From 2e4aa474a9d5c5508473e51762bbad6960d27c2e Mon Sep 17 00:00:00 2001
From: Maxence Lange <maxence@artificial-owl.com>
Date: Mon, 26 Oct 2026 18:12:07 -0100
Subject: [PATCH] feat(logger): lazy logger

Signed-off-by: Maxence Lange <maxence@artificial-owl.com>
---
 lib/private/Log/LazyLogger.php          | 46 +++++++++++++++++++++++++
 lib/private/Log/LazyLoggerInterface.php | 24 +++++++++++++
 lib/private/Server.php                  |  1 +
 lib/public/Log/ILazyLogger.php          | 25 ++++++++++++++
 lib/public/Log/ILazyLoggerInterface.php | 13 +++++++
 5 files changed, 109 insertions(+)
 create mode 100644 lib/private/Log/LazyLogger.php
 create mode 100644 lib/private/Log/LazyLoggerInterface.php
 create mode 100644 lib/public/Log/ILazyLogger.php
 create mode 100644 lib/public/Log/ILazyLoggerInterface.php

diff --git a/lib/private/Log/LazyLogger.php b/lib/private/Log/LazyLogger.php
new file mode 100644
index 0000000000000..9c23334423c0b
--- /dev/null
+++ b/lib/private/Log/LazyLogger.php
@@ -0,0 +1,46 @@
+<?php
+
+declare(strict_types=1);
+/**
+ * SPDX-FileCopyrightText: 2026 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+namespace OC\Log;
+
+use OCP\IConfig;
+use OCP\ILogger;
+use OCP\Log\ILazyLogger;
+use Psr\Log\LoggerInterface;
+
+/**
+ * @inheritDoc
+ * @since 39.0.0
+ */
+class LazyLogger implements ILazyLogger {
+	public ?LazyLoggerInterface $debug = null;
+	public ?LazyLoggerInterface $info = null;
+	public ?LazyLoggerInterface $warning = null;
+	public ?LazyLoggerInterface $error = null;
+	public ?LazyLoggerInterface $fatal = null;
+
+	public function __construct(
+		LoggerInterface $logger,
+		IConfig $config,
+	) {
+		$logLevel = $config->getSystemValueInt('loglevel', ILogger::WARN);
+		if ($logLevel === ILogger::DEBUG) {
+			$this->debug = new LazyLoggerInterface($logger, ILogger::DEBUG);
+		}
+		if ($logLevel <= ILogger::INFO) {
+			$this->info = new LazyLoggerInterface($logger, ILogger::INFO);
+		}
+		if ($logLevel <= ILogger::WARN) {
+			$this->warning = new LazyLoggerInterface($logger, ILogger::WARN);
+		}
+		if ($logLevel <= ILogger::ERROR) {
+			$this->error = new LazyLoggerInterface($logger, ILogger::ERROR);
+		}
+		$this->fatal = new LazyLoggerInterface($logger, ILogger::FATAL);
+	}
+}
diff --git a/lib/private/Log/LazyLoggerInterface.php b/lib/private/Log/LazyLoggerInterface.php
new file mode 100644
index 0000000000000..fe5943521241f
--- /dev/null
+++ b/lib/private/Log/LazyLoggerInterface.php
@@ -0,0 +1,24 @@
+<?php
+
+declare(strict_types=1);
+/**
+ * SPDX-FileCopyrightText: 2026 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+namespace OC\Log;
+
+use OCP\Log\ILazyLoggerInterface;
+use Psr\Log\LoggerInterface;
+
+class LazyLoggerInterface implements ILazyLoggerInterface {
+	public function __construct(
+		private readonly LoggerInterface $logger,
+		private readonly int $level,
+	) {
+	}
+
+	public function print(string $message, array $context = []): void {
+		$this->logger->log($this->level, $message, $context);
+	}
+}
diff --git a/lib/private/Server.php b/lib/private/Server.php
index 9d6dde25f4220..e9c57741e0e6a 100644
--- a/lib/private/Server.php
+++ b/lib/private/Server.php
@@ -576,6 +576,7 @@ public function __construct(
 		});
 		// PSR-3 logger
 		$this->registerAlias(LoggerInterface::class, PsrLoggerAdapter::class);
+		$this->registerAlias(\OCP\Log\ILazyLogger::class, \OC\Log\LazyLogger::class);
 
 		$this->registerAlias(ILogFactory::class, LogFactory::class);
 		$this->registerAlias(IJobList::class, JobList::class);
diff --git a/lib/public/Log/ILazyLogger.php b/lib/public/Log/ILazyLogger.php
new file mode 100644
index 0000000000000..0c838b18c78c0
--- /dev/null
+++ b/lib/public/Log/ILazyLogger.php
@@ -0,0 +1,25 @@
+<?php
+
+declare(strict_types=1);
+/**
+ * SPDX-FileCopyrightText: 2026 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+namespace OCP\Log;
+
+/**
+ * will only initialize the payload if needed:
+ *    $this->logger->debug?->print('my message', ['data' => my_heavy_process()]);
+ *
+ * if loglevel does not allow it, the payload will not be loaded/initialized
+ *
+ * @since 39.0.0
+ */
+interface ILazyLogger {
+	public ?ILazyLoggerInterface $debug { get; }
+	public ?ILazyLoggerInterface $info { get; }
+	public ?ILazyLoggerInterface $warning { get; }
+	public ?ILazyLoggerInterface $error { get; }
+	public ?ILazyLoggerInterface $fatal { get; }
+}
diff --git a/lib/public/Log/ILazyLoggerInterface.php b/lib/public/Log/ILazyLoggerInterface.php
new file mode 100644
index 0000000000000..c0e092ba70ce7
--- /dev/null
+++ b/lib/public/Log/ILazyLoggerInterface.php
@@ -0,0 +1,13 @@
+<?php
+
+declare(strict_types=1);
+/**
+ * SPDX-FileCopyrightText: 2026 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+namespace OCP\Log;
+
+interface ILazyLoggerInterface {
+	public function print(string $message, array $context = []): void;
+}