Fix LocalStack container hostname resolution (#834)

packages/modules/localstack/src/localstack-container.test.ts

@@ -68,5 +68,39 @@ describe("LocalStackContainer", () => {
     expect(response).toContain(`http://localstack:${LOCALSTACK_PORT}`);
     await container.stop();
     await awsCliInDockerNetwork.stop();
+    await network.stop();
+  });
+
+  it("should not override LOCALSTACK_HOST assignment", async () => {
+    const container = await new LocalstackContainer()
+      .withEnvironment({ LOCALSTACK_HOST: "myhost" })
+      .withNetworkAliases("myalias")
+      .start();
+
+    const { output, exitCode } = await container.exec(["printenv", "LOCALSTACK_HOST"]);
+    expect(exitCode).toBe(0);
+    expect(output).toContain("myhost");
+
+    await container.stop();
+  });
+
+  it("should override LOCALSTACK_HOST with last network alias", async () => {
+    const container = await new LocalstackContainer().withNetworkAliases("other", "myalias").start();
+
+    const { output, exitCode } = await container.exec(["printenv", "LOCALSTACK_HOST"]);
+    expect(exitCode).toBe(0);
+    expect(output).toContain("myalias");
+
+    await container.stop();
+  });
+
+  it("should assign LOCALSTACK_HOST to localhost", async () => {
+    const container = await new LocalstackContainer().start();
+
+    const { output, exitCode } = await container.exec(["printenv", "LOCALSTACK_HOST"]);
+    expect(exitCode).toBe(0);
+    expect(output).toContain("localhost");
+
+    await container.stop();
   });
 });

packages/modules/localstack/src/localstack-container.ts

@@ -5,7 +5,6 @@ export const LOCALSTACK_PORT = 4566;
 export class LocalstackContainer extends GenericContainer {
   constructor(image = "localstack/localstack:2.2.0") {
     super(image);
-    this.resolveHostname();
     this.withExposedPorts(LOCALSTACK_PORT).withWaitStrategy(Wait.forLogMessage("Ready", 1)).withStartupTimeout(120_000);
   }
 
@@ -16,13 +15,18 @@ export class LocalstackContainer extends GenericContainer {
       // do nothing
       hostnameExternalReason = "explicitly as environment variable";
     } else if (this.networkAliases && this.networkAliases.length > 0) {
-      this.environment[envVar] = this.networkAliases.at(this.networkAliases.length - 1) || ""; // use the last network alias set
+      // use the last network alias set
+      this.withEnvironment({ [envVar]: this.networkAliases.at(this.networkAliases.length - 1) ?? "" });
       hostnameExternalReason = "to match last network alias on container with non-default network";
     } else {
-      this.withEnvironment({ LOCALSTACK_HOST: "localhost" });
+      this.withEnvironment({ [envVar]: "localhost" });
       hostnameExternalReason = "to match host-routable address for container";
     }
-    log.info(`${envVar} environment variable set to ${this.environment[envVar]} (${hostnameExternalReason})"`);
+    log.info(`${envVar} environment variable set to "${this.environment[envVar]}" (${hostnameExternalReason})`);
+  }
+
+  protected override async beforeContainerCreated(): Promise<void> {
+    this.resolveHostname();
   }
 
   public override async start(): Promise<StartedLocalStackContainer> {