internal/testutil/request: add ReadJSONResponse utility

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
2026-01-11 18:51:37 +00:00 · 2025-10-18 22:15:31 +02:00
parent ec83dd46ed
commit 3906199019
3 changed files with 110 additions and 6 deletions
--- a/internal/testutil/request/helpers.go
+++ b/internal/testutil/request/helpers.go
@@ -0,0 +1,33 @@
+package request
+
+import (
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"mime"
+	"net/http"
+)
+
+// ReadBody read the specified ReadCloser content and returns it.
+func ReadBody(b io.ReadCloser) ([]byte, error) {
+	defer func() { _ = b.Close() }()
+	return io.ReadAll(b)
+}
+
+// ReadJSONResponse reads a JSON response body into the given variable. it
+// returns an error for non-jSON responses, or when failing to unmarshal.
+func ReadJSONResponse[T any](resp *http.Response, v *T) error {
+	if resp == nil {
+		return errors.New("nil *http.Response")
+	}
+	defer func() { _ = resp.Body.Close() }()
+
+	mt, _, _ := mime.ParseMediaType(resp.Header.Get("Content-Type"))
+	if mt != "application/json" {
+		raw, _ := io.ReadAll(io.LimitReader(resp.Body, 8<<10))
+		return fmt.Errorf("unexpected Content-Type: '%s' (body: %s)", mt, string(raw))
+	}
+
+	return json.NewDecoder(resp.Body).Decode(v)
+}
--- a/internal/testutil/request/helpers_test.go
+++ b/internal/testutil/request/helpers_test.go
@@ -0,0 +1,77 @@
+package request_test
+
+import (
+	"bytes"
+	"io"
+	"net/http"
+	"testing"
+
+	"github.com/moby/moby/v2/internal/testutil/request"
+	"gotest.tools/v3/assert"
+)
+
+func TestReadJSONResponse(t *testing.T) {
+	type someResponse struct {
+		Hello string `json:"Hello"`
+	}
+
+	tests := []struct {
+		name        string
+		body        string
+		contentType string
+		expected    someResponse
+		expErr      string
+	}{
+		{
+			name:        "valid JSON",
+			body:        `{"hello": "world"}`,
+			contentType: "application/json",
+			expected:    someResponse{Hello: "world"},
+		},
+		{
+			name:        "valid JSON, utf-8",
+			body:        `{"hello": "world"}`,
+			contentType: "application/json; charset=utf-8",
+			expected:    someResponse{Hello: "world"},
+		},
+		{
+			name:        "malformed JSON",
+			body:        `{"hello": "world"`,
+			contentType: "application/json",
+			expErr:      "unexpected EOF",
+		},
+		{
+			name:        "non-JSON",
+			body:        `<html><head><title>Page not found</title></head></html>`,
+			contentType: "text/html",
+			expErr:      "unexpected Content-Type: 'text/html'",
+		},
+		{
+			name:   "nil response",
+			expErr: "nil *http.Response",
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			var v someResponse
+
+			var resp *http.Response
+			if tc.name != "nil response" {
+				resp = &http.Response{
+					Header: make(http.Header),
+					Body:   io.NopCloser(bytes.NewBufferString(tc.body)),
+				}
+				resp.Header.Set("Content-Type", tc.contentType)
+			}
+
+			err := request.ReadJSONResponse(resp, &v)
+			if tc.expErr != "" {
+				assert.ErrorContains(t, err, tc.expErr)
+			} else {
+				assert.NilError(t, err)
+				assert.DeepEqual(t, tc.expected, v)
+			}
+		})
+	}
+}
--- a/internal/testutil/request/request.go
+++ b/internal/testutil/request/request.go
@@ -105,12 +105,6 @@ func Do(ctx context.Context, endpoint string, modifiers ...func(*Options)) (*htt
 	return resp, body, err
 }

-// ReadBody read the specified ReadCloser content and returns it
-func ReadBody(b io.ReadCloser) ([]byte, error) {
-	defer b.Close()
-	return io.ReadAll(b)
-}
-
 // newRequest creates a new http Request to the specified host and endpoint, with the specified request modifiers
 func newRequest(endpoint string, opts *Options) (*http.Request, error) {
 	hostURL, err := client.ParseHostURL(opts.host)