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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 2019 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;

import org.jspecify.nullness.Nullable;

/** A warnings guard that suppresses some warnings incompatible with J2CL. */
public final class J2clSuppressWarningsGuard extends WarningsGuard {

  // TODO(b/128554878): Cleanup and document all file level suppressions for J2CL generated code.
  private static final DiagnosticGroup DEFAULT_J2CL_SUPRRESIONS =
      new DiagnosticGroup(
          "j2clIncomaptible",
          // Do not warn when static overrides do not match. This is safe, because J2CL generated
          // code directly points to declaration and this is also required with collapse properties
          // pass, which does not support dynamic dispatch for static methods.
          DiagnosticGroups.CHECK_STATIC_OVERRIDES,
          // Do not warn on valid Java constructs like "if(false) {...}" and other situations that
          // may arise from transormation of complex Kotlin constructs.
          DiagnosticGroups.CHECK_USELESS_CODE,
          DiagnosticGroups.CONST,
          DiagnosticGroups.EXTRA_REQUIRE,
          // Kotlin allows provably invalid casts so long as it's via a safe cast. This causes J2CL
          // to generate code of the form:
          //   Foo.$isInstance(value) ? /**@type {!Foo}*/ (value) : null
          // However, if value is obviously never a instance of Foo then this will cause invalid
          // cast error. At runtime it's guarded so it would be safe regardless.
          // This also suppresses casts from non-lambda JsFunction implementations to functions.
          // This particular feature is deprecated and will be removed (b/159954752).
          DiagnosticGroups.INVALID_CASTS,
          DiagnosticGroups.LATE_PROVIDE,
          DiagnosticGroups.MISSING_OVERRIDE,
          DiagnosticGroups.MISSING_REQUIRE,
          DiagnosticGroups.STRICT_MODULE_DEP_CHECK,
          DiagnosticGroups.SUSPICIOUS_CODE,
          DiagnosticGroups.UNUSED_LOCAL_VARIABLE,
          // TODO(b/78521031): J2CL targets are not strict missing property compatible.
          DiagnosticGroups.STRICT_MISSING_PROPERTIES,
          DiagnosticGroups.forName("transitionalSuspiciousCodeWarnings"));

  @Override
  public @Nullable CheckLevel level(JSError error) {
    if (error.getSourceName() == null || !error.getSourceName().endsWith(".java.js")) {
      return null;
    }

    return DEFAULT_J2CL_SUPRRESIONS.matches(error) ? CheckLevel.OFF : null;
  }

  @Override
  protected int getPriority() {
    return Priority.MAX.getValue();
  }
}