com.google.javascript.jscomp.type.ClosureReverseAbstractInterpreter Maven / Gradle / Ivy

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Closure Compiler is a JavaScript optimizing compiler. It parses your JavaScript, analyzes it, removes dead code and rewrites and minimizes what's left. It also checks syntax, variable references, and types, and warns about common JavaScript pitfalls. It is used in many of Google's JavaScript apps, including Gmail, Google Web Search, Google Maps, and Google Docs.

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/*
 * Copyright 2007 The Closure Compiler Authors.
 *
 * 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.javascript.jscomp.type;

import static com.google.javascript.rhino.jstype.JSTypeNative.NO_OBJECT_TYPE;
import static com.google.javascript.rhino.jstype.JSTypeNative.OBJECT_TYPE;

import com.google.common.base.Function;
import com.google.common.collect.ImmutableMap;
import com.google.errorprone.annotations.CheckReturnValue;
import com.google.javascript.rhino.Node;
import com.google.javascript.rhino.Outcome;
import com.google.javascript.rhino.jstype.FunctionType;
import com.google.javascript.rhino.jstype.JSType;
import com.google.javascript.rhino.jstype.JSTypeRegistry;
import com.google.javascript.rhino.jstype.ObjectType;
import com.google.javascript.rhino.jstype.Visitor;
import org.jspecify.nullness.Nullable;

/**
 * A reverse abstract interpreter (RAI) for specific closure patterns such as {@code goog.isObject}.
 */
public final class ClosureReverseAbstractInterpreter extends ChainableReverseAbstractInterpreter {

  /** For when {@code goog.isObject} returns true. This includes functions, but not {@code null}. */
  private final Visitor restrictToObjectVisitor =
      new RestrictByTrueTypeOfResultVisitor() {
        @Override
        protected JSType caseTopType(JSType topType) {
          return getNativeType(NO_OBJECT_TYPE);
        }

        @Override
        public JSType caseObjectType(ObjectType type) {
          return type;
        }

        @Override
        public JSType caseFunctionType(FunctionType type) {
          return type;
        }
      };

  /** For when {@code goog.isObject} returns false. */
  private final Visitor restrictToNotObjectVisitor =
      new RestrictByFalseTypeOfResultVisitor() {
        @Override
        public @Nullable JSType caseObjectType(ObjectType type) {
          return null;
        }

        @Override
        public @Nullable JSType caseFunctionType(FunctionType type) {
          return null;
        }
      };

  /** Functions used to restrict types. */
  private final ImmutableMap> restricters;

  public ClosureReverseAbstractInterpreter(final JSTypeRegistry typeRegistry) {
    super(typeRegistry);
    this.restricters =
        ImmutableMap.of(
            "isObject",
            p -> {
              if (p.type == null) {
                return p.outcome ? getNativeType(OBJECT_TYPE) : null;
              }

              Visitor visitor =
                  p.outcome ? restrictToObjectVisitor : restrictToNotObjectVisitor;
              return p.type.visit(visitor);
            });
  }

  @Override
  public FlowScope getPreciserScopeKnowingConditionOutcome(
      Node condition, FlowScope blindScope, Outcome outcome) {
    if (condition.isCall() && condition.hasTwoChildren()) {
      Node callee = condition.getFirstChild();
      Node param = condition.getLastChild();
      if (callee.isGetProp() && param.isQualifiedName()) {
        JSType paramType = getTypeIfRefinable(param, blindScope);
        Node receiver = callee.getFirstChild();
        if (receiver.isName() && "goog".equals(receiver.getString())) {
          Function restricter = restricters.get(callee.getString());
          if (restricter != null) {
            return restrictParameter(param, paramType, blindScope, restricter, outcome.isTruthy());
          }
        }
      }
    }
    return nextPreciserScopeKnowingConditionOutcome(condition, blindScope, outcome);
  }

  @CheckReturnValue
  private FlowScope restrictParameter(
      Node parameter,
      JSType type,
      FlowScope blindScope,
      Function restriction,
      boolean outcome) {
    // restricting
    type = restriction.apply(new TypeRestriction(type, outcome));

    // changing the scope
    if (type != null) {
      return declareNameInScope(blindScope, parameter, type);
    } else {
      return blindScope;
    }
  }

  private static class TypeRestriction {
    private final JSType type;
    private final boolean outcome;

    private TypeRestriction(JSType type, boolean outcome) {
      this.type = type;
      this.outcome = outcome;
    }
  }
}