net/http: path values are not passed to other *http.ServeMux #69077
Comments
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This comes from the way you've shallow cloned internal http.Request state, resulting in the SetPathValue being set to path matches which will be overridden by ServeMux. Closing as not a bug. |
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Change https://go.dev/cl/608655 mentions this issue: |
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@seankhliao but no other way to do this! http.Request.Clone() do the same. Using new Request is too much. |
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It is not possible to simply create a router that would use path values from an upstream router that uses wildcards. |
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I think this can help you package main
import (
"fmt"
"io"
"net/http"
"net/http/httptest"
"net/url"
"testing"
)
func Test_main(t *testing.T) {
rt1 := http.NewServeMux()
rt2 := http.NewServeMux()
rt1.HandleFunc("GET /{myid}/{tail...}", func(w http.ResponseWriter, r *http.Request) {
t.Logf("r1.GET /{myid}/{tail...}: myid=%q tail=%q", r.PathValue("myid"), r.PathValue("tail"))
p := stripToLastSlash(r.URL.Path, 2)
rp := stripToLastSlash(r.URL.RawPath, 2)
r2 := new(http.Request)
*r2 = *r
r2.URL = new(url.URL)
*r2.URL = *r.URL
r2.URL.Path = p
r2.URL.RawPath = rp
tail := r.PathValue("tail")
if tail == "" {
t.Error("r1: tail not found")
}
r2.SetPathValue("tail", tail)
rt2.ServeHTTP(w, r2)
})
rt2.HandleFunc("GET /{tail...}", func(w http.ResponseWriter, r *http.Request) {
t.Logf("r2.GET /: tail=%q", r.PathValue("tail"))
if r.PathValue("tail") == "" {
t.Error("r2: tail not found")
}
fmt.Fprintf(w, "%s", r.PathValue("tail"))
})
ts := httptest.NewServer(rt1)
defer ts.Close()
if _, body := testRequest(t, ts, "GET", "/123/456/789", nil); body != "456/789" {
t.Error("tail was not provided")
}
}
func stripToLastSlash(s string, cnt int) string {
pos := 0
for i, r := range s {
if r == '/' {
pos = i
cnt--
if cnt <= 0 {
break
}
}
}
return s[pos:]
}
func testRequest(t *testing.T, ts *httptest.Server, method, path string, body io.Reader) (*http.Response, string) {
req, err := http.NewRequest(method, ts.URL+path, body)
if err != nil {
t.Fatal(err)
return nil, ""
}
resp, err := http.DefaultClient.Do(req)
if err != nil {
t.Fatal(err)
return nil, ""
}
respBody, err := io.ReadAll(resp.Body)
if err != nil {
t.Fatal(err)
return nil, ""
}
defer resp.Body.Close()
return resp, string(respBody)
} |
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@w3nl1ng Ok, that's fine for 'tail'. But what about 'myid'? What if we need to pass 'myid' without wildcard in rt2.HandleFunc? func TestPathValueProviding(t *testing.T) {
rt1 := http.NewServeMux()
rt2 := http.NewServeMux()
rt1.HandleFunc("GET /{myid}/{tail...}", func(w http.ResponseWriter, r *http.Request) {
myid := r.PathValue("myid")
if myid == "" {
t.Error("r1: myid not found")
}
r2 := r.Clone(r.Context())
r2.SetPathValue("myid", myid)
r2.URL.Path = "/" + r.PathValue("tail")
r2.URL.RawPath = ""
rt2.ServeHTTP(w, r2)
})
rt2.HandleFunc("GET /", func(w http.ResponseWriter, r *http.Request) {
if r.PathValue("myid") == "" {
t.Error("r2: myid not found")
}
t.Log(r.URL.Path)
})
ts := httptest.NewServer(rt1)
defer ts.Close()
res, err := http.Get(ts.URL + "/123/456/789")
if err != nil {
t.Fatal(err)
}
res.Body.Close()
if res.StatusCode != 200 {
t.Error("status code", res.StatusCode)
}
} |
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@covrom If you want get 'myid' in rt2, you should register it at url. // Lastly, match the pattern (there can be at most one) that has a multi
// wildcard in this position to the rest of the path.
if c := n.multiChild; c != nil {
// Don't record a match for a nameless wildcard (which arises from a
// trailing slash in the pattern).
if c.pattern.lastSegment().s != "" {
matches = append(matches, pathUnescape(path[1:])) // remove initial slash
}
return c, matches
}
return nil, nil |
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@covrom This means if you call HandleFunc like this, it won't match any pattern for you. The value pairs you previously set yourself will also be overwritten rt2.HandleFunc("GET /", xxx)And if you call it like this, it will try to set the value of 'a', 'b' and 'c' for you. rt2.HandleFunc("GET /{a}{b}{c...}", xxx)let's back to this line, what is important is that your r2 are not passed to rt2 unchanged, ServeHTTP will dispatch r2 according to rt2's internal information rt2.ServeHTTP(w, r2) |
Go version
go version go1.23.0 linux/amd64
Output of
go envin your module/workspace:What did you do?
I create a test with a main router and a subrouter and try to provide the path value from the main router into subrouter handler:
What did you see happen?
tailpath value is not provided to subrouter:What did you expect to see?
r2.GET /must returns body "456/789"The text was updated successfully, but these errors were encountered: