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fix render: write content length in Data.Render #4206

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fix render: write content length in Data.Render #4206

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0fe6896
init test
dengaleev Mar 31, 2025
c4e549a
fix test
dengaleev Mar 31, 2025
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8 changes: 7 additions & 1 deletion render/data.go
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Original file line number Diff line number Diff line change
Expand Up @@ -4,7 +4,10 @@

package render

import "net/http"
import (
"net/http"
"strconv"
)

// Data contains ContentType and bytes data.
type Data struct {
Expand All @@ -15,6 +18,9 @@ type Data struct {
// Render (Data) writes data with custom ContentType.
func (r Data) Render(w http.ResponseWriter) (err error) {
r.WriteContentType(w)
if len(r.Data) > 0 {
w.Header().Set("Content-Length", strconv.Itoa(len(r.Data)))
}
Comment on lines +21 to +23
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Copilot AI May 20, 2025

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The condition 'if len(r.Data) > 0' prevents setting the Content-Length header when the data length is 0, causing test failures for zero-length responses. Consider removing the condition so the header is always set to strconv.Itoa(len(r.Data)).

Suggested change
if len(r.Data) > 0 {
w.Header().Set("Content-Length", strconv.Itoa(len(r.Data)))
}
w.Header().Set("Content-Length", strconv.Itoa(len(r.Data)))

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_, err = w.Write(r.Data)
return
}
Expand Down
31 changes: 31 additions & 0 deletions render/render_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -8,6 +8,7 @@ import (
"encoding/xml"
"errors"
"html/template"
"io"
"net"
"net/http"
"net/http/httptest"
Expand Down Expand Up @@ -420,6 +421,36 @@ func TestRenderData(t *testing.T) {
require.NoError(t, err)
assert.Equal(t, "#!PNG some raw data", w.Body.String())
assert.Equal(t, "image/png", w.Header().Get("Content-Type"))
assert.Equal(t, "19", w.Header().Get("Content-Length"))
}

func TestRenderDataContentLength(t *testing.T) {
srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
size, err := strconv.Atoi(r.URL.Query().Get("size"))
assert.NoError(t, err)

data := Data{
ContentType: "application/octet-stream",
Data: make([]byte, size),
}
assert.NoError(t, data.Render(w))
}))
t.Cleanup(srv.Close)

for _, size := range []int{0, 1, 100, 100_000} {
t.Run(strconv.Itoa(size), func(t *testing.T) {
resp, err := http.Get(srv.URL + "?size=" + strconv.Itoa(size))
require.NoError(t, err)
defer resp.Body.Close()

assert.Equal(t, "application/octet-stream", resp.Header.Get("Content-Type"))
assert.EqualValues(t, strconv.Itoa(size), resp.Header.Get("Content-Length"))

actual, err := io.Copy(io.Discard, resp.Body)
require.NoError(t, err)
assert.EqualValues(t, size, actual)
})
}
}

func TestRenderString(t *testing.T) {
Expand Down