keep empty environment variables as those must be UNSET in container

loader/normalize.go

@@ -52,14 +52,14 @@ func Normalize(dict map[string]any, env types.Mapping) (map[string]any, error) {
 				}
 
 				if a, ok := build["args"]; ok {
-					build["args"], _ = resolve(a, fn)
+					build["args"], _ = resolve(a, fn, false)
 				}
 
 				service["build"] = build
 			}
 
 			if e, ok := service["environment"]; ok {
-				service["environment"], _ = resolve(e, fn)
+				service["environment"], _ = resolve(e, fn, true)
 			}
 
 			var dependsOn map[string]any
@@ -178,12 +178,12 @@ func normalizeNetworks(dict map[string]any) {
 	}
 }
 
-func resolve(a any, fn func(s string) (string, bool)) (any, bool) {
+func resolve(a any, fn func(s string) (string, bool), keepEmpty bool) (any, bool) {
 	switch v := a.(type) {
 	case []any:
 		var resolved []any
 		for _, val := range v {
-			if r, ok := resolve(val, fn); ok {
+			if r, ok := resolve(val, fn, keepEmpty); ok {
 				resolved = append(resolved, r)
 			}
 		}
@@ -197,6 +197,8 @@ func resolve(a any, fn func(s string) (string, bool)) (any, bool) {
 			}
 			if s, ok := fn(key); ok {
 				resolved[key] = s
+			} else if keepEmpty {
+				resolved[key] = nil
 			}
 		}
 		return resolved, true
@@ -205,6 +207,9 @@ func resolve(a any, fn func(s string) (string, bool)) (any, bool) {
 			if val, ok := fn(v); ok {
 				return fmt.Sprintf("%s=%s", v, val), true
 			}
+			if keepEmpty {
+				return v, true
+			}
 			return "", false
 		}
 		return v, true

loader/normalize_test.go

@@ -336,3 +336,43 @@ services:
 	assert.NilError(t, err)
 	assert.DeepEqual(t, expect, model)
 }
+
+func TestNormalizeEnvironment(t *testing.T) {
+	project := `
+name: myProject
+services:  
+  test: 
+    environment:
+      - FOO
+      - BAR
+      - ZOT=QIX
+`
+
+	expected := `
+name: myProject
+networks:
+  default:
+    name: myProject_default
+services:  
+  test: 
+    environment:
+      - FOO
+      - BAR=bar
+      - ZOT=QIX
+    networks:
+      default: null
+`
+	var model map[string]any
+	err := yaml.Unmarshal([]byte(project), &model)
+	assert.NilError(t, err)
+	model, err = Normalize(model, map[string]string{
+		"BAR": "bar",
+		"ZOT": "zot",
+	})
+	assert.NilError(t, err)
+
+	var expect map[string]any
+	err = yaml.Unmarshal([]byte(expected), &expect)
+	assert.NilError(t, err)
+	assert.DeepEqual(t, expect, model)
+}