net/url: add JoinPath, URL.JoinPath

concatenates baseUrl and the elements

Fixes golang#47005

Change-Id: I71d638be9d451435dddf135091d8b1db54d174fd

api/except.txt

@@ -505,3 +505,5 @@ pkg unicode, const Version = "6.3.0"
 pkg unicode, const Version = "7.0.0"
 pkg unicode, const Version = "8.0.0"
 pkg unicode, const Version = "9.0.0"
+pkg net/url, func JoinPath(string, ...string) (string, error)
+pkg net/url, method (*URL) JoinPath(...string) *URL

src/net/url/url.go

@@ -13,6 +13,7 @@ package url
 import (
 	"errors"
 	"fmt"
+	"path"
 	"sort"
 	"strconv"
 	"strings"
@@ -1176,6 +1177,15 @@ func (u *URL) UnmarshalBinary(text []byte) error {
 	return nil
 }
 
+func (u *URL) JoinPath(elem ...string) *URL {
+	url := *u
+	if len(elem) > 0 {
+		elem = append([]string{u.Path}, elem...)
+		url.Path = path.Join(elem...)
+	}
+	return &url
+}
+
 // validUserinfo reports whether s is a valid userinfo string per RFC 3986
 // Section 3.2.1:
 //     userinfo    = *( unreserved / pct-encoded / sub-delims / ":" )
@@ -1216,3 +1226,15 @@ func stringContainsCTLByte(s string) bool {
 	}
 	return false
 }
+
+// JoinPath  concatenates baseUrl and the elements
+// - check baseUrl format
+// - concatenates baseUrl and the elements
+func JoinPath(baseUrl string, elem ...string) (result string, err error) {
+	url, err := Parse(baseUrl)
+	if err != nil {
+		return
+	}
+	result = url.JoinPath(elem...).String()
+	return
+}

src/net/url/url_test.go

@@ -2062,3 +2062,74 @@ func BenchmarkPathUnescape(b *testing.B) {
 		})
 	}
 }
+
+func TestJoinPath(t *testing.T) {
+	type args struct {
+		baseUrl string
+		elem    []string
+	}
+	tests := []struct {
+		name       string
+		args       args
+		wantResult string
+		wantErr    bool
+	}{
+		{
+			name: "test normal url",
+			args: args{
+				baseUrl: "https://go.googlesource.com",
+				elem:    []string{"go"},
+			},
+			wantResult: "https://go.googlesource.com/go",
+			wantErr:    false,
+		},
+		{
+			name: "test .. parent url",
+			args: args{
+				baseUrl: "https://go.googlesource.com/a/b/c",
+				elem:    []string{"../../../go"},
+			},
+			wantResult: "https://go.googlesource.com/go",
+			wantErr:    false,
+		},
+		{
+			name: "test . cul path",
+			args: args{
+				baseUrl: "https://go.googlesource.com/",
+				elem:    []string{"./go"},
+			},
+			wantResult: "https://go.googlesource.com/go",
+			wantErr:    false,
+		},
+		{
+			name: "test multiple Separator",
+			args: args{
+				baseUrl: "https://go.googlesource.com//",
+				elem:    []string{"/go"},
+			},
+			wantResult: "https://go.googlesource.com/go",
+			wantErr:    false,
+		},
+		{
+			name: "test more elems",
+			args: args{
+				baseUrl: "https://go.googlesource.com//",
+				elem:    []string{"/go", "a", "b", "c"},
+			},
+			wantResult: "https://go.googlesource.com/go/a/b/c",
+			wantErr:    false,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			gotResult, err := JoinPath(tt.args.baseUrl, tt.args.elem...)
+			if (err != nil) != tt.wantErr {
+				t.Errorf("JoinPath() error = %v, wantErr %v", err, tt.wantErr)
+				return
+			}
+			if gotResult != tt.wantResult {
+				t.Errorf("JoinPath() = %v, want %v", gotResult, tt.wantResult)
+			}
+		})
+	}
+}