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Type-check the ports passed to `getMappedPort`

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評価

難易度
4/5
見積もり時間
1〜2日
初心者へのやさしさ
68/100
issue の種類
機能追加
明瞭さ
明確に書かれている
活発さ
活発
技術スタック
docker, node.js, typescript
領域
backend, testing

調査の方向性

Start by reading withExposedPorts and start in packages/testcontainers/src/test-container.ts and packages/testcontainers/src/generic-container/generic-container.ts, then inspect getMappedPort on StartedTestContainer. Check the repository’s existing TypeScript type tests and add cases for literal exposed ports, UDP ports, repeated calls, and dynamic ports. Done means exposed literal ports are type-checked while dynamic ports retain current behavior; coordinate the interface changes with #1529 and #1563.

索引モデルが issue の本文から書いたものです。

説明

enhancement minor

What happens

getMappedPort accepts any number. Asking for a port that was never exposed compiles, and fails when the test runs:

const container = await new GenericContainer(image).withExposedPorts(8080).start();

container.getMappedPort(8081); // compiles
// Error: No port binding found for :8081/tcp

The mistake is usually a typo, or a port constant that drifted from the one passed to withExposedPorts.

Expected

The ports given to withExposedPorts are carried in the builder's type, and getMappedPort on the started container accepts only those:

const container = await new GenericContainer(image).withExposedPorts(8080, "53/udp").start();

container.getMappedPort(8080);
container.getMappedPort(53, "udp");
container.getMappedPort(8081); // compile error

Where the ports are not known statically, nothing changes: getMappedPort accepts any number, as it does today.

Where

  • withExposedPorts and start in packages/testcontainers/src/test-container.ts and packages/testcontainers/src/generic-container/generic-container.ts
  • getMappedPort on StartedTestContainer

Notes

A prototype of the types compiles under the repo's TypeScript (7.0.2) with these cases checked. It needs no class type parameter, so the fluent this return type and module subclasses are unaffected:

declare const exposed: unique symbol;
type Exposed<P extends number> = { readonly [exposed]: { readonly [K in P]: true } };
type PortsOf<T> = T extends { readonly [exposed]: infer M } ? keyof M & number : number;

interface StartedTestContainer<P extends number = number> {
  getMappedPort(port: P, protocol?: string): number;
  getMappedPort(portWithProtocol: `${P}/${"tcp" | "udp"}`): number;
}

class GenericContainer {
  withExposedPorts<const T extends PortWithOptionalBinding[]>(...ports: T): this & Exposed<ContainerPort<T[number]>>;
  start(): Promise<StartedTestContainer<PortsOf<this>>>;
}
  • Each withExposedPorts call intersects a marker onto this. Later with* calls return this, so the marker survives the rest of the chain, and repeated calls accumulate.
  • It falls back to number, and so to today's behaviour, when a port is a number variable, when the builder is stored in a variable typed GenericContainer, and when withExposedPorts was never called.
  • Module containers are unaffected, because their start() returns their own started type. A module could opt in later.
  • Ports that a subclass exposes in its constructor or hooks are not visible to the caller's type.
  • The const type parameter needs TypeScript 5.0 or later in consuming projects. Without it, only the object form ({ container, host }) loses precision.
  • The intersection shows up in editor hovers, for example GenericContainer & Exposed<8080 | 53>.
  • Changing the signature on the TestContainer interface is a compile error for anyone who implements that interface without extending GenericContainer.

Dependencies

  • Nothing blocks this. It can start now.
  • Coordinate with #1529: both change the TestContainer interface.
  • Coordinate with #1563: the started type gains a type parameter, which the forwarding wrapper has to pass through until it is removed.
主要言語
TypeScript
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マージ済み PR（30日）
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