feat: [CI-18951]: added a log when harness fallback is used

docker.go

@@ -597,7 +597,8 @@ func addProxyValue(build *Build, key string) {
 
 // helper function to get a proxy value from the environment.
 //
-// assumes that the upper and lower case versions of are the same.
+// Checks in order: lowercase key, uppercase key, then HARNESS_<UPPERCASE_KEY>.
+// Assumes that the upper and lower case versions are the same value.
 func getProxyValue(key string) string {
 	value := os.Getenv(key)
 
@@ -605,15 +606,26 @@ func getProxyValue(key string) string {
 		return value
 	}
 
-	return os.Getenv(strings.ToUpper(key))
+	value = os.Getenv(strings.ToUpper(key))
+
+	if len(value) > 0 {
+		return value
+	}
+
+	harnessValue := os.Getenv("HARNESS_" + strings.ToUpper(key))
+	if len(harnessValue) > 0 {
+		fmt.Printf("Using HARNESS_%s as proxy value for %s\n", strings.ToUpper(key), key)
+	}
+	return harnessValue
 }
 
 // helper function that looks to see if a proxy value was set in the build args.
 func hasProxyBuildArg(build *Build, key string) bool {
 	keyUpper := strings.ToUpper(key)
+	harnessKey := "HARNESS_" + keyUpper
 
 	for _, s := range build.Args {
-		if strings.HasPrefix(s, key) || strings.HasPrefix(s, keyUpper) {
+		if strings.HasPrefix(s, key) || strings.HasPrefix(s, keyUpper) || strings.HasPrefix(s, harnessKey) {
 			return true
 		}
 	}
@@ -622,9 +634,10 @@ func hasProxyBuildArg(build *Build, key string) bool {
 }
 func hasProxyBuildArgNew(build *Build, key string) bool {
 	keyUpper := strings.ToUpper(key)
+	harnessKey := "HARNESS_" + keyUpper
 
 	for _, s := range build.ArgsNew {
-		if strings.HasPrefix(s, key) || strings.HasPrefix(s, keyUpper) {
+		if strings.HasPrefix(s, key) || strings.HasPrefix(s, keyUpper) || strings.HasPrefix(s, harnessKey) {
 			return true
 		}
 	}

docker_test.go

@@ -1,6 +1,7 @@
 package docker
 
 import (
+	"os"
 	"os/exec"
 	"reflect"
 	"strings"
@@ -179,3 +180,90 @@ func TestCommandBuild(t *testing.T) {
 		})
 	}
 }
+
+func TestGetProxyValue(t *testing.T) {
+	tests := []struct {
+		name     string
+		key      string
+		envVars  map[string]string
+		expected string
+	}{
+		{
+			name:     "lowercase env var set",
+			key:      "http_proxy",
+			envVars:  map[string]string{"http_proxy": "http://proxy:8080"},
+			expected: "http://proxy:8080",
+		},
+		{
+			name:     "uppercase env var set",
+			key:      "http_proxy",
+			envVars:  map[string]string{"HTTP_PROXY": "http://proxy:8080"},
+			expected: "http://proxy:8080",
+		},
+		{
+			name:     "HARNESS prefixed env var set",
+			key:      "http_proxy",
+			envVars:  map[string]string{"HARNESS_HTTP_PROXY": "http://harness-proxy:8080"},
+			expected: "http://harness-proxy:8080",
+		},
+		{
+			name: "standard takes precedence over HARNESS",
+			key:  "http_proxy",
+			envVars: map[string]string{
+				"HTTP_PROXY":         "http://standard:8080",
+				"HARNESS_HTTP_PROXY": "http://harness:8080",
+			},
+			expected: "http://standard:8080",
+		},
+		{
+			name: "lowercase takes precedence over uppercase",
+			key:  "no_proxy",
+			envVars: map[string]string{
+				"no_proxy":        "localhost,127.0.0.1",
+				"NO_PROXY":         "*.example.com",
+				"HARNESS_NO_PROXY": "*.local",
+			},
+			expected: "localhost,127.0.0.1",
+		},
+		{
+			name: "lowercase takes precedence over HARNESS",
+			key:  "https_proxy",
+			envVars: map[string]string{
+				"https_proxy":        "https://standard:8080",
+				"HARNESS_HTTPS_PROXY": "https://harness:8080",
+			},
+			expected: "https://standard:8080",
+		},
+		{
+			name:     "no env var set",
+			key:      "http_proxy",
+			envVars:  map[string]string{},
+			expected: "",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			// Clean env
+			lowercaseKey := tt.key
+			uppercaseKey := strings.ToUpper(tt.key)
+			harnessKey := "HARNESS_" + strings.ToUpper(tt.key)
+
+			os.Unsetenv(lowercaseKey)
+			os.Unsetenv(uppercaseKey)
+			os.Unsetenv(harnessKey)
+
+			// Set test environment variables
+			for k, v := range tt.envVars {
+				os.Setenv(k, v)
+				defer os.Unsetenv(k)
+			}
+
+			// Execute and verify
+			result := getProxyValue(tt.key)
+			if result != tt.expected {
+				t.Errorf("getProxyValue(%q) = %q, want %q", tt.key, result, tt.expected)
+			}
+		})
+	}
+}