From 06c9fb3da571bf7780533cb52221073dff22a16c Mon Sep 17 00:00:00 2001
From: Jacopo Rota <jacopo.rota@canonical.com>
Date: Thu, 12 Oct 2023 09:14:13 +0200
Subject: [PATCH] fix: do not duplicate the oauth headers in case of retry

---
 client_test.go | 20 ++++++++++++++++++++
 oauth.go       |  2 +-
 testing.go     |  9 +++++++--
 3 files changed, 28 insertions(+), 3 deletions(-)

diff --git a/client_test.go b/client_test.go
index a0db8b3..1cff8a4 100644
--- a/client_test.go
+++ b/client_test.go
@@ -94,6 +94,26 @@ func (suite *ClientSuite) TestClientDispatchRequestRetries409(c *gc.C) {
 	c.Check(*server.nbRequests, gc.Equals, NumberOfRetries+1)
 }
 
+// See https://bugs.launchpad.net/maas/+bug/2039105
+func (suite *ClientSuite) TestClientDispatchRequestRetries409WithoutDuplicatedHeaders(c *gc.C) {
+	URI := "/some/url/?param1=test"
+	server := newFlakyServer(URI, 409, NumberOfRetries)
+	defer server.Close()
+	client, err := NewAuthenticatedClient(server.URL, "the:api:key")
+	c.Assert(err, jc.ErrorIsNil)
+	content := "content"
+	request, err := http.NewRequest("GET", server.URL+URI, io.NopCloser(strings.NewReader(content)))
+	c.Assert(err, jc.ErrorIsNil)
+
+	_, err = client.dispatchRequest(request)
+
+	c.Assert(err, jc.ErrorIsNil)
+	c.Check(*server.nbRequests, gc.Equals, NumberOfRetries+1)
+	for _, headers := range *server.headers {
+		c.Check(len(headers.Values("Authorization")), gc.Equals, 1)
+	}
+}
+
 func (suite *ClientSuite) TestTLSClientDispatchRequestRetries503NilBody(c *gc.C) {
 	URI := "/some/path"
 	server := newFlakyTLSServer(URI, 503, NumberOfRetries)
diff --git a/oauth.go b/oauth.go
index 920960d..b6d5e2d 100644
--- a/oauth.go
+++ b/oauth.go
@@ -75,6 +75,6 @@ func (signer plainTextOAuthSigner) OAuthSign(request *http.Request) error {
 		authHeader = append(authHeader, fmt.Sprintf(`%s="%s"`, key, url.QueryEscape(value)))
 	}
 	strHeader := "OAuth " + strings.Join(authHeader, ", ")
-	request.Header.Add("Authorization", strHeader)
+	request.Header.Set("Authorization", strHeader)
 	return nil
 }
diff --git a/testing.go b/testing.go
index 8d45759..4794965 100644
--- a/testing.go
+++ b/testing.go
@@ -51,6 +51,7 @@ type flakyServer struct {
 	*httptest.Server
 	nbRequests *int
 	requests   *[][]byte
+	headers    *[]http.Header
 }
 
 // newFlakyServer creates a "flaky" test http server which will
@@ -58,6 +59,7 @@ type flakyServer struct {
 func newFlakyServer(uri string, code int, nbFlakyResponses int) *flakyServer {
 	nbRequests := 0
 	requests := make([][]byte, nbFlakyResponses+1)
+	headers := make([]http.Header, nbFlakyResponses+1)
 	handler := func(writer http.ResponseWriter, request *http.Request) {
 		nbRequests += 1
 		body, err := readAndClose(request.Body)
@@ -65,6 +67,7 @@ func newFlakyServer(uri string, code int, nbFlakyResponses int) *flakyServer {
 			panic(err)
 		}
 		requests[nbRequests-1] = body
+		headers[nbRequests-1] = request.Header
 		if request.URL.String() != uri {
 			errorMsg := fmt.Sprintf("Error 404: page not found (expected '%v', got '%v').", uri, request.URL.String())
 			http.Error(writer, errorMsg, http.StatusNotFound)
@@ -81,12 +84,13 @@ func newFlakyServer(uri string, code int, nbFlakyResponses int) *flakyServer {
 
 	}
 	server := httptest.NewServer(http.HandlerFunc(handler))
-	return &flakyServer{server, &nbRequests, &requests}
+	return &flakyServer{server, &nbRequests, &requests, &headers}
 }
 
 func newFlakyTLSServer(uri string, code int, nbFlakyResponses int) *flakyServer {
 	nbRequests := 0
 	requests := make([][]byte, nbFlakyResponses+1)
+	headers := make([]http.Header, nbFlakyResponses+1)
 	var server *httptest.Server
 
 	handler := func(writer http.ResponseWriter, request *http.Request) {
@@ -96,6 +100,7 @@ func newFlakyTLSServer(uri string, code int, nbFlakyResponses int) *flakyServer
 			panic(err)
 		}
 		requests[nbRequests-1] = body
+		headers[nbRequests-1] = request.Header
 		if request.URL.String() != uri {
 			errorMsg := fmt.Sprintf("Error 404: page not found (expected '%v', got '%v').", uri, request.URL.String())
 			http.Error(writer, errorMsg, http.StatusNotFound)
@@ -111,7 +116,7 @@ func newFlakyTLSServer(uri string, code int, nbFlakyResponses int) *flakyServer
 		}
 	}
 	server = httptest.NewTLSServer(http.HandlerFunc(handler))
-	return &flakyServer{server, &nbRequests, &requests}
+	return &flakyServer{server, &nbRequests, &requests, &headers}
 }
 
 type simpleResponse struct {