Add csv formatter.

src/FormatterManager.php

@@ -16,6 +16,7 @@ public function __construct()
             'print-r' => \Consolidation\OutputFormatters\Formatters\PrintRFormatter::class,
             'var_export' => \Consolidation\OutputFormatters\Formatters\VarExportFormatter::class,
             'list' => \Consolidation\OutputFormatters\Formatters\ListFormatter::class,
+            'csv' => \Consolidation\OutputFormatters\Formatters\CsvFormatter::class,
             'table' => \Consolidation\OutputFormatters\Formatters\TableFormatter::class,
         ];
     }

src/Formatters/CsvFormatter.php

@@ -0,0 +1,45 @@
+<?php
+namespace Consolidation\OutputFormatters\Formatters;
+
+use Consolidation\OutputFormatters\FormatterInterface;
+use Symfony\Component\Console\Output\OutputInterface;
+
+class CsvFormatter implements FormatterInterface
+{
+    /**
+     * @inheritdoc
+     */
+    public function write($data, $options, OutputInterface $output)
+    {
+        if (empty($data) || !is_array($data)) {
+            return;
+        }
+        if (!is_array($data[0])) {
+            $this->writeCsvLine($data, $options, $output);
+            return;
+        }
+        $this->writeCsvLines($data, $options, $output);
+    }
+
+    public function writeCsvLines($data, $options, OutputInterface $output)
+    {
+        foreach ($data as $line) {
+            $this->writeCsvLine($line, $options, $output);
+        }
+    }
+
+    public function writeCsvLine($data, $options, OutputInterface $output)
+    {
+        $output->write($this->csvEscape($data));
+    }
+
+    protected function csvEscape($data, $delimiter = ',')
+    {
+        $buffer = fopen('php://temp', 'r+');
+        fputcsv($buffer, $data, $delimiter);
+        rewind($buffer);
+        $csv = fgets($buffer);
+        fclose($buffer);
+        return $csv;
+    }
+}

tests/testFormatters.php

@@ -298,6 +298,60 @@ function testList()
         $this->assertFormattedOutputMatches($expected, 'list', $data);
     }
 
+    function testSimpleCsv()
+    {
+        $data = ['a', 'b', 'c'];
+        $expected = "a,b,c";
+
+        $this->assertFormattedOutputMatches($expected, 'csv', $data);
+    }
+
+    function testLinesOfCsv()
+    {
+        $data = [['a', 'b', 'c'], ['x', 'y', 'z']];
+        $expected = "a,b,c\nx,y,z";
+
+        $this->assertFormattedOutputMatches($expected, 'csv', $data);
+    }
+
+    function testCsvWithEscapedValues()
+    {
+        $data = ["Red apple", "Yellow lemon"];
+        $expected = '"Red apple","Yellow lemon"';
+
+        $this->assertFormattedOutputMatches($expected, 'csv', $data);
+    }
+
+    function testCsvWithEmbeddedSingleQuote()
+    {
+        $data = ["John's book", "Mary's laptop"];
+        $expected = <<<EOT
+"John's book","Mary's laptop"
+EOT;
+
+        $this->assertFormattedOutputMatches($expected, 'csv', $data);
+    }
+
+    function testCsvWithEmbeddedDoubleQuote()
+    {
+        $data = ['The "best" solution'];
+        $expected = <<<EOT
+"The ""best"" solution"
+EOT;
+
+        $this->assertFormattedOutputMatches($expected, 'csv', $data);
+    }
+
+    function testCsvBothKindsOfQuotes()
+    {
+        $data = ["John's \"new\" book", "Mary's \"modified\" laptop"];
+        $expected = <<<EOT
+"John's ""new"" book","Mary's ""modified"" laptop"
+EOT;
+
+        $this->assertFormattedOutputMatches($expected, 'csv', $data);
+    }
+
     function testSimpleTable()
     {
         $data = [