Add stdout and stderr fields to container exec result (#874)

Author: chungjung-d

docs/features/containers.md

@@ -503,15 +503,16 @@ const container = await new GenericContainer("alpine")
 
 ## Running commands
 
-To run a command inside an already started container use the `exec` method. The command will be run in the container's
-working directory, returning the command output and exit code:
+To run a command inside an already started container, use the exec method. 
+The command will be run in the container's working directory,
+returning the combined output (`output`), standard output (`stdout`), standard error (`stderr`), and exit code (`exitCode`).
 
 ```javascript
 const container = await new GenericContainer("alpine")
   .withCommand(["sleep", "infinity"])
   .start();
 
-const { output, exitCode } = await container.exec(["echo", "hello", "world"]);
+const { output, stdout, stderr, exitCode } = await container.exec(["echo", "hello", "world"]);
 ```
 
 The following options can be provided to modify the command execution:
@@ -528,7 +529,7 @@ const container = await new GenericContainer("alpine")
   .withCommand(["sleep", "infinity"])
   .start();
 
-const { output, exitCode } = await container.exec(["echo", "hello", "world"], {
+const { output, stdout, stderr, exitCode } = await container.exec(["echo", "hello", "world"], {
 	workingDir: "/app/src/",
 	user: "1000:1000",
 	env: {
@@ -538,6 +539,8 @@ const { output, exitCode } = await container.exec(["echo", "hello", "world"], {
 });
 ```
 
+
+
 ## Streaming logs
 
 Logs can be consumed either from a started container:

packages/testcontainers/src/container-runtime/clients/client.ts

@@ -12,7 +12,6 @@ import { ComposeInfo, ContainerRuntimeInfo, Info, NodeInfo } from "./types";
 import Dockerode, { DockerOptions } from "dockerode";
 import { getRemoteContainerRuntimeSocketPath } from "../utils/remote-container-runtime-socket-path";
 import { resolveHost } from "../utils/resolve-host";
-import { PodmanContainerClient } from "./container/podman-container-client";
 import { DockerContainerClient } from "./container/docker-container-client";
 import { DockerImageClient } from "./image/docker-image-client";
 import { DockerNetworkClient } from "./network/docker-network-client";
@@ -105,9 +104,7 @@ async function initStrategy(strategy: ContainerRuntimeClientStrategy): Promise<C
   const hostIps = await lookupHostIps(host);
 
   log.trace("Initialising clients...");
-  const containerClient = result.uri.includes("podman.sock")
-    ? new PodmanContainerClient(dockerode)
-    : new DockerContainerClient(dockerode);
+  const containerClient = new DockerContainerClient(dockerode);
   const imageClient = new DockerImageClient(dockerode, indexServerAddress);
   const networkClient = new DockerNetworkClient(dockerode);
 

packages/testcontainers/src/container-runtime/clients/container/container-client.ts

@@ -11,12 +11,15 @@ import { ContainerStatus, ExecOptions, ExecResult } from "./types";
 
 export interface ContainerClient {
   dockerode: Dockerode;
+
   getById(id: string): Container;
+
   fetchByLabel(
     labelName: string,
     labelValue: string,
     opts?: { status?: ContainerStatus[] }
   ): Promise<Container | undefined>;
+
   fetchArchive(container: Container, path: string): Promise<NodeJS.ReadableStream>;
   putArchive(container: Dockerode.Container, stream: Readable, path: string): Promise<void>;
   list(): Promise<ContainerInfo[]>;

packages/testcontainers/src/container-runtime/clients/container/docker-container-client.ts

@@ -10,7 +10,6 @@ import Dockerode, {
 import { PassThrough, Readable } from "stream";
 import { IncomingMessage } from "http";
 import { ContainerStatus, ExecOptions, ExecResult } from "./types";
-import byline from "byline";
 import { ContainerClient } from "./container-client";
 import { execLog, log, streamToString } from "../../../common";
 
@@ -201,34 +200,55 @@ export class DockerContainerClient implements ContainerClient {
       execOptions.User = opts.user;
     }
 
-    const chunks: string[] = [];
+    const outputChunks: string[] = [];
+    const stdoutChunks: string[] = [];
+    const stderrChunks: string[] = [];
+
     try {
       if (opts?.log) {
         log.debug(`Execing container with command "${command.join(" ")}"...`, { containerId: container.id });
       }
 
       const exec = await container.exec(execOptions);
-      const stream = await exec.start({ stdin: true, Detach: false, Tty: true });
-      if (opts?.log && execLog.enabled()) {
-        byline(stream).on("data", (line) => execLog.trace(line, { containerId: container.id }));
-      }
+      const stream = await exec.start({ stdin: true, Detach: false, Tty: false });
+
+      const stdoutStream = new PassThrough();
+      const stderrStream = new PassThrough();
+
+      this.dockerode.modem.demuxStream(stream, stdoutStream, stderrStream);
+
+      const processStream = (stream: Readable, chunks: string[]) => {
+        stream.on("data", (chunk) => {
+          chunks.push(chunk.toString());
+          outputChunks.push(chunk.toString());
+
+          if (opts?.log && execLog.enabled()) {
+            execLog.trace(chunk.toString(), { containerId: container.id });
+          }
+        });
+      };
+
+      processStream(stdoutStream, stdoutChunks);
+      processStream(stderrStream, stderrChunks);
 
       await new Promise((res, rej) => {
-        stream.on("data", (chunk) => chunks.push(chunk));
         stream.on("end", res);
         stream.on("error", rej);
       });
       stream.destroy();
 
       const inspectResult = await exec.inspect();
       const exitCode = inspectResult.ExitCode ?? -1;
-      const output = chunks.join("");
+      const output = outputChunks.join("");
+      const stdout = stdoutChunks.join("");
+      const stderr = stderrChunks.join("");
+
       if (opts?.log) {
         log.debug(`Execed container with command "${command.join(" ")}"...`, { containerId: container.id });
       }
-      return { output, exitCode };
+      return { output, stdout, stderr, exitCode };
     } catch (err) {
-      log.error(`Failed to exec container with command "${command.join(" ")}": ${err}: ${chunks.join("")}`, {
+      log.error(`Failed to exec container with command "${command.join(" ")}": ${err}: ${outputChunks.join("")}`, {
         containerId: container.id,
       });
       throw err;

packages/testcontainers/src/container-runtime/clients/container/podman-container-client.ts

@@ -2,7 +2,7 @@ export type Environment = { [key in string]: string };
 
 export type ExecOptions = { workingDir: string; user: string; env: Environment; log: boolean };
 
-export type ExecResult = { output: string; exitCode: number };
+export type ExecResult = { output: string; stdout: string; stderr: string; exitCode: number };
 
 export const CONTAINER_STATUSES = ["created", "restarting", "running", "removing", "paused", "exited", "dead"] as const;
 

packages/testcontainers/src/container-runtime/clients/container/types.ts

@@ -42,32 +42,38 @@ describe("GenericContainer", () => {
   it("should execute a command on a running container", async () => {
     const container = await new GenericContainer("cristianrgreco/testcontainer:1.1.14").withExposedPorts(8080).start();
 
-    const { output, exitCode } = await container.exec(["echo", "hello", "world"]);
+    const { output, stdout, stderr, exitCode } = await container.exec(["echo", "hello", "world"]);
 
     expect(exitCode).toBe(0);
-    expect(output).toEqual(expect.stringContaining("hello world"));
+    expect(stdout).toEqual(expect.stringContaining("hello world"));
+    expect(stderr).toBe("");
+    expect(output).toEqual(stdout);
 
     await container.stop();
   });
 
   it("should execute a command in a different working directory", async () => {
     const container = await new GenericContainer("cristianrgreco/testcontainer:1.1.14").withExposedPorts(8080).start();
 
-    const { output, exitCode } = await container.exec(["pwd"], { workingDir: "/var/log" });
+    const { output, stdout, stderr, exitCode } = await container.exec(["pwd"], { workingDir: "/var/log" });
 
     expect(exitCode).toBe(0);
-    expect(output).toEqual(expect.stringContaining("/var/log"));
+    expect(stdout).toEqual(expect.stringContaining("/var/log"));
+    expect(stderr).toBe("");
+    expect(output).toEqual(stdout);
 
     await container.stop();
   });
 
   it("should execute a command with custom environment variables", async () => {
     const container = await new GenericContainer("cristianrgreco/testcontainer:1.1.14").withExposedPorts(8080).start();
 
-    const { output, exitCode } = await container.exec(["env"], { env: { TEST_ENV: "test" } });
+    const { output, stdout, stderr, exitCode } = await container.exec(["env"], { env: { TEST_ENV: "test" } });
 
     expect(exitCode).toBe(0);
-    expect(output).toEqual(expect.stringContaining("TEST_ENV=test"));
+    expect(stdout).toEqual(expect.stringContaining("TEST_ENV=test"));
+    expect(stderr).toBe("");
+    expect(output).toEqual(stdout);
 
     await container.stop();
   });
@@ -76,10 +82,43 @@ describe("GenericContainer", () => {
     // By default, node:alpine runs as root
     const container = await new GenericContainer("cristianrgreco/testcontainer:1.1.14").withExposedPorts(8080).start();
 
-    const { output, exitCode } = await container.exec("whoami", { user: "node" });
+    const { output, stdout, stderr, exitCode } = await container.exec(["whoami"], { user: "node" });
 
     expect(exitCode).toBe(0);
-    expect(output).toEqual(expect.stringContaining("node"));
+    expect(stdout).toEqual(expect.stringContaining("node"));
+    expect(stderr).toBe("");
+    expect(output).toEqual(stdout);
+
+    await container.stop();
+  });
+
+  it("should capture stderr when a command fails", async () => {
+    const container = await new GenericContainer("cristianrgreco/testcontainer:1.1.14").withExposedPorts(8080).start();
+
+    const { output, stdout, stderr, exitCode } = await container.exec(["ls", "/nonexistent/path"]);
+
+    expect(exitCode).not.toBe(0);
+    expect(stdout).toBe("");
+    expect(stderr).toEqual(expect.stringContaining("No such file or directory"));
+    expect(output).toEqual(stderr);
+
+    await container.stop();
+  });
+
+  it("should capture stdout and stderr in the correct order", async () => {
+    const container = await new GenericContainer("cristianrgreco/testcontainer:1.1.14").withExposedPorts(8080).start();
+
+    // The command first writes to stdout and then tries to access a nonexistent file (stderr)
+    const { output, stdout, stderr, exitCode } = await container.exec([
+      "sh",
+      "-c",
+      "echo 'This is stdout'; ls /nonexistent/path",
+    ]);
+
+    expect(exitCode).not.toBe(0); // The command should fail due to the ls error
+    expect(stdout).toEqual(expect.stringContaining("This is stdout"));
+    expect(stderr).toEqual(expect.stringContaining("No such file or directory"));
+    expect(output).toMatch(/This is stdout[\s\S]*No such file or directory/);
 
     await container.stop();
   });

packages/testcontainers/src/generic-container/generic-container.test.ts

@@ -81,5 +81,6 @@ export interface StartedTestContainer {
 
 export interface StoppedTestContainer {
   getId(): string;
+
   copyArchiveFromContainer(path: string): Promise<NodeJS.ReadableStream>;
 }

packages/testcontainers/src/test-container.ts

@@ -83,7 +83,7 @@ export type BuildArgs = { [key in string]: string };
 
 export type ExecOptions = { workingDir: string; user: string; env: Environment };
 
-export type ExecResult = { output: string; exitCode: number };
+export type ExecResult = { output: string; stdout: string; stderr: string; exitCode: number };
 
 export type HealthCheckStatus = "none" | "starting" | "unhealthy" | "healthy";