src/main/java/com/google/devtools/build/lib/packages/RequiredProviders.java - bazel - Git at Google

 // Copyright 2016 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.packages;

 import com.google.common.base.Joiner;
 import com.google.common.base.Preconditions;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableSet;
 import com.google.devtools.build.lib.analysis.TransitiveInfoProvider;
 import com.google.devtools.build.lib.concurrent.ThreadSafety.Immutable;
 import com.google.devtools.build.lib.skyframe.serialization.autocodec.AutoCodec.VisibleForSerialization;
 import com.google.errorprone.annotations.CanIgnoreReturnValue;
 import java.util.Objects;
 import java.util.function.Function;
 import java.util.function.Predicate;
 import javax.annotation.Nullable;

 /**
  * Represents a constraint on a set of providers required by a dependency (of a rule or an aspect).
  *
  * <p>Currently we support three kinds of constraints:
  *
  * <ul>
  *   <li>accept any dependency.
  *   <li>accept no dependency (used for aspects-on-aspects to indicate that an aspect never wants to
  *       see any other aspect applied to a target.
  *   <li>accept a dependency that provides all providers from one of several sets of providers. It
  *       just so happens that in all current usages these sets are either all builtin providers or
  *       all Starlark providers, so this is the only use case this class currently supports.
  * </ul>
  */
 @Immutable
 public final class RequiredProviders {
   /** A constraint: either ANY, NONE, or RESTRICTED */
   private final Constraint constraint;
   /**
    * Sets of builtin providers. If non-empty, {@link #constraint} is {@link Constraint#RESTRICTED}
    */
   private final ImmutableList<ImmutableSet<Class<? extends TransitiveInfoProvider>>>
       builtinProviders;
   /**
    * Sets of builtin providers. If non-empty, {@link #constraint} is {@link Constraint#RESTRICTED}
    */
   private final ImmutableList<ImmutableSet<StarlarkProviderIdentifier>> starlarkProviders;

   public String getDescription() {
     return constraint.getDescription(this);
   }

   @Override
   public String toString() {
     return getDescription();
   }

   /**
    * Returns the list of sets of acceptable Starlark providers for a restricted constraint, or an
    * empty list for an "any" or "none" constraint.
    *
    * <p>This method is intended for documentation generation. Do not use it for evaluating whether
    * provider constraints are satisfied: it does not distinguish between {@code acceptsAny} and
    * {@code acceptsNone}, and it does not export built-in TransitiveInfoProvider constraints.
    */
   public ImmutableList<ImmutableSet<StarlarkProviderIdentifier>> getStarlarkProviders() {
     return starlarkProviders;
   }

   /** Represents one of the constraints as desctibed in {@link RequiredProviders} */
   @VisibleForSerialization
   enum Constraint {
     /** Accept any dependency */
     ANY {
       @Override
       public boolean satisfies(
           AdvertisedProviderSet advertisedProviderSet,
           RequiredProviders requiredProviders,
           Builder missing) {
         return true;
       }

       @Override
       public boolean satisfies(
           Predicate<Class<? extends TransitiveInfoProvider>> hasBuiltinProvider,
           Predicate<StarlarkProviderIdentifier> hasStarlarkProvider,
           RequiredProviders requiredProviders,
           Builder missingProviders) {
         return true;
       }

       @Override
       Builder copyAsBuilder(RequiredProviders providers) {
         return acceptAnyBuilder();
       }

       @Override
       public String getDescription(RequiredProviders providers) {
         return "no providers required";
       }
     },
     /** Accept no dependency */
     NONE {
       @Override
       public boolean satisfies(
           AdvertisedProviderSet advertisedProviderSet,
           RequiredProviders requiredProviders,
           Builder missing) {
         return false;
       }

       @Override
       public boolean satisfies(
           Predicate<Class<? extends TransitiveInfoProvider>> hasBuiltinProvider,
           Predicate<StarlarkProviderIdentifier> hasStarlarkProvider,
           RequiredProviders requiredProviders,
           Builder missingProviders) {
         return false;
       }

       @Override
       Builder copyAsBuilder(RequiredProviders providers) {
         return acceptNoneBuilder();
       }

       @Override
       public String getDescription(RequiredProviders providers) {
         return "no providers accepted";
       }
     },

     /** Accept a dependency that has all providers from one of the sets. */
     RESTRICTED {
       @Override
       public boolean satisfies(
           final AdvertisedProviderSet advertisedProviderSet,
           RequiredProviders requiredProviders,
           Builder missing) {
         if (advertisedProviderSet.canHaveAnyProvider()) {
           return true;
         }
         return satisfies(
             advertisedProviderSet.getBuiltinProviders()::contains,
             advertisedProviderSet.getStarlarkProviders()::contains,
             requiredProviders,
             missing);
       }

       @Override
       boolean satisfies(
           Predicate<Class<? extends TransitiveInfoProvider>> hasBuiltinProvider,
           Predicate<StarlarkProviderIdentifier> hasStarlarkProvider,
           RequiredProviders requiredProviders,
           Builder missingProviders) {
         for (ImmutableSet<Class<? extends TransitiveInfoProvider>> builtinProviderSet :
             requiredProviders.builtinProviders) {
           if (builtinProviderSet.stream().allMatch(hasBuiltinProvider)) {
             return true;
           }

           // Collect missing providers
           if (missingProviders != null) {
             missingProviders.addBuiltinSet(
                 builtinProviderSet.stream()
                     .filter(hasBuiltinProvider.negate())
                     .collect(ImmutableSet.toImmutableSet()));
           }
         }

         for (ImmutableSet<StarlarkProviderIdentifier> starlarkProviderSet :
             requiredProviders.starlarkProviders) {
           if (starlarkProviderSet.stream().allMatch(hasStarlarkProvider)) {
             return true;
           }
           // Collect missing providers
           if (missingProviders != null) {
             missingProviders.addStarlarkSet(
                 starlarkProviderSet.stream()
                     .filter(hasStarlarkProvider.negate())
                     .collect(ImmutableSet.toImmutableSet()));
           }
         }
         return false;
       }

       @Override
       Builder copyAsBuilder(RequiredProviders providers) {
         Builder result = acceptAnyBuilder();
         for (ImmutableSet<Class<? extends TransitiveInfoProvider>> builtinProviderSet :
             providers.builtinProviders) {
           result.addBuiltinSet(builtinProviderSet);
         }
         for (ImmutableSet<StarlarkProviderIdentifier> starlarkProviderSet :
             providers.starlarkProviders) {
           result.addStarlarkSet(starlarkProviderSet);
         }
         return result;
       }

       @Override
       public String getDescription(RequiredProviders providers) {
         StringBuilder result = new StringBuilder();
         describe(result, providers.builtinProviders, Class::getSimpleName);
         describe(result, providers.starlarkProviders, id -> "'" + id.toString() + "'");
         return result.toString();
       }
     };

     /** Checks if {@code advertisedProviderSet} satisfies these {@code RequiredProviders} */
     protected abstract boolean satisfies(
         AdvertisedProviderSet advertisedProviderSet,
         RequiredProviders requiredProviders,
         Builder missing);

     /**
      * Checks if a set of providers encoded by predicates {@code hasBuiltinProvider} and {@code
      * hasStarlarkProvider} satisfies these {@code RequiredProviders}
      */
     abstract boolean satisfies(
         Predicate<Class<? extends TransitiveInfoProvider>> hasBuiltinProvider,
         Predicate<StarlarkProviderIdentifier> hasStarlarkProvider,
         RequiredProviders requiredProviders,
         @Nullable Builder missingProviders);

     abstract Builder copyAsBuilder(RequiredProviders providers);

     /** Returns a string describing the providers that can be presented to the user. */
     abstract String getDescription(RequiredProviders providers);
   }

   /** Checks if {@code advertisedProviderSet} satisfies this {@code RequiredProviders} instance. */
   public boolean isSatisfiedBy(AdvertisedProviderSet advertisedProviderSet) {
     return constraint.satisfies(advertisedProviderSet, this, null);
   }

   /**
    * Checks if a set of providers encoded by predicates {@code hasBuiltinProvider} and {@code
    * hasStarlarkProvider} satisfies this {@code RequiredProviders} instance.
    */
   public boolean isSatisfiedBy(
       Predicate<Class<? extends TransitiveInfoProvider>> hasBuiltinProvider,
       Predicate<StarlarkProviderIdentifier> hasStarlarkProvider) {
     return constraint.satisfies(hasBuiltinProvider, hasStarlarkProvider, this, null);
   }

   /**
    * Returns providers that are missing. If none are missing, returns {@code RequiredProviders} that
    * accept anything.
    */
   public RequiredProviders getMissing(
       Predicate<Class<? extends TransitiveInfoProvider>> hasBuiltinProvider,
       Predicate<StarlarkProviderIdentifier> hasStarlarkProvider) {
     Builder builder = acceptAnyBuilder();
     if (constraint.satisfies(hasBuiltinProvider, hasStarlarkProvider, this, builder)) {
       // Ignore all collected missing providers.
       return acceptAnyBuilder().build();
     }
     return builder.build();
   }

   /**
    * Returns providers that are missing. If none are missing, returns {@code RequiredProviders} that
    * accept anything.
    */
   public RequiredProviders getMissing(AdvertisedProviderSet set) {
     Builder builder = acceptAnyBuilder();
     if (constraint.satisfies(set, this, builder)) {
       // Ignore all collected missing providers.
       return acceptAnyBuilder().build();
     }
     return builder.build();
   }

   /** Returns true if this {@code RequiredProviders} instance accept any set of providers. */
   public boolean acceptsAny() {
     return constraint.equals(Constraint.ANY);
   }

   @VisibleForSerialization
   RequiredProviders(
       Constraint constraint,
       ImmutableList<ImmutableSet<Class<? extends TransitiveInfoProvider>>> builtinProviders,
       ImmutableList<ImmutableSet<StarlarkProviderIdentifier>> starlarkProviders) {
     this.constraint = constraint;

     Preconditions.checkState(
         constraint.equals(Constraint.RESTRICTED)
             || (builtinProviders.isEmpty() && starlarkProviders.isEmpty()));

     this.builtinProviders = builtinProviders;
     this.starlarkProviders = starlarkProviders;
   }

   /** Helper method to describe lists of sets of things. */
   private static <T> void describe(
       StringBuilder result,
       ImmutableList<ImmutableSet<T>> listOfSets,
       Function<T, String> describeOne) {
     Joiner joiner = Joiner.on(", ");
     for (ImmutableSet<T> ids : listOfSets) {
       if (result.length() > 0) {
         result.append(" or ");
       }
       result.append((ids.size() > 1) ? "[" : "");
       joiner.appendTo(result, ids.stream().map(describeOne).iterator());
       result.append((ids.size() > 1) ? "]" : "");
     }
   }

   @Override
   public boolean equals(Object o) {
     if (this == o) {
       return true;
     }
     if (o == null || getClass() != o.getClass()) {
       return false;
     }
     RequiredProviders that = (RequiredProviders) o;
     return constraint == that.constraint
         && Objects.equals(builtinProviders, that.builtinProviders)
         && Objects.equals(starlarkProviders, that.starlarkProviders);
   }

   @Override
   public int hashCode() {
     return Objects.hash(constraint, builtinProviders, starlarkProviders);
   }

   /**
    * A builder for {@link RequiredProviders} that accepts any dependency
    * unless restriction provider sets are added.
    */
   public static Builder acceptAnyBuilder() {
     return new Builder(false);
   }

   /**
    * Mutates the given {@link AspectDefinition.Builder}, adding in the required providers specified
    * by this {@link RequiredProviders}.
    *
    * <p>We use this indirection for the sake of encapsulating the internal representation of {@link
    * RequiredProviders}.
    */
   void addToAspectDefinitionBuilder(AspectDefinition.Builder aspectDefinitionBuilder) {
     aspectDefinitionBuilder.requireProviderSets(builtinProviders);
     aspectDefinitionBuilder.requireStarlarkProviderSets(starlarkProviders);
   }

   /**
    * A builder for {@link RequiredProviders} that accepts no dependency
    * unless restriction provider sets are added.
    */
   public static Builder acceptNoneBuilder() {
     return new Builder(true);
   }

   /** Returns a Builder initialized to the same value as this {@code RequiredProvider} */
   public Builder copyAsBuilder() {
     return constraint.copyAsBuilder(this);
   }

   /** A builder for {@link RequiredProviders} */
   public static class Builder {
     private final ImmutableList.Builder<ImmutableSet<Class<? extends TransitiveInfoProvider>>>
         builtinProviders;
     private final ImmutableList.Builder<ImmutableSet<StarlarkProviderIdentifier>> starlarkProviders;
     private Constraint constraint;

     private Builder(boolean acceptNone) {
       constraint = acceptNone ? Constraint.NONE : Constraint.ANY;
       builtinProviders = ImmutableList.builder();
       starlarkProviders = ImmutableList.builder();
     }

     /**
      * Add an alternative set of Starlark providers.
      *
      * <p>If all of these providers are present in the dependency, the dependency satisfies {@link
      * RequiredProviders}.
      */
     @CanIgnoreReturnValue
     public Builder addStarlarkSet(ImmutableSet<StarlarkProviderIdentifier> starlarkProviderSet) {
       constraint = Constraint.RESTRICTED;
       Preconditions.checkState(!starlarkProviderSet.isEmpty());
       this.starlarkProviders.add(starlarkProviderSet);
       return this;
     }

     /**
      * Add an alternative set of builtin providers.
      *
      * <p>If all of these providers are present in the dependency, the dependency satisfies {@link
      * RequiredProviders}.
      */
     @CanIgnoreReturnValue
     public Builder addBuiltinSet(
         ImmutableSet<Class<? extends TransitiveInfoProvider>> builtinProviderSet) {
       constraint = Constraint.RESTRICTED;
       Preconditions.checkState(!builtinProviderSet.isEmpty());
       this.builtinProviders.add(builtinProviderSet);
       return this;
     }

     public RequiredProviders build() {
       return new RequiredProviders(constraint, builtinProviders.build(), starlarkProviders.build());
     }
   }
 }
	// Copyright 2016 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.packages;

	import com.google.common.base.Joiner;
	import com.google.common.base.Preconditions;
	import com.google.common.collect.ImmutableList;
	import com.google.common.collect.ImmutableSet;
	import com.google.devtools.build.lib.analysis.TransitiveInfoProvider;
	import com.google.devtools.build.lib.concurrent.ThreadSafety.Immutable;
	import com.google.devtools.build.lib.skyframe.serialization.autocodec.AutoCodec.VisibleForSerialization;
	import com.google.errorprone.annotations.CanIgnoreReturnValue;
	import java.util.Objects;
	import java.util.function.Function;
	import java.util.function.Predicate;
	import javax.annotation.Nullable;

	/**
	* Represents a constraint on a set of providers required by a dependency (of a rule or an aspect).
	*
	* <p>Currently we support three kinds of constraints:
	*
	* <ul>
	* <li>accept any dependency.
	* <li>accept no dependency (used for aspects-on-aspects to indicate that an aspect never wants to
	* see any other aspect applied to a target.
	* <li>accept a dependency that provides all providers from one of several sets of providers. It
	* just so happens that in all current usages these sets are either all builtin providers or
	* all Starlark providers, so this is the only use case this class currently supports.
	* </ul>
	*/
	@Immutable
	public final class RequiredProviders {
	/** A constraint: either ANY, NONE, or RESTRICTED */
	private final Constraint constraint;
	/**
	* Sets of builtin providers. If non-empty, {@link #constraint} is {@link Constraint#RESTRICTED}
	*/
	private final ImmutableList<ImmutableSet<Class<? extends TransitiveInfoProvider>>>
	builtinProviders;
	/**
	* Sets of builtin providers. If non-empty, {@link #constraint} is {@link Constraint#RESTRICTED}
	*/
	private final ImmutableList<ImmutableSet<StarlarkProviderIdentifier>> starlarkProviders;

	public String getDescription() {
	return constraint.getDescription(this);
	}

	@Override
	public String toString() {
	return getDescription();
	}

	/**
	* Returns the list of sets of acceptable Starlark providers for a restricted constraint, or an
	* empty list for an "any" or "none" constraint.
	*
	* <p>This method is intended for documentation generation. Do not use it for evaluating whether
	* provider constraints are satisfied: it does not distinguish between {@code acceptsAny} and
	* {@code acceptsNone}, and it does not export built-in TransitiveInfoProvider constraints.
	*/
	public ImmutableList<ImmutableSet<StarlarkProviderIdentifier>> getStarlarkProviders() {
	return starlarkProviders;
	}

	/** Represents one of the constraints as desctibed in {@link RequiredProviders} */
	@VisibleForSerialization
	enum Constraint {
	/** Accept any dependency */
	ANY {
	@Override
	public boolean satisfies(
	AdvertisedProviderSet advertisedProviderSet,
	RequiredProviders requiredProviders,
	Builder missing) {
	return true;
	}

	@Override
	public boolean satisfies(
	Predicate<Class<? extends TransitiveInfoProvider>> hasBuiltinProvider,
	Predicate<StarlarkProviderIdentifier> hasStarlarkProvider,
	RequiredProviders requiredProviders,
	Builder missingProviders) {
	return true;
	}

	@Override
	Builder copyAsBuilder(RequiredProviders providers) {
	return acceptAnyBuilder();
	}

	@Override
	public String getDescription(RequiredProviders providers) {
	return "no providers required";
	}
	},
	/** Accept no dependency */
	NONE {
	@Override
	public boolean satisfies(
	AdvertisedProviderSet advertisedProviderSet,
	RequiredProviders requiredProviders,
	Builder missing) {
	return false;
	}

	@Override
	public boolean satisfies(
	Predicate<Class<? extends TransitiveInfoProvider>> hasBuiltinProvider,
	Predicate<StarlarkProviderIdentifier> hasStarlarkProvider,
	RequiredProviders requiredProviders,
	Builder missingProviders) {
	return false;
	}

	@Override
	Builder copyAsBuilder(RequiredProviders providers) {
	return acceptNoneBuilder();
	}

	@Override
	public String getDescription(RequiredProviders providers) {
	return "no providers accepted";
	}
	},

	/** Accept a dependency that has all providers from one of the sets. */
	RESTRICTED {
	@Override
	public boolean satisfies(
	final AdvertisedProviderSet advertisedProviderSet,
	RequiredProviders requiredProviders,
	Builder missing) {
	if (advertisedProviderSet.canHaveAnyProvider()) {
	return true;
	}
	return satisfies(
	advertisedProviderSet.getBuiltinProviders()::contains,
	advertisedProviderSet.getStarlarkProviders()::contains,
	requiredProviders,
	missing);
	}

	@Override
	boolean satisfies(
	Predicate<Class<? extends TransitiveInfoProvider>> hasBuiltinProvider,
	Predicate<StarlarkProviderIdentifier> hasStarlarkProvider,
	RequiredProviders requiredProviders,
	Builder missingProviders) {
	for (ImmutableSet<Class<? extends TransitiveInfoProvider>> builtinProviderSet :
	requiredProviders.builtinProviders) {
	if (builtinProviderSet.stream().allMatch(hasBuiltinProvider)) {
	return true;
	}

	// Collect missing providers
	if (missingProviders != null) {
	missingProviders.addBuiltinSet(
	builtinProviderSet.stream()
	.filter(hasBuiltinProvider.negate())
	.collect(ImmutableSet.toImmutableSet()));
	}
	}

	for (ImmutableSet<StarlarkProviderIdentifier> starlarkProviderSet :
	requiredProviders.starlarkProviders) {
	if (starlarkProviderSet.stream().allMatch(hasStarlarkProvider)) {
	return true;
	}
	// Collect missing providers
	if (missingProviders != null) {
	missingProviders.addStarlarkSet(
	starlarkProviderSet.stream()
	.filter(hasStarlarkProvider.negate())
	.collect(ImmutableSet.toImmutableSet()));
	}
	}
	return false;
	}

	@Override
	Builder copyAsBuilder(RequiredProviders providers) {
	Builder result = acceptAnyBuilder();
	for (ImmutableSet<Class<? extends TransitiveInfoProvider>> builtinProviderSet :
	providers.builtinProviders) {
	result.addBuiltinSet(builtinProviderSet);
	}
	for (ImmutableSet<StarlarkProviderIdentifier> starlarkProviderSet :
	providers.starlarkProviders) {
	result.addStarlarkSet(starlarkProviderSet);
	}
	return result;
	}

	@Override
	public String getDescription(RequiredProviders providers) {
	StringBuilder result = new StringBuilder();
	describe(result, providers.builtinProviders, Class::getSimpleName);
	describe(result, providers.starlarkProviders, id -> "'" + id.toString() + "'");
	return result.toString();
	}
	};

	/** Checks if {@code advertisedProviderSet} satisfies these {@code RequiredProviders} */
	protected abstract boolean satisfies(
	AdvertisedProviderSet advertisedProviderSet,
	RequiredProviders requiredProviders,
	Builder missing);

	/**
	* Checks if a set of providers encoded by predicates {@code hasBuiltinProvider} and {@code
	* hasStarlarkProvider} satisfies these {@code RequiredProviders}
	*/
	abstract boolean satisfies(
	Predicate<Class<? extends TransitiveInfoProvider>> hasBuiltinProvider,
	Predicate<StarlarkProviderIdentifier> hasStarlarkProvider,
	RequiredProviders requiredProviders,
	@Nullable Builder missingProviders);

	abstract Builder copyAsBuilder(RequiredProviders providers);

	/** Returns a string describing the providers that can be presented to the user. */
	abstract String getDescription(RequiredProviders providers);
	}

	/** Checks if {@code advertisedProviderSet} satisfies this {@code RequiredProviders} instance. */
	public boolean isSatisfiedBy(AdvertisedProviderSet advertisedProviderSet) {
	return constraint.satisfies(advertisedProviderSet, this, null);
	}

	/**
	* Checks if a set of providers encoded by predicates {@code hasBuiltinProvider} and {@code
	* hasStarlarkProvider} satisfies this {@code RequiredProviders} instance.
	*/
	public boolean isSatisfiedBy(
	Predicate<Class<? extends TransitiveInfoProvider>> hasBuiltinProvider,
	Predicate<StarlarkProviderIdentifier> hasStarlarkProvider) {
	return constraint.satisfies(hasBuiltinProvider, hasStarlarkProvider, this, null);
	}

	/**
	* Returns providers that are missing. If none are missing, returns {@code RequiredProviders} that
	* accept anything.
	*/
	public RequiredProviders getMissing(
	Predicate<Class<? extends TransitiveInfoProvider>> hasBuiltinProvider,
	Predicate<StarlarkProviderIdentifier> hasStarlarkProvider) {
	Builder builder = acceptAnyBuilder();
	if (constraint.satisfies(hasBuiltinProvider, hasStarlarkProvider, this, builder)) {
	// Ignore all collected missing providers.
	return acceptAnyBuilder().build();
	}
	return builder.build();
	}

	/**
	* Returns providers that are missing. If none are missing, returns {@code RequiredProviders} that
	* accept anything.
	*/
	public RequiredProviders getMissing(AdvertisedProviderSet set) {
	Builder builder = acceptAnyBuilder();
	if (constraint.satisfies(set, this, builder)) {
	// Ignore all collected missing providers.
	return acceptAnyBuilder().build();
	}
	return builder.build();
	}

	/** Returns true if this {@code RequiredProviders} instance accept any set of providers. */
	public boolean acceptsAny() {
	return constraint.equals(Constraint.ANY);
	}

	@VisibleForSerialization
	RequiredProviders(
	Constraint constraint,
	ImmutableList<ImmutableSet<Class<? extends TransitiveInfoProvider>>> builtinProviders,
	ImmutableList<ImmutableSet<StarlarkProviderIdentifier>> starlarkProviders) {
	this.constraint = constraint;

	Preconditions.checkState(
	constraint.equals(Constraint.RESTRICTED)
	\|\| (builtinProviders.isEmpty() && starlarkProviders.isEmpty()));

	this.builtinProviders = builtinProviders;
	this.starlarkProviders = starlarkProviders;
	}

	/** Helper method to describe lists of sets of things. */
	private static <T> void describe(
	StringBuilder result,
	ImmutableList<ImmutableSet<T>> listOfSets,
	Function<T, String> describeOne) {
	Joiner joiner = Joiner.on(", ");
	for (ImmutableSet<T> ids : listOfSets) {
	if (result.length() > 0) {
	result.append(" or ");
	}
	result.append((ids.size() > 1) ? "[" : "");
	joiner.appendTo(result, ids.stream().map(describeOne).iterator());
	result.append((ids.size() > 1) ? "]" : "");
	}
	}

	@Override
	public boolean equals(Object o) {
	if (this == o) {
	return true;
	}
	if (o == null \|\| getClass() != o.getClass()) {
	return false;
	}
	RequiredProviders that = (RequiredProviders) o;
	return constraint == that.constraint
	&& Objects.equals(builtinProviders, that.builtinProviders)
	&& Objects.equals(starlarkProviders, that.starlarkProviders);
	}

	@Override
	public int hashCode() {
	return Objects.hash(constraint, builtinProviders, starlarkProviders);
	}

	/**
	* A builder for {@link RequiredProviders} that accepts any dependency
	* unless restriction provider sets are added.
	*/
	public static Builder acceptAnyBuilder() {
	return new Builder(false);
	}

	/**
	* Mutates the given {@link AspectDefinition.Builder}, adding in the required providers specified
	* by this {@link RequiredProviders}.
	*
	* <p>We use this indirection for the sake of encapsulating the internal representation of {@link
	* RequiredProviders}.
	*/
	void addToAspectDefinitionBuilder(AspectDefinition.Builder aspectDefinitionBuilder) {
	aspectDefinitionBuilder.requireProviderSets(builtinProviders);
	aspectDefinitionBuilder.requireStarlarkProviderSets(starlarkProviders);
	}

	/**
	* A builder for {@link RequiredProviders} that accepts no dependency
	* unless restriction provider sets are added.
	*/
	public static Builder acceptNoneBuilder() {
	return new Builder(true);
	}

	/** Returns a Builder initialized to the same value as this {@code RequiredProvider} */
	public Builder copyAsBuilder() {
	return constraint.copyAsBuilder(this);
	}

	/** A builder for {@link RequiredProviders} */
	public static class Builder {
	private final ImmutableList.Builder<ImmutableSet<Class<? extends TransitiveInfoProvider>>>
	builtinProviders;
	private final ImmutableList.Builder<ImmutableSet<StarlarkProviderIdentifier>> starlarkProviders;
	private Constraint constraint;

	private Builder(boolean acceptNone) {
	constraint = acceptNone ? Constraint.NONE : Constraint.ANY;
	builtinProviders = ImmutableList.builder();
	starlarkProviders = ImmutableList.builder();
	}

	/**
	* Add an alternative set of Starlark providers.
	*
	* <p>If all of these providers are present in the dependency, the dependency satisfies {@link
	* RequiredProviders}.
	*/
	@CanIgnoreReturnValue
	public Builder addStarlarkSet(ImmutableSet<StarlarkProviderIdentifier> starlarkProviderSet) {
	constraint = Constraint.RESTRICTED;
	Preconditions.checkState(!starlarkProviderSet.isEmpty());
	this.starlarkProviders.add(starlarkProviderSet);
	return this;
	}

	/**
	* Add an alternative set of builtin providers.
	*
	* <p>If all of these providers are present in the dependency, the dependency satisfies {@link
	* RequiredProviders}.
	*/
	@CanIgnoreReturnValue
	public Builder addBuiltinSet(
	ImmutableSet<Class<? extends TransitiveInfoProvider>> builtinProviderSet) {
	constraint = Constraint.RESTRICTED;
	Preconditions.checkState(!builtinProviderSet.isEmpty());
	this.builtinProviders.add(builtinProviderSet);
	return this;
	}

	public RequiredProviders build() {
	return new RequiredProviders(constraint, builtinProviders.build(), starlarkProviders.build());
	}
	}
	}