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/*
 * Copyright 2016 The Error Prone 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.errorprone.annotations;

import static java.lang.annotation.RetentionPolicy.CLASS;

import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.Target;

/**
 * Annotation for a method that takes a printf-style format string as an argument followed by
 * arguments for that format string.
 *
 * 

This annotation is used in conjunction with {@link FormatString} to denote a method that takes * a printf-style format string and its format arguments. In any method annotated as {@code * FormatMethod} without a {@link FormatString} parameter, the first {@code String} parameter is * assumed to be the format string. For example, the following two methods are equivalent: * *

 * @FormatMethod void log(Locale l, @FormatString String logMessage, Object... args) {}
 * @FormatMethod void log(Locale l, String logMessage, Object... args) {}
 * 
* *

Using {@link FormatMethod} on a method header will ensure the following for the parameters * passed to the method: * *

    *
  1. A format string is either: *
      *
    • A compile time constant value (see {@link CompileTimeConstant} for more info). *

      The following example is valid: *

       * public class Foo {
       *   static final String staticFinalLogMessage = "foo";
       *   @FormatMethod void log(@FormatString String format, Object... args) {}
       *   void validLogs() {
       *     log("String literal");
       *     log(staticFinalLogMessage);
       *   }
       * }
      *

      However the following would be invalid: *

       * public class Foo{
       *   @FormatMethod void log(@FormatString String format, Object... args) {}
       *   void invalidLog(String notCompileTimeConstant) {
       *     log(notCompileTimeConstant);
       *   }
       * }
      *
    • An effectively final variable that was assigned to a compile time constant value. * This is to permit the following common case: *
       * String format = "Some long format string: %s";
       * log(format, arg);
       * 
      *
    • Another {@link FormatString} annotated parameter. Ex: *
       * public class Foo {
       *   static final String staticFinalLogMessage = "foo";
       *   @FormatMethod void log(@FormatString String format, Object... args) {}
       *   @FormatMethod void validLog(@FormatString String format, Object... args) {
       *     log(format, args);
       *   }
       * }
      *
    *
  2. The format string will be valid for the input format arguments. In the case that the actual * format string parameter has a compile time constant value, this will compare the actual * format string value to the types of the passed in format arguments to ensure validity. In * the case that the actual format string parameter is a parameter that was annotated {@link * FormatString} itself, this will ensure that the types of the arguments passed to the callee * match the types of the arguments in the caller. *
*/ @Documented @Retention(CLASS) @Target({ElementType.METHOD, ElementType.CONSTRUCTOR}) public @interface FormatMethod {}




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