Adding toolchain provider and function to Skylark.

Change-Id: Ied06efd4bc68f604975b1e8e3fc70817a577d563
PiperOrigin-RevId: 152412538

2 files changed, 213 insertions, 0 deletions

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
index ff4b0c3dfe..147d872296 100644
--- 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
@@ -14,9 +14,20 @@
 
 package com.google.devtools.build.lib.rules.platform;
 
+import com.google.common.collect.ImmutableMap;
+import com.google.devtools.build.lib.analysis.TransitiveInfoCollection;
+import com.google.devtools.build.lib.events.Location;
 import com.google.devtools.build.lib.packages.ClassObjectConstructor;
+import com.google.devtools.build.lib.skylarkinterface.Param;
 import com.google.devtools.build.lib.skylarkinterface.SkylarkCallable;
 import com.google.devtools.build.lib.skylarkinterface.SkylarkModule;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkSignature;
+import com.google.devtools.build.lib.syntax.BuiltinFunction;
+import com.google.devtools.build.lib.syntax.EvalException;
+import com.google.devtools.build.lib.syntax.SkylarkDict;
+import com.google.devtools.build.lib.syntax.SkylarkList;
+import com.google.devtools.build.lib.syntax.SkylarkSignatureProcessor;
+import com.google.devtools.build.lib.syntax.Type.ConversionException;
 
 /** Skylark namespace used to interact with Blaze's platform APIs. */
 @SkylarkModule(
@@ -51,4 +62,75 @@ public class PlatformCommon {
   public ClassObjectConstructor getConstraintValueInfoConstructor() {
     return ConstraintValueInfo.SKYLARK_CONSTRUCTOR;
   }
+
+  @SkylarkCallable(
+      name = ToolchainInfo.SKYLARK_NAME,
+      doc = "The key used to retrieve the provider containing toolchain data.",
+      structField = true
+  )
+  public ClassObjectConstructor getToolchainInfoConstructor() {
+    return ToolchainInfo.SKYLARK_CONSTRUCTOR;
+  }
+
+  @SkylarkSignature(
+    name = "toolchain",
+    doc =
+        "<i>(Experimental)</i> "
+            + "Returns a toolchain provider that can be configured to provide rule implementations "
+            + "access to needed configuration.",
+    objectType = PlatformCommon.class,
+    returnType = ToolchainInfo.class,
+    parameters = {
+      @Param(name = "self", type = PlatformCommon.class, doc = "the platform_rules instance"),
+      @Param(
+        name = "exec_compatible_with",
+        type = SkylarkList.class,
+        defaultValue = "[]",
+        named = true,
+        positional = false,
+        doc = "Constraints the platform must fulfill to execute this toolchain."
+      ),
+      @Param(
+        name = "target_compatible_with",
+        type = SkylarkList.class,
+        defaultValue = "[]",
+        named = true,
+        positional = false,
+        doc = "Constraints fulfilled by the target platform for this toolchain."
+      ),
+    },
+    extraKeywords =
+        @Param(
+          name = "toolchainData",
+          doc = "Extra information stored for the consumer of the toolchain."
+        ),
+    useLocation = true
+  )
+  private static final BuiltinFunction createToolchain =
+      new BuiltinFunction("toolchain") {
+        @SuppressWarnings("unchecked")
+        public ToolchainInfo invoke(
+            PlatformCommon self,
+            SkylarkList<TransitiveInfoCollection> execCompatibleWith,
+            SkylarkList<TransitiveInfoCollection> targetCompatibleWith,
+            SkylarkDict<String, Object> skylarkToolchainData,
+            Location loc)
+            throws ConversionException, EvalException {
+
+          Iterable<ConstraintValueInfo> execConstraints =
+              ConstraintValueInfo.fromTargets(execCompatibleWith);
+          Iterable<ConstraintValueInfo> targetConstraints =
+              ConstraintValueInfo.fromTargets(targetCompatibleWith);
+          ImmutableMap<String, Object> toolchainData =
+              ImmutableMap.copyOf(
+                  SkylarkDict.castSkylarkDictOrNoneToDict(
+                      skylarkToolchainData, String.class, Object.class, "toolchainData"));
+
+          return new ToolchainInfo(execConstraints, targetConstraints, toolchainData, loc);
+        }
+      };
+
+  static {
+    SkylarkSignatureProcessor.configureSkylarkFunctions(PlatformCommon.class);
+  }
 }
diff --git a/src/main/java/com/google/devtools/build/lib/rules/platform/ToolchainInfo.java b/src/main/java/com/google/devtools/build/lib/rules/platform/ToolchainInfo.java
new file mode 100644
index 0000000000..320ee5e9df
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/rules/platform/ToolchainInfo.java
@@ -0,0 +1,131 @@
+// 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.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.analysis.TransitiveInfoProvider;
+import com.google.devtools.build.lib.concurrent.ThreadSafety.Immutable;
+import com.google.devtools.build.lib.events.Location;
+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;
+
+/**
+ * A provider that supplied information about a specific language toolchain, including what platform
+ * constraints are required for execution and for the target platform.
+ */
+@SkylarkModule(
+  name = "ToolchainInfo",
+  doc = "Provides access to data about a specific toolchain.",
+  category = SkylarkModuleCategory.PROVIDER
+)
+@Immutable
+public class ToolchainInfo extends SkylarkClassObject implements TransitiveInfoProvider {
+
+  /** Name used in Skylark for accessing this provider. */
+  static final String SKYLARK_NAME = "ToolchainInfo";
+
+  /** 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. */
+  private static final SkylarkProviderIdentifier SKYLARK_IDENTIFIER =
+      SkylarkProviderIdentifier.forKey(SKYLARK_CONSTRUCTOR.getKey());
+
+  private final ImmutableList<ConstraintValueInfo> execConstraints;
+  private final ImmutableList<ConstraintValueInfo> targetConstraints;
+
+  public ToolchainInfo(
+      Iterable<ConstraintValueInfo> execConstraints,
+      Iterable<ConstraintValueInfo> targetConstraints,
+      Map<String, Object> toolchainData,
+      Location loc) {
+    this(
+        ImmutableList.copyOf(execConstraints),
+        ImmutableList.copyOf(targetConstraints),
+        toolchainData,
+        loc);
+  }
+
+  public ToolchainInfo(
+      ImmutableList<ConstraintValueInfo> execConstraints,
+      ImmutableList<ConstraintValueInfo> targetConstraints,
+      Map<String, Object> toolchainData,
+      Location loc) {
+    super(
+        SKYLARK_CONSTRUCTOR,
+        ImmutableMap.<String, Object>builder()
+            .put("exec_compatible_with", execConstraints)
+            .put("target_compatible_with", targetConstraints)
+            .putAll(toolchainData)
+            .build(),
+        loc);
+
+    this.execConstraints = execConstraints;
+    this.targetConstraints = targetConstraints;
+  }
+
+  @SkylarkCallable(
+    name = "exec_compatible_with",
+    doc = "The constraints on the execution platforms this toolchain supports.",
+    structField = true
+  )
+  public ImmutableList<ConstraintValueInfo> execConstraints() {
+    return execConstraints;
+  }
+
+  @SkylarkCallable(
+    name = "target_compatible_with",
+    doc = "The constraints on the target platforms this toolchain supports.",
+    structField = true
+  )
+  public ImmutableList<ConstraintValueInfo> targetConstraints() {
+    return targetConstraints;
+  }
+
+  /** Retrieves and casts the provider from the given target. */
+  public static ToolchainInfo fromTarget(TransitiveInfoCollection target) {
+    Object provider = target.get(SKYLARK_IDENTIFIER);
+    if (provider == null) {
+      return null;
+    }
+    Preconditions.checkState(provider instanceof ToolchainInfo);
+    return (ToolchainInfo) provider;
+  }
+
+  /** Retrieves and casts the providers from the given targets. */
+  public static Iterable<ToolchainInfo> fromTargets(
+      Iterable<? extends TransitiveInfoCollection> targets) {
+    return Iterables.transform(
+        targets,
+        new Function<TransitiveInfoCollection, ToolchainInfo>() {
+          @Override
+          public ToolchainInfo apply(TransitiveInfoCollection target) {
+            return fromTarget(target);
+          }
+        });
+  }
+}