Add capability for PlatformInfo providers to inherit from another Pla…

…tformInfo.

Part of work on #6218.

Closes #6465.

PiperOrigin-RevId: 218388951

src/main/java/com/google/devtools/build/lib/analysis/platform/ConstraintCollection.java

@@ -39,18 +39,28 @@
 @AutoCodec
 public final class ConstraintCollection
     implements ConstraintCollectionApi<ConstraintSettingInfo, ConstraintValueInfo> {
+  @Nullable private final ConstraintCollection parent;
   private final ImmutableMap<ConstraintSettingInfo, ConstraintValueInfo> constraints;
 
   ConstraintCollection(ImmutableList<ConstraintValueInfo> constraints) {
+    this(null, constraints);
+  }
+
+  ConstraintCollection(
+      @Nullable ConstraintCollection parent, ImmutableList<ConstraintValueInfo> constraints) {
     this(
+        parent,
         constraints.stream()
             .collect(
                 ImmutableMap.toImmutableMap(ConstraintValueInfo::constraint, Function.identity())));
   }
 
   @AutoCodec.Instantiator
   @VisibleForSerialization
-  ConstraintCollection(ImmutableMap<ConstraintSettingInfo, ConstraintValueInfo> constraints) {
+  ConstraintCollection(
+      @Nullable ConstraintCollection parent,
+      ImmutableMap<ConstraintSettingInfo, ConstraintValueInfo> constraints) {
+    this.parent = parent;
     this.constraints = constraints;
   }
 
@@ -66,18 +76,39 @@ private ConstraintSettingInfo convertKey(Object key, Location loc) throws EvalEx
     return (ConstraintSettingInfo) key;
   }
 
+  @Override
+  public boolean has(ConstraintSettingInfo constraint) {
+    // First, check locally.
+    if (constraints.containsKey(constraint)) {
+      return true;
+    }
+
+    // Then, check the parent, directly to ignore defaults.
+    if (parent != null && parent.constraints.containsKey(constraint)) {
+      return true;
+    }
+
+    return constraint.hasDefaultConstraintValue();
+  }
+
   /**
    * Returns the {@link ConstraintValueInfo} for the given {@link ConstraintSettingInfo}, or {@code
    * null} if none exists.
    */
   @Nullable
   @Override
   public ConstraintValueInfo get(ConstraintSettingInfo constraint) {
+    // First, check locally.
     if (constraints.containsKey(constraint)) {
       return constraints.get(constraint);
     }
 
-    // Since this constraint isn't set, fall back to the default.
+    // Then, check the parent, directly to ignore defaults.
+    if (parent != null && parent.constraints.containsKey(constraint)) {
+      return parent.constraints.get(constraint);
+    }
+
+    // Finally, Since this constraint isn't set, fall back to the default.
     return constraint.defaultConstraintValue();
   }
 

src/main/java/com/google/devtools/build/lib/analysis/platform/ConstraintSettingInfo.java

@@ -54,10 +54,15 @@ public Label label() {
     return label;
   }
 
+  @Override
+  public boolean hasDefaultConstraintValue() {
+    return defaultConstraintValueLabel != null;
+  }
+
   @Override
   @Nullable
   public ConstraintValueInfo defaultConstraintValue() {
-    if (defaultConstraintValueLabel == null) {
+    if (!hasDefaultConstraintValue()) {
       return null;
     }
     return ConstraintValueInfo.create(this, defaultConstraintValueLabel);

src/main/java/com/google/devtools/build/lib/analysis/platform/PlatformInfo.java

@@ -19,6 +19,7 @@
 import static java.util.stream.Collectors.joining;
 
 import com.google.common.base.Functions;
+import com.google.common.base.Strings;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableListMultimap;
 import com.google.common.collect.ListMultimap;
@@ -33,17 +34,27 @@
 import com.google.devtools.build.lib.skylarkbuildapi.platform.PlatformInfoApi;
 import com.google.devtools.build.lib.skylarkinterface.SkylarkPrinter;
 import com.google.devtools.build.lib.util.Fingerprint;
+import com.google.devtools.build.lib.util.StringUtilities;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.List;
 import java.util.Map;
 import java.util.Objects;
+import javax.annotation.Nullable;
 
 /** Provider for a platform, which is a group of constraints and values. */
 @Immutable
 @AutoCodec
 public class PlatformInfo extends NativeInfo
     implements PlatformInfoApi<ConstraintSettingInfo, ConstraintValueInfo> {
+
+  /**
+   * The literal key that will be used to copy the {@link #remoteExecutionProperties} from the
+   * parent {@link PlatformInfo} into a new {@link PlatformInfo}'s {@link
+   * #remoteExecutionProperties}.
+   */
+  public static final String PARENT_REMOTE_EXECUTION_KEY = "{PARENT_REMOTE_EXECUTION_PROPERTIES}";
+
   /** Name used in Skylark for accessing this provider. */
   public static final String SKYLARK_NAME = "PlatformInfo";
 
@@ -66,7 +77,7 @@ public class PlatformInfo extends NativeInfo
 
     this.label = label;
     this.constraints = constraints;
-    this.remoteExecutionProperties = remoteExecutionProperties;
+    this.remoteExecutionProperties = Strings.nullToEmpty(remoteExecutionProperties);
   }
 
   @Override
@@ -103,11 +114,26 @@ public void addTo(Fingerprint fp) {
 
   /** Builder class to facilitate creating valid {@link PlatformInfo} instances. */
   public static class Builder {
+
+    private PlatformInfo parent = null;
     private Label label;
     private final List<ConstraintValueInfo> constraints = new ArrayList<>();
-    private String remoteExecutionProperties = "";
+    private String remoteExecutionProperties = null;
     private Location location = Location.BUILTIN;
 
+    /**
+     * Sets the parent {@link PlatformInfo} that this platform inherits from. Constraint values set
+     * directly on this instance will be kept, but any other constraint settings will be found from
+     * the parent, if set.
+     *
+     * @param parent the platform that is the parent of this platform
+     * @return the {@link Builder} instance for method chaining
+     */
+    public Builder setParent(PlatformInfo parent) {
+      this.parent = parent;
+      return this;
+    }
+
     /**
      * Sets the {@link Label} for this {@link PlatformInfo}.
      *
@@ -150,7 +176,24 @@ public String getRemoteExecutionProperties() {
     }
 
     /**
-     * Sets the data being sent to a potential remote executor.
+     * Sets the data being sent to a potential remote executor. If there is a parent {@link
+     * PlatformInfo} set, the literal string "{PARENT_REMOTE_EXECUTION_PROPERTIES}" will be replaced
+     * by the {@link #remoteExecutionProperties} from that parent. Also if the parent is set, and
+     * this instance's {@link #remoteExecutionProperties} is blank or unset, the parent's will be
+     * used directly.
+     *
+     * <p>Specific examples:
+     *
+     * <ul>
+     *   <li>parent.remoteExecutionProperties is unset: use the child's value
+     *   <li>parent.remoteExecutionProperties is set, child.remoteExecutionProperties is unset: use
+     *       the parent's value
+     *   <li>parent.remoteExecutionProperties is set, child.remoteExecutionProperties is set, and
+     *       does not contain {PARENT_REMOTE_EXECUTION_PROPERTIES}: use the child's value
+     *   <li>parent.remoteExecutionProperties is set, child.remoteExecutionProperties is set, and
+     *       does contain {PARENT_REMOTE_EXECUTION_PROPERTIES}: use the child's value, but
+     *       substitute the parent's value for {PARENT_REMOTE_EXECUTION_PROPERTIES}
+     * </ul>
      *
      * @param properties the properties to be added
      * @return the {@link Builder} instance for method chaining
@@ -178,11 +221,43 @@ public Builder setLocation(Location location) {
      *     constraint setting
      */
     public PlatformInfo build() throws DuplicateConstraintException {
+      // Validate that there are no collisions in the directly set constraint values.
       ImmutableList<ConstraintValueInfo> validatedConstraints = validateConstraints(constraints);
-      ConstraintCollection platformConstraints = new ConstraintCollection(validatedConstraints);
+
+      // Merge parent constraints and the validated constraints to a single set and create a
+      // collection.
+      ConstraintCollection platformConstraints =
+          new ConstraintCollection(parentConstraints(), validatedConstraints);
+
+      // Merge the remote execution properties.
+      String remoteExecutionProperties =
+          mergeRemoteExecutionProperties(parent, this.remoteExecutionProperties);
       return new PlatformInfo(label, platformConstraints, remoteExecutionProperties, location);
     }
 
+    @Nullable
+    private ConstraintCollection parentConstraints() {
+      if (parent == null) {
+        return null;
+      }
+      return parent.constraints();
+    }
+
+    private static String mergeRemoteExecutionProperties(
+        PlatformInfo parent, String remoteExecutionProperties) {
+      String parentRemoteExecutionProperties = "";
+      if (parent != null) {
+        parentRemoteExecutionProperties = parent.remoteExecutionProperties();
+      }
+
+      if (remoteExecutionProperties == null) {
+        return parentRemoteExecutionProperties;
+      }
+
+      return StringUtilities.replaceAllLiteral(
+          remoteExecutionProperties, PARENT_REMOTE_EXECUTION_KEY, parentRemoteExecutionProperties);
+    }
+
     public static ImmutableList<ConstraintValueInfo> validateConstraints(
         Iterable<ConstraintValueInfo> constraintValues) throws DuplicateConstraintException {
 

src/main/java/com/google/devtools/build/lib/skylarkbuildapi/platform/ConstraintCollectionApi.java

@@ -59,4 +59,19 @@ public interface ConstraintCollectionApi<
       enableOnlyWithFlag = FlagIdentifier.EXPERIMENTAL_PLATFORM_API)
   @Nullable
   ConstraintValueInfoT get(ConstraintSettingInfoT constraint);
+
+  @SkylarkCallable(
+      name = "has",
+      doc = "Returns whether the specific ConstraintSettingInfo is set.",
+      parameters = {
+        @Param(
+            name = "constraint",
+            type = ConstraintSettingInfoApi.class,
+            defaultValue = "None",
+            noneable = true,
+            named = true,
+            doc = "The constraint setting to check.")
+      },
+      enableOnlyWithFlag = FlagIdentifier.EXPERIMENTAL_PLATFORM_API)
+  boolean has(ConstraintSettingInfoT constraint);
 }

src/main/java/com/google/devtools/build/lib/skylarkbuildapi/platform/ConstraintSettingInfoApi.java

@@ -46,4 +46,10 @@ public interface ConstraintSettingInfoApi extends StructApi {
       enableOnlyWithFlag = FlagIdentifier.EXPERIMENTAL_PLATFORM_API)
   @Nullable
   ConstraintValueInfoApi defaultConstraintValue();
+
+  @SkylarkCallable(
+      name = "has_default_constraint_value",
+      doc = "Whether there is a default constraint_value for this setting.",
+      structField = true)
+  boolean hasDefaultConstraintValue();
 }