formatter: Sort labels for stable output

Several Labels() methods iterated over maps without sorting, producing
non-deterministic output.

In early versions of Go, map iteration order happened to be stable in
practice, so the original code appeared to work correctly.
Since Go 1.12, the runtime intentionally randomizes map iteration order,
making the output unpredictable between runs.

The API response produces sorted labels and the container formatter
already sorted its labels (changed in 5ee17eef).

Apply the same fix to the volume, network, config, and secret
formatters, and update tests to assert exact ordering instead of using
order-independent comparison.

Signed-off-by: Paweł Gronowski <pawel.gronowski@docker.com>

cli/command/config/formatter.go

@@ -1,7 +1,11 @@
+// FIXME(thaJeztah): remove once we are a module; the go:build directive prevents go from downgrading language version to go1.16:
+//go:build go1.25
+
 package config
 
 import (
 	"fmt"
+	"slices"
 	"strings"
 	"time"
 
@@ -102,6 +106,7 @@ func (c *configContext) Labels() string {
 	for k, v := range mapLabels {
 		joinLabels = append(joinLabels, k+"="+v)
 	}
+	slices.Sort(joinLabels)
 	return strings.Join(joinLabels, ",")
 }
 

cli/command/formatter/volume.go

@@ -1,7 +1,11 @@
+// FIXME(thaJeztah): remove once we are a module; the go:build directive prevents go from downgrading language version to go1.16:
+//go:build go1.25
+
 package formatter
 
 import (
 	"fmt"
+	"slices"
 	"strconv"
 	"strings"
 
@@ -104,6 +108,7 @@ func (c *volumeContext) Labels() string {
 	for k, v := range c.v.Labels {
 		joinLabels = append(joinLabels, k+"="+v)
 	}
+	slices.Sort(joinLabels)
 	return strings.Join(joinLabels, ",")
 }
 

cli/command/formatter/volume_test.go

@@ -48,9 +48,7 @@ func TestVolumeContext(t *testing.T) {
 	for _, c := range cases {
 		ctx = c.volumeCtx
 		v := c.call()
-		if strings.Contains(v, ",") {
-			test.CompareMultipleValues(t, v, c.expValue)
-		} else if v != c.expValue {
+		if v != c.expValue {
 			t.Fatalf("Expected %s, was %s\n", c.expValue, v)
 		}
 	}

cli/command/network/formatter.go

@@ -1,6 +1,10 @@
+// FIXME(thaJeztah): remove once we are a module; the go:build directive prevents go from downgrading language version to go1.16:
+//go:build go1.25
+
 package network
 
 import (
+	"slices"
 	"strconv"
 	"strings"
 
@@ -115,6 +119,7 @@ func (c *networkContext) Labels() string {
 	for k, v := range c.n.Labels {
 		joinLabels = append(joinLabels, k+"="+v)
 	}
+	slices.Sort(joinLabels)
 	return strings.Join(joinLabels, ",")
 }
 

cli/command/network/formatter_test.go

@@ -68,9 +68,7 @@ func TestNetworkContext(t *testing.T) {
 	for _, c := range cases {
 		ctx = c.networkCtx
 		v := c.call()
-		if strings.Contains(v, ",") {
-			test.CompareMultipleValues(t, v, c.expValue)
-		} else if v != c.expValue {
+		if v != c.expValue {
 			t.Fatalf("Expected %s, was %s\n", c.expValue, v)
 		}
 	}

cli/command/secret/formatter.go

@@ -1,7 +1,11 @@
+// FIXME(thaJeztah): remove once we are a module; the go:build directive prevents go from downgrading language version to go1.16:
+//go:build go1.25
+
 package secret
 
 import (
 	"fmt"
+	"slices"
 	"strings"
 	"time"
 
@@ -109,6 +113,7 @@ func (c *secretContext) Labels() string {
 	for k, v := range mapLabels {
 		joinLabels = append(joinLabels, k+"="+v)
 	}
+	slices.Sort(joinLabels)
 	return strings.Join(joinLabels, ",")
 }