fix: remove the headers that caused the precondition to fail

Author: Lordfirespeed

.changeset/khaki-doors-stare.md

@@ -0,0 +1,5 @@
+---
+"@otterhttp/response": patch
+---
+
+remove `etag`, `last-modified` headers before throwing 'precondition failed' errors

packages/response/src/preconditions/index.ts

@@ -9,6 +9,11 @@ import { noneMatch } from "./if-none-match"
 import { rangePrecondition } from "./if-range"
 import { isUnmodifiedSince } from "./if-unmodified-since"
 
+function clearPreconditionHeadersFromResponse(response: HasOutgoingHeaders) {
+  response.removeHeader("etag")
+  response.removeHeader("last-modified")
+}
+
 /**
  * Checks that the provided response's associated request passes its
  * [preconditions]{@link https://datatracker.ietf.org/doc/html/rfc9110#name-conditional-requests},
@@ -44,6 +49,7 @@ export function validatePreconditions(
   if (ifMatch != null) {
     if (!Object.hasOwnProperty.call(current, "etag")) current.etag = res.getHeader("etag")
     if (!someMatch(current.etag, ifMatch)) {
+      clearPreconditionHeadersFromResponse(res)
       throw new ClientError("If-Match Precondition Failed", {
         statusCode: HttpStatus.PreconditionFailed,
         code: "ERR_PRECONDITION_FAILED_IF_MATCH",
@@ -60,6 +66,7 @@ export function validatePreconditions(
   if (ifMatch == null && ifUnmodifiedSince != null) {
     if (!Object.hasOwnProperty.call(current, "lastModified")) current.lastModified = res.getHeader("last-modified")
     if (!isUnmodifiedSince(current.lastModified, ifUnmodifiedSince)) {
+      clearPreconditionHeadersFromResponse(res)
       throw new ClientError("If-Unmodified-Since Precondition Failed", {
         statusCode: HttpStatus.PreconditionFailed,
         code: "ERR_PRECONDITION_FAILED_IF_UNMODIFIED_SINCE",
@@ -77,13 +84,15 @@ export function validatePreconditions(
     const failed = !noneMatch(current.etag, ifNoneMatch)
 
     if (failed && (method === "GET" || method === "HEAD")) {
+      clearPreconditionHeadersFromResponse(res)
       throw new NotModifiedError("If-None-Match Precondition Failed", {
         code: "ERR_PRECONDITION_FAILED_IF_NONE_MATCH",
         expected: true,
       })
     }
 
     if (failed) {
+      clearPreconditionHeadersFromResponse(res)
       throw new ClientError("If-None-Match Precondition Failed", {
         statusCode: HttpStatus.PreconditionFailed,
         code: "ERR_PRECONDITION_FAILED_IF_NONE_MATCH",
@@ -100,6 +109,7 @@ export function validatePreconditions(
   if ((method === "GET" || method === "HEAD") && ifNoneMatch == null && ifModifiedSince != null) {
     if (!Object.hasOwnProperty.call(current, "lastModified")) current.lastModified = res.getHeader("last-modified")
     if (!hasBeenModifiedSince(current.lastModified, ifModifiedSince)) {
+      clearPreconditionHeadersFromResponse(res)
       throw new NotModifiedError("If-Modified-Since Precondition Failed", {
         code: "ERR_PRECONDITION_FAILED_IF_MODIFIED_SINCE",
         expected: true,