Refactoring: Types report what class of labels they contain.

Currently label-type attributes are detected in many places across the
codebase by simply reference-comparing against each of the label types.
This CL aims to generalize most of these cases, moving the encoding of
this logic into a single place (Type/BuildType itself). Not all of these
cases can be made general without further refactoring, and some perhaps
shouldn't be - serialization and Skylark rule context, for example, need
to do exotic things based on the type. But most sites can avoid having to
enumerate all the types they work with explicitly.

This causes LABEL_DICT_UNARY to start being treated like the other label
types, which means that CcToolchainSuiteRule and JavaRuntimeSuiteRule
need to include a set of allowed file types (none, in their case).
Skylark will continue treating it as a dictionary from String to Label
in its rule context, however, to avoid visible behavior changes.

--
PiperOrigin-RevId: 147471542
MOS_MIGRATED_REVID=147471542

1 files changed, 24 insertions, 4 deletions

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 7e7b69cda1..8dfc1579d8 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
@@ -64,6 +64,7 @@ import com.google.devtools.build.lib.syntax.SkylarkDict;
 import com.google.devtools.build.lib.syntax.SkylarkList;
 import com.google.devtools.build.lib.syntax.SkylarkType;
 import com.google.devtools.build.lib.syntax.Type;
+import com.google.devtools.build.lib.syntax.Type.LabelClass;
 import com.google.devtools.build.lib.util.Preconditions;
 import com.google.devtools.build.lib.vfs.PathFragment;
 import java.util.ArrayList;
@@ -206,7 +207,7 @@ public final class SkylarkRuleContext {
       for (Attribute a : attributes) {
         String attrName = a.getName();
         Type<?> type = a.getType();
-        if (type != BuildType.OUTPUT && type != BuildType.OUTPUT_LIST) {
+        if (type.getLabelClass() != LabelClass.OUTPUT) {
           continue;
         }
         ImmutableList.Builder<Artifact> artifactsBuilder = ImmutableList.builder();
@@ -290,7 +291,10 @@ public final class SkylarkRuleContext {
     for (Attribute a : attributes) {
       Type<?> type = a.getType();
       Object val = attributeValueExtractor.apply(a);
-      if (type != BuildType.LABEL && type != BuildType.LABEL_LIST) {
+      // TODO(mstaib): Remove the LABEL_DICT_UNARY special case of this conditional
+      // LABEL_DICT_UNARY was previously not treated as a dependency-bearing type, and was put into
+      // Skylark as a Map<String, Label>; this special case preserves that behavior temporarily.
+      if (type.getLabelClass() != LabelClass.DEPENDENCY || type == BuildType.LABEL_DICT_UNARY) {
         attrBuilder.put(a.getPublicName(), val == null ? Runtime.NONE
             // Attribute values should be type safe
             : SkylarkType.convertToSkylark(val, null));
@@ -336,10 +340,26 @@ public final class SkylarkRuleContext {
           prereq = Runtime.NONE;
         }
         attrBuilder.put(skyname, prereq);
-      } else {
-        // Type.LABEL_LIST
+      } else if (type == BuildType.LABEL_LIST
+          || (type == BuildType.LABEL && a.hasSplitConfigurationTransition())) {
         List<?> allPrereq = ruleContext.getPrerequisites(a.getName(), Mode.DONT_CHECK);
         attrBuilder.put(skyname, SkylarkList.createImmutable(allPrereq));
+      } else if (type == BuildType.LABEL_DICT_UNARY) {
+        Map<Label, TransitiveInfoCollection> prereqsByLabel = new LinkedHashMap<>();
+        for (TransitiveInfoCollection target
+              : ruleContext.getPrerequisites(a.getName(), Mode.DONT_CHECK)) {
+          prereqsByLabel.put(target.getLabel(), target);
+        }
+        ImmutableMap.Builder<String, TransitiveInfoCollection> attrValue =
+            new ImmutableMap.Builder<>();
+        for (Map.Entry<String, Label> entry : ((Map<String, Label>) val).entrySet()) {
+          attrValue.put(entry.getKey(), prereqsByLabel.get(entry.getValue()));
+        }
+        attrBuilder.put(skyname, attrValue.build());
+      } else {
+        throw new IllegalArgumentException(
+            "Can't transform attribute " + a.getName() + " of type " + type
+            + " to a Skylark object");
       }
     }