Fix rawsetenv nil-pointer guard for inherit-from-shell env vars

When a service declares an env var without a value (e.g. `- KEY` or
`KEY:`), MappingWithEquals stores it as a nil *string. The previous
condition `existing != nil && ...` skipped the warning for this case,
allowing silent overwrites. Change to `existing == nil || ...` so the
warning fires for both nil (shell-inherit) and value-mismatch cases.

Add e2e tests for both list-style (`- KEY`) and map-style (`KEY:`)
YAML forms to lock in the behavior.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Signed-off-by: Yohta Kimura <38206553+rajyan@users.noreply.github.com>

pkg/compose/plugins.go

@@ -94,7 +94,7 @@ func (s *composeService) runPlugin(ctx context.Context, project *types.Project,
 				s.Environment[prefix+key] = &val
 			}
 			for key, val := range variables.raw {
-				if existing, ok := s.Environment[key]; ok && existing != nil && *existing != val {
+				if existing, ok := s.Environment[key]; ok && (existing == nil || *existing != val) {
 					logrus.Warnf("provider %q overrides environment variable %q in service %q", service.Name, key, name)
 				}
 				s.Environment[key] = &val

pkg/e2e/fixtures/providers/rawsetenv-inherit-map.yaml

@@ -0,0 +1,15 @@
+services:
+  test:
+    image: alpine
+    command: env
+    environment:
+      CLOUD_REGION:
+    depends_on:
+      - secrets
+  secrets:
+    provider:
+      type: example-provider
+      options:
+        name: secrets
+        type: test1
+        size: 1

pkg/e2e/fixtures/providers/rawsetenv-inherit.yaml

@@ -0,0 +1,15 @@
+services:
+  test:
+    image: alpine
+    command: env
+    environment:
+      - CLOUD_REGION
+    depends_on:
+      - secrets
+  secrets:
+    provider:
+      type: example-provider
+      options:
+        name: secrets
+        type: test1
+        size: 1

pkg/e2e/providers_test.go

@@ -119,6 +119,42 @@ func TestProviderRawSetEnvOverridesUserEnv(t *testing.T) {
 	assert.Check(t, strings.Contains(res.Combined(), "overrides environment variable"), res.Combined())
 }
 
+func TestProviderRawSetEnvOverridesInheritedEnv(t *testing.T) {
+	provider, err := findExecutable("example-provider")
+	assert.NilError(t, err)
+
+	path := fmt.Sprintf("%s%s%s", os.Getenv("PATH"), string(os.PathListSeparator), filepath.Dir(provider))
+	c := NewParallelCLI(t, WithEnv("PATH="+path))
+	const projectName = "rawsetenv-inherit"
+	t.Cleanup(func() {
+		c.cleanupWithDown(t, projectName)
+	})
+
+	res := c.RunDockerComposeCmd(t, "-f", "fixtures/providers/rawsetenv-inherit.yaml", "--project-name", projectName, "up")
+	res.Assert(t, icmd.Success)
+	env := getEnv(res.Combined())
+	assert.Check(t, slices.Contains(env, "CLOUD_REGION=us-east-1"), env)
+	assert.Check(t, strings.Contains(res.Combined(), "overrides environment variable"), res.Combined())
+}
+
+func TestProviderRawSetEnvOverridesInheritedEnvMapForm(t *testing.T) {
+	provider, err := findExecutable("example-provider")
+	assert.NilError(t, err)
+
+	path := fmt.Sprintf("%s%s%s", os.Getenv("PATH"), string(os.PathListSeparator), filepath.Dir(provider))
+	c := NewParallelCLI(t, WithEnv("PATH="+path))
+	const projectName = "rawsetenv-inherit-map"
+	t.Cleanup(func() {
+		c.cleanupWithDown(t, projectName)
+	})
+
+	res := c.RunDockerComposeCmd(t, "-f", "fixtures/providers/rawsetenv-inherit-map.yaml", "--project-name", projectName, "up")
+	res.Assert(t, icmd.Success)
+	env := getEnv(res.Combined())
+	assert.Check(t, slices.Contains(env, "CLOUD_REGION=us-east-1"), env)
+	assert.Check(t, strings.Contains(res.Combined(), "overrides environment variable"), res.Combined())
+}
+
 func getEnv(out string) []string {
 	var env []string
 	scanner := bufio.NewScanner(strings.NewReader(out))