bug #25858 [DI] Fix initialization of legacy containers by delaying include_once (nicolas-grekas)

This PR was merged into the 3.4 branch.

Discussion
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[DI] Fix initialization of legacy containers by delaying include_once

| Q             | A
| ------------- | ---
| Branch?       | 3.4
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

Best reviewed ignoring whitespaces:
https://github.com/symfony/symfony/pull/25858/files?w=1

Noticed while removing a package: silencing the failing `include_once` as introduced in #25255 is not working for the `$oldContainer` in `Kernel`, and fails with a fatal error when an include succeeds but the class inside misses a parent.

Delaying the calls to `include_once` to the moment where the fresh container is actually used first,  when setting the "kernel" service, works around the situation.

Commits
-------

5e750ec4b5 [DI] Fix initialization of legacy containers by delaying include_once

Author: fabpot

Container.php

@@ -167,6 +167,13 @@ public function setParameter($name, $value)
      */
     public function set($id, $service)
     {
+        // Runs the internal initializer; used by the dumped container to include always-needed files
+        if (isset($this->privates['service_container']) && $this->privates['service_container'] instanceof \Closure) {
+            $initialize = $this->privates['service_container'];
+            unset($this->privates['service_container']);
+            $initialize();
+        }
+
         $id = $this->normalizeId($id);
 
         if ('service_container' === $id) {

Dumper/PhpDumper.php

@@ -1243,16 +1243,16 @@ private function addInlineRequires()
             }
         }
 
-        $code = "\n";
+        $code = '';
 
         foreach ($lineage as $file) {
             if (!isset($this->inlinedRequires[$file])) {
                 $this->inlinedRequires[$file] = true;
-                $code .= sprintf("        include_once %s;\n", $file);
+                $code .= sprintf("\n            include_once %s;", $file);
             }
         }
 
-        return "\n" === $code ? '' : $code;
+        return $code ? sprintf("\n        \$this->privates['service_container'] = function () {%s\n        };\n", $code) : '';
     }
 
     /**

Tests/Fixtures/php/services_inline_requires.php

@@ -46,10 +46,12 @@ public function __construct()
 
         $this->aliases = array();
 
-        include_once $this->targetDirs[1].'/includes/HotPath/I1.php';
-        include_once $this->targetDirs[1].'/includes/HotPath/P1.php';
-        include_once $this->targetDirs[1].'/includes/HotPath/T1.php';
-        include_once $this->targetDirs[1].'/includes/HotPath/C1.php';
+        $this->privates['service_container'] = function () {
+            include_once $this->targetDirs[1].'/includes/HotPath/I1.php';
+            include_once $this->targetDirs[1].'/includes/HotPath/P1.php';
+            include_once $this->targetDirs[1].'/includes/HotPath/T1.php';
+            include_once $this->targetDirs[1].'/includes/HotPath/C1.php';
+        };
     }
 
     public function getRemovedIds()