2 files changed, 76 insertions, 2 deletions
diff --git a/pkg/html/html.go b/pkg/html/html.go
index 72c2956e0..930fdd923 100644
--- a/pkg/html/html.go
+++ b/pkg/html/html.go
@@ -194,6 +194,30 @@ func commitLink(repo, commit string) string {
 }
 
 func AmendURL(baseURL, key, value string) string {
+	return TransformURL(baseURL, key, func(_ []string) []string {
+		if value == "" {
+			return nil
+		}
+		return []string{value}
+	})
+}
+
+func DropParam(baseURL, key, value string) string {
+	return TransformURL(baseURL, key, func(oldValues []string) []string {
+		if value == "" {
+			return nil
+		}
+		var newValues []string
+		for _, iterVal := range oldValues {
+			if iterVal != value {
+				newValues = append(newValues, iterVal)
+			}
+		}
+		return newValues
+	})
+}
+
+func TransformURL(baseURL, key string, f func([]string) []string) string {
 	if baseURL == "" {
 		return ""
 	}
@@ -202,10 +226,11 @@ func AmendURL(baseURL, key, value string) string {
 		return ""
 	}
 	values := parsed.Query()
-	if value == "" {
+	ret := f(values[key])
+	if len(ret) == 0 {
 		values.Del(key)
 	} else {
-		values.Set(key, value)
+		values[key] = ret
 	}
 	parsed.RawQuery = values.Encode()
 	return parsed.String()
diff --git a/pkg/html/html_test.go b/pkg/html/html_test.go
new file mode 100644
index 000000000..d824e0246
--- /dev/null
+++ b/pkg/html/html_test.go
@@ -0,0 +1,49 @@
+// Copyright 2023 syzkaller project authors. All rights reserved.
+// Use of this source code is governed by Apache 2 LICENSE that can be found in the LICENSE file.
+
+package html
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestDropParam(t *testing.T) {
+	tests := []struct {
+		in    string
+		key   string
+		value string
+		out   string
+	}{
+		{
+			in:    `/upstream?first=a&second=b`,
+			key:   `first`,
+			value: ``,
+			out:   `/upstream?second=b`,
+		},
+		{
+			in:    `/upstream?first=a&first=b&second=c`,
+			key:   `second`,
+			value: ``,
+			out:   `/upstream?first=a&first=b`,
+		},
+		{
+			in:    `/upstream?first=a&first=b&second=c`,
+			key:   `first`,
+			value: ``,
+			out:   `/upstream?second=c`,
+		},
+		{
+			in:    `/upstream?first=a&first=b&second=c`,
+			key:   `first`,
+			value: `b`,
+			out:   `/upstream?first=a&second=c`,
+		},
+	}
+
+	for _, test := range tests {
+		got := DropParam(test.in, test.key, test.value)
+		assert.Equal(t, test.out, got)
+	}
+}