Package org.spongepowered.asm.mixin.injection

Annotation Type ModifyArgs

  • @Target(METHOD)
@Retention(RUNTIME)
public @interface ModifyArgs
    Specifies that this mixin method should inject an multi-argument modifier callback to itself in the target method(s) identified by method(). This type of injector provides a powerful but inefficient method for modifying multiple arguments of a method at once without making use of a Redirect injector. In general it is better to use redirectors where possible, however this type of injector can also function where Redirect cannot, such as modifying arguments of a super-constructor call. To modify a single method argument, use ModifyArg instead.

    This injector works by creating an argument bundle in the form of Args which is passed to your handler method. You can manipulate the method arguments via the bundle in your handler method. The bundle is then unpacked and the original subject method is called with the modified arguments.

    Since the argument bundle is created for every invocation of the target method, and primitive types must undergo boxing and unboxing, this injector is intrinsically less efficient than other methods. However for certain uses this injector is more powerful:

    • For modifying arguments of a superconstructor call, it would normally be necessary to employ multiple ModifyArg callbacks (one for each argument you wish to modify). However access to the enclosing scope is not provided by ModifyArg, which can be problematic.
    • This injector can be used to target multiple methods with differing argument types and counts.

    Methods decorated with this injector should return void and consume either:

    • A single argument of type Args
    • A single Args argument followed by the arguments of the enclosing target method.

    • Required Element Summary

      Required Elements 
      Modifier and Type Required Element Description
      At at
      An At annotation which describes the InjectionPoint in the target method.

    • Optional Element Summary

      Optional Elements 
      Modifier and Type Optional Element Description
      int allow
      Injection points are in general expected to match every candidate instruction in the target method or slice, except in cases where options such as At.ordinal() are specified which naturally limit the number of results.
      java.lang.String constraints
      Returns constraints which must be validated for this injector to succeed.
      int expect
      Like require() but only enabled if the mixin.debug.countInjections option is set to true and defaults to 1.
      java.lang.String[] method
      String representation of one or more target selectors which identify the target methods.
      int order
      By default almost all injectors for a target class apply their injections at the same time.
      boolean remap
      By default, the annotation processor will attempt to locate an obfuscation mapping for all ModifyArgs methods since it is anticipated that in general the target of a ModifyArgs annotation will be an obfuscated method in the target class.
      int require
      In general, injectors are intended to "fail soft" in that a failure to locate the injection point in the target method is not considered an error condition.
      Slice slice
      A Slice annotation which describes the method bisection used in the at() query for this injector.
      Desc[] target
      Literal representation of one or more @Desc annotations which identify the target methods.

    • Element Detail

      • at

        At at
        An At annotation which describes the InjectionPoint in the target method. The specified InjectionPoint must only return MethodInsnNode instances and an exception will be thrown if this is not the case.
        Returns:
        At which identifies the target method invocation

      • method

        java.lang.String[] method
        String representation of one or more target selectors which identify the target methods.
        Returns:
        target method(s) for this injector
        Default:
        {}

      • target

        Desc[] target
        Literal representation of one or more @Desc annotations which identify the target methods.
        Returns:
        target method(s) for this injector as descriptors
        Default:
        {}

      • slice

        Slice slice
        A Slice annotation which describes the method bisection used in the at() query for this injector.
        Returns:
        slice
        Default:
        @org.spongepowered.asm.mixin.injection.Slice

      • remap

        boolean remap
        By default, the annotation processor will attempt to locate an obfuscation mapping for all ModifyArgs methods since it is anticipated that in general the target of a ModifyArgs annotation will be an obfuscated method in the target class. However since it is possible to also apply mixins to non-obfuscated targets (or non- obfuscated methods in obfuscated targets, such as methods added by Forge) it may be necessary to suppress the compiler error which would otherwise be generated. Setting this value to false will cause the annotation processor to skip this annotation when attempting to build the obfuscation table for the mixin.
        Returns:
        True to instruct the annotation processor to search for obfuscation mappings for this annotation
        Default:
        true

      • require

        int require
        In general, injectors are intended to "fail soft" in that a failure to locate the injection point in the target method is not considered an error condition. Another transformer may have changed the method structure or any number of reasons may cause an injection to fail. This also makes it possible to define several injections to achieve the same task given expected mutation of the target class and the injectors which fail are simply ignored.

        However, this behaviour is not always desirable. For example, if your application depends on a particular injection succeeding you may wish to detect the injection failure as an error condition. This argument is thus provided to allow you to stipulate a minimum number of successful injections for this callback handler. If the number of injections specified is not achieved then an InjectionError is thrown at application time. Use this option with care.

        Returns:
        Minimum required number of injected callbacks, default specified by the containing config
        Default:
        -1

      • expect

        int expect
        Like require() but only enabled if the mixin.debug.countInjections option is set to true and defaults to 1. Use this option during debugging to perform simple checking of your injectors. Causes the injector to throw a InvalidInjectionException if the expected number of injections is not realised.
        Returns:
        Minimum number of expected callbacks, default 1
        Default:
        1

      • allow

        int allow
        Injection points are in general expected to match every candidate instruction in the target method or slice, except in cases where options such as At.ordinal() are specified which naturally limit the number of results.

        This option allows for sanity-checking to be performed on the results of an injection point by specifying a maximum allowed number of matches, similar to that afforded by Group.max(). For example if your injection is expected to match 4 invocations of a target method, but instead matches 5, this can become a detectable tamper condition by setting this value to 4.

        Setting any value 1 or greater is allowed. Values less than 1 or less than require() are ignored. require() supercedes this argument such that if allow is less than require the value of require is always used.

        Note that this option is not a limit on the query behaviour of this injection point. It is only a sanity check used to ensure that the number of matches is not too high

        Returns:
        Maximum allowed number of injections for this
        Default:
        -1

      • constraints

        java.lang.String constraints
        Returns constraints which must be validated for this injector to succeed. See ConstraintParser.Constraint for details of constraint formats.
        Returns:
        Constraints for this annotation
        Default:
        ""

      • order

        int order
        By default almost all injectors for a target class apply their injections at the same time. In other words, if multiple mixins target the same class then injectors are applied in priority order (since the mixins themselves are merged in priority order, and injectors run in the order they were merged). The exception being redirect injectors, which apply in a later pass.

        The default order for injectors is 1000, and redirect injectors use 10000.

        Specifying a value for order alters this default behaviour and causes the injector to inject either earlier or later than it normally would. For example specifying 900 will cause the injector to apply before others, while 1100 will apply later. Injectors with the same order will still apply in order of their mixin's priority.

        Returns:
        the application order for this injector, uses DEFAULT (1000) if not specified
        Default:
        1000