minor symfony#23582 [Console] Improve Table performance (ro0NL)

This PR was submitted for the 3.4 branch but it was merged into the 4.1-dev branch instead (closes symfony#23582).

Discussion
----------

[Console] Improve Table performance

| Q             | A
| ------------- | ---
| Branch?       | 3.4
| Bug fix?      | might
| New feature?  | might as well
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #... <!-- #-prefixed issue number(s), if any -->
| License       | MIT
| Doc PR        | symfony/symfony-docs#... <!--highly recommended for new features-->

Little memory gain for console tables :)

`setRows(array_fill(0, 1000000, [str_repeat('x', 100)]))`

Before: +-20ms / +- 900mb
After: +- 20ms / +- 530mb

Next step could be to open public API for `iterable`, although we pre-iterate rows for calculation interally, it could be a nice feature :)

Commits
-------

2c9922e [Console] Improve Table performance

Author: fabpot

src/Symfony/Component/Console/Helper/Table.php

@@ -275,29 +275,40 @@ public function setRow($column, array $row)
      */
     public function render()
     {
-        $this->calculateNumberOfColumns();
-        $rows = $this->buildTableRows($this->rows);
-        $headers = $this->buildTableRows($this->headers);
+        $rows = array_merge($this->headers, array($divider = new TableSeparator()), $this->rows);
+        $this->calculateNumberOfColumns($rows);
 
-        $this->calculateColumnsWidth(array_merge($headers, $rows));
+        $rows = $this->buildTableRows($rows);
+        $this->calculateColumnsWidth($rows);
 
-        $this->renderRowSeparator();
-        if (!empty($headers)) {
-            foreach ($headers as $header) {
-                $this->renderRow($header, $this->style->getCellHeaderFormat());
-                $this->renderRowSeparator();
-            }
-        }
+        $isHeader = true;
+        $isFirstRow = false;
         foreach ($rows as $row) {
+            if ($divider === $row) {
+                $isHeader = false;
+                $isFirstRow = true;
+
+                continue;
+            }
             if ($row instanceof TableSeparator) {
                 $this->renderRowSeparator();
-            } else {
-                $this->renderRow($row, $this->style->getCellRowFormat());
+
+                continue;
             }
+            if (!$row) {
+                continue;
+            }
+
+            if ($isHeader || $isFirstRow) {
+                $this->renderRowSeparator();
+                if ($isFirstRow) {
+                    $isFirstRow = false;
+                }
+            }
+
+            $this->renderRow($row, $isHeader ? $this->style->getCellHeaderFormat() : $this->style->getCellRowFormat());
         }
-        if (!empty($rows)) {
-            $this->renderRowSeparator();
-        }
+        $this->renderRowSeparator();
 
         $this->cleanup();
     }
@@ -340,10 +351,6 @@ private function renderColumnSeparator()
      */
     private function renderRow(array $row, string $cellFormat)
     {
-        if (empty($row)) {
-            return;
-        }
-
         $rowContent = $this->renderColumnSeparator();
         foreach ($this->getRowColumns($row) as $column) {
             $rowContent .= $this->renderCell($row, $column, $cellFormat);
@@ -386,14 +393,10 @@ private function renderCell(array $row, int $column, string $cellFormat)
     /**
      * Calculate number of columns for this table.
      */
-    private function calculateNumberOfColumns()
+    private function calculateNumberOfColumns($rows)
     {
-        if (null !== $this->numberOfColumns) {
-            return;
-        }
-
         $columns = array(0);
-        foreach (array_merge($this->headers, $this->rows) as $row) {
+        foreach ($rows as $row) {
             if ($row instanceof TableSeparator) {
                 continue;
             }
@@ -429,15 +432,17 @@ private function buildTableRows($rows)
             }
         }
 
-        $tableRows = array();
-        foreach ($rows as $rowKey => $row) {
-            $tableRows[] = $this->fillCells($row);
-            if (isset($unmergedRows[$rowKey])) {
-                $tableRows = array_merge($tableRows, $unmergedRows[$rowKey]);
-            }
-        }
+        return new TableRows(function () use ($rows, $unmergedRows) {
+            foreach ($rows as $rowKey => $row) {
+                yield $this->fillCells($row);
 
-        return $tableRows;
+                if (isset($unmergedRows[$rowKey])) {
+                    foreach ($unmergedRows[$rowKey] as $row) {
+                        yield $row;
+                    }
+                }
+            }
+        });
     }
 
     /**

src/Symfony/Component/Console/Helper/TableRows.php

@@ -0,0 +1,32 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <[email protected]>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\Console\Helper;
+
+/**
+ * @internal
+ */
+class TableRows implements \IteratorAggregate
+{
+    private $generator;
+
+    public function __construct(callable $generator)
+    {
+        $this->generator = $generator;
+    }
+
+    public function getIterator()
+    {
+        $g = $this->generator;
+
+        return $g();
+    }
+}