Python provider is now available in Skylark

Using mandatoryProvidersList to validate python rules' dependency.
Added a SkylarkProvider named 'py' which is a SkylarkClassObject in Java and a
struct in Skylark. Native python rule and Skylark python rule should have this provider
so that they can depend on each other.

RELNOTES[NEW]: Native python rule can depend on skylark rule as long as skylark
rule provides 'py' provider.

--
MOS_MIGRATED_REVID=116241504

1 files changed, 14 insertions, 0 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/analysis/SkylarkProviders.java b/src/main/java/com/google/devtools/build/lib/analysis/SkylarkProviders.java
index 53708cf243..1f8f1280a0 100644
--- a/src/main/java/com/google/devtools/build/lib/analysis/SkylarkProviders.java
+++ b/src/main/java/com/google/devtools/build/lib/analysis/SkylarkProviders.java
@@ -16,6 +16,8 @@ package com.google.devtools.build.lib.analysis;
 import com.google.common.collect.ImmutableCollection;
 import com.google.common.collect.ImmutableMap;
 import com.google.devtools.build.lib.concurrent.ThreadSafety.Immutable;
+import com.google.devtools.build.lib.syntax.EvalException;
+import com.google.devtools.build.lib.syntax.SkylarkType;
 import com.google.devtools.build.lib.util.Preconditions;
 
 import java.util.HashSet;
@@ -49,6 +51,18 @@ public final class SkylarkProviders implements TransitiveInfoProvider {
   }
 
   /**
+   * Returns a Skylark provider and try to cast it into the specified type
+   */
+  public <TYPE> TYPE getValue(String key, Class<TYPE> type) throws EvalException {
+    Object obj = skylarkProviders.get(key);
+    if (obj == null) {
+      return null;
+    }
+    SkylarkType.checkType(obj, type, key);
+    return type.cast(obj);
+  }
+
+  /**
    * Merges skylark providers. The set of providers must be disjoint.
    *
    * @param providers providers to merge {@code this} with.