Add 'http://' to http(s)_proxy if there is no protocol (#2663)

* Add 'http://' to http(s)_proxy if there is no protocol

Before this commit, these URIs used to be ignored (nullproxy).

The new behaviour aligns with go style http(s)_proxy

* Update src/Runner.Sdk/RunnerWebProxy.cs

Co-authored-by: Nikola Jokic <jokicnikola07@gmail.com>

* Assert that original protocol is preserved

* Use startsWith for testing protocol

* Only modify proxy if useful

---------

Co-authored-by: Nikola Jokic <jokicnikola07@gmail.com>

src/Runner.Sdk/RunnerWebProxy.cs

@@ -69,6 +69,10 @@ namespace GitHub.Runner.Sdk
                 return;
             }
 
+            if (!string.IsNullOrEmpty(httpProxyAddress) && !Uri.TryCreate(httpProxyAddress, UriKind.Absolute, out var _))
+            {
+                httpProxyAddress = PrependHttpIfMissing(httpProxyAddress);
+            }
             if (!string.IsNullOrEmpty(httpProxyAddress) && Uri.TryCreate(httpProxyAddress, UriKind.Absolute, out var proxyHttpUri))
             {
                 _httpProxyAddress = proxyHttpUri.OriginalString;
@@ -99,6 +103,10 @@ namespace GitHub.Runner.Sdk
                 }
             }
 
+            if (!string.IsNullOrEmpty(httpsProxyAddress) && !Uri.TryCreate(httpsProxyAddress, UriKind.Absolute, out var _))
+            {
+                httpsProxyAddress = PrependHttpIfMissing(httpsProxyAddress);
+            }
             if (!string.IsNullOrEmpty(httpsProxyAddress) && Uri.TryCreate(httpsProxyAddress, UriKind.Absolute, out var proxyHttpsUri))
             {
                 _httpsProxyAddress = proxyHttpsUri.OriginalString;
@@ -240,5 +248,20 @@ namespace GitHub.Runner.Sdk
 
             return false;
         }
+
+        private string PrependHttpIfMissing(string proxyAddress)
+        {
+            // much like in golang, see https://github.com/golang/net/blob/f5464ddb689c015d1abf4df78a806a54af977e6c/http/httpproxy/proxy.go#LL156C31-L156C31
+            if (!proxyAddress.StartsWith("http://", StringComparison.Ordinal) && !proxyAddress.StartsWith("https://", StringComparison.Ordinal))
+            {
+                var prependedProxyAddress = "http://" + proxyAddress;
+                if (Uri.TryCreate(prependedProxyAddress, UriKind.Absolute, out var _))
+                {
+                    // if prepending http:// turns the proxyAddress into a valid Uri, then use that
+                    return prependedProxyAddress;
+                }
+            }
+            return proxyAddress;
+        }
     }
 }

src/Test/L0/RunnerWebProxyL0.cs

@@ -186,8 +186,8 @@ namespace GitHub.Runner.Common.Tests
         {
             try
             {
-                Environment.SetEnvironmentVariable("http_proxy", "127.0.0.1:7777");
+                Environment.SetEnvironmentVariable("http_proxy", "#fragment");
-                Environment.SetEnvironmentVariable("https_proxy", "127.0.0.1");
+                Environment.SetEnvironmentVariable("https_proxy", "#fragment");
                 var proxy = new RunnerWebProxy();
 
                 Assert.Null(proxy.HttpProxyAddress);
@@ -206,6 +206,68 @@ namespace GitHub.Runner.Common.Tests
             }
         }
 
+        [Fact]
+        [Trait("Level", "L0")]
+        [Trait("Category", "Common")]
+        public void WebProxyPrependsHTTPforHTTP_PROXY_IfNoProtocol()
+        {
+            try
+            {
+                Environment.SetEnvironmentVariable("http_proxy", "127.0.0.1:7777");
+                var proxy = new RunnerWebProxy();
+
+                Assert.Equal("http://127.0.0.1:7777", proxy.HttpProxyAddress);
+                Assert.Null(proxy.HttpProxyUsername);
+                Assert.Null(proxy.HttpProxyPassword);
+
+                Assert.Equal(0, proxy.NoProxyList.Count);
+
+                Environment.SetEnvironmentVariable("http_proxy", "http://127.0.0.1:7777");
+                proxy = new RunnerWebProxy();
+
+                Assert.Equal("http://127.0.0.1:7777", proxy.HttpProxyAddress);
+                Assert.Null(proxy.HttpProxyUsername);
+                Assert.Null(proxy.HttpProxyPassword);
+
+                Assert.Equal(0, proxy.NoProxyList.Count);
+            }
+            finally
+            {
+                CleanProxyEnv();
+            }
+        }
+
+        [Fact]
+        [Trait("Level", "L0")]
+        [Trait("Category", "Common")]
+        public void WebProxyPrependsHTTPforHTTPS_PROXY_IfNoProtocol()
+        {
+            try
+            {
+                Environment.SetEnvironmentVariable("https_proxy", "127.0.0.1:7777");
+                var proxy = new RunnerWebProxy();
+
+                Assert.Equal("http://127.0.0.1:7777", proxy.HttpsProxyAddress);
+                Assert.Null(proxy.HttpProxyUsername);
+                Assert.Null(proxy.HttpProxyPassword);
+
+                Assert.Equal(0, proxy.NoProxyList.Count);
+
+                Environment.SetEnvironmentVariable("https_proxy", "https://127.0.0.1:7777");
+                proxy = new RunnerWebProxy();
+
+                Assert.Equal("https://127.0.0.1:7777", proxy.HttpsProxyAddress); // existing protocol 'https' is not removed
+                Assert.Null(proxy.HttpProxyUsername);
+                Assert.Null(proxy.HttpProxyPassword);
+
+                Assert.Equal(0, proxy.NoProxyList.Count);
+            }
+            finally
+            {
+                CleanProxyEnv();
+            }
+        }
+
         [Fact]
         [Trait("Level", "L0")]
         [Trait("Category", "Common")]