Update proxy failure hint (#17761)

* Update proxy failure hint

* Format

* Format

* Format

* Retry checks

1 files changed, 19 insertions, 5 deletions

diff --git a/scripts/cmake/vcpkg_download_distfile.cmake b/scripts/cmake/vcpkg_download_distfile.cmake
index 8dd193f64..2e72726b6 100644
--- a/scripts/cmake/vcpkg_download_distfile.cmake
+++ b/scripts/cmake/vcpkg_download_distfile.cmake
@@ -183,12 +183,26 @@ function(vcpkg_download_distfile VAR)
             if (NOT download_success)
                 message(FATAL_ERROR
                 "    \n"
-                "    Failed to download file.\n"
-                "    If you use a proxy, please set the HTTPS_PROXY and HTTP_PROXY environment\n"
-                "    variables to \"https://user:password@your-proxy-ip-address:port/\".\n"
+                "    Failed to download file.\n"  
+                "    If you use a proxy, please check your proxy setting. Possible causes are:\n"
                 "    \n"
-                "    If error with status 4 (Issue #15434),\n"
-                "    try setting \"http://user:password@your-proxy-ip-address:port/\".\n"
+                "    1. You are actually using an HTTP proxy, but setting HTTPS_PROXY variable\n"
+                "       to `https://address:port`. This is not correct, because `https://` prefix\n"
+                "       claims the proxy is an HTTPS proxy, while your proxy (v2ray, shadowsocksr\n"
+                "       , etc..) is an HTTP proxy. Try setting `http://address:port` to both\n"
+                "       HTTP_PROXY and HTTPS_PROXY instead.\n"
+                "    \n"
+                "    2. You are using Fiddler. Currently a bug (https://github.com/microsoft/vcpkg/issues/17752)\n"
+                "       will set HTTPS_PROXY to `https://fiddler_address:port` which lead to problem 1 above.\n"
+                "       Workaround is open Windows 10 Settings App, and search for Proxy Configuration page,\n"
+                "       Change `http=address:port;https=address:port` to `address`, and fill the port number.\n"
+                "    \n"
+                "    3. You proxy's remote server is out of service.\n"
+                "    \n"
+                "    In future vcpkg releases, if you are using Windows, you no longer need to set\n"
+                "    HTTP(S)_PROXY environment variables. Vcpkg will simply apply Windows IE Proxy\n"
+                "    Settings set by your proxy software. See (https://github.com/microsoft/vcpkg-tool/pull/49)\n"
+                "    and (https://github.com/microsoft/vcpkg-tool/pull/77)\n"
                 "    \n"
                 "    Otherwise, please submit an issue at https://github.com/Microsoft/vcpkg/issues\n")
             else()