implement 'urlQueryEscape' and 'urlQueryUnescape' template functions …

…in filter builder (#1194)

This commit adds the 'urlQueryEscape' and 'urlQueryUnescape' functions to the template's extra functions ('extraFuncs'). These functions provide URL encoding and decoding capabilities.

docs/07.Reference/7.02.Filters.md

@@ -2071,6 +2071,10 @@ package, and extra functions defined by Easegress:
   also an object, its type must also be `map[string]interface{}`.
 * **jsonEscape**: escape a string so that it can be used as the key or value
   in JSON text.
+* **urlQueryEscape**: escapes the string so that it can be safely placed inside
+  a URL query, equivalent to the `urlquery` template function.
+* **urlQueryUnescape**: performs the inverse transformation of `urlQueryEscape`,
+  decoding a URL-encoded string back to its origin form.
 
 Easegress injects existing requests/responses of the current context into
 the template engine at runtime, so we can use `.requests.<namespace>.<field>`

pkg/filters/builder/extrafuncs.go

@@ -21,6 +21,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"net/http"
+	"net/url"
 	"strconv"
 	"strings"
 	"text/template"
@@ -154,4 +155,16 @@ var extraFuncs = template.FuncMap{
 		username, _, _ := req.(BasicAuth).BasicAuth()
 		return username
 	},
+
+	"urlQueryUnescape": func(s string) string {
+		unescapedStr, err := url.QueryUnescape(s)
+		if err != nil {
+			panic(err)
+		}
+		return unescapedStr
+	},
+
+	"urlQueryEscape": func(s string) string {
+		return url.QueryEscape(s)
+	},
 }

pkg/filters/builder/extrafuncs_test.go

@@ -59,6 +59,11 @@ func TestExtraFuncs(t *testing.T) {
 
 	assert.Equal(`abcd\"ABCD`, extraFuncs["jsonEscape"].(func(s string) string)(`abcd"ABCD`))
 
+	assert.Equal("https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FUTF-8%23Description",
+		extraFuncs["urlQueryEscape"].(func(s string) string)("https://en.wikipedia.org/wiki/UTF-8#Description"))
+	assert.Equal("https://en.wikipedia.org/wiki/UTF-8#Description",
+		extraFuncs["urlQueryUnescape"].(func(s string) string)("https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FUTF-8%23Description"))
+
 	assert.Panics(func() { extraFuncs["panic"].(func(v interface{}))("") })
 }