Advanced Features

Dependency Pruning

distage performs pruning of all unused bindings by default. When you configure a set of “root” keys - either explicitly by passing Roots or implicitly by using Injector#produceRun or Injector#produceGet methods, distage will remove all bindings that aren’t required to create the supplied roots – these bindings will be thrown out and not even considered, much less executed.

Pruning serves two important purposes:

• It enables faster tests by omitting unused instantiations and allocations of potentially heavy resources,
• It enables multiple independent applications, aka “Roles” to be hosted within a single binary.

Example:

import distage.{Roots, ModuleDef, Injector}

class A(b: B) {
  println("A!")
}
class B() {
  println("B!")
}
class C() {
  println("C!")
}

def module = new ModuleDef {
  make[A]
  make[B]
  make[C]
}

// create an object graph from description in `module`
// with `A` as the GC root

val objects = Injector().produce(module, Roots.target[A]).unsafeGet()
// B!
// A!
// objects: distage.package.Identity[izumi.distage.model.Locator] = Locator izumi.distage.LocatorDefaultImpl@589ac680 with 2 parent(s)
//   with exposed keys:  
//      - {type.MdocSession::MdocApp0::B}
//      - {type.MdocSession::MdocApp0::A}
//   with confined keys:  ø

// A and B are in the object graph

objects.find[A]
// res1: Option[A] = Some(repl.MdocSession$MdocApp0$A@527a1823)

objects.find[B]
// res2: Option[B] = Some(repl.MdocSession$MdocApp0$B@26425a8)

// C is missing

objects.find[C]
// res3: Option[C] = None

Class C was removed because neither B nor A depended on it. It’s neither present in the Locator nor the "C!" message from it’s constructor was ever printed.

If you add c: C parameter to class B , like class B(c: C) - then C will be instantiated, because A - the “root”, will now depend on B, and B will depend on C.

class B(c: C) {
  println("B!")
}

val objects = Injector().produce(module, Roots.target[A]).unsafeGet()
// C!
// B!
// A!
// objects: Identity[Locator] = Locator izumi.distage.LocatorDefaultImpl@2da0df92 with 2 parent(s)
//   with exposed keys:  
//      - {type.MdocSession::MdocApp4::C}
//      - {type.MdocSession::MdocApp4::B}
//      - {type.MdocSession::MdocApp4::A}
//   with confined keys:  ø

objects.find[C]
// res5: Option[C] = Some(repl.MdocSession$MdocApp4$C@6a593711)

Circular Dependencies Support

distage automatically resolves arbitrary circular dependencies, including self-references:

import distage.{DIKey, Roots, ModuleDef, Injector}

class A(val b: B)
class B(val a: A)
class C(val c: C)

def module = new ModuleDef {
  make[A]
  make[B]
  make[C]
}

val objects = Injector().produce(module, Roots(DIKey[A], DIKey[C])).unsafeGet()
// objects: distage.package.Identity[izumi.distage.model.Locator] = Locator izumi.distage.LocatorDefaultImpl@7eeb82ea with 2 parent(s)
//   with exposed keys:  
//      - {type.MdocSession::MdocApp6::B}
//      - {proxyref.{type.MdocSession::MdocApp6::B}}
//      - {type.MdocSession::MdocApp6::C}
//      - {proxyref.{type.MdocSession::MdocApp6::C}}
//      - {type.MdocSession::MdocApp6::A}
//      - {proxyinit.{type.MdocSession::MdocApp6::C}}
//      - {proxyinit.{type.MdocSession::MdocApp6::B}}
//   with confined keys:  ø

objects.get[A] eq objects.get[B].a
// res7: Boolean = true

objects.get[B] eq objects.get[A].b
// res8: Boolean = true

objects.get[C] eq objects.get[C].c
// res9: Boolean = true

Automatic Resolution with generated proxies

The above strategy depends on distage-core-proxy-bytebuddy module and is enabled by default.

If you want to disable it, use NoProxies bootstrap configuration:

Injector.NoProxies()
// res10: Injector[distage.package.Identity] = izumi.distage.InjectorDefaultImpl@481d085a

Proxies are not supported on Scala.js.

Manual Resolution with by-name parameters

Most cycles can be resolved without proxies, using By-Name parameters:

import distage.{DIKey, Roots, ModuleDef, Injector}

class A(b0: => B) {
  def b: B = b0
}

class B(a0: => A) {
  def a: A = a0
}

class C(self: => C) {
  def c: C = self
}

def module = new ModuleDef {
  make[A]
  make[B]
  make[C]
}

// disable proxies and execute the module

val locator = Injector.NoProxies()
  .produce(module, Roots(DIKey[A], DIKey[C]))
  .unsafeGet()
// locator: distage.package.Identity[izumi.distage.model.Locator] = Locator izumi.distage.LocatorDefaultImpl@17169a22 with 2 parent(s)
//   with exposed keys:  
//      - {type.MdocSession::MdocApp11::B}
//      - {proxyref.{type.MdocSession::MdocApp11::B}}
//      - {type.MdocSession::MdocApp11::C}
//      - {proxyref.{type.MdocSession::MdocApp11::C}}
//      - {type.MdocSession::MdocApp11::A}
//      - {proxyinit.{type.MdocSession::MdocApp11::C}}
//      - {proxyinit.{type.MdocSession::MdocApp11::B}}
//   with confined keys:  ø

assert(locator.get[A].b eq locator.get[B])

assert(locator.get[B].a eq locator.get[A])

assert(locator.get[C].c eq locator.get[C])

The proxy generation via bytebuddy is enabled by default, because in scenarios with extreme late-binding cycles can emerge unexpectedly, out of control of the origin module.

Note: Currently a limitation applies to by-names - ALL dependencies of a class engaged in a by-name circular dependency must be by-name, otherwise distage will revert to generating proxies.

Weak Sets

Set bindings can contain weak references. References designated as weak will be retained only if there are other dependencies on the referred bindings, NOT if there’s a dependency only on the entire Set.

Example:

import distage.{Roots, ModuleDef, Injector}

sealed trait Elem

final case class Strong() extends Elem {
  println("Strong constructed")
}

final case class Weak() extends Elem {
  println("Weak constructed")
}

def module = new ModuleDef {
  make[Strong]
  make[Weak]

  many[Elem]
    .ref[Strong]
    .weak[Weak]
}

// Designate Set[Elem] as the garbage collection root,
// everything that Set[Elem] does not strongly depend on will be garbage collected
// and will not be constructed.

val roots = Roots.target[Set[Elem]]
// roots: Roots = Of(NESet({type.scala.collection.immutable.Set[repl.MdocSession.MdocApp15.Elem]}))

val objects = Injector().produce(module, roots).unsafeGet()
// Strong constructed
// objects: distage.package.Identity[izumi.distage.model.Locator] = Locator izumi.distage.LocatorDefaultImpl@69faaae7 with 2 parent(s)
//   with exposed keys:  
//      - {type.MdocSession::MdocApp15::Strong}
//      - {set.{type.Set[=MdocSession::MdocApp15::Elem]}/{type.MdocSession::MdocApp15::Strong}#impl:72492860}
//      - {type.Set[=MdocSession::MdocApp15::Elem]}
//   with confined keys:  ø

// Strong is around

objects.find[Strong]
// res16: Option[Strong] = Some(Strong())

// Weak is not

objects.find[Weak]
// res17: Option[Weak] = None

// There's only Strong in the Set

objects.get[Set[Elem]]
// res18: Set[Elem] = Set(Strong())

The Weak class was not required by any dependency of Set[Elem], so it was pruned. The Strong class remained, because the reference to it was strong, so it was counted as a dependency of Set[Elem].

If we change Strong to depend on the Weak, then Weak will be retained:

final class Strong(weak: Weak) extends Elem {
  println("Strong constructed")
}

val objects = Injector().produce(module, roots).unsafeGet()
// Weak constructed
// Strong constructed
// objects: distage.package.Identity[izumi.distage.model.Locator] = Locator izumi.distage.LocatorDefaultImpl@67d874a9 with 2 parent(s)
//   with exposed keys:  
//      - {type.MdocSession::MdocApp19::Weak}
//      - {type.MdocSession::MdocApp19::Strong}
//      - {set.{type.Set[=MdocSession::MdocApp19::Elem]}/{type.MdocSession::MdocApp19::Weak}#impl:-1275558662}
//      - {set.{type.Set[=MdocSession::MdocApp19::Elem]}/{type.MdocSession::MdocApp19::Strong}#impl:1052012979}
//      - {type.Set[=MdocSession::MdocApp19::Elem]}
//   with confined keys:  ø

// Weak is around

objects.find[Weak]
// res20: Option[Weak] = Some(repl.MdocSession$MdocApp19$Weak@7ad9cba4)

// both Strong and Weak are in the Set

objects.get[Set[Elem]]
// res21: Set[Elem] = Set(repl.MdocSession$MdocApp19$Weak@7ad9cba4, repl.MdocSession$MdocApp19$Strong@11a5ab2d)

Auto-Sets

AutoSet Planner Hooks can traverse the plan and collect all future objects that match a predicate.

Using Auto-Sets you can e.g. collect all AutoCloseable classes and .close() them after the application has finished work. NOTE: please use Resource bindings for real lifecycle, this is just an example.

import distage.{BootstrapModuleDef, ModuleDef, Injector}
import izumi.distage.model.planning.PlanningHook
import izumi.distage.planning.AutoSetHook

class PrintResource(name: String) {
  def start(): Unit = println(s"$name started")
  def stop(): Unit = println(s"$name stopped")
}

class A extends PrintResource("A")
class B(val a: A) extends PrintResource("B")
class C(val b: B) extends PrintResource("C")

def bootstrapModule = new BootstrapModuleDef {
  many[PlanningHook]
    .add(AutoSetHook[PrintResource])
}

def appModule = new ModuleDef {
  make[A]
  make[B]
  make[C]
}

val resources = Injector(bootstrapModule)
  .produceGet[Set[PrintResource]](appModule)
  .use(set => set)
// resources: izumi.fundamentals.platform.functional.package.Identity[Set[PrintResource]] = Set()

resources.foreach(_.start())
resources.toSeq.reverse.foreach(_.stop())

Calling .foreach on an auto-set is safe; the actions will be executed in order of dependencies - Auto-Sets preserve ordering, unlike user-defined Sets

e.g. If C depends on B depends on A, autoset order is: A, B, C, to start call: A, B, C, to close call: C, B, A. When using an auto-set for finalization, you must .reverse the autoset.

Note: Auto-Sets are assembled after Garbage Collection, as such they cannot contain garbage by construction. Because of this they effectively cannot be used as GC Roots.

Further reading:

• MacWire calls the same concept “Multi Wiring”

Depending on Locator

Objects can depend on the outer object graph that contains them (Locator), by including a LocatorRef parameter:

import distage.{DIKey, ModuleDef, LocatorRef, Injector, Roots}

class A(
  objects: LocatorRef
) {
  def c = objects.get.get[C]
}
class B
class C

def module = new ModuleDef {
  make[A]
  make[B]
  make[C]
}

val objects = Injector().produce(module, Roots(DIKey[A], DIKey[B], DIKey[C])).unsafeGet()
// objects: distage.package.Identity[izumi.distage.model.Locator] = Locator izumi.distage.LocatorDefaultImpl@1f70eec with 2 parent(s)
//   with exposed keys:  
//      - {type.MdocSession::MdocApp25::B}
//      - {type.MdocSession::MdocApp25::C}
//      - {type.MdocSession::MdocApp25::A}
//   with confined keys:  ø

// A took C from the object graph

objects.get[A].c
// res26: C = repl.MdocSession$MdocApp25$C@353b951e

// this C is the same C as in this `objects` value

val thisC = objects.get[C]
// thisC: C = repl.MdocSession$MdocApp25$C@353b951e

val thatC = objects.get[A].c
// thatC: C = repl.MdocSession$MdocApp25$C@353b951e

assert(thisC == thatC)

Locator contains metadata about the plan, and the bindings from which it was ultimately created:

import distage.{Plan, ModuleBase}

// Plan that created this locator

val plan: Plan = objects.plan
// plan: Plan = 1: {type.LocatorRef} BindingOrigin((advanced-features.md:347)) := locator {type.LocatorRef} // required for {type.MdocSession::MdocApp25::A}
// 2: {type.MdocSession::MdocApp25::B} BindingOrigin((advanced-features.md:348)) := call(π:Constructor(): MdocSession::MdocApp25::B) {}
// 3: {type.MdocSession::MdocApp25::C} BindingOrigin((advanced-features.md:349)) := call(π:Constructor(): MdocSession::MdocApp25::C) {}
// 4: {type.MdocSession::MdocApp25::A} BindingOrigin((advanced-features.md:347)) :=
// 5:     call(π:Constructor(LocatorRef): MdocSession::MdocApp25::A) {
// 6:       arg objects: LocatorRef <- {type.LocatorRef}
// 7:     }

// Bindings from which the Plan was built (after GC)

val bindings: ModuleBase = plan.definition
// bindings: ModuleBase = 
// make[{type.repl.MdocSession.MdocApp25.B}].from(call(π:Constructor(): repl.MdocSession::MdocApp25::B)) (BindingOrigin((advanced-features.md:348)))
// make[{type.repl.MdocSession.MdocApp25.A}].from(call(π:Constructor(izumi.distage.model.recursive.LocatorRef): repl.MdocSession::MdocApp25::A)) (BindingOrigin((advanced-features.md:347)))
// make[{type.repl.MdocSession.MdocApp25.C}].from(call(π:Constructor(): repl.MdocSession::MdocApp25::C)) (BindingOrigin((advanced-features.md:349)))

Directly depending on Locator is a low-level API. If you only need to wire a subgraph within a larger object graph, you may be able to do this using a high-level Subcontexts API.

Injector inheritance

You may run a new planning cycle, inheriting the instances from an existing Locator into your new object subgraph:

val childInjector = Injector.inherit(objects)
// childInjector: Injector[[A]izumi.fundamentals.platform.functional.package.Identity[A]] = izumi.distage.InjectorDefaultImpl@7c7b0da8

class Printer(a: A, b: B, c: C) {
  def printEm(): Unit =
    println(s"I've got A=$a, B=$b, C=$c, all here!")
}

childInjector.produceRun(new ModuleDef { make[Printer] }) {
  (_: Printer).printEm()
}
// I've got A=repl.MdocSession$MdocApp25$A@6b9a50b0, B=repl.MdocSession$MdocApp25$B@43982d98, C=repl.MdocSession$MdocApp25$C@353b951e, all here!
// res28: izumi.fundamentals.platform.functional.package.Identity[Unit] = ()

It’s safe, performance-wise, to run Injector to create nested graphs – Injector is extremely fast.

Bootloader

The plan and bindings in Locator are saved in the state they were AFTER Garbage Collection has been performed. Objects can request the original input via a PlannerInput parameter:

import distage.{Roots, ModuleDef, PlannerInput, Injector, Activation}

class InjectionInfo(val plannerInput: PlannerInput)

def module = new ModuleDef {
  make[InjectionInfo]
}

val input = PlannerInput(module, Roots.target[InjectionInfo], Activation.empty)
// input: PlannerInput = PlannerInput(
// make[{type.repl.MdocSession.MdocApp29.InjectionInfo}].from(call(π:Constructor(izumi.distage.model.PlannerInput): repl.MdocSession::MdocApp29::InjectionInfo)) (BindingOrigin((advanced-features.md:410))),Of(NESet({type.repl.MdocSession.MdocApp29.InjectionInfo})),Activation(Map()),PublicByDefault)

val injectionInfo = Injector().produce(input).unsafeGet().get[InjectionInfo]
// injectionInfo: InjectionInfo = repl.MdocSession$MdocApp29$InjectionInfo@34834268

// the PlannerInput in `InjectionInfo` is the same as `input`

assert(injectionInfo.plannerInput == input)

Bootloader is another summonable parameter that contains the above information in aggregate and lets you create another object graph from the same inputs as the current or with alterations.

Inner Classes and Path-Dependent Types

Path-dependent types with a value prefix will be instantiated normally:

import distage.{Roots, ModuleDef, Injector}

class Path {
  class A
}
val path = new Path
// path: Path = repl.MdocSession$MdocApp31$Path@3de4efd6

def module = new ModuleDef {
  make[path.A]
}

Injector()
  .produce(module, Roots.Everything)
  .use(_.get[path.A])
// res32: distage.package.Identity[path.A] = repl.MdocSession$MdocApp31$Path$A@3ab19fcf

Since version 0.10, support for types with a non-value prefix (type projections) has been dropped.

However, there’s a gotcha with value prefixes, when seen by distage they’re based on the literal variable name of the prefix, not the full type information available to the compiler, therefore the following usage, a simple rename, will fail:

def pathModule(p: Path) = new ModuleDef {
  make[p.A]
}

val path1 = new Path
// path1: Path = repl.MdocSession$MdocApp31$Path@47772dca
val path2 = new Path
// path2: Path = repl.MdocSession$MdocApp31$Path@59404fd2

Try {
  Injector().produceRun(pathModule(path1) ++ pathModule(path2)) {
    (p1a: path1.A, p2a: path2.A) =>
      println((p1a, p2a))
  }
}.isFailure
// res33: Boolean = true

This will fail because while path1.A and p.A inside new ModuleDef are the same type as far as Scala is concerned, the variables path1 & p are spelled differently and this causes a mismatch in distage.

There’s one way to workaround this - turn the type member A into a type parameter using the Aux Pattern, and then for that type parameter in turn, summon the type information using Tag implicit (as described in Tagless Final Style chapter) and summon the constructor using the ClassConstructor implicit, example:

import distage.{ClassConstructor, ModuleDef, Injector, Tag}

object Path {
  type Aux[A0] = Path { type A = A0 }
}

def pathModule[A: Tag: ClassConstructor](p: Path.Aux[A]) = new ModuleDef {
  make[A]
}

val path1 = new Path
// path1: Path = repl.MdocSession$MdocApp34$Path@655a9cf2
val path2 = new Path
// path2: Path = repl.MdocSession$MdocApp34$Path@54c53281

Injector().produceRun(pathModule(path1) ++ pathModule(path2)) {
  (p1a: path1.A, p2a: path2.A) =>
    println((p1a, p2a))
}
// (repl.MdocSession$MdocApp34$Path$A@78836370,repl.MdocSession$MdocApp34$Path$A@3f22a50a)
// res35: distage.package.Identity[Unit] = ()

Now the example works, because the A type inside pathModule(path1) is path1.A and for pathModule(path2) it’s path2.A, which matches their subsequent spelling in (p1a: path1.A, p2a: path2.A) => in produceRun

Locator-private bindings

You may use locator-private bindings, which will not be exposed inLocator produced by the interpreter.

If the instance is locator-private, it cannot be seen by inherited locators. There are 3 locator privacy (LocatorPrivacy) modes: - PublicByDefault - PrivateByDefault - PublicRoots

Public By Default

All the bindings are public, unless explicitly marked as confined This is default behaviour.

import distage.{Injector, LocatorPrivacy, ModuleDef, PlannerInput}

class A
class B
class C

def module = new ModuleDef {
  make[A]
  make[B].confined
}
val input = PlannerInput.everything(module).withLocatorPrivacy(LocatorPrivacy.PublicByDefault)
// input: PlannerInput = PlannerInput(
// make[{type.repl.MdocSession.MdocApp36.B}].from(call(π:Constructor(): repl.MdocSession::MdocApp36::B)).tagged(Set(Confined)) (BindingOrigin((advanced-features.md:540)))
// make[{type.repl.MdocSession.MdocApp36.A}].from(call(π:Constructor(): repl.MdocSession::MdocApp36::A)) (BindingOrigin((advanced-features.md:539))),Everything,Activation(Map()),PublicByDefault)
val mainLocator = Injector().produce(Injector().planUnsafe(input)).unsafeGet()
// mainLocator: distage.package.Identity[izumi.distage.model.Locator] = Locator izumi.distage.LocatorDefaultImpl@12f1293f with 2 parent(s)
//   with exposed keys:  
//      - {type.InjectorFactory}
//      - {type.PlannerInput}
//      - {type.Activation}
//      - {type.BootstrapModule}
//      - {id.Module@defaultModule}
//      - {type.Clock1[=λ %1:0 → 1:0]}
//      - {type.Entropy1[=λ %1:0 → 1:0]}
//      - {type.QuasiApplicative[=λ %1:0 → 1:0]}
//      - {type.QuasiAsync[=λ %1:0 → 1:0]}
//      - {type.QuasiFunctor[=λ %1:0 → 1:0]}
//      - {type.QuasiIORunner[=λ %1:0 → 1:0]}
//      - {type.QuasiIO[=λ %1:0 → 1:0]}
//      - {type.QuasiPrimitives[=λ %1:0 → 1:0]}
//      - {type.QuasiTemporal[=λ %1:0 → 1:0]}
//      - {type.HKTag[=(Object {type Arg = λ %2:0 → 2:0})]}
//      - {type.MdocSession::MdocApp36::A}
//      - {type.Bootloader}
//   with confined keys:  
//      - {type.MdocSession::MdocApp36::B}

val inheritedInjector = Injector.inherit(mainLocator)
// inheritedInjector: Injector[[A]izumi.fundamentals.platform.functional.package.Identity[A]] = izumi.distage.InjectorDefaultImpl@62a5ee52

def module2 = new ModuleDef {
  make[C]
}
val input2 = PlannerInput.everything(module2)
// input2: PlannerInput = PlannerInput(
// make[{type.repl.MdocSession.MdocApp36.C}].from(call(π:Constructor(): repl.MdocSession::MdocApp36::C)) (BindingOrigin((advanced-features.md:554))),Everything,Activation(Map()),PublicByDefault)
val inheritedLocator = inheritedInjector.produce(inheritedInjector.planUnsafe(input2)).unsafeGet()
// inheritedLocator: izumi.fundamentals.platform.functional.package.Identity[izumi.distage.model.Locator] = Locator izumi.distage.LocatorDefaultImpl@899d2af with 3 parent(s)
//   with exposed keys:  
//      - {type.InjectorFactory}
//      - {type.PlannerInput}
//      - {type.Activation}
//      - {type.BootstrapModule}
//      - {id.Module@defaultModule}
//      - {type.MdocSession::MdocApp36::C}
//      - {type.Bootloader}
//   with confined keys:  ø

assert(inheritedLocator.find[A].nonEmpty)
assert(inheritedLocator.find[C].nonEmpty)
// inherited and new binding are available

assert(inheritedLocator.find[B].isEmpty)
// but confined binding is not

Private By Default

All the bindings are private, unless explicitly marked as exposed

import distage.{Injector, LocatorPrivacy, ModuleDef, PlannerInput}

class A
class B
class C

def module = new ModuleDef {
  make[A]
  make[B].exposed
}
val input = PlannerInput.everything(module).withLocatorPrivacy(LocatorPrivacy.PrivateByDefault)
// input: PlannerInput = PlannerInput(
// make[{type.repl.MdocSession.MdocApp40.B}].from(call(π:Constructor(): repl.MdocSession::MdocApp40::B)).tagged(Set(Exposed)) (BindingOrigin((advanced-features.md:593)))
// make[{type.repl.MdocSession.MdocApp40.A}].from(call(π:Constructor(): repl.MdocSession::MdocApp40::A)) (BindingOrigin((advanced-features.md:592))),Everything,Activation(Map()),PrivateByDefault)

val mainLocator = Injector().produce(Injector().planUnsafe(input)).unsafeGet()
// mainLocator: distage.package.Identity[izumi.distage.model.Locator] = Locator izumi.distage.LocatorDefaultImpl@31cefe88 with 2 parent(s)
//   with exposed keys:  
//      - {type.MdocSession::MdocApp40::B}
//   with confined keys:  
//      - {type.InjectorFactory}
//      - {type.PlannerInput}
//      - {type.Activation}
//      - {type.BootstrapModule}
//      - {id.Module@defaultModule}
//      - {type.Clock1[=λ %1:0 → 1:0]}
//      - {type.Entropy1[=λ %1:0 → 1:0]}
//      - {type.QuasiApplicative[=λ %1:0 → 1:0]}
//      - {type.QuasiAsync[=λ %1:0 → 1:0]}
//      - {type.QuasiFunctor[=λ %1:0 → 1:0]}
//      - {type.QuasiIORunner[=λ %1:0 → 1:0]}
//      - {type.QuasiIO[=λ %1:0 → 1:0]}
//      - {type.QuasiPrimitives[=λ %1:0 → 1:0]}
//      - {type.QuasiTemporal[=λ %1:0 → 1:0]}
//      - {type.HKTag[=(Object {type Arg = λ %2:0 → 2:0})]}
//      - {type.MdocSession::MdocApp40::A}
//      - {type.Bootloader}

val inheritedInjector = Injector.inherit(mainLocator)
// inheritedInjector: Injector[[A]izumi.fundamentals.platform.functional.package.Identity[A]] = izumi.distage.InjectorDefaultImpl@51c5b15a

def module2 = new ModuleDef {
  make[C]
}
val input2 = PlannerInput.everything(module2)
// input2: PlannerInput = PlannerInput(
// make[{type.repl.MdocSession.MdocApp40.C}].from(call(π:Constructor(): repl.MdocSession::MdocApp40::C)) (BindingOrigin((advanced-features.md:607))),Everything,Activation(Map()),PublicByDefault)
val inheritedLocator = inheritedInjector.produce(inheritedInjector.planUnsafe(input2)).unsafeGet()
// inheritedLocator: izumi.fundamentals.platform.functional.package.Identity[izumi.distage.model.Locator] = Locator izumi.distage.LocatorDefaultImpl@1ba509c6 with 3 parent(s)
//   with exposed keys:  
//      - {type.InjectorFactory}
//      - {type.PlannerInput}
//      - {type.Activation}
//      - {type.BootstrapModule}
//      - {id.Module@defaultModule}
//      - {type.MdocSession::MdocApp40::C}
//      - {type.Bootloader}
//   with confined keys:  ø

assert(inheritedLocator.find[A].isEmpty)
// binding is not available

assert(inheritedLocator.find[B].nonEmpty)
assert(inheritedLocator.find[C].nonEmpty)
// but new and 'exposed' are

Public Roots

Only planning GC roots are public This is default behaviour for bootstrap injectors. All bootstrap bindings, which need to be available in inherited locators, must be explicitly marked as exposed

import distage.{Injector, LocatorPrivacy, ModuleDef, PlannerInput}

class A
class B
class C

def module = new ModuleDef {
  make[A]
  make[B]
}
val input = PlannerInput.target[A](module).withLocatorPrivacy(LocatorPrivacy.PublicRoots)
// input: PlannerInput = PlannerInput(
// make[{type.repl.MdocSession.MdocApp44.A}].from(call(π:Constructor(): repl.MdocSession::MdocApp44::A)) (BindingOrigin((advanced-features.md:645)))
// make[{type.repl.MdocSession.MdocApp44.B}].from(call(π:Constructor(): repl.MdocSession::MdocApp44::B)) (BindingOrigin((advanced-features.md:646))),Of(NESet({type.repl.MdocSession.MdocApp44.A})),Activation(Map()),PublicRoots)

val mainLocator = Injector().produce(Injector().planUnsafe(input)).unsafeGet()
// mainLocator: distage.package.Identity[izumi.distage.model.Locator] = Locator izumi.distage.LocatorDefaultImpl@61376eb4 with 2 parent(s)
//   with exposed keys:  
//      - {type.MdocSession::MdocApp44::A}
//   with confined keys:  ø

val inheritedInjector = Injector.inherit(mainLocator)
// inheritedInjector: Injector[[A]izumi.fundamentals.platform.functional.package.Identity[A]] = izumi.distage.InjectorDefaultImpl@7a01a060

def module2 = new ModuleDef {
  make[C]
}
val input2 = PlannerInput.everything(module2)
// input2: PlannerInput = PlannerInput(
// make[{type.repl.MdocSession.MdocApp44.C}].from(call(π:Constructor(): repl.MdocSession::MdocApp44::C)) (BindingOrigin((advanced-features.md:660))),Everything,Activation(Map()),PublicByDefault)
val inheritedLocator = inheritedInjector.produce(inheritedInjector.planUnsafe(input2)).unsafeGet()
// inheritedLocator: izumi.fundamentals.platform.functional.package.Identity[izumi.distage.model.Locator] = Locator izumi.distage.LocatorDefaultImpl@76c63fb4 with 3 parent(s)
//   with exposed keys:  
//      - {type.InjectorFactory}
//      - {type.PlannerInput}
//      - {type.Activation}
//      - {type.BootstrapModule}
//      - {id.Module@defaultModule}
//      - {type.MdocSession::MdocApp44::C}
//      - {type.Bootloader}
//   with confined keys:  ø

assert(inheritedLocator.find[A].nonEmpty)
// targeted binding is available

assert(inheritedLocator.find[B].isEmpty)
// but unrelated one is not