From 472d6b6af8f53b9b43d1df994d189aed8e0bc276 Mon Sep 17 00:00:00 2001
From: Mohammed Daudali <mdaudali@palantir.com>
Date: Mon, 9 Feb 2026 22:30:04 +0000
Subject: [PATCH] add stderr

---
 .../docker/compose/execution/Command.java     | 12 +++++-
 .../compose/execution/CommandShould.java      | 41 ++++++++++++++++++-
 2 files changed, 50 insertions(+), 3 deletions(-)

diff --git a/docker-compose-rule-core/src/main/java/com/palantir/docker/compose/execution/Command.java b/docker-compose-rule-core/src/main/java/com/palantir/docker/compose/execution/Command.java
index 1abe44cc0..6594e1a69 100644
--- a/docker-compose-rule-core/src/main/java/com/palantir/docker/compose/execution/Command.java
+++ b/docker-compose-rule-core/src/main/java/com/palantir/docker/compose/execution/Command.java
@@ -80,10 +80,20 @@ private ProcessResult run(String... commands) throws IOException, InterruptedExc
     }
 
     private String processOutputFrom(Process process) {
-        return asReader(process.getInputStream())
+        String stdout = asReader(process.getInputStream())
                 .lines()
                 .peek(logConsumer)
                 .collect(Collectors.joining(System.lineSeparator()));
+
+        String stderr = asReader(process.getErrorStream())
+                .lines()
+                .peek(logConsumer)
+                .collect(Collectors.joining(System.lineSeparator()));
+
+        return String.format(
+                "STDERR: %s\n\n------\n\nSTDOUT: %s\n",
+                stderr.isEmpty() ? "<empty>" : stderr,
+                stdout.isEmpty() ? "<empty>" : stdout);
     }
 
     private static String waitForResultFrom(Future<String> outputProcessing) {
diff --git a/docker-compose-rule-core/src/test/java/com/palantir/docker/compose/execution/CommandShould.java b/docker-compose-rule-core/src/test/java/com/palantir/docker/compose/execution/CommandShould.java
index ced6ed63e..512f3886a 100644
--- a/docker-compose-rule-core/src/test/java/com/palantir/docker/compose/execution/CommandShould.java
+++ b/docker-compose-rule-core/src/test/java/com/palantir/docker/compose/execution/CommandShould.java
@@ -53,6 +53,7 @@ public void before() throws IOException {
         dockerComposeCommand = new Command(dockerComposeExecutable, logConsumer);
 
         givenTheUnderlyingProcessHasOutput("");
+        givenTheUnderlyingProcessHasError("");
         givenTheUnderlyingProcessTerminatesWithAnExitCodeOf(0);
     }
 
@@ -72,7 +73,7 @@ public void return_output_when_exit_code_of_the_executed_process_is_non_0()
         givenTheUnderlyingProcessHasOutput(expectedOutput);
         String commandOutput = dockerComposeCommand.execute(errorHandler, "rm", "-f");
 
-        assertThat(commandOutput).isEqualTo(expectedOutput);
+        assertThat(commandOutput).isEqualTo("STDERR: <empty>\n\n------\n\nSTDOUT: " + expectedOutput + "\n");
     }
 
     @Test
@@ -81,7 +82,29 @@ public void return_output_when_exit_code_of_the_executed_process_is_0() throws I
         givenTheUnderlyingProcessHasOutput(expectedOutput);
         String commandOutput = dockerComposeCommand.execute(errorHandler, "rm", "-f");
 
-        assertThat(commandOutput).isEqualTo(expectedOutput);
+        assertThat(commandOutput).isEqualTo("STDERR: <empty>\n\n------\n\nSTDOUT: " + expectedOutput + "\n");
+    }
+
+    @Test
+    public void return_output_when_only_stderr_is_present() throws IOException, InterruptedException {
+        String expectedStderr = "error output";
+        givenTheUnderlyingProcessHasError(expectedStderr);
+        String commandOutput = dockerComposeCommand.execute(errorHandler, "rm", "-f");
+
+        assertThat(commandOutput)
+                .isEqualTo("STDERR: " + expectedStderr + "\n\n------\n\nSTDOUT: <empty>\n");
+    }
+
+    @Test
+    public void return_output_containing_both_stderr_and_stdout() throws IOException, InterruptedException {
+        String expectedStdout = "standard output";
+        String expectedStderr = "error output";
+        givenTheUnderlyingProcessHasOutput(expectedStdout);
+        givenTheUnderlyingProcessHasError(expectedStderr);
+        String commandOutput = dockerComposeCommand.execute(errorHandler, "rm", "-f");
+
+        assertThat(commandOutput)
+                .isEqualTo("STDERR: " + expectedStderr + "\n\n------\n\nSTDOUT: " + expectedStdout + "\n");
     }
 
     @Test
@@ -94,6 +117,16 @@ public void give_the_output_to_the_specified_consumer_as_it_is_available()
         assertThat(consumedLogLines).containsExactly("line 1", "line 2");
     }
 
+    @Test
+    public void give_both_stdout_and_stderr_to_the_specified_consumer() throws IOException, InterruptedException {
+        givenTheUnderlyingProcessHasOutput("stdout line");
+        givenTheUnderlyingProcessHasError("stderr line");
+
+        dockerComposeCommand.execute(errorHandler, "rm", "-f");
+
+        assertThat(consumedLogLines).containsExactly("stdout line", "stderr line");
+    }
+
     // flaky test: https://circleci.com/gh/palantir/docker-compose-rule/378, 370, 367, 366
     @Ignore
     @Test
@@ -110,6 +143,10 @@ private void givenTheUnderlyingProcessHasOutput(String output) {
         when(executedProcess.getInputStream()).thenReturn(toInputStream(output));
     }
 
+    private void givenTheUnderlyingProcessHasError(String error) {
+        when(executedProcess.getErrorStream()).thenReturn(toInputStream(error));
+    }
+
     private void givenTheUnderlyingProcessTerminatesWithAnExitCodeOf(int exitCode) {
         when(executedProcess.exitValue()).thenReturn(exitCode);
     }