Feat/shard filter optimisation

src/Plugins/Shard.php

@@ -21,6 +21,13 @@ final class Shard implements AddsOutput, HandlesArguments
 
     private const string SHARD_OPTION = 'shard';
 
+    /**
+     * The maximum length allowed for the filter argument.
+     * While ARG_MAX can be 2MB, individual arguments are often limited to 128KB (MAX_ARG_STRLEN).
+     * Practical limits in CI environments (like Docker or pipeline runners) can be even lower.
+     */
+    private const int MAX_FILTER_LENGTH = 32768;
+
     /**
      * The shard index and total number of shards.
      *
@@ -72,7 +79,11 @@ public function handleArguments(array $arguments): array
             'testsCount' => count($tests),
         ];
 
-        return [...$arguments, '--filter', $this->buildFilterArgument($testsToRun)];
+        $filter = $this->buildFilterArgument($testsToRun);
+
+        $this->ensureFilterLengthIsSafe($filter);
+
+        return [...$arguments, '--filter', $filter];
     }
 
     /**
@@ -105,10 +116,63 @@ private function removeParallelArguments(array $arguments): array
 
     /**
      * Builds the filter argument for the given tests to run.
+     *
+     * @param  array<int, string>  $testsToRun
      */
-    private function buildFilterArgument(mixed $testsToRun): string
+    private function buildFilterArgument(array $testsToRun): string
     {
-        return addslashes(implode('|', $testsToRun));
+        if ($testsToRun === []) {
+            return '';
+        }
+
+        /** @var array<string, mixed> $tree */
+        $tree = [];
+        foreach ($testsToRun as $class) {
+            $parts = explode('\\', $class);
+            $current = &$tree;
+            foreach ($parts as $part) {
+                if (! isset($current[$part])) {
+                    $current[$part] = [];
+                }
+                $current = &$current[$part];
+            }
+        }
+
+        $buildRegex = function (array $tree) use (&$buildRegex): string {
+            $parts = [];
+            foreach ($tree as $key => $sub) {
+                $subRegex = $buildRegex($sub);
+                if ($subRegex === '') {
+                    $parts[] = preg_quote($key, '/');
+                } else {
+                    $parts[] = preg_quote($key, '/').'\\\\'.(count($sub) > 1 ? '('.$subRegex.')' : $subRegex);
+                }
+            }
+
+            return implode('|', $parts);
+        };
+
+        return $buildRegex($tree);
+    }
+
+    /**
+     * Ensures that the filter length is safe for the current environment.
+     *
+     * @throws InvalidOption
+     */
+    private function ensureFilterLengthIsSafe(string $filter): void
+    {
+        $maxLength = (int) (getenv('PEST_SHARD_MAX_FILTER_LENGTH') ?: self::MAX_FILTER_LENGTH);
+
+        if (strlen($filter) > $maxLength) {
+            throw new InvalidOption(sprintf(
+                'The generated filter for this shard is too long (%d characters). '.
+                'This can cause issues with some environments (limit is %d characters). '.
+                'Please increase the number of shards (e.g., use 1/4 instead of 1/2) to reduce the filter length.',
+                strlen($filter),
+                $maxLength
+            ));
+        }
     }
 
     /**