Add SkylarkClassObjectConstructor - a future return value of "provider" function.

--
MOS_MIGRATED_REVID=129726780

12 files changed, 124 insertions, 26 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/bazel/repository/skylark/SkylarkRepositoryContext.java b/src/main/java/com/google/devtools/build/lib/bazel/repository/skylark/SkylarkRepositoryContext.java
index f8d10cfab5..4ed66e965b 100644
--- a/src/main/java/com/google/devtools/build/lib/bazel/repository/skylark/SkylarkRepositoryContext.java
+++ b/src/main/java/com/google/devtools/build/lib/bazel/repository/skylark/SkylarkRepositoryContext.java
@@ -26,6 +26,7 @@ import com.google.devtools.build.lib.events.Location;
 import com.google.devtools.build.lib.packages.AggregatingAttributeMapper;
 import com.google.devtools.build.lib.packages.Rule;
 import com.google.devtools.build.lib.packages.SkylarkClassObject;
+import com.google.devtools.build.lib.packages.SkylarkClassObjectConstructor;
 import com.google.devtools.build.lib.rules.repository.RepositoryFunction.RepositoryFunctionException;
 import com.google.devtools.build.lib.skyframe.FileSymlinkException;
 import com.google.devtools.build.lib.skyframe.FileValue;
@@ -108,7 +109,8 @@ public class SkylarkRepositoryContext {
                 : SkylarkType.convertToSkylark(val, null));
       }
     }
-    attrObject = new SkylarkClassObject(attrBuilder.build(), "No such attribute '%s'");
+    attrObject = SkylarkClassObjectConstructor.STRUCT.create(
+        attrBuilder.build(), "No such attribute '%s'");
   }
 
   @SkylarkCallable(
diff --git a/src/main/java/com/google/devtools/build/lib/packages/Attribute.java b/src/main/java/com/google/devtools/build/lib/packages/Attribute.java
index f2fb3355e9..996371494d 100644
--- a/src/main/java/com/google/devtools/build/lib/packages/Attribute.java
+++ b/src/main/java/com/google/devtools/build/lib/packages/Attribute.java
@@ -1250,7 +1250,8 @@ public final class Attribute implements Comparable<Attribute> {
           }
         }
       }
-      ClassObject attrs = new SkylarkClassObject(attrValues,
+      ClassObject attrs = SkylarkClassObjectConstructor.STRUCT.create(
+          attrValues,
           "No such regular (non late-bound) attribute '%s'.");
       return callback.call(attrs, o);
     }
diff --git a/src/main/java/com/google/devtools/build/lib/packages/ImplicitOutputsFunction.java b/src/main/java/com/google/devtools/build/lib/packages/ImplicitOutputsFunction.java
index 3789091663..8ddffdd764 100644
--- a/src/main/java/com/google/devtools/build/lib/packages/ImplicitOutputsFunction.java
+++ b/src/main/java/com/google/devtools/build/lib/packages/ImplicitOutputsFunction.java
@@ -94,7 +94,9 @@ public abstract class ImplicitOutputsFunction {
           attrValues.put(attrName, value == null ? Runtime.NONE : value);
         }
       }
-      ClassObject attrs = new SkylarkClassObject(attrValues, "Attribute '%s' either doesn't exist "
+      ClassObject attrs = SkylarkClassObjectConstructor.STRUCT.create(
+          attrValues,
+          "Attribute '%s' either doesn't exist "
           + "or uses a select() (i.e. could have multiple values)");
       try {
         ImmutableMap.Builder<String, String> builder = ImmutableMap.builder();
diff --git a/src/main/java/com/google/devtools/build/lib/packages/PackageFactory.java b/src/main/java/com/google/devtools/build/lib/packages/PackageFactory.java
index 7b8e57f500..df26e80295 100644
--- a/src/main/java/com/google/devtools/build/lib/packages/PackageFactory.java
+++ b/src/main/java/com/google/devtools/build/lib/packages/PackageFactory.java
@@ -1526,7 +1526,8 @@ public final class PackageFactory {
         builder.put(function.getName(), function);
       }
     }
-    return new SkylarkClassObject(builder.build(), "no native function or rule '%s'");
+    return SkylarkClassObjectConstructor.STRUCT.create(
+        builder.build(), "no native function or rule '%s'");
   }
 
   private void buildPkgEnv(Environment pkgEnv, PackageContext context, RuleFactory ruleFactory) {
diff --git a/src/main/java/com/google/devtools/build/lib/packages/SkylarkClassObject.java b/src/main/java/com/google/devtools/build/lib/packages/SkylarkClassObject.java
index d28146a526..f5190965b7 100644
--- a/src/main/java/com/google/devtools/build/lib/packages/SkylarkClassObject.java
+++ b/src/main/java/com/google/devtools/build/lib/packages/SkylarkClassObject.java
@@ -46,6 +46,7 @@ public class SkylarkClassObject implements ClassObject, SkylarkValue, Concatable
   /** Error message to use when errorMessage argument is null. */
   private static final String DEFAULT_ERROR_MESSAGE = "'struct' object has no attribute '%s'";
 
+  private final SkylarkClassObjectConstructor constructor;
   private final ImmutableMap<String, Object> values;
   private final Location creationLoc;
   private final String errorMessage;
@@ -54,7 +55,9 @@ public class SkylarkClassObject implements ClassObject, SkylarkValue, Concatable
    * Primarily for testing purposes where no location is available and the default
    * errorMessage suffices.
    */
-  public SkylarkClassObject(Map<String, Object> values) {
+  public SkylarkClassObject(SkylarkClassObjectConstructor constructor,
+      Map<String, Object> values) {
+    this.constructor = constructor;
     this.values = copyValues(values);
     this.creationLoc = null;
     this.errorMessage = DEFAULT_ERROR_MESSAGE;
@@ -64,13 +67,17 @@ public class SkylarkClassObject implements ClassObject, SkylarkValue, Concatable
    * Creates a built-in struct (i.e. without creation loc). The errorMessage has to have
    * exactly one '%s' parameter to substitute the struct field name.
    */
-  public SkylarkClassObject(Map<String, Object> values, String errorMessage) {
+  public SkylarkClassObject(SkylarkClassObjectConstructor constructor,
+      Map<String, Object> values, String errorMessage) {
+    this.constructor = constructor;
     this.values = copyValues(values);
     this.creationLoc = null;
     this.errorMessage = Preconditions.checkNotNull(errorMessage);
   }
 
-  public SkylarkClassObject(Map<String, Object> values, Location creationLoc) {
+  public SkylarkClassObject(SkylarkClassObjectConstructor constructor,
+      Map<String, Object> values, Location creationLoc) {
+    this.constructor = constructor;
     this.values = copyValues(values);
     this.creationLoc = Preconditions.checkNotNull(creationLoc);
     this.errorMessage = DEFAULT_ERROR_MESSAGE;
@@ -133,8 +140,12 @@ public class SkylarkClassObject implements ClassObject, SkylarkValue, Concatable
         throw new EvalException(loc, "Cannot concat structs with common field(s): "
             + Joiner.on(",").join(commonFields));
       }
-      return new SkylarkClassObject(ImmutableMap.<String, Object>builder()
-          .putAll(lval.values).putAll(rval.values).build(), loc);
+      return new SkylarkClassObject(lval.constructor,
+          ImmutableMap.<String, Object>builder()
+              .putAll(lval.values)
+              .putAll(rval.values)
+              .build(),
+          loc);
     }
   }
 
@@ -163,7 +174,8 @@ public class SkylarkClassObject implements ClassObject, SkylarkValue, Concatable
   @Override
   public void write(Appendable buffer, char quotationMark) {
     boolean first = true;
-    Printer.append(buffer, "struct(");
+    Printer.append(buffer, constructor.getName());
+    Printer.append(buffer, "(");
     // Sort by key to ensure deterministic output.
     for (String key : Ordering.natural().sortedCopy(values.keySet())) {
       if (!first) {
diff --git a/src/main/java/com/google/devtools/build/lib/packages/SkylarkClassObjectConstructor.java b/src/main/java/com/google/devtools/build/lib/packages/SkylarkClassObjectConstructor.java
new file mode 100644
index 0000000000..b451efe583
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/packages/SkylarkClassObjectConstructor.java
@@ -0,0 +1,76 @@
+// Copyright 2016 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.packages;
+
+import com.google.devtools.build.lib.events.Location;
+import com.google.devtools.build.lib.syntax.BaseFunction;
+import com.google.devtools.build.lib.syntax.Environment;
+import com.google.devtools.build.lib.syntax.EvalException;
+import com.google.devtools.build.lib.syntax.FuncallExpression;
+import com.google.devtools.build.lib.syntax.FunctionSignature;
+import com.google.devtools.build.lib.syntax.FunctionSignature.WithValues;
+import com.google.devtools.build.lib.syntax.SkylarkType;
+import com.google.devtools.build.lib.syntax.Type.ConversionException;
+import java.util.Map;
+import javax.annotation.Nullable;
+
+/**
+ * A constructor for {@link SkylarkClassObject}.
+ */
+public final class SkylarkClassObjectConstructor extends BaseFunction {
+  /**
+   * "struct" function.
+   */
+  public static final SkylarkClassObjectConstructor STRUCT =
+      new SkylarkClassObjectConstructor("struct");
+
+
+  private static final FunctionSignature.WithValues<Object, SkylarkType> SIGNATURE =
+      WithValues.create(FunctionSignature.KWARGS);
+
+  public SkylarkClassObjectConstructor(String name, Location location) {
+    super(name, SIGNATURE, location);
+  }
+
+  public SkylarkClassObjectConstructor(String name) {
+    this(name, Location.BUILTIN);
+  }
+
+  @Override
+  protected Object call(Object[] args, @Nullable FuncallExpression ast, @Nullable Environment env)
+      throws EvalException, ConversionException, InterruptedException {
+    @SuppressWarnings("unchecked")
+    Map<String, Object> kwargs = (Map<String, Object>) args[0];
+    return new SkylarkClassObject(this, kwargs, ast != null ? ast.getLocation() : Location.BUILTIN);
+  }
+
+  /**
+   * Creates a built-in class object (i.e. without creation loc). The errorMessage has to have
+   * exactly one '%s' parameter to substitute the field name.
+   */
+  public SkylarkClassObject create(Map<String, Object> values, String message) {
+    return new SkylarkClassObject(this, values, message);
+  }
+
+  @Override
+  public int hashCode() {
+    return System.identityHashCode(this);
+  }
+
+  @Override
+  public boolean equals(@Nullable Object other) {
+    return other == this;
+  }
+}
diff --git a/src/main/java/com/google/devtools/build/lib/packages/WorkspaceFactory.java b/src/main/java/com/google/devtools/build/lib/packages/WorkspaceFactory.java
index 54b393a7dc..12c5caa66b 100644
--- a/src/main/java/com/google/devtools/build/lib/packages/WorkspaceFactory.java
+++ b/src/main/java/com/google/devtools/build/lib/packages/WorkspaceFactory.java
@@ -454,7 +454,8 @@ public class WorkspaceFactory {
     }
 
     builder.put("bazel_version", version);
-    return new SkylarkClassObject(builder.build(), "no native function or rule '%s'");
+    return SkylarkClassObjectConstructor.STRUCT.create(
+        builder.build(), "no native function or rule '%s'");
   }
 
   public static ClassObject newNativeModule(RuleClassProvider ruleClassProvider, String version) {
diff --git a/src/main/java/com/google/devtools/build/lib/rules/SkylarkRuleClassFunctions.java b/src/main/java/com/google/devtools/build/lib/rules/SkylarkRuleClassFunctions.java
index cb22b50ba3..9433807410 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/SkylarkRuleClassFunctions.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/SkylarkRuleClassFunctions.java
@@ -63,6 +63,7 @@ import com.google.devtools.build.lib.packages.RuleFactory.BuildLangTypedAttribut
 import com.google.devtools.build.lib.packages.RuleFactory.InvalidRuleException;
 import com.google.devtools.build.lib.packages.SkylarkAspect;
 import com.google.devtools.build.lib.packages.SkylarkClassObject;
+import com.google.devtools.build.lib.packages.SkylarkClassObjectConstructor;
 import com.google.devtools.build.lib.packages.TargetUtils;
 import com.google.devtools.build.lib.packages.TestSize;
 import com.google.devtools.build.lib.rules.SkylarkAttr.Descriptor;
@@ -199,13 +200,8 @@ public class SkylarkRuleClassFunctions {
           + "return s.x + getattr(s, \"y\")  # returns 5</pre>",
       extraKeywords = @Param(name = "kwargs", doc = "the struct attributes"),
       useLocation = true)
-  private static final BuiltinFunction struct = new BuiltinFunction("struct") {
-    @SuppressWarnings("unchecked")
-    public SkylarkClassObject invoke(SkylarkDict<String, Object> kwargs, Location loc)
-        throws EvalException {
-      return new SkylarkClassObject(kwargs, loc);
-    }
-  };
+  private static final SkylarkClassObjectConstructor struct =
+      SkylarkClassObjectConstructor.STRUCT;
 
 
   // TODO(bazel-team): implement attribute copy and other rule properties
diff --git a/src/main/java/com/google/devtools/build/lib/rules/SkylarkRuleContext.java b/src/main/java/com/google/devtools/build/lib/rules/SkylarkRuleContext.java
index 248bbfd33b..b95554cfe8 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/SkylarkRuleContext.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/SkylarkRuleContext.java
@@ -43,6 +43,7 @@ import com.google.devtools.build.lib.packages.OutputFile;
 import com.google.devtools.build.lib.packages.Package;
 import com.google.devtools.build.lib.packages.RawAttributeMapper;
 import com.google.devtools.build.lib.packages.SkylarkClassObject;
+import com.google.devtools.build.lib.packages.SkylarkClassObjectConstructor;
 import com.google.devtools.build.lib.shell.ShellUtils;
 import com.google.devtools.build.lib.shell.ShellUtils.TokenizationException;
 import com.google.devtools.build.lib.skylarkinterface.SkylarkCallable;
@@ -219,7 +220,7 @@ public final class SkylarkRuleContext {
 
       this.artifactsLabelMap = artifactLabelMapBuilder.build();
       this.outputsObject =
-          new SkylarkClassObject(
+          SkylarkClassObjectConstructor.STRUCT.create(
               outputsBuilder,
               "No attribute '%s' in outputs. Make sure you declared a rule output with this name.");
 
@@ -351,21 +352,21 @@ public final class SkylarkRuleContext {
         ImmutableMap<Artifact, FilesToRunProvider> executableRunfilesMap) {
       this.ruleClassName = ruleClassName;
       attrObject =
-          new SkylarkClassObject(
+          SkylarkClassObjectConstructor.STRUCT.create(
               attrs,
               "No attribute '%s' in attr. Make sure you declared a rule attribute with this name.");
       executableObject =
-          new SkylarkClassObject(
+          SkylarkClassObjectConstructor.STRUCT.create(
               executables,
               "No attribute '%s' in executable. Make sure there is a label type attribute marked "
                   + "as 'executable' with this name");
       fileObject =
-          new SkylarkClassObject(
+          SkylarkClassObjectConstructor.STRUCT.create(
               singleFiles,
               "No attribute '%s' in file. Make sure there is a label type attribute marked "
                   + "as 'single_file' with this name");
       filesObject =
-          new SkylarkClassObject(
+          SkylarkClassObjectConstructor.STRUCT.create(
               files,
               "No attribute '%s' in files. Make sure there is a label or label_list type attribute "
                   + "with this name");
diff --git a/src/main/java/com/google/devtools/build/lib/rules/objc/ObjcProvider.java b/src/main/java/com/google/devtools/build/lib/rules/objc/ObjcProvider.java
index 8249fd121a..4051f81ff5 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/objc/ObjcProvider.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/objc/ObjcProvider.java
@@ -27,6 +27,7 @@ import com.google.devtools.build.lib.collect.nestedset.NestedSetBuilder;
 import com.google.devtools.build.lib.collect.nestedset.Order;
 import com.google.devtools.build.lib.concurrent.ThreadSafety.Immutable;
 import com.google.devtools.build.lib.packages.SkylarkClassObject;
+import com.google.devtools.build.lib.packages.SkylarkClassObjectConstructor;
 import com.google.devtools.build.lib.rules.cpp.CppModuleMap;
 import com.google.devtools.build.lib.rules.cpp.LinkerInputs;
 import com.google.devtools.build.lib.skylarkinterface.SkylarkModule;
@@ -416,12 +417,15 @@ public final class ObjcProvider extends SkylarkClassObject implements Transitive
   // Items which should be passed to strictly direct dependers, but not transitive dependers.
   private final ImmutableMap<Key<?>, NestedSet<?>> strictDependencyItems;
 
+  private static final SkylarkClassObjectConstructor OBJC_PROVIDER =
+      new SkylarkClassObjectConstructor("objc_provider");
+
   private ObjcProvider(
       ImmutableMap<Key<?>, NestedSet<?>> items,
       ImmutableMap<Key<?>, NestedSet<?>> nonPropagatedItems,
       ImmutableMap<Key<?>, NestedSet<?>> strictDependencyItems,
       ImmutableMap<String, Object> skylarkFields) {
-    super(skylarkFields, "ObjcProvider field %s could not be instantiated");
+    super(OBJC_PROVIDER, skylarkFields, "ObjcProvider field %s could not be instantiated");
     this.items = Preconditions.checkNotNull(items);
     this.nonPropagatedItems = Preconditions.checkNotNull(nonPropagatedItems);
     this.strictDependencyItems = Preconditions.checkNotNull(strictDependencyItems);
diff --git a/src/main/java/com/google/devtools/build/lib/rules/objc/ObjcProviderSkylarkConverters.java b/src/main/java/com/google/devtools/build/lib/rules/objc/ObjcProviderSkylarkConverters.java
index 727891e820..caf0021c8c 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/objc/ObjcProviderSkylarkConverters.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/objc/ObjcProviderSkylarkConverters.java
@@ -25,6 +25,7 @@ import com.google.devtools.build.lib.actions.Artifact;
 import com.google.devtools.build.lib.collect.nestedset.NestedSet;
 import com.google.devtools.build.lib.collect.nestedset.NestedSetBuilder;
 import com.google.devtools.build.lib.packages.SkylarkClassObject;
+import com.google.devtools.build.lib.packages.SkylarkClassObjectConstructor;
 import com.google.devtools.build.lib.rules.objc.ObjcProvider.Key;
 import com.google.devtools.build.lib.syntax.EvalException;
 import com.google.devtools.build.lib.syntax.EvalUtils;
@@ -133,7 +134,7 @@ public class ObjcProviderSkylarkConverters {
     public Object valueForSkylark(Key<?> javaKey, NestedSet<?> javaValue) {
       NestedSetBuilder<SkylarkClassObject> result = NestedSetBuilder.stableOrder();
       for (BundleableFile bundleableFile : (Iterable<BundleableFile>) javaValue) {
-        result.add(new SkylarkClassObject(
+        result.add(SkylarkClassObjectConstructor.STRUCT.create(
             ImmutableMap.<String, Object>of(
                 BUNDLED_FIELD, bundleableFile.getBundled(),
                 BUNDLE_PATH_FIELD, bundleableFile.getBundlePath()
diff --git a/src/main/java/com/google/devtools/build/lib/rules/python/PyCommon.java b/src/main/java/com/google/devtools/build/lib/rules/python/PyCommon.java
index 842e9b7d7b..d03f380e9d 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/python/PyCommon.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/python/PyCommon.java
@@ -44,6 +44,7 @@ import com.google.devtools.build.lib.concurrent.ThreadSafety.Immutable;
 import com.google.devtools.build.lib.packages.BuildType;
 import com.google.devtools.build.lib.packages.Rule;
 import com.google.devtools.build.lib.packages.SkylarkClassObject;
+import com.google.devtools.build.lib.packages.SkylarkClassObjectConstructor;
 import com.google.devtools.build.lib.rules.cpp.CppFileTypes;
 import com.google.devtools.build.lib.rules.test.InstrumentedFilesCollector;
 import com.google.devtools.build.lib.rules.test.InstrumentedFilesCollector.LocalMetadataCollector;
@@ -161,7 +162,7 @@ public final class PyCommon {
    */
   public static SkylarkClassObject createSourceProvider(
       NestedSet<Artifact> transitivePythonSources, boolean isUsingSharedLibrary) {
-    return new SkylarkClassObject(
+    return SkylarkClassObjectConstructor.STRUCT.create(
         ImmutableMap.<String, Object>of(
             TRANSITIVE_PYTHON_SRCS,
             SkylarkNestedSet.of(Artifact.class, transitivePythonSources),