add an error case for http_request_error

Author: lukewagner

proxy.md

@@ -676,6 +676,12 @@ be used.</p>
 <li><a name="tls_alert_received_payload.alert_id"><code>alert-ID</code></a>: <code>u8</code></li>
 <li><a name="tls_alert_received_payload.alert_message"><code>alert-message</code></a>: <code>string</code></li>
 </ul>
+<h4><a name="http_request_error_payload"><code>record HTTP-request-error-payload</code></a></h4>
+<h5>Record Fields</h5>
+<ul>
+<li><a name="http_request_error_payload.status_code"><a href="#status_code"><code>status-code</code></a></a>: <code>u16</code></li>
+<li><a name="http_request_error_payload.status_phrase"><code>status-phrase</code></a>: <code>string</code></li>
+</ul>
 <h4><a name="dns_error_payload"><code>record DNS-error-payload</code></a></h4>
 <h5>Record Fields</h5>
 <ul>
@@ -700,6 +706,7 @@ be used.</p>
 <li><a name="error.tls_protocol_error"><code>TLS-protocol-error</code></a></li>
 <li><a name="error.tls_certificate_error"><code>TLS-certificate-error</code></a></li>
 <li><a name="error.tls_alert_received"><code>TLS-alert-received</code></a>: <a href="#tls_alert_received_payload"><a href="#tls_alert_received_payload"><code>TLS-alert-received-payload</code></a></a></li>
+<li><a name="error.http_request_error"><code>HTTP-request-error</code></a>: <a href="#http_request_error_payload"><a href="#http_request_error_payload"><code>HTTP-request-error-payload</code></a></a></li>
 <li><a name="error.http_request_denied"><code>HTTP-request-denied</code></a></li>
 <li><a name="error.http_response_incomplete"><code>HTTP-response-incomplete</code></a></li>
 <li><a name="error.http_response_header_section_size"><code>HTTP-response-header-section-size</code></a>: <code>u32</code></li>

wit/types.wit

@@ -28,8 +28,6 @@ interface types {
 
   // The cases of this variant correspond to the IANA HTTP Proxy Error Types:
   //   https://www.iana.org/assignments/http-proxy-status/http-proxy-status.xhtml#table-http-proxy-error-types
-  // Note: the `http_request_error` case maps to an `ok` response with a 4xx
-  // `status-code`.
   variant error {
     DNS-timeout,
     DNS-error(DNS-error-payload),
@@ -46,6 +44,7 @@ interface types {
     TLS-protocol-error,
     TLS-certificate-error,
     TLS-alert-received(TLS-alert-received-payload),
+    HTTP-request-error(HTTP-request-error-payload),
     HTTP-request-denied,
     HTTP-response-incomplete,
     HTTP-response-header-section-size(u32),
@@ -76,6 +75,12 @@ interface types {
     alert-message: string
   }
 
+  // Defines the case payload type for `HTTP-request-error` above:
+  record HTTP-request-error-payload {
+    status-code: u16,
+    status-phrase: string
+  }
+
   // Defines the case payload type for `HTTP-response-{header,trailer}-size` above:
   record field-size-payload {
     field-name: string,