Expose platform-related providers to Skylark.

Change-Id: I7615d3e6e33e0c48f18b2506a135f45ce3705a38
PiperOrigin-RevId: 152256914

13 files changed, 382 insertions, 148 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/rules/platform/BUILD b/src/main/java/com/google/devtools/build/lib/rules/platform/BUILD
index d8c6ca9b79..5808889ba9 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/platform/BUILD
+++ b/src/main/java/com/google/devtools/build/lib/rules/platform/BUILD
@@ -13,6 +13,7 @@ java_library(
     deps = [
         "//src/main/java/com/google/devtools/build/lib:build-base",
         "//src/main/java/com/google/devtools/build/lib:packages",
+        "//src/main/java/com/google/devtools/build/lib:skylarkinterface",
         "//third_party:auto_value",
         "//third_party:guava",
     ],
diff --git a/src/main/java/com/google/devtools/build/lib/rules/platform/ConstraintSetting.java b/src/main/java/com/google/devtools/build/lib/rules/platform/ConstraintSetting.java
index 03e924f1db..653ea2fe4f 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/platform/ConstraintSetting.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/platform/ConstraintSetting.java
@@ -20,7 +20,6 @@ import com.google.devtools.build.lib.analysis.FilesToRunProvider;
 import com.google.devtools.build.lib.analysis.RuleConfiguredTargetBuilder;
 import com.google.devtools.build.lib.analysis.RuleContext;
 import com.google.devtools.build.lib.analysis.RunfilesProvider;
-import com.google.devtools.build.lib.packages.RuleClass.ConfiguredTargetFactory.RuleErrorException;
 import com.google.devtools.build.lib.rules.RuleConfiguredTargetFactory;
 
 /**
@@ -37,9 +36,7 @@ public class ConstraintSetting implements RuleConfiguredTargetFactory {
         .addProvider(RunfilesProvider.class, RunfilesProvider.EMPTY)
         .addProvider(FileProvider.class, FileProvider.EMPTY)
         .addProvider(FilesToRunProvider.class, FilesToRunProvider.EMPTY)
-        .addProvider(
-            ConstraintSettingProvider.class,
-            ConstraintSettingProvider.create(ruleContext.getLabel()))
+        .addNativeDeclaredProvider(ConstraintSettingInfo.create(ruleContext.getLabel()))
         .build();
   }
 }
diff --git a/src/main/java/com/google/devtools/build/lib/rules/platform/ConstraintSettingInfo.java b/src/main/java/com/google/devtools/build/lib/rules/platform/ConstraintSettingInfo.java
new file mode 100644
index 0000000000..e921050eba
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/rules/platform/ConstraintSettingInfo.java
@@ -0,0 +1,92 @@
+// Copyright 2017 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.rules.platform;
+
+import com.google.auto.value.AutoValue;
+import com.google.common.base.Function;
+import com.google.common.collect.ImmutableMap;
+import com.google.common.collect.Iterables;
+import com.google.devtools.build.lib.analysis.TransitiveInfoCollection;
+import com.google.devtools.build.lib.cmdline.Label;
+import com.google.devtools.build.lib.concurrent.ThreadSafety.Immutable;
+import com.google.devtools.build.lib.packages.ClassObjectConstructor;
+import com.google.devtools.build.lib.packages.NativeClassObjectConstructor;
+import com.google.devtools.build.lib.packages.SkylarkClassObject;
+import com.google.devtools.build.lib.packages.SkylarkProviderIdentifier;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkCallable;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkModule;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkModuleCategory;
+import com.google.devtools.build.lib.util.Preconditions;
+
+/** Provider for a platform constraint setting that is available to be fulfilled. */
+@SkylarkModule(
+  name = "ConstraintSettingInfo",
+  doc = "A specific constraint setting that may be used to define a platform.",
+  category = SkylarkModuleCategory.PROVIDER
+)
+@AutoValue
+@Immutable
+public abstract class ConstraintSettingInfo extends SkylarkClassObject {
+
+  /** Name used in Skylark for accessing this provider. */
+  static final String SKYLARK_NAME = "ConstraintSettingInfo";
+
+  /** Skylark constructor and identifier for this provider. */
+  static final ClassObjectConstructor SKYLARK_CONSTRUCTOR =
+      new NativeClassObjectConstructor(SKYLARK_NAME) {};
+
+  /** Identifier used to retrieve this provider from rules which export it. */
+  public static final SkylarkProviderIdentifier SKYLARK_IDENTIFIER =
+      SkylarkProviderIdentifier.forKey(SKYLARK_CONSTRUCTOR.getKey());
+
+  ConstraintSettingInfo() {
+    super(SKYLARK_CONSTRUCTOR, ImmutableMap.<String, Object>of());
+  }
+
+  @SkylarkCallable(
+    name = "label",
+    doc = "The label used to identify this constraint setting.",
+    structField = true
+  )
+  public abstract Label label();
+
+  /** Retrieves and casts the provider from the given target. */
+  public static ConstraintSettingInfo fromTarget(TransitiveInfoCollection target) {
+    Object provider = target.get(SKYLARK_IDENTIFIER);
+    if (provider == null) {
+      return null;
+    }
+    Preconditions.checkState(provider instanceof ConstraintSettingInfo);
+    return (ConstraintSettingInfo) provider;
+  }
+
+  /** Retrieves and casts the providers from the given targets. */
+  public static Iterable<ConstraintSettingInfo> fromTargets(
+      Iterable<? extends TransitiveInfoCollection> targets) {
+    return Iterables.transform(
+        targets,
+        new Function<TransitiveInfoCollection, ConstraintSettingInfo>() {
+          @Override
+          public ConstraintSettingInfo apply(TransitiveInfoCollection target) {
+            return fromTarget(target);
+          }
+        });
+  }
+
+  /** Returns a new {@link ConstraintSettingInfo} with the given data. */
+  public static ConstraintSettingInfo create(Label constraintSetting) {
+    return new AutoValue_ConstraintSettingInfo(constraintSetting);
+  }
+}
diff --git a/src/main/java/com/google/devtools/build/lib/rules/platform/ConstraintSettingProvider.java b/src/main/java/com/google/devtools/build/lib/rules/platform/ConstraintSettingProvider.java
deleted file mode 100644
index 9459a07e91..0000000000
--- a/src/main/java/com/google/devtools/build/lib/rules/platform/ConstraintSettingProvider.java
+++ /dev/null
@@ -1,31 +0,0 @@
-// Copyright 2017 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.rules.platform;
-
-import com.google.auto.value.AutoValue;
-import com.google.devtools.build.lib.analysis.TransitiveInfoProvider;
-import com.google.devtools.build.lib.cmdline.Label;
-import com.google.devtools.build.lib.concurrent.ThreadSafety.Immutable;
-
-/** Provider for a platform constraint setting that is available to be fulfilled. */
-@AutoValue
-@Immutable
-public abstract class ConstraintSettingProvider implements TransitiveInfoProvider {
-  public abstract Label constraintSetting();
-
-  public static ConstraintSettingProvider create(Label constraintSetting) {
-    return new AutoValue_ConstraintSettingProvider(constraintSetting);
-  }
-}
diff --git a/src/main/java/com/google/devtools/build/lib/rules/platform/ConstraintValue.java b/src/main/java/com/google/devtools/build/lib/rules/platform/ConstraintValue.java
index c232c92212..e1aa6d933b 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/platform/ConstraintValue.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/platform/ConstraintValue.java
@@ -30,19 +30,16 @@ public class ConstraintValue implements RuleConfiguredTargetFactory {
   public ConfiguredTarget create(RuleContext ruleContext)
       throws InterruptedException, RuleErrorException {
 
-    ConstraintSettingProvider constraint =
-        ruleContext.getPrerequisite(
-            ConstraintValueRule.CONSTRAINT_SETTING_ATTR,
-            Mode.DONT_CHECK,
-            ConstraintSettingProvider.class);
+    ConstraintSettingInfo constraint =
+        ConstraintSettingInfo.fromTarget(
+            ruleContext.getPrerequisite(
+                ConstraintValueRule.CONSTRAINT_SETTING_ATTR, Mode.DONT_CHECK));
 
     return new RuleConfiguredTargetBuilder(ruleContext)
         .addProvider(RunfilesProvider.class, RunfilesProvider.EMPTY)
         .addProvider(FileProvider.class, FileProvider.EMPTY)
         .addProvider(FilesToRunProvider.class, FilesToRunProvider.EMPTY)
-        .addProvider(
-            ConstraintValueProvider.class,
-            ConstraintValueProvider.create(constraint, ruleContext.getLabel()))
+        .addNativeDeclaredProvider(ConstraintValueInfo.create(constraint, ruleContext.getLabel()))
         .build();
   }
 }
diff --git a/src/main/java/com/google/devtools/build/lib/rules/platform/ConstraintValueInfo.java b/src/main/java/com/google/devtools/build/lib/rules/platform/ConstraintValueInfo.java
new file mode 100644
index 0000000000..f2cecb277e
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/rules/platform/ConstraintValueInfo.java
@@ -0,0 +1,99 @@
+// Copyright 2017 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.rules.platform;
+
+import com.google.auto.value.AutoValue;
+import com.google.common.base.Function;
+import com.google.common.collect.ImmutableMap;
+import com.google.common.collect.Iterables;
+import com.google.devtools.build.lib.analysis.TransitiveInfoCollection;
+import com.google.devtools.build.lib.cmdline.Label;
+import com.google.devtools.build.lib.concurrent.ThreadSafety.Immutable;
+import com.google.devtools.build.lib.packages.ClassObjectConstructor;
+import com.google.devtools.build.lib.packages.NativeClassObjectConstructor;
+import com.google.devtools.build.lib.packages.SkylarkClassObject;
+import com.google.devtools.build.lib.packages.SkylarkProviderIdentifier;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkCallable;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkModule;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkModuleCategory;
+import com.google.devtools.build.lib.util.Preconditions;
+
+/** Provider for a platform constraint value that fulfills a {@link ConstraintSettingInfo}. */
+@SkylarkModule(
+  name = "ConstraintValueProvider",
+  doc = "A value for a constraint setting that can be used to define a platform.",
+  category = SkylarkModuleCategory.PROVIDER
+)
+@AutoValue
+@Immutable
+public abstract class ConstraintValueInfo extends SkylarkClassObject {
+
+  /** Name used in Skylark for accessing this provider. */
+  static final String SKYLARK_NAME = "ConstraintValueInfo";
+
+  /** Skylark constructor and identifier for this provider. */
+  static final ClassObjectConstructor SKYLARK_CONSTRUCTOR =
+      new NativeClassObjectConstructor(SKYLARK_NAME) {};
+
+  /** Identifier used to retrieve this provider from rules which export it. */
+  public static final SkylarkProviderIdentifier SKYLARK_IDENTIFIER =
+      SkylarkProviderIdentifier.forKey(SKYLARK_CONSTRUCTOR.getKey());
+
+  ConstraintValueInfo() {
+    super(SKYLARK_CONSTRUCTOR, ImmutableMap.<String, Object>of());
+  }
+
+  @SkylarkCallable(
+    name = "constraint",
+    doc = "The constraint setting that this value fulfills.",
+    structField = true
+  )
+  public abstract ConstraintSettingInfo constraint();
+
+  @SkylarkCallable(
+    name = "label",
+    doc = "The label used to identify this constraint value.",
+    structField = true
+  )
+  public abstract Label label();
+
+  /** Retrieves and casts the provider from the given target. */
+  public static ConstraintValueInfo fromTarget(TransitiveInfoCollection target) {
+    Object provider = target.get(SKYLARK_IDENTIFIER);
+    if (provider == null) {
+      return null;
+    }
+    Preconditions.checkState(provider instanceof ConstraintValueInfo);
+    return (ConstraintValueInfo) provider;
+  }
+
+  /** Retrieves and casts the providers from the given targets. */
+  public static Iterable<ConstraintValueInfo> fromTargets(
+      Iterable<? extends TransitiveInfoCollection> targets) {
+    return Iterables.transform(
+        targets,
+        new Function<TransitiveInfoCollection, ConstraintValueInfo>() {
+          @Override
+          public ConstraintValueInfo apply(TransitiveInfoCollection target) {
+            return fromTarget(target);
+          }
+        });
+  }
+
+  /** Returns a new {@link ConstraintValueInfo} with the given data. */
+  public static ConstraintValueInfo create(ConstraintSettingInfo constraint, Label value) {
+    return new AutoValue_ConstraintValueInfo(constraint, value);
+  }
+}
diff --git a/src/main/java/com/google/devtools/build/lib/rules/platform/ConstraintValueProvider.java b/src/main/java/com/google/devtools/build/lib/rules/platform/ConstraintValueProvider.java
deleted file mode 100644
index 1ade6ddded..0000000000
--- a/src/main/java/com/google/devtools/build/lib/rules/platform/ConstraintValueProvider.java
+++ /dev/null
@@ -1,33 +0,0 @@
-// Copyright 2017 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.rules.platform;
-
-import com.google.auto.value.AutoValue;
-import com.google.devtools.build.lib.analysis.TransitiveInfoProvider;
-import com.google.devtools.build.lib.cmdline.Label;
-import com.google.devtools.build.lib.concurrent.ThreadSafety.Immutable;
-
-/** Provider for a platform constraint value that fulfills a {@link ConstraintSettingProvider}. */
-@AutoValue
-@Immutable
-public abstract class ConstraintValueProvider implements TransitiveInfoProvider {
-  public abstract ConstraintSettingProvider constraint();
-
-  public abstract Label value();
-
-  public static ConstraintValueProvider create(ConstraintSettingProvider constraint, Label value) {
-    return new AutoValue_ConstraintValueProvider(constraint, value);
-  }
-}
diff --git a/src/main/java/com/google/devtools/build/lib/rules/platform/ConstraintValueRule.java b/src/main/java/com/google/devtools/build/lib/rules/platform/ConstraintValueRule.java
index 55e85b1048..5593862754 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/platform/ConstraintValueRule.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/platform/ConstraintValueRule.java
@@ -20,7 +20,6 @@ import com.google.common.collect.ImmutableList;
 import com.google.devtools.build.lib.analysis.BaseRuleClasses;
 import com.google.devtools.build.lib.analysis.RuleDefinition;
 import com.google.devtools.build.lib.analysis.RuleDefinitionEnvironment;
-import com.google.devtools.build.lib.analysis.TransitiveInfoProvider;
 import com.google.devtools.build.lib.packages.BuildType;
 import com.google.devtools.build.lib.packages.RuleClass;
 import com.google.devtools.build.lib.syntax.Type;
@@ -48,9 +47,7 @@ public class ConstraintValueRule implements RuleDefinition {
                 .mandatory()
                 .allowedRuleClasses(ConstraintSettingRule.RULE_NAME)
                 .allowedFileTypes(FileTypeSet.NO_FILE)
-                .mandatoryNativeProviders(
-                    ImmutableList.<Class<? extends TransitiveInfoProvider>>of(
-                        ConstraintSettingProvider.class)))
+                .mandatoryProviders(ImmutableList.of(ConstraintSettingInfo.SKYLARK_IDENTIFIER)))
         .removeAttribute("deps")
         .removeAttribute("data")
         .exemptFromConstraintChecking("this rule *defines* a constraint")
diff --git a/src/main/java/com/google/devtools/build/lib/rules/platform/Platform.java b/src/main/java/com/google/devtools/build/lib/rules/platform/Platform.java
index f5d7e88832..b029240e26 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/platform/Platform.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/platform/Platform.java
@@ -35,20 +35,20 @@ public class Platform implements RuleConfiguredTargetFactory {
   public ConfiguredTarget create(RuleContext ruleContext)
       throws InterruptedException, RuleErrorException {
 
-    Iterable<ConstraintValueProvider> constraintValues =
-        ruleContext.getPrerequisites(
-            PlatformRule.CONSTRAINT_VALUES_ATTR, Mode.DONT_CHECK, ConstraintValueProvider.class);
+    Iterable<ConstraintValueInfo> constraintValues =
+        ConstraintValueInfo.fromTargets(
+            ruleContext.getPrerequisites(PlatformRule.CONSTRAINT_VALUES_ATTR, Mode.DONT_CHECK));
 
     // Verify the constraints - no two values for the same setting, and construct the map.
-    ImmutableMap<ConstraintSettingProvider, ConstraintValueProvider> constraints =
+    ImmutableMap<ConstraintSettingInfo, ConstraintValueInfo> constraints =
         validateConstraints(ruleContext, constraintValues);
     if (constraints == null) {
       // An error occurred, return null.
       return null;
     }
 
-    PlatformProvider.Builder platformProviderBuilder = PlatformProvider.builder();
-    platformProviderBuilder.constraints(constraints);
+    PlatformInfo.Builder platformProviderBuilder = PlatformInfo.builder();
+    platformProviderBuilder.constraints(constraints.values());
 
     Map<String, String> remoteExecutionProperties =
         ruleContext.attributes().get(PlatformRule.REMOTE_EXECUTION_PROPS_ATTR, Type.STRING_DICT);
@@ -58,37 +58,36 @@ public class Platform implements RuleConfiguredTargetFactory {
         .addProvider(RunfilesProvider.class, RunfilesProvider.EMPTY)
         .addProvider(FileProvider.class, FileProvider.EMPTY)
         .addProvider(FilesToRunProvider.class, FilesToRunProvider.EMPTY)
-        .addProvider(PlatformProvider.class, platformProviderBuilder.build())
+        .addNativeDeclaredProvider(platformProviderBuilder.build())
         .build();
   }
 
-  private ImmutableMap<ConstraintSettingProvider, ConstraintValueProvider> validateConstraints(
-      RuleContext ruleContext, Iterable<ConstraintValueProvider> constraintValues) {
-    Multimap<ConstraintSettingProvider, ConstraintValueProvider> constraints =
-        ArrayListMultimap.create();
+  private ImmutableMap<ConstraintSettingInfo, ConstraintValueInfo> validateConstraints(
+      RuleContext ruleContext, Iterable<ConstraintValueInfo> constraintValues) {
+    Multimap<ConstraintSettingInfo, ConstraintValueInfo> constraints = ArrayListMultimap.create();
 
-    for (ConstraintValueProvider constraintValue : constraintValues) {
+    for (ConstraintValueInfo constraintValue : constraintValues) {
       constraints.put(constraintValue.constraint(), constraintValue);
     }
 
     // Are there any settings with more than one value?
     boolean foundError = false;
-    for (ConstraintSettingProvider constraintSetting : constraints.keySet()) {
+    for (ConstraintSettingInfo constraintSetting : constraints.keySet()) {
       if (constraints.get(constraintSetting).size() > 1) {
         foundError = true;
         // error
         StringBuilder constraintValuesDescription = new StringBuilder();
-        for (ConstraintValueProvider constraintValue : constraints.get(constraintSetting)) {
+        for (ConstraintValueInfo constraintValue : constraints.get(constraintSetting)) {
           if (constraintValuesDescription.length() > 0) {
             constraintValuesDescription.append(", ");
           }
-          constraintValuesDescription.append(constraintValue.value());
+          constraintValuesDescription.append(constraintValue.label());
         }
         ruleContext.attributeError(
             PlatformRule.CONSTRAINT_VALUES_ATTR,
             String.format(
                 "Duplicate constraint_values for constraint_setting %s: %s",
-                constraintSetting.constraintSetting(), constraintValuesDescription.toString()));
+                constraintSetting.label(), constraintValuesDescription.toString()));
       }
     }
 
@@ -97,10 +96,10 @@ public class Platform implements RuleConfiguredTargetFactory {
     }
 
     // Convert to a flat map.
-    ImmutableMap.Builder<ConstraintSettingProvider, ConstraintValueProvider> builder =
+    ImmutableMap.Builder<ConstraintSettingInfo, ConstraintValueInfo> builder =
         new ImmutableMap.Builder<>();
-    for (ConstraintSettingProvider constraintSetting : constraints.keySet()) {
-      ConstraintValueProvider constraintValue =
+    for (ConstraintSettingInfo constraintSetting : constraints.keySet()) {
+      ConstraintValueInfo constraintValue =
           Iterables.getOnlyElement(constraints.get(constraintSetting));
       builder.put(constraintSetting, constraintValue);
     }
diff --git a/src/main/java/com/google/devtools/build/lib/rules/platform/PlatformCommon.java b/src/main/java/com/google/devtools/build/lib/rules/platform/PlatformCommon.java
new file mode 100644
index 0000000000..ff4b0c3dfe
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/rules/platform/PlatformCommon.java
@@ -0,0 +1,54 @@
+// Copyright 2017 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.rules.platform;
+
+import com.google.devtools.build.lib.packages.ClassObjectConstructor;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkCallable;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkModule;
+
+/** Skylark namespace used to interact with Blaze's platform APIs. */
+@SkylarkModule(
+  name = "platform_common",
+  doc = "Functions for Skylark to interact with Blaze's platform APIs."
+)
+public class PlatformCommon {
+
+  @SkylarkCallable(
+    name = PlatformInfo.SKYLARK_NAME,
+    doc = "The key used to retrieve the provider containing platform_info's value.",
+    structField = true
+  )
+  public ClassObjectConstructor getPlatformInfoConstructor() {
+    return PlatformInfo.SKYLARK_CONSTRUCTOR;
+  }
+
+  @SkylarkCallable(
+    name = ConstraintSettingInfo.SKYLARK_NAME,
+    doc = "The key used to retrieve the provider containing constraint_setting_info's value.",
+    structField = true
+  )
+  public ClassObjectConstructor getConstraintSettingInfoConstructor() {
+    return ConstraintSettingInfo.SKYLARK_CONSTRUCTOR;
+  }
+
+  @SkylarkCallable(
+    name = ConstraintValueInfo.SKYLARK_NAME,
+    doc = "The key used to retrieve the provider containing constraint_value_info's value.",
+    structField = true
+  )
+  public ClassObjectConstructor getConstraintValueInfoConstructor() {
+    return ConstraintValueInfo.SKYLARK_CONSTRUCTOR;
+  }
+}
diff --git a/src/main/java/com/google/devtools/build/lib/rules/platform/PlatformInfo.java b/src/main/java/com/google/devtools/build/lib/rules/platform/PlatformInfo.java
new file mode 100644
index 0000000000..7fe10724da
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/rules/platform/PlatformInfo.java
@@ -0,0 +1,110 @@
+// Copyright 2017 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.rules.platform;
+
+import com.google.auto.value.AutoValue;
+import com.google.common.base.Function;
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.ImmutableMap;
+import com.google.common.collect.Iterables;
+import com.google.devtools.build.lib.analysis.TransitiveInfoCollection;
+import com.google.devtools.build.lib.concurrent.ThreadSafety.Immutable;
+import com.google.devtools.build.lib.packages.ClassObjectConstructor;
+import com.google.devtools.build.lib.packages.NativeClassObjectConstructor;
+import com.google.devtools.build.lib.packages.SkylarkClassObject;
+import com.google.devtools.build.lib.packages.SkylarkProviderIdentifier;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkCallable;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkModule;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkModuleCategory;
+import com.google.devtools.build.lib.util.Preconditions;
+import java.util.Map;
+
+/** Provider for a platform, which is a group of constraints and values. */
+@SkylarkModule(
+  name = "PlatformInfo",
+  doc = "Provides access to data about a specific platform.",
+  category = SkylarkModuleCategory.PROVIDER
+)
+@AutoValue
+@Immutable
+public abstract class PlatformInfo extends SkylarkClassObject {
+
+  /** Name used in Skylark for accessing this provider. */
+  static final String SKYLARK_NAME = "PlatformInfo";
+
+  /** Skylark constructor and identifier for this provider. */
+  static final ClassObjectConstructor SKYLARK_CONSTRUCTOR =
+      new NativeClassObjectConstructor(SKYLARK_NAME) {};
+
+  /** Identifier used to retrieve this provider from rules which export it. */
+  public static final SkylarkProviderIdentifier SKYLARK_IDENTIFIER =
+      SkylarkProviderIdentifier.forKey(SKYLARK_CONSTRUCTOR.getKey());
+
+  PlatformInfo() {
+    super(SKYLARK_CONSTRUCTOR, ImmutableMap.<String, Object>of());
+  }
+
+  @SkylarkCallable(
+    name = "constraints",
+    doc = "The constraint values fulfilled by this Platform.",
+    structField = true
+  )
+  public abstract ImmutableList<ConstraintValueInfo> constraints();
+
+  @SkylarkCallable(
+    name = "remoteExecutionProperties",
+    doc = "Properties that are available for the use of remote execution.",
+    structField = true
+  )
+  public abstract ImmutableMap<String, String> remoteExecutionProperties();
+
+  /** Retrieves and casts the provider from the given target. */
+  public static PlatformInfo fromTarget(TransitiveInfoCollection target) {
+    Object provider = target.get(SKYLARK_IDENTIFIER);
+    if (provider == null) {
+      return null;
+    }
+    Preconditions.checkState(provider instanceof PlatformInfo);
+    return (PlatformInfo) provider;
+  }
+
+  /** Retrieves and casts the providers from the given targets. */
+  public static Iterable<PlatformInfo> fromTargets(
+      Iterable<? extends TransitiveInfoCollection> targets) {
+    return Iterables.transform(
+        targets,
+        new Function<TransitiveInfoCollection, PlatformInfo>() {
+          @Override
+          public PlatformInfo apply(TransitiveInfoCollection target) {
+            return fromTarget(target);
+          }
+        });
+  }
+
+  /** Returns a {@link Builder} to create a new provider instance. */
+  public static Builder builder() {
+    return new AutoValue_PlatformInfo.Builder();
+  }
+
+  /** A Builder instance to configure a new {@link PlatformInfo}. */
+  @AutoValue.Builder
+  public abstract static class Builder {
+    public abstract Builder constraints(Iterable<ConstraintValueInfo> constraints);
+
+    public abstract Builder remoteExecutionProperties(Map<String, String> properties);
+
+    public abstract PlatformInfo build();
+  }
+}
diff --git a/src/main/java/com/google/devtools/build/lib/rules/platform/PlatformProvider.java b/src/main/java/com/google/devtools/build/lib/rules/platform/PlatformProvider.java
deleted file mode 100644
index 1cf5b5017f..0000000000
--- a/src/main/java/com/google/devtools/build/lib/rules/platform/PlatformProvider.java
+++ /dev/null
@@ -1,45 +0,0 @@
-// Copyright 2017 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.rules.platform;
-
-import com.google.auto.value.AutoValue;
-import com.google.common.collect.ImmutableMap;
-import com.google.devtools.build.lib.analysis.TransitiveInfoProvider;
-import com.google.devtools.build.lib.concurrent.ThreadSafety.Immutable;
-import java.util.Map;
-
-/** Provider for a platform, which is a group of constraints and values. */
-@AutoValue
-@Immutable
-public abstract class PlatformProvider implements TransitiveInfoProvider {
-  public abstract ImmutableMap<ConstraintSettingProvider, ConstraintValueProvider> constraints();
-
-  public abstract ImmutableMap<String, String> remoteExecutionProperties();
-
-  public static Builder builder() {
-    return new AutoValue_PlatformProvider.Builder();
-  }
-
-  /** A Builder instance to configure a new {@link PlatformProvider}. */
-  @AutoValue.Builder
-  public abstract static class Builder {
-    public abstract Builder constraints(
-        Map<ConstraintSettingProvider, ConstraintValueProvider> constraints);
-
-    public abstract Builder remoteExecutionProperties(Map<String, String> properties);
-
-    public abstract PlatformProvider build();
-  }
-}
diff --git a/src/main/java/com/google/devtools/build/lib/rules/platform/PlatformRule.java b/src/main/java/com/google/devtools/build/lib/rules/platform/PlatformRule.java
index fd965ee171..cd332435ca 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/platform/PlatformRule.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/platform/PlatformRule.java
@@ -20,7 +20,6 @@ import com.google.common.collect.ImmutableList;
 import com.google.devtools.build.lib.analysis.BaseRuleClasses;
 import com.google.devtools.build.lib.analysis.RuleDefinition;
 import com.google.devtools.build.lib.analysis.RuleDefinitionEnvironment;
-import com.google.devtools.build.lib.analysis.TransitiveInfoProvider;
 import com.google.devtools.build.lib.packages.BuildType;
 import com.google.devtools.build.lib.packages.RuleClass;
 import com.google.devtools.build.lib.syntax.Type;
@@ -45,9 +44,7 @@ public class PlatformRule implements RuleDefinition {
         .add(
             attr(CONSTRAINT_VALUES_ATTR, BuildType.LABEL_LIST)
                 .allowedFileTypes(FileTypeSet.NO_FILE)
-                .mandatoryNativeProviders(
-                    ImmutableList.<Class<? extends TransitiveInfoProvider>>of(
-                        ConstraintValueProvider.class)))
+                .mandatoryProviders(ImmutableList.of(ConstraintValueInfo.SKYLARK_IDENTIFIER)))
         .add(attr(REMOTE_EXECUTION_PROPS_ATTR, Type.STRING_DICT))
         .removeAttribute("deps")
         .removeAttribute("data")