Clear Output Buffering Only When It's Been Started (#3741)

Fix #3739. User is seeing an intermittent notice when running samples using a web browser. The notice is comming from ob_clean, complaining that there is no buffer to delete. I frankly do not understand what the ob_clean is supposed to be paired with, nor why I cannot duplicate this result. Possibly, a better solution would be to eliminate the ob_clean; but using ob_get_length beforehand to see if there is anything to clean up seems safer, and I can't think of a downside.

The code in question is never executed when a sample is run from the command line. Consequently, no formal unit test is possible. The user reporting the problem was asked to test the change, and confirmed that the problem went away; no new problem arose on my system.

Author: oleibman

samples/bootstrap/css/bootstrap.min.css

@@ -4,6 +4,12 @@
 
 use PhpOffice\PhpSpreadsheet\Exception;
 
+/**
+ * Assist downloading files when samples are run in browser.
+ * Never run as part of unit tests, which are command line.
+ *
+ * @codeCoverageIgnore
+ */
 class Downloader
 {
     protected string $filepath;
@@ -49,7 +55,13 @@ public function download(): void
 
     public function headers(): void
     {
-        ob_clean();
+        // I cannot tell what this ob_clean is paired with.
+        // I have never seen a problem with it, but someone has - issue 3739.
+        // Perhaps it should be removed altogether,
+        // but making it conditional seems harmless, and safer.
+        if ((int) ob_get_length() > 0) {
+            ob_clean();
+        }
 
         $this->contentType();
         $this->contentDisposition();

src/PhpSpreadsheet/Helper/Downloader.php

@@ -131,7 +131,9 @@ public function write(Spreadsheet $spreadsheet, $filename, array $writers = ['Xl
             $writer->save($path);
             $this->logWrite($writer, $path, /** @scrutinizer ignore-type */ $callStartTime);
             if ($this->isCli() === false) {
+                // @codeCoverageIgnoreStart
                 echo '<a href="/download.php?type=' . pathinfo($path, PATHINFO_EXTENSION) . '&name=' . basename($path) . '">Download ' . basename($path) . '</a><br />';
+                // @codeCoverageIgnoreEnd
             }
         }
 
@@ -190,12 +192,17 @@ public function log(string $message): void
         echo($this->isCli() ? date('H:i:s ') : '') . $message . $eol;
     }
 
+    /**
+     * Render chart as part of running chart samples in browser.
+     * Charts are not rendered in unit tests, which are command line.
+     *
+     * @codeCoverageIgnore
+     */
     public function renderChart(Chart $chart, string $fileName): void
     {
         if ($this->isCli() === true) {
             return;
         }
-
         Settings::setChartRenderer(MtJpGraphRenderer::class);
 
         $fileName = $this->getFilename($fileName, 'png');
@@ -261,9 +268,8 @@ public function logWrite(IWriter $writer, $path, $callStartTime): void
         $reflection = new ReflectionClass($writer);
         $format = $reflection->getShortName();
 
-        $message = ($this->isCli() === true)
-            ? "Write {$format} format to {$path}  in " . sprintf('%.4f', $callTime) . ' seconds'
-            : "Write {$format} format to <code>{$path}</code>  in " . sprintf('%.4f', $callTime) . ' seconds';
+        $codePath = $this->isCli() ? $path : "<code>$path</code>";
+        $message = "Write {$format} format to {$codePath}  in " . sprintf('%.4f', $callTime) . ' seconds';
 
         $this->log($message);
     }