fix(lifecycle): log why the user environment probe failed

When the userEnvProbe could not run in the container, the lifecycle
commands got an empty environment and nothing said why. The reference
CLI (injectHeadless.ts runUserEnvProbe) also falls back to an empty
environment, but writes the error first with toErrorText; Go now does
the same, through a log.ToErrorText that renders TS's red text.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Author: aledbf

internal/lifecycle/probe.go

@@ -171,7 +171,10 @@ func ProbedRemoteEnv(ctx context.Context, exec ContainerExecutor, logger log.Log
 	}
 	server := NewShellServer(ctx, exec, containerID, remoteUser)
 	defer server.Close()
-	env, _ := ProbeRemoteEnv(logger, server, strategy, remoteUser, sessionDataFolder)
+	env, err := ProbeRemoteEnv(logger, server, strategy, remoteUser, sessionDataFolder)
+	if err != nil {
+		logger.Write(log.ToErrorText(err.Error()), log.LevelInfo)
+	}
 	if env == nil {
 		env = map[string]string{}
 	}

internal/lifecycle/shell_test.go

@@ -1,8 +1,10 @@
 package lifecycle
 
 import (
+	"bytes"
 	"context"
 	"errors"
+	"strings"
 	"testing"
 
 	"github.com/devcontainers/cli/internal/log"
@@ -119,7 +121,12 @@ func TestProbedRemoteEnv(t *testing.T) {
 	}
 
 	fe = &fakeExecutor{fn: func(string) (string, string, int, error) { return "", "", 1, errors.New("no shell") }}
-	if env := ProbedRemoteEnv(t.Context(), fe, log.Null, "cid", "vscode", ProbeLoginShell, ""); env == nil || len(env) != 0 {
+	var logged bytes.Buffer
+	logger := log.New(log.Options{Level: log.LevelInfo, Format: "text", Writer: &logged})
+	if env := ProbedRemoteEnv(t.Context(), fe, logger, "cid", "vscode", ProbeLoginShell, ""); env == nil || len(env) != 0 {
 		t.Fatalf("failed probe: env = %v, want empty", env)
 	}
+	if !strings.Contains(logged.String(), "no shell") {
+		t.Errorf("failed probe logged %q, want the probe's error", logged.String())
+	}
 }

internal/log/log.go

@@ -284,6 +284,14 @@ const (
 	numberColor    = "38;2;86;156;214"
 )
 
+func ToErrorText(s string) string {
+	lines := newlines.Split(s, -1)
+	for i, l := range lines {
+		lines[i] = color("31", l)
+	}
+	return strings.Join(lines, "\r\n") + "\r\n"
+}
+
 func color(c, s string) string {
 	return "\x1b[1m\x1b[" + c + "m" + s + "\x1b[39m\x1b[22m"
 }

internal/log/log_test.go

@@ -189,3 +189,10 @@ func TestLogLevelFilter_TerminalVsJSON(t *testing.T) {
 		t.Errorf("json must emit all levels, got %q", js)
 	}
 }
+
+func TestToErrorTextMatchesTheReference(t *testing.T) {
+	want := "\x1b[1m\x1b[31mfirst\x1b[39m\x1b[22m\r\n\x1b[1m\x1b[31msecond\x1b[39m\x1b[22m\r\n"
+	if got := ToErrorText("first\r\nsecond"); got != want {
+		t.Errorf("ToErrorText = %q, want %q", got, want)
+	}
+}