Handle the case where no items has been returned (#178)

Closes #176

src/Configuration.php

@@ -15,6 +15,7 @@
 
 use Webmozart\Assert\Assert;
 use function ceil;
+use function max;
 use function min;
 use function sprintf;
 
@@ -185,10 +186,10 @@ private static function createForWithChildProcesses(
             );
         }
 
-        $numberOfSegments = (int) ceil($numberOfItems / $segmentSize);
+        $numberOfSegments = max(1, (int) ceil($numberOfItems / $segmentSize));
         Assert::positiveInteger($numberOfSegments);
 
-        $numberOfSegmentsRequired = (int) ceil($numberOfItems / $segmentSize);
+        $numberOfSegmentsRequired = max(1, (int) ceil($numberOfItems / $segmentSize));
         Assert::positiveInteger($numberOfSegmentsRequired);
 
         $requiredNumberOfProcesses = min($numberOfProcesses, $numberOfSegmentsRequired);

tests/ConfigurationTest.php

@@ -293,6 +293,16 @@ private static function childValuesProvider(): iterable
             2,
             2,
         );
+
+        yield 'no item' => $createSet(
+            0,
+            1,
+            5,
+            5,
+            1,
+            1,
+            0,
+        );
     }
 
     /**

tests/Fixtures/Command/NoItemCommand.php

@@ -0,0 +1,40 @@
+<?php
+
+/*
+ * This file is part of the Webmozarts Console Parallelization package.
+ *
+ * (c) Webmozarts GmbH <office@webmozarts.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+declare(strict_types=1);
+
+namespace Webmozarts\Console\Parallelization\Fixtures\Command;
+
+use Symfony\Component\Console\Input\InputInterface;
+use Symfony\Component\Console\Output\OutputInterface;
+use Webmozarts\Console\Parallelization\Fixtures\ItemNamingCapabilities;
+use Webmozarts\Console\Parallelization\ParallelCommand;
+use Webmozarts\Console\Parallelization\UnexpectedCall;
+
+final class NoItemCommand extends ParallelCommand
+{
+    use ItemNamingCapabilities;
+
+    public function __construct()
+    {
+        parent::__construct('test:no-item');
+    }
+
+    protected function fetchItems(InputInterface $input, OutputInterface $output): iterable
+    {
+        return [];
+    }
+
+    protected function runSingleCommand(string $item, InputInterface $input, OutputInterface $output): void
+    {
+        throw UnexpectedCall::forMethod(__METHOD__);
+    }
+}

tests/Fixtures/ItemNamingCapabilities.php

@@ -0,0 +1,29 @@
+<?php
+
+/*
+ * This file is part of the Webmozarts Console Parallelization package.
+ *
+ * (c) Webmozarts GmbH <office@webmozarts.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+declare(strict_types=1);
+
+namespace Webmozarts\Console\Parallelization\Fixtures;
+
+trait ItemNamingCapabilities
+{
+    /**
+     * @param positive-int|0|null $count
+     */
+    protected function getItemName(?int $count): string
+    {
+        if (null === $count) {
+            return 'item(s)';
+        }
+
+        return $count > 1 ? 'items' : 'item';
+    }
+}

tests/Integration/NoItemCommandTest.php

@@ -0,0 +1,74 @@
+<?php
+
+/*
+ * This file is part of the Webmozarts Console Parallelization package.
+ *
+ * (c) Webmozarts GmbH <office@webmozarts.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+declare(strict_types=1);
+
+namespace Webmozarts\Console\Parallelization\Integration;
+
+use PHPUnit\Framework\TestCase;
+use Symfony\Component\Console\Application;
+use Symfony\Component\Console\Command\Command;
+use Symfony\Component\Console\Tester\CommandTester;
+use Webmozarts\Console\Parallelization\Fixtures\Command\NoItemCommand;
+
+/**
+ * @coversNothing
+ *
+ * @internal
+ */
+class NoItemCommandTest extends TestCase
+{
+    private Command $command;
+    private CommandTester $commandTester;
+
+    protected function setUp(): void
+    {
+        $this->command = (new Application())->add(new NoItemCommand());
+        $this->commandTester = new CommandTester($this->command);
+    }
+
+    protected function tearDown(): void
+    {
+        unset($this->command, $this->commandTester);
+    }
+
+    public function test_it_can_execute_a_command_that_gives_no_item(): void
+    {
+        $this->commandTester->execute(
+            ['command' => 'test:no-item'],
+            ['interactive' => true],
+        );
+
+        $expected = <<<'EOF'
+            Processing 0 item in segments of 50, batches of 50, 1 round, 0 batch, with 1 child process.
+
+                0 [>---------------------------] 10 secs 10.0 MiB
+
+             // Memory usage: 10.0 MB (peak: 10.0 MB), time: 10 secs
+
+            Processed 0 item.
+
+            EOF;
+
+        $actual = OutputNormalizer::removeIntermediateFixedProgressBars(
+            $this->getOutput($this->commandTester),
+        );
+
+        self::assertSame($expected, $actual, $actual);
+    }
+
+    private function getOutput(CommandTester $commandTester): string
+    {
+        $output = $commandTester->getDisplay(true);
+
+        return OutputNormalizer::normalize($output);
+    }
+}