From 9fedecf4ab6035dca596648cd31ce85798ad69d5 Mon Sep 17 00:00:00 2001
From: Frank Denis <124872+jedisct1@users.noreply.github.com>
Date: Thu, 23 Mar 2023 10:05:58 +0100
Subject: [PATCH] http.Client: don't prematurely check
 transfer_{encoding,compression} (#15040)

Common headers in a response are:

    Content-Encoding: gzip
    Transfer-Encoding: chunked

We used to return `HttpHeadersInvalid` if a `Transfer-Encoding` header
was received while the compression was already set.

However, Transfer-Encoding may not include compression. We should
only return an error if we are setting a value that was already set.

Fixes compatibility with a bunch of websites.
---
 lib/std/http/Client/Response.zig | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/lib/std/http/Client/Response.zig b/lib/std/http/Client/Response.zig
index 8b2a9a4918..f1a3b07dd8 100644
--- a/lib/std/http/Client/Response.zig
+++ b/lib/std/http/Client/Response.zig
@@ -74,8 +74,6 @@ pub const Headers = struct {
                 if (headers.content_length != null) return error.HttpHeadersInvalid;
                 headers.content_length = try std.fmt.parseInt(u64, header_value, 10);
             } else if (std.ascii.eqlIgnoreCase(header_name, "transfer-encoding")) {
-                if (headers.transfer_encoding != null or headers.transfer_compression != null) return error.HttpHeadersInvalid;
-
                 // Transfer-Encoding: second, first
                 // Transfer-Encoding: deflate, chunked
                 var iter = std.mem.splitBackwards(u8, header_value, ",");
@@ -84,8 +82,10 @@ pub const Headers = struct {
                     const trimmed = std.mem.trim(u8, first, " ");
 
                     if (std.meta.stringToEnum(http.TransferEncoding, trimmed)) |te| {
+                        if (headers.transfer_encoding != null) return error.HttpHeadersInvalid;
                         headers.transfer_encoding = te;
                     } else if (std.meta.stringToEnum(http.ContentEncoding, trimmed)) |ce| {
+                        if (headers.transfer_compression != null) return error.HttpHeadersInvalid;
                         headers.transfer_compression = ce;
                     } else {
                         return error.HttpTransferEncodingUnsupported;