Fix bad body encoding and allow list of intervals

src/AsyncResult.php

@@ -105,18 +105,34 @@
 
 	/**
 	 * Wait until task is ready, and return its final result.
+	 *
+	 * @param float|list<float> $interval Either a single interval in which to
+	 *     try fetching the result, or a list of intervals which will be used in
+	 *     specified order - the last interval is then tried repeatedly.
 	 */
-	public function get(?float $timeout = 10, float $interval = 0.4): mixed {
+	public function get(
+		?float $timeout = 10,
+		float|array $interval = 0.4,
+	): mixed {
 
 		$startTime = Functions::monotonicTime();
 		$timeoutTime = $timeout !== null
 			? $startTime + $timeout
 			: null;
 
-		$uInterval = (int) ($interval * 1_000_000);
+		$waits = is_array($interval) ? $interval : [$interval];
+
 		while (!$this->isReady()) {
 
-			usleep($uInterval);
+			// For intervals specified as [0.1, 0.6, 10] we'll first wait
+			// 0.1s, then 0.6s, then 10s repeatedly, until the task is ready (or
+			// we time out).
+			if ($waits) {
+				$wait = array_shift($waits);
+			}
+
+			$uWait = (int) ($wait * 1_000_000);
+			usleep($uWait);
 
 			if (
 				$timeoutTime !== null

src/Serializers/JsonSerializer.php

@@ -6,12 +6,16 @@
 
 class JsonSerializer implements ISerializer {
 
+	private const JSON_ENCODE_FLAGS
+		= JSON_THROW_ON_ERROR
+		| JSON_INVALID_UTF8_SUBSTITUTE;
+
 	public function getContentType(): string {
 		return "application/json";
 	}
 
 	public function encode(mixed $input): string {
-		return json_encode($input, JSON_UNESCAPED_SLASHES);
+		return json_encode($input, self::JSON_ENCODE_FLAGS);
 	}
 
 	/**

tests/suite/JsonSerializer.phpt

@@ -0,0 +1,25 @@
+<?php
+
+use Tester\Assert;
+
+use Smuuf\CeleryForPhp\Serializers\JsonSerializer;
+
+require __DIR__ . '/../bootstrap.php';
+
+$s = new JsonSerializer();
+
+//
+// Serializing JSOn with broken unicode doesn't fail completely.
+// Broken unicode will be substituted with "\ufffd" (REPLACEMENT CHARACTER).
+//
+
+$brokenUnicode = "\xC3Hello";
+Assert::same('"\ufffdHello"', $s->encode("\xC3Hello"));
+
+//
+// JSON encoded crashes if the encoding is not successful, instead of returning
+// false.
+//
+
+$unEncodable = [STDERR]; // File descriptor cannot be JSON-encoded.
+Assert::exception(fn() => $s->encode($unEncodable), \JsonException::class);