fix: merge User field in MergeSpecImage

MergeSpecImage merges all ImageConfig fields from the target-level config
into the spec-level config, but the User field was omitted. This caused
the user field set under targets.<target>.image to be silently ignored
when building a container image.

Add the User field merge following the same override-if-non-empty pattern
used for all other string fields (Entrypoint, Cmd, WorkingDir, StopSignal,
Base). Also add comprehensive unit tests for MergeSpecImage covering all
field merge behaviors.

Fixes #1013

Signed-off-by: Asish Kumar <officialasishkumar@gmail.com>

Author: officialasishkumar

imgconfig.go

@@ -57,6 +57,10 @@ func MergeSpecImage(spec *Spec, targetKey string) *ImageConfig {
 		if i.Base != "" {
 			cfg.Base = i.Base
 		}
+
+		if i.User != "" {
+			cfg.User = i.User
+		}
 	}
 
 	return &cfg

imgconfig_test.go

@@ -0,0 +1,183 @@
+package dalec
+
+import (
+	"testing"
+
+	"gotest.tools/v3/assert"
+	"gotest.tools/v3/assert/cmp"
+)
+
+func TestMergeSpecImage(t *testing.T) {
+	t.Run("nil spec image returns empty config", func(t *testing.T) {
+		spec := &Spec{}
+		cfg := MergeSpecImage(spec, "foo")
+		assert.Check(t, cmp.DeepEqual(cfg, &ImageConfig{}))
+	})
+
+	t.Run("spec image with no target returns spec image", func(t *testing.T) {
+		spec := &Spec{
+			Image: &ImageConfig{
+				Entrypoint: "/bin/sh",
+				Cmd:        "-c",
+				User:       "1000",
+				WorkingDir: "/app",
+				StopSignal: "SIGTERM",
+			},
+		}
+		cfg := MergeSpecImage(spec, "foo")
+		assert.Check(t, cmp.Equal(cfg.Entrypoint, "/bin/sh"))
+		assert.Check(t, cmp.Equal(cfg.Cmd, "-c"))
+		assert.Check(t, cmp.Equal(cfg.User, "1000"))
+		assert.Check(t, cmp.Equal(cfg.WorkingDir, "/app"))
+		assert.Check(t, cmp.Equal(cfg.StopSignal, "SIGTERM"))
+	})
+
+	t.Run("target overrides user", func(t *testing.T) {
+		spec := &Spec{
+			Image: &ImageConfig{
+				User: "1000",
+			},
+			Targets: map[string]Target{
+				"azlinux3": {
+					Image: &ImageConfig{
+						User: "999",
+					},
+				},
+			},
+		}
+		cfg := MergeSpecImage(spec, "azlinux3")
+		assert.Check(t, cmp.Equal(cfg.User, "999"))
+	})
+
+	t.Run("target sets user when spec has none", func(t *testing.T) {
+		spec := &Spec{
+			Targets: map[string]Target{
+				"azlinux3": {
+					Image: &ImageConfig{
+						User: "999",
+					},
+				},
+			},
+		}
+		cfg := MergeSpecImage(spec, "azlinux3")
+		assert.Check(t, cmp.Equal(cfg.User, "999"))
+	})
+
+	t.Run("spec user preserved when target does not set it", func(t *testing.T) {
+		spec := &Spec{
+			Image: &ImageConfig{
+				User: "1000",
+			},
+			Targets: map[string]Target{
+				"azlinux3": {
+					Image: &ImageConfig{
+						Cmd: "echo hello",
+					},
+				},
+			},
+		}
+		cfg := MergeSpecImage(spec, "azlinux3")
+		assert.Check(t, cmp.Equal(cfg.User, "1000"))
+	})
+
+	t.Run("target overrides all string fields", func(t *testing.T) {
+		spec := &Spec{
+			Image: &ImageConfig{
+				Entrypoint: "/bin/old",
+				Cmd:        "old",
+				WorkingDir: "/old",
+				StopSignal: "SIGINT",
+				Base:       "old:latest",
+				User:       "root",
+			},
+			Targets: map[string]Target{
+				"t1": {
+					Image: &ImageConfig{
+						Entrypoint: "/bin/new",
+						Cmd:        "new",
+						WorkingDir: "/new",
+						StopSignal: "SIGTERM",
+						Base:       "new:latest",
+						User:       "nobody",
+					},
+				},
+			},
+		}
+		cfg := MergeSpecImage(spec, "t1")
+		assert.Check(t, cmp.Equal(cfg.Entrypoint, "/bin/new"))
+		assert.Check(t, cmp.Equal(cfg.Cmd, "new"))
+		assert.Check(t, cmp.Equal(cfg.WorkingDir, "/new"))
+		assert.Check(t, cmp.Equal(cfg.StopSignal, "SIGTERM"))
+		assert.Check(t, cmp.Equal(cfg.Base, "new:latest"))
+		assert.Check(t, cmp.Equal(cfg.User, "nobody"))
+	})
+
+	t.Run("target env appends to spec env", func(t *testing.T) {
+		spec := &Spec{
+			Image: &ImageConfig{
+				Env: []string{"A=1"},
+			},
+			Targets: map[string]Target{
+				"t1": {
+					Image: &ImageConfig{
+						Env: []string{"B=2"},
+					},
+				},
+			},
+		}
+		cfg := MergeSpecImage(spec, "t1")
+		assert.Check(t, cmp.DeepEqual(cfg.Env, []string{"A=1", "B=2"}))
+	})
+
+	t.Run("target volumes merge with spec volumes", func(t *testing.T) {
+		spec := &Spec{
+			Image: &ImageConfig{
+				Volumes: map[string]struct{}{"/data": {}},
+			},
+			Targets: map[string]Target{
+				"t1": {
+					Image: &ImageConfig{
+						Volumes: map[string]struct{}{"/logs": {}},
+					},
+				},
+			},
+		}
+		cfg := MergeSpecImage(spec, "t1")
+		assert.Check(t, cmp.Len(cfg.Volumes, 2))
+		_, hasData := cfg.Volumes["/data"]
+		_, hasLogs := cfg.Volumes["/logs"]
+		assert.Check(t, hasData)
+		assert.Check(t, hasLogs)
+	})
+
+	t.Run("target labels merge with spec labels", func(t *testing.T) {
+		spec := &Spec{
+			Image: &ImageConfig{
+				Labels: map[string]string{"a": "1"},
+			},
+			Targets: map[string]Target{
+				"t1": {
+					Image: &ImageConfig{
+						Labels: map[string]string{"b": "2"},
+					},
+				},
+			},
+		}
+		cfg := MergeSpecImage(spec, "t1")
+		assert.Check(t, cmp.Len(cfg.Labels, 2))
+		assert.Check(t, cmp.Equal(cfg.Labels["a"], "1"))
+		assert.Check(t, cmp.Equal(cfg.Labels["b"], "2"))
+	})
+
+	t.Run("nonexistent target key returns spec image unchanged", func(t *testing.T) {
+		spec := &Spec{
+			Image: &ImageConfig{
+				User:       "1000",
+				Entrypoint: "/bin/sh",
+			},
+		}
+		cfg := MergeSpecImage(spec, "nonexistent")
+		assert.Check(t, cmp.Equal(cfg.User, "1000"))
+		assert.Check(t, cmp.Equal(cfg.Entrypoint, "/bin/sh"))
+	})
+}