test(actions/docker): unit coverage for runArgs parser and overlays

Covers:
  - nil and empty input return nil, nil
  - every supported flag parses into the expected field, including
    repeated -v/--volume, -e/--env, --cap-add, --cap-drop
  - unknown bare flags (e.g. --rm) are rejected with a clear message
  - non-flag bare values are rejected with the space-separated hint
  - empty/whitespace entries are skipped
  - ApplyToContainerConfig is a no-op on nil receiver or nil cfg
  - ApplyToContainerConfig sets User and appends Env preserving existing
  - ApplyToHostConfig is a no-op on nil receiver or nil hc
  - ApplyToHostConfig overrides NetworkMode only when provided, appends
    Binds / ExtraHosts / CapAdd / CapDrop, unions Tmpfs, and honours
    Privileged=true

Author: bogdannazarenko

pkg/skaffold/actions/docker/runargs.go

@@ -73,6 +73,10 @@ func ParseRunArgs(args []string) (*RunArgs, error) {
 		}
 		key, val, ok := strings.Cut(arg, "=")
 		if !ok {
+			// No '=' means either an unknown bare flag or the space-separated form.
+			if strings.HasPrefix(arg, "--") || strings.HasPrefix(arg, "-") {
+				return nil, fmt.Errorf("runArgs[%d] %q: unsupported flag %q (only --flag=value form is supported; allowed: --network, -v/--volume, -e/--env, --user, --add-host, --tmpfs, --privileged, --cap-add, --cap-drop)", i, raw, arg)
+			}
 			return nil, fmt.Errorf("runArgs[%d] %q: only --flag=value form is supported (no space-separated values)", i, raw)
 		}
 		switch key {

pkg/skaffold/actions/docker/runargs_test.go

@@ -0,0 +1,142 @@
+/*
+Copyright 2026 The Skaffold Authors
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package docker
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/docker/docker/api/types/container"
+
+	"github.com/GoogleContainerTools/skaffold/v2/testutil"
+)
+
+func TestParseRunArgs_Empty(t *testing.T) {
+	got, err := ParseRunArgs(nil)
+	testutil.CheckError(t, false, err)
+	if got != nil {
+		t.Fatalf("expected nil, got %+v", got)
+	}
+
+	got, err = ParseRunArgs([]string{})
+	testutil.CheckError(t, false, err)
+	if got != nil {
+		t.Fatalf("expected nil, got %+v", got)
+	}
+}
+
+func TestParseRunArgs_Supported(t *testing.T) {
+	got, err := ParseRunArgs([]string{
+		"--network=host",
+		"-v=/host:/container:ro",
+		"--volume=/data:/data",
+		"-e=FOO=bar",
+		"--env=BAZ=qux",
+		"--user=1000:1000",
+		"--add-host=db:127.0.0.1",
+		"--tmpfs=/tmp:size=64m",
+		"--privileged",
+		"--cap-add=NET_ADMIN",
+		"--cap-drop=AUDIT_WRITE",
+	})
+	testutil.CheckError(t, false, err)
+	testutil.CheckDeepEqual(t, "host", got.NetworkMode)
+	testutil.CheckDeepEqual(t, []string{"/host:/container:ro", "/data:/data"}, got.Binds)
+	testutil.CheckDeepEqual(t, []string{"FOO=bar", "BAZ=qux"}, got.Env)
+	testutil.CheckDeepEqual(t, "1000:1000", got.User)
+	testutil.CheckDeepEqual(t, []string{"db:127.0.0.1"}, got.ExtraHosts)
+	testutil.CheckDeepEqual(t, map[string]string{"/tmp": "size=64m"}, got.Tmpfs)
+	testutil.CheckDeepEqual(t, true, got.Privileged)
+	testutil.CheckDeepEqual(t, []string{"NET_ADMIN"}, got.CapAdd)
+	testutil.CheckDeepEqual(t, []string{"AUDIT_WRITE"}, got.CapDrop)
+}
+
+func TestParseRunArgs_UnsupportedFlag(t *testing.T) {
+	_, err := ParseRunArgs([]string{"--rm"})
+	if err == nil || !strings.Contains(err.Error(), "unsupported flag") {
+		t.Fatalf("expected unsupported flag error, got %v", err)
+	}
+}
+
+func TestParseRunArgs_SpaceSeparated(t *testing.T) {
+	_, err := ParseRunArgs([]string{"plain value"})
+	if err == nil || !strings.Contains(err.Error(), "only --flag=value form") {
+		t.Fatalf("expected only --flag=value error, got %v", err)
+	}
+}
+
+func TestParseRunArgs_SkipsEmptyEntries(t *testing.T) {
+	got, err := ParseRunArgs([]string{"", "   ", "--network=host"})
+	testutil.CheckError(t, false, err)
+	testutil.CheckDeepEqual(t, "host", got.NetworkMode)
+}
+
+func TestApplyToContainerConfig_NilSafe(t *testing.T) {
+	var r *RunArgs
+	r.ApplyToContainerConfig(nil)       // nil config, nil receiver
+	r.ApplyToContainerConfig(&container.Config{})
+	(&RunArgs{}).ApplyToContainerConfig(nil)
+}
+
+func TestApplyToContainerConfig_SetsUserAndAppendsEnv(t *testing.T) {
+	r := &RunArgs{User: "1000", Env: []string{"A=1", "B=2"}}
+	cfg := &container.Config{Env: []string{"PRE=existing"}}
+	r.ApplyToContainerConfig(cfg)
+	testutil.CheckDeepEqual(t, "1000", cfg.User)
+	testutil.CheckDeepEqual(t, []string{"PRE=existing", "A=1", "B=2"}, cfg.Env)
+}
+
+func TestApplyToHostConfig_NilSafe(t *testing.T) {
+	var r *RunArgs
+	r.ApplyToHostConfig(nil)
+	r.ApplyToHostConfig(&container.HostConfig{})
+	(&RunArgs{}).ApplyToHostConfig(nil)
+}
+
+func TestApplyToHostConfig_OverridesAndAppends(t *testing.T) {
+	r := &RunArgs{
+		NetworkMode: "host",
+		Binds:       []string{"/a:/a"},
+		ExtraHosts:  []string{"h:1.2.3.4"},
+		Tmpfs:       map[string]string{"/tmp": "size=16m"},
+		Privileged:  true,
+		CapAdd:      []string{"NET_ADMIN"},
+		CapDrop:     []string{"AUDIT_WRITE"},
+	}
+	hc := &container.HostConfig{
+		NetworkMode: container.NetworkMode("bridge"),
+		Binds:       []string{"/pre:/pre"},
+		ExtraHosts:  []string{"pre:0.0.0.0"},
+		Tmpfs:       map[string]string{"/run": "size=8m"},
+		CapAdd:      []string{"SYS_TIME"},
+	}
+	r.ApplyToHostConfig(hc)
+	testutil.CheckDeepEqual(t, "host", string(hc.NetworkMode))
+	testutil.CheckDeepEqual(t, []string{"/pre:/pre", "/a:/a"}, hc.Binds)
+	testutil.CheckDeepEqual(t, []string{"pre:0.0.0.0", "h:1.2.3.4"}, hc.ExtraHosts)
+	testutil.CheckDeepEqual(t, map[string]string{"/run": "size=8m", "/tmp": "size=16m"}, hc.Tmpfs)
+	testutil.CheckDeepEqual(t, true, hc.Privileged)
+	testutil.CheckDeepEqual(t, []string{"SYS_TIME", "NET_ADMIN"}, []string(hc.CapAdd))
+	testutil.CheckDeepEqual(t, []string{"AUDIT_WRITE"}, []string(hc.CapDrop))
+}
+
+func TestApplyToHostConfig_EmptyRunArgsDoesNotOverrideNetwork(t *testing.T) {
+	r := &RunArgs{}
+	hc := &container.HostConfig{NetworkMode: container.NetworkMode("bridge")}
+	r.ApplyToHostConfig(hc)
+	testutil.CheckDeepEqual(t, "bridge", string(hc.NetworkMode))
+}