Add more tests and comments

caddyhttp/proxy/proxy.go

@@ -394,9 +394,11 @@ func mutateHeadersByRules(headers, rules http.Header, repl httpserver.Replacer,
 
 	for ruleField, ruleValues := range replacements {
 		for _, ruleValue := range ruleValues {
+			// Replace variables in replacement string
 			replacement := repl.Replace(ruleValue.to)
 			original := headers.Get(ruleField)
 			if len(replacement) > 0 && len(original) > 0 {
+				// Replace matches in original string with replacement string
 				replaced := ruleValue.regexp.ReplaceAllString(original, replacement)
 				headers.Set(ruleField, replaced)
 			}

caddyhttp/proxy/upstream.go

@@ -78,11 +78,14 @@ type srvResolver interface {
 	LookupSRV(context.Context, string, string, string) (string, []*net.SRV, error)
 }
 
+// headerReplacement stores a compiled regex matcher and a string replacer, for replacement rules
 type headerReplacement struct {
 	regexp *regexp.Regexp
 	to     string
 }
 
+// headerReplacements stores a mapping of canonical MIME header to headerReplacement
+// Implements a subset of http.Header functions, to allow convenient addition and deletion of rules
 type headerReplacements map[string][]headerReplacement
 
 func (h headerReplacements) Add(key string, value headerReplacement) {

caddyhttp/proxy/upstream_test.go

@@ -325,6 +325,61 @@ func TestParseBlockTransparent(t *testing.T) {
 	}
 }
 
+func TestParseBlockRegex(t *testing.T) {
+	// tests for regex replacement of headers
+	r, _ := http.NewRequest("GET", "/", nil)
+	tests := []struct {
+		config string
+	}{
+		// Test #1: transparent preset with replacement of Host
+		{"proxy / localhost:8080 {\n transparent \nheader_upstream Host (.*) NewHost \n}"},
+
+		// Test #2: transparent preset with replacement of another param
+		{"proxy / localhost:8080 {\n transparent \nheader_upstream X-Test Tester \nheader_upstream X-Test Test Host \n}"},
+
+		// Test #3: transparent preset with multiple params
+		{"proxy / localhost:8080 {\n transparent \nheader_upstream X-Test Tester \nheader_upstream X-Test Test Host \nheader_upstream X-Test er ing \n}"},
+	}
+
+	for i, test := range tests {
+		upstreams, err := NewStaticUpstreams(caddyfile.NewDispenser("Testfile", strings.NewReader(test.config)), "")
+		if err != nil {
+			t.Errorf("Expected no error. Got: %s", err.Error())
+		}
+		for _, upstream := range upstreams {
+			headers := upstream.Select(r).UpstreamHeaderReplacements
+
+			switch i {
+			case 0:
+				if host, ok := headers["Host"]; !ok || host[0].to != "NewHost" {
+					t.Errorf("Test %d: Incorrect Host replacement: %v", i+1, host[0])
+				}
+			case 1:
+				if v, ok := headers["X-Test"]; !ok {
+					t.Errorf("Test %d: Incorrect X-Test replacement", i+1)
+				} else {
+					if v[0].to != "Host" {
+						t.Errorf("Test %d: Incorrect X-Test replacement: %v", i+1, v[0])
+					}
+				}
+			case 2:
+				if v, ok := headers["X-Test"]; !ok {
+					t.Errorf("Test %d: Incorrect X-Test replacement", i+1)
+				} else {
+					if v[0].to != "Host" {
+						t.Errorf("Test %d: Incorrect X-Test replacement: %v", i+1, v[0])
+					}
+					if v[1].to != "ing" {
+						t.Errorf("Test %d: Incorrect X-Test replacement: %v", i+1, v[1])
+					}
+				}
+			default:
+				t.Error("Testing error")
+			}
+		}
+	}
+}
+
 func TestHealthSetUp(t *testing.T) {
 	// tests for insecure skip verify
 	tests := []struct {