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fix(core): hide dependencyRoots from public API #2668

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May 30, 2019
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17 changes: 7 additions & 10 deletions packages/@aws-cdk/cdk/lib/construct.ts
Original file line number Diff line number Diff line change
@@ -1,7 +1,7 @@
import cxapi = require('@aws-cdk/cx-api');
import { IAspect } from './aspect';
import { CLOUDFORMATION_TOKEN_RESOLVER, CloudFormationLang } from './cloudformation-lang';
import { IDependable } from './dependency';
import { DependableTrait, IDependable } from './dependency';
import { resolve } from './resolve';
import { Token } from './token';
import { makeUniqueId } from './uniqueid';
Expand Down Expand Up @@ -521,7 +521,7 @@ export class ConstructNode {

for (const source of this.findAll()) {
for (const dependable of source.node.dependencies) {
for (const target of dependable.dependencyRoots) {
for (const target of DependableTrait.get(dependable).dependencyRoots) {
let foundTargets = found.get(source);
if (!foundTargets) { found.set(source, foundTargets = new Set()); }

Expand Down Expand Up @@ -578,14 +578,6 @@ export class Construct implements IConstruct {
*/
public readonly node: ConstructNode;

/**
* The set of constructs that form the root of this dependable
*
* All resources under all returned constructs are included in the ordering
* dependency.
*/
public readonly dependencyRoots: IConstruct[] = [this];

/**
* Creates a new construct node.
*
Expand All @@ -596,6 +588,11 @@ export class Construct implements IConstruct {
*/
constructor(scope: Construct, id: string) {
this.node = new ConstructNode(this, scope, id);

const self = this;
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put a wee comment explaining what this does

DependableTrait.implement(this, {
get dependencyRoots() { return [self]; },
});
}

/**
Expand Down
63 changes: 52 additions & 11 deletions packages/@aws-cdk/cdk/lib/dependency.ts
Original file line number Diff line number Diff line change
@@ -1,21 +1,18 @@
import { IConstruct } from "./construct";

/**
* A set of constructs that can be depended upon
* Trait marker for classes that can be depended upon
*
* The presence of this interface indicates that an object has
* an `IDependableTrait` implementation.
*
* This interface can be used to take an (ordering) dependency on a set of
* constructs. An ordering dependency implies that the resources represented by
* those constructs are deployed before the resources depending ON them are
* deployed.
*/
export interface IDependable {
/**
* The set of constructs that form the root of this dependable
*
* All resources under all returned constructs are included in the ordering
* dependency.
*/
readonly dependencyRoots: IConstruct[];
// Empty, this interface is a trait marker
}

/**
Expand All @@ -27,17 +24,61 @@ export interface IDependable {
export class ConcreteDependable implements IDependable {
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Where is this used?

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Oh nice. for some reason I thought it is just introduced now.

private readonly _dependencyRoots = new Array<IConstruct>();

constructor() {
const self = this;
DependableTrait.implement(this, {
get dependencyRoots() { return self._dependencyRoots; },
});
}

/**
* Add a construct to the dependency roots
*/
public add(construct: IConstruct) {
this._dependencyRoots.push(construct);
}
}

/**
* Trait for IDependable
*
* Traits are interfaces that are privately implemented by objects. Instead of
* showing up in the public interface of a class, they need to be queried
* explicitly. This is used to implement certain framework features that are
* not intended to be used by Construct consumers, and so should be hidden
* from accidental use.
*/
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Example on how this is used

export abstract class DependableTrait {
/**
* Register `instance` to have the given DependableTrait
*
* Should be called in the class constructor.
*/
public static implement(instance: IDependable, trait: DependableTrait) {
// I would also like to reference classes (to cut down on the list of objects
// we need to manage), but we can't do that either since jsii doesn't have the
// concept of a class reference.
DependableTrait.traitMap.set(instance, trait);
}

/**
* Retrieve the current set of dependency roots
* Return the matching DependableTrait for the given class instance.
*/
public get dependencyRoots(): IConstruct[] {
return this._dependencyRoots;
public static get(instance: IDependable): DependableTrait {
const ret = DependableTrait.traitMap.get(instance);
if (!ret) {
throw new Error(`${instance} does not implement DependableTrait`);
}
return ret;
}

private static traitMap = new WeakMap<IDependable, DependableTrait>();

/**
* The set of constructs that form the root of this dependable
*
* All resources under all returned constructs are included in the ordering
* dependency.
*/
public abstract readonly dependencyRoots: IConstruct[];
}