fix(compose): preserve environment variable semantics (#11794)

tests/Unit/ExtractHardcodedEnvironmentVariablesTest.php

@@ -93,6 +93,70 @@ YAML;
         ->and($result[1]['value'])->toBe('false');
 });
 
+test('distinguishes passthrough variables from explicit empty values', function () {
+    $yaml = <<<'YAML'
+services:
+  list-app:
+    environment:
+      - PASSTHROUGH
+      - EMPTY=
+  map-app:
+    environment:
+      MAPPED_PASSTHROUGH:
+      MAPPED_EMPTY: ""
+YAML;
+
+    $result = extractHardcodedEnvironmentVariables($yaml)->keyBy('key');
+
+    expect($result['PASSTHROUGH']['is_passthrough'])->toBeTrue()
+        ->and($result['EMPTY']['is_passthrough'])->toBeFalse()
+        ->and($result['MAPPED_PASSTHROUGH']['is_passthrough'])->toBeTrue()
+        ->and($result['MAPPED_EMPTY']['is_passthrough'])->toBeFalse();
+});
+
+test('detects Compose inputs that must remain unset when blank', function () {
+    $yaml = <<<'YAML'
+services:
+  app:
+    environment:
+      BARE:
+      DASH: ${DASH-default}
+      QUESTION: ${QUESTION?required}
+      COLON_DASH: ${COLON_DASH:-default}
+      ESCAPED: $${ESCAPED-nope}
+YAML;
+
+    expect(dockerComposeEnvironmentVariableShouldBeUnset($yaml, 'BARE', null))->toBeTrue()
+        ->and(dockerComposeEnvironmentVariableShouldBeUnset($yaml, 'DASH', null))->toBeTrue()
+        ->and(dockerComposeEnvironmentVariableShouldBeUnset($yaml, 'QUESTION', null))->toBeTrue()
+        ->and(dockerComposeEnvironmentVariableShouldBeUnset($yaml, 'COLON_DASH', null))->toBeTrue()
+        ->and(dockerComposeEnvironmentVariableShouldBeUnset($yaml, 'ESCAPED', null))->toBeFalse()
+        ->and(dockerComposeEnvironmentVariableShouldBeUnset($yaml, 'DASH', ''))->toBeFalse()
+        ->and(dockerComposeEnvironmentVariableShouldBeUnset($yaml, 'COLON_DASH', 'debug'))->toBeFalse();
+});
+
+test('extracts fallback and required metadata from derived Compose values', function () {
+    $compose = <<<'YAML'
+services:
+  app:
+    environment:
+      URL: https://${HOST:-${INNER_HOST:-localhost}/api}
+      PATH: ${TOKEN?TOKEN is required}/v1
+YAML;
+
+    expect(dockerComposeEnvironmentVariableInfo($compose, 'HOST'))->toMatchArray([
+        'services' => ['app'],
+        'default' => '${INNER_HOST:-localhost}/api',
+        'operator' => ':-',
+        'required' => false,
+    ])->and(dockerComposeEnvironmentVariableInfo($compose, 'TOKEN'))->toMatchArray([
+        'services' => ['app'],
+        'default' => null,
+        'operator' => '?',
+        'required' => true,
+    ]);
+});
+
 test('returns empty collection for malformed YAML', function () {
     $yaml = 'invalid: yaml: content::: [[[';