1 files changed, 38 insertions, 7 deletions
diff --git a/cmd/generate/httpcache.go b/cmd/generate/httpcache.go
index 1fb0429..2192737 100644
--- a/cmd/generate/httpcache.go
+++ b/cmd/generate/httpcache.go
@@ -11,7 +11,32 @@ import (
 	"sort"
 )
 
-var httpCache = map[string]string{}
+type httpCacheEntry struct {
+	Body string
+	Err  error
+}
+
+var httpCache = map[string]httpCacheEntry{}
+
+type httpStatusError struct {
+	StatusCode int
+	Status     string
+}
+
+// Is implements the interface for [errors.Is].
+func (e *httpStatusError) Is(target error) bool {
+	switch target {
+	case os.ErrNotExist:
+		return e.StatusCode == http.StatusNotFound
+	default:
+		return false
+	}
+}
+
+// Error implements [error].
+func (e *httpStatusError) Error() string {
+	return fmt.Sprintf("unexpected HTTP status: %v", e.Status)
+}
 
 func httpGet(u string, hdr map[string]string) (string, error) {
 	cacheKey := url.QueryEscape(u)
@@ -26,23 +51,25 @@ func httpGet(u string, hdr map[string]string) (string, error) {
 
 	if cache, ok := httpCache[cacheKey]; ok {
 		fmt.Printf("CACHE-GET %q\n", u)
-		return cache, nil
+		return cache.Body, cache.Err
 	}
 	if err := os.Mkdir(".http-cache", 0777); err != nil && !os.IsExist(err) {
 		return "", err
 	}
 	cacheFile := filepath.Join(".http-cache", cacheKey)
 	if bs, err := os.ReadFile(cacheFile); err == nil {
-		httpCache[cacheKey] = string(bs)
 		fmt.Printf("CACHE-GET %q\n", u)
-		return httpCache[cacheKey], nil
+		httpCache[cacheKey] = httpCacheEntry{Body: string(bs)}
+		return httpCache[cacheKey].Body, nil
 	} else if !os.IsNotExist(err) {
+		httpCache[cacheKey] = httpCacheEntry{Err: err}
 		return "", err
 	}
 
 	fmt.Printf("GET %q...", u)
 	req, err := http.NewRequest(http.MethodGet, u, nil)
 	if err != nil {
+		httpCache[cacheKey] = httpCacheEntry{Err: err}
 		return "", err
 	}
 	for k, v := range hdr {
@@ -51,23 +78,27 @@ func httpGet(u string, hdr map[string]string) (string, error) {
 	resp, err := http.DefaultClient.Do(req)
 	if err != nil {
 		fmt.Printf(" err\n")
+		httpCache[cacheKey] = httpCacheEntry{Err: err}
 		return "", err
 	}
 	if resp.StatusCode != http.StatusOK {
 		fmt.Printf(" err\n")
-		return "", fmt.Errorf("unexpected HTTP status: %v", resp.Status)
+		httpCache[cacheKey] = httpCacheEntry{Err: err}
+		return "", &httpStatusError{StatusCode: resp.StatusCode, Status: resp.Status}
 	}
 	bs, err := io.ReadAll(resp.Body)
 	if err != nil {
 		fmt.Printf(" err\n")
+		httpCache[cacheKey] = httpCacheEntry{Err: err}
+		httpCache[cacheKey] = httpCacheEntry{Err: err}
 		return "", err
 	}
 	fmt.Printf(" ok\n")
 	if err := os.WriteFile(cacheFile, bs, 0666); err != nil {
 		return "", err
 	}
-	httpCache[cacheKey] = string(bs)
-	return httpCache[cacheKey], nil
+	httpCache[cacheKey] = httpCacheEntry{Body: string(bs)}
+	return httpCache[cacheKey].Body, nil
 }
 
 func httpGetJSON(u string, hdr map[string]string, out any) error {