Keep Symfony inventory and order writes on one Doctrine transaction

A transaction can commit invalid business state if the application ignores the result of a conditional write. The stock predicate prevents an overdraw, and the affected-row check prevents creating an order that reserved nothing.

Save this requirement in Perch and check it after each agent edit. The rule gives your agent a named check to run, a finding to repair, and the same command to recheck.

Implement the Symfony boundary

Save this illustrative integration module as src/Service/ReserveOrder.php.

<?php
namespace App\Service;
use Doctrine\DBAL\Connection;

class ReserveOrder {
    public function __construct(private Connection $connection) {}
    public function reserve(string $tenant, string $sku, int $quantity): void {
        if ($quantity <= 0) throw new \InvalidArgumentException('Positive quantity required');
        $this->connection->transactional(function (Connection $tx) use ($tenant, $sku, $quantity) {
            $changed = $tx->executeStatement(
                'UPDATE inventory SET available=available-? WHERE tenant_id=? AND sku=? AND available>=?',
                [$quantity, $tenant, $sku, $quantity]
            );
            if ($changed !== 1) throw new \RuntimeException('Insufficient stock');
            $tx->executeStatement('INSERT INTO orders (tenant_id, sku, quantity) VALUES (?, ?, ?)', [$tenant, $sku, $quantity]);
        });
    }
}

The order, inventory, or resource-lifetime scenario is adapted from Perch’s public order-service source at commit 4af67af. This Symfony implementation is an illustrative adaptation.

Integrate with your application

Inject a Doctrine DBAL Connection to the primary database, with a unique tenant/SKU stock row. Keep every related statement on the callback’s tx connection. Use your authenticated tenant scope at the controller boundary and database constraints as a second defense. Add an outbox record within this transaction for downstream work.

Exercise the boundary and failure paths

Add regression tests for these cases in your existing Symfony test project. Use separate connections or deliberately reordered completion where the case involves concurrency; a sequential happy-path test does not exercise that failure. Run the test command after creating the matching test file or suite:

php bin/phpunit tests/Service/ReserveOrderTest.php

The scenarios above specify tests to implement. A completed Perch source check below is separate from running these application integration tests.

Introduce the specific agent regression

In a throwaway copy, replace this source span:

if ($changed !== 1) throw new \RuntimeException('Insufficient stock');

with:

// Remove the source span shown above.

Run the relevant negative test and the Perch command on that broken copy. Restore the corrected source before committing the application. The supplied mutation reproduces the exact regression for the rule check.

Preserve the requirement as a Perch rule

Save this in .perch/rules/perch-guide-symfony-dbal-transaction-handle.yaml at the repository root, keeping your existing perch.yaml:

- name: failed-reservation-prevents-order
  where: "src/Service/ReserveOrder.php"
  ensure: >-
    When the conditional inventory UPDATE changes no row, reserve must throw before inserting an order.

Install and authenticate the CLI once, then check the current working file:

npm install -g @lakeday/perch
perch login
perch check src/Service/ReserveOrder.php --rules failed-reservation-prevents-order --json

Use Node 22 or newer. The framework can use another language; Perch’s CLI remains a Node command. A gated finding exits 3. Exits 1 or 2 mean the check did not complete and must be reported as a blocker.

Inspect the captured rule check

On 2026-10-14, Perch using jev-latest checked the exact fixed and broken source provided here. The capture records SHA-256 hashes of both sources and the requirement.

The rule distinguished these controls in this run. Raw Perch capture · Exact sources and mutation.

Install the rule pack and configure your agent

Download this rule pack ZIP · Download the YAML rules · Agent task. The pack contains the rule, its example paths and the repair/recheck instructions. Review the where selector before using it in an existing project. Keep your root perch.yaml; install this rule as a separate file under .perch/rules/.

1. Install Perch using Node 22 or newer and sign in once:

npm install -g @lakeday/perch
perch login

2. Download the pack, inspect it, and extract it from your repository root. The extraction preserves any existing files:

curl -fL 'https://frameworkrecipes.dev/symfony/dbal-transaction-handle/rule-pack.zip' -o 'perch-guide-symfony-dbal-transaction-handle.zip'
unzip -n 'perch-guide-symfony-dbal-transaction-handle.zip'

The installed rule is .perch/rules/perch-guide-symfony-dbal-transaction-handle.yaml. Its selector matches src/Service/ReserveOrder.php in this example; adapt the selector to your application file before checking an existing project.

3. Configure the coding agent you use. Run one of these commands:

Claude Code:

perch setup claude-code

Codex:

perch setup codex

Cursor:

perch setup cursor

Pi:

perch setup pi

4. Ask the agent to edit the implementation and check the saved requirement:

Use the installed Perch skill while editing src/Service/ReserveOrder.php. Preserve failed-reservation-prevents-order. Run perch check src/Service/ReserveOrder.php --rules failed-reservation-prevents-order --json after the edit. Read each finding and the affected code, fix the implementation, and run the identical check again after the fix. Keep the rule and regression tests intact. Run the application's relevant regression tests and report the commands and actual results. Exit 3 means a rule finding; exit 1 or 2 means the check did not complete. Report an unavailable or incomplete check as blocked. Do not claim the application tests ran if only the Perch check ran.

5. After repairing a finding, run the same check again and inspect the result:

perch check src/Service/ReserveOrder.php --rules failed-reservation-prevents-order --json

Commit the downloaded rule and the installed agent configuration with your application. The rule file adds no guarantee of correctness; keep the regression tests from this guide.

With the base reference fetched, use perch scan --since origin/main --filter type=lint in CI.

Framework references and verification scope

• www.doctrine-project.org reference

The dated capture records the source check shown above. Implement the adapters, schema and regression tests described in this guide in your application. Unchanged requests reuse cached answers; fresh model judgments can vary. Model analysis sends relevant source to the configured service.