From 067b04aaf148cd57aff57ca2b52efcf95b4f70e7 Mon Sep 17 00:00:00 2001
From: epriestley <git@epriestley.com>
Date: Fri, 3 Apr 2020 12:12:37 -0700
Subject: [PATCH] If HTTP response headers are already sent, don't fiddle with
 "zlib.output_compression"

Summary:
We write some synthetic HTTP responses inside unit tests. Some responses have an indirect side effect of adjusting "zlib.output_compression", but this adjustment fails if headers have already been output. From a CLI context, headers appear to count as already-output after we write anything to stdout:

```
<?php

echo headers_sent() ? "Y" : "N";
echo "\n";
echo headers_sent() ? "Y" : "N";
echo "\n";
```

This script prints "N", then "Y".

Recently, the default severity of warnings was increased in libphutil; this has been a long-standing warning but now causes test failures.

This behavior is sort of silly but the whole thing is kind of moot anyway. Just skip it if "headers_sent()" is true.

Test Plan: Ran "arc unit --everything", got clean results.

Differential Revision: https://secure.phabricator.com/D21055
---
 src/aphront/response/AphrontResponse.php | 20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

diff --git a/src/aphront/response/AphrontResponse.php b/src/aphront/response/AphrontResponse.php
index 9cfda0f5c1..8a94adf38d 100644
--- a/src/aphront/response/AphrontResponse.php
+++ b/src/aphront/response/AphrontResponse.php
@@ -417,13 +417,19 @@ abstract class AphrontResponse extends Phobject {
   }
 
   public function willBeginWrite() {
-    if ($this->shouldCompressResponse()) {
-      // Enable automatic compression here. Webservers sometimes do this for
-      // us, but we now detect the absence of compression and warn users about
-      // it so try to cover our bases more thoroughly.
-      ini_set('zlib.output_compression', 1);
-    } else {
-      ini_set('zlib.output_compression', 0);
+    // If we've already sent headers, these "ini_set()" calls will warn that
+    // they have no effect. Today, this always happens because we're inside
+    // a unit test, so just skip adjusting the setting.
+
+    if (!headers_sent()) {
+      if ($this->shouldCompressResponse()) {
+        // Enable automatic compression here. Webservers sometimes do this for
+        // us, but we now detect the absence of compression and warn users about
+        // it so try to cover our bases more thoroughly.
+        ini_set('zlib.output_compression', 1);
+      } else {
+        ini_set('zlib.output_compression', 0);
+      }
     }
   }