Fix(curl): surface auth errors and avoid panic on nil HTTP response

MakeCurlRequest assumed that a non-nil error always came with an HTTP
response (e.g. a 4xx/5xx from the API). That assumption breaks when the
request fails before reaching the API — for example a token refresh /
client-credentials authentication failure in the UAA request wrapper,
which returns an error with a nil *http.Response.

In that case:
- Without --fail, the error was swallowed and cf curl printed empty
  output, giving the user no indication anything went wrong.
- With --fail, the code dereferenced httpResponse.StatusCode on the nil
  response and panicked.

Only surface CurlExit22Error when an HTTP response is actually present;
when the response is nil, return the underlying error directly so the
user sees a real message (e.g. "Bad credentials") and cf curl exits
cleanly instead of panicking. Existing behavior for real HTTP error
responses (print body by default, fail only with --fail) is unchanged.

Signed-off-by: Prem Kumar Kalle <prem.kalle@broadcom.com>

Author: prkalle

actor/v7action/curl.go

@@ -47,8 +47,19 @@ func (actor Actor) MakeCurlRequest(
 		requestBodyBytes,
 	)
 
-	if err != nil && failOnHTTPError {
-		return nil, nil, translatableerror.CurlExit22Error{StatusCode: httpResponse.StatusCode}
+	if err != nil {
+		// A nil HTTP response means the request never reached the API (e.g. a token
+		// refresh or other authentication failure in the request wrapper). There is no
+		// status code to read and no response body to print, so surface the error
+		// directly. This also avoids a nil-pointer dereference on httpResponse below
+		// when the fail-on-http-error flag is set.
+		if httpResponse == nil {
+			return nil, nil, err
+		}
+
+		if failOnHTTPError {
+			return nil, nil, translatableerror.CurlExit22Error{StatusCode: httpResponse.StatusCode}
+		}
 	}
 
 	return responseBody, httpResponse, nil

actor/v7action/curl_test.go

@@ -247,5 +247,33 @@ var _ = Describe("Curl Actions", func() {
 				})
 			})
 		})
+
+		When("the request fails before an HTTP response is received", func() {
+			// e.g. a token refresh / authentication failure in the request wrapper, where
+			// no request reaches the API and there is no HTTP response.
+			BeforeEach(func() {
+				mockErr = errors.New("Bad credentials")
+				mockResponseBody = nil
+				mockHTTPResponse = nil
+			})
+
+			It("surfaces the error instead of returning empty output", func() {
+				Expect(executeErr).To(MatchError("Bad credentials"))
+				Expect(responseBody).To(BeNil())
+				Expect(httpResponse).To(BeNil())
+			})
+
+			When("the fail-on-http-errors flag is set", func() {
+				BeforeEach(func() {
+					failOnHTTPError = true
+				})
+
+				It("surfaces the error without panicking on the nil response", func() {
+					Expect(executeErr).To(MatchError("Bad credentials"))
+					Expect(responseBody).To(BeNil())
+					Expect(httpResponse).To(BeNil())
+				})
+			})
+		})
 	})
 })