fix: detect silent wget failures in container DownloadFile

internal/container/controller.go

@@ -81,6 +81,10 @@ func (c Controller) ContainerRun(
 	unitTestFailure bool,
 ) string {
 	hostConfig := &container.HostConfig{
+		// On Linux Docker Engine, host.docker.internal is not set by default
+		// (Docker Desktop sets it automatically). Add it so containers can
+		// reach host services, e.g. for bak-file restore from a local HTTP server.
+		ExtraHosts:   []string{"host.docker.internal:host-gateway"},
 		PortBindings: network.PortMap{
 			network.MustParsePort("1433/tcp"): []network.PortBinding{
 				{
@@ -250,23 +254,30 @@ func (c Controller) DownloadFile(id string, src string, destFolder string) {
 		panic("Must pass in non-empty destFolder")
 	}
 
-	cmd := []string{"mkdir", destFolder}
-	c.runCmdInContainer(id, cmd)
-
 	_, file := filepath.Split(src)
+	if file == "" {
+		panic("src URL has no filename: " + src)
+	}
+	dest := destFolder + "/" + file // not using filepath.Join here, this is in the *nix container. always /
 
-	// Wget the .bak file from the http src, and place it in /var/opt/sql/backup
-	cmd = []string{
-		"wget",
-		"-O",
-		destFolder + "/" + file, // not using filepath.Join here, this is in the *nix container. always /
-		src,
+	cmd := []string{"mkdir", "-p", destFolder}
+	_, _, mkdirExit := c.runCmdInContainer(id, cmd)
+	if mkdirExit != 0 {
+		panic("mkdir failed for " + destFolder)
 	}
 
-	c.runCmdInContainer(id, cmd)
+	cmd = []string{"wget", "-O", dest, src}
+	_, stderr, exitCode := c.runCmdInContainer(id, cmd)
+	if exitCode != 0 {
+		msg := "download failed: " + src
+		if len(stderr) > 0 {
+			msg += "\nwget output: " + string(stderr)
+		}
+		panic(msg)
+	}
 }
 
-func (c Controller) runCmdInContainer(id string, cmd []string) ([]byte, []byte) {
+func (c Controller) runCmdInContainer(id string, cmd []string) ([]byte, []byte, int) {
 	trace("Running command in container: " + strings.Join(cmd, " "))
 
 	response, err := c.cli.ExecCreate(
@@ -308,7 +319,17 @@ func (c Controller) runCmdInContainer(id string, cmd []string) ([]byte, []byte)
 	trace("Stdout: " + string(stdout))
 	trace("Stderr: " + string(stderr))
 
-	return stdout, stderr
+	// ExecInspect may rarely return Running:true after output is drained
+	// (moby/moby#42408). In practice the race window is negligible for
+	// short-lived commands like mkdir and wget.
+	inspect, err := c.cli.ExecInspect(
+		context.Background(),
+		response.ID,
+		client.ExecInspectOptions{},
+	)
+	checkErr(err)
+
+	return stdout, stderr, inspect.ExitCode
 }
 
 // ContainerRunning returns true if the container with the given ID is running.

internal/container/controller_test.go

@@ -5,10 +5,12 @@ package container
 
 import (
 	"fmt"
-	"github.com/stretchr/testify/assert"
+	"net"
 	"net/http"
 	"net/http/httptest"
 	"testing"
+
+	"github.com/stretchr/testify/assert"
 )
 
 func TestController_ListTags(t *testing.T) {
@@ -49,12 +51,23 @@ func TestController_EnsureImage(t *testing.T) {
 	c.ContainerExists(id)
 	c.ContainerFiles(id, "*.mdf")
 
-	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+	// Bind to 0.0.0.0 so the container can reach the server via the
+	// Docker bridge network (host.docker.internal resolves to 172.17.0.1).
+	ts := httptest.NewUnstartedServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		_, _ = w.Write([]byte("test"))
 	}))
+	l, err := net.Listen("tcp4", "0.0.0.0:0")
+	checkErr(err)
+	ts.Listener = l
+	ts.Start()
 	defer ts.Close()
 
-	c.DownloadFile(id, ts.URL, "test.txt")
+	// Build URL from listener port so it works regardless of whether
+	// the OS returns 127.0.0.1, localhost, or [::] in ts.URL.
+	_, tsPort, _ := net.SplitHostPort(ts.Listener.Addr().String())
+	tsURL := fmt.Sprintf("http://host.docker.internal:%s", tsPort)
+
+	c.DownloadFile(id, tsURL+"/test.bak", "/tmp")
 
 	err = c.ContainerStop(id)
 	checkErr(err)
@@ -187,3 +200,10 @@ func TestController_DownloadFileNeg3(t *testing.T) {
 		c.DownloadFile("not_blank", "not_blank", "")
 	})
 }
+
+func TestController_DownloadFileNoFilename(t *testing.T) {
+	c := NewController()
+	assert.Panics(t, func() {
+		c.DownloadFile("not_blank", "http://host:9999/", "/tmp")
+	})
+}