDependencies() {
     return starlarkFileDependencies;

src/main/java/com/google/devtools/build/lib/packages/PackageFactory.java

@@ -440,7 +440,7 @@ public boolean isImmutable() {
     }
   }
 
-  @VisibleForTesting // exposed to WorkspaceFileFunction
+  @VisibleForTesting // exposed to WorkspaceFileFunction and BzlmodRepoRuleFunction
   public Package.Builder newExternalPackageBuilder(
       RootedPath workspacePath, String workspaceName, StarlarkSemantics starlarkSemantics) {
     return Package.newExternalPackageBuilder(

src/main/java/com/google/devtools/build/lib/packages/RuleFactory.java

@@ -73,7 +73,7 @@ public RuleClass getRuleClass(String ruleClassName) {
    * <p>It is the caller's responsibility to add the rule to the package (the caller may choose not
    * to do so if, for example, the rule has errors).
    */
-  static Rule createRule(
+  public static Rule createRule(
       Package.Builder pkgBuilder,
       RuleClass ruleClass,
       BuildLangTypedAttributeValuesMap attributeValues,
@@ -203,7 +203,7 @@ public static Rule createAndAddRule(
    * not be constructed. It contains an error message.
    */
   public static class InvalidRuleException extends Exception {
-    private InvalidRuleException(String message) {
+    public InvalidRuleException(String message) {
       super(message);
     }
   }

src/main/java/com/google/devtools/build/lib/skyframe/BUILD

@@ -27,6 +27,7 @@ java_library(
         "BuildConfigurationFunction.java",
         "BuildInfoCollectionFunction.java",
         "BzlLoadFunction.java",
+        "BzlmodRepoRuleFunction.java",
         "CompletionFunction.java",
         "ConfiguredTargetFunction.java",
         "ConstraintValueLookupUtil.java",
@@ -271,6 +272,9 @@ java_library(
         "//src/main/java/com/google/devtools/build/lib/analysis:workspace_status_action",
         "//src/main/java/com/google/devtools/build/lib/analysis/platform",
         "//src/main/java/com/google/devtools/build/lib/analysis/platform:utils",
+        "//src/main/java/com/google/devtools/build/lib/bazel/bzlmod:common",
+        "//src/main/java/com/google/devtools/build/lib/bazel/bzlmod:repo_rule_helper",
+        "//src/main/java/com/google/devtools/build/lib/bazel/bzlmod:repo_rule_value",
         "//src/main/java/com/google/devtools/build/lib/bugreport",
         "//src/main/java/com/google/devtools/build/lib/buildeventstream",
         "//src/main/java/com/google/devtools/build/lib/buildeventstream/proto:build_event_stream_java_proto",