🐛 Treat only network TypeErrors on body read as connectivity errors

process-response-type turned every TypeError from a body read into a
:network error, so a bug such as "body stream already read" showed a
connection toast. It now uses network-failure?, which moves to
app.util.http so that both the http client and the global error
handlers share it. Add Firefox's "Error in body stream" message.

Tests now check :offline and :network separately by setting
navigator.onLine, and read-error builds on async/->promise.

AI-assisted-by: claude-opus-5-5

frontend/src/app/main/errors.cljs

@@ -22,6 +22,7 @@
    [app.main.worker]
    [app.util.dom :as dom]
    [app.util.globals :as g]
+   [app.util.http :as http]
    [app.util.i18n :refer [tr]]
    [app.util.timers :as ts]
    [app.util.webapi :as wapi]
@@ -1123,26 +1124,6 @@
         (and (= (.-name ^js cause) "NotFoundError")
              (str/includes? message "removeChild")))))
 
-;; Messages of the TypeError a failed `fetch` rejects with, or a failed
-;; read of its response body.
-(def ^:private network-failure-messages
-  #{"Failed to fetch"                                 ; Chrome
-    "NetworkError when attempting to fetch resource." ; Firefox
-    "Load failed"                                     ; Safari
-    "network error"})                                 ; Chrome, body read
-
-(defn network-failure?
-  "True when the error is the browser's TypeError for a request that never
-  got an answer. `app.util.http` wraps its own failures as `:network`; this
-  catches the raw ones from third-party code (zip.js, plugins, schema
-  loads) that reach the global handlers."
-  [cause]
-  (and (= (.-name ^js cause) "TypeError")
-       (let [message (ex-message cause)]
-         (or (contains? network-failure-messages message)
-             ;; Newer Chrome versions append the host in parentheses
-             (str/starts-with? message "Failed to fetch (")))))
-
 (defn network-failure->error
   "Wrap a raw network TypeError as a connectivity error, so it is reported
   as an environment failure instead of an application crash."
@@ -1179,7 +1160,7 @@
                 nil
 
                 ;; Raw fetch failures: connectivity, not a crash
-                (network-failure? cause)
+                (http/network-failure? cause)
                 (on-error (network-failure->error cause))
 
                 ;; All other errors: show exception page
@@ -1210,7 +1191,7 @@
                 nil
 
                 ;; Raw fetch failures: connectivity, not a crash
-                (network-failure? cause)
+                (http/network-failure? cause)
                 (on-error (network-failure->error cause))
 
                 ;; All other errors: show exception page

frontend/src/app/util/http.cljs

@@ -146,6 +146,26 @@
    :body    (.-body ^js response)
    ::response response})
 
+;; Messages of the TypeError a failed `fetch` rejects with, or a failed
+;; read of its response body.
+(def ^:private network-failure-messages
+  #{"Failed to fetch"                                 ; Chrome
+    "NetworkError when attempting to fetch resource." ; Firefox
+    "Load failed"                                     ; Safari
+    "network error"                                   ; Chrome, body read
+    "Error in body stream"})                          ; Firefox, body read
+
+(defn network-failure?
+  "True when the error is the browser's TypeError for a request that never
+  got an answer. Other TypeErrors, such as reading a body twice, are bugs
+  and do not match."
+  [cause]
+  (and (= (.-name ^js cause) "TypeError")
+       (let [message (ex-message cause)]
+         (or (contains? network-failure-messages message)
+             ;; Newer Chrome versions append the host in parentheses
+             (str/starts-with? message "Failed to fetch (")))))
+
 (defn process-response-type
   [response-type response]
   (let [native-response (::response response)
@@ -159,9 +179,10 @@
                    (assoc response :body body)))
          ;; The connection can drop while the body streams in, after
          ;; `fetch` already resolved; the browser then rejects the read
-         ;; with a bare TypeError. Parse failures (SyntaxError) pass as is.
+         ;; with a bare TypeError. Other errors, such as parse failures
+         ;; (SyntaxError), pass as is.
          (rx/catch (fn [cause]
-                     (if (= (.-name ^js cause) "TypeError")
+                     (if (network-failure? cause)
                        (rx/throw (ex-info (ex-message cause)
                                           {:type :network
                                            :hint "unable to read response body"

frontend/test/frontend_tests/errors_test.cljs

@@ -7,6 +7,7 @@
 (ns frontend-tests.errors-test
   (:require
    [app.main.errors :as errors]
+   [app.util.globals :as g]
    [cljs.test :as t :include-macros true]))
 
 (defn- make-error
@@ -150,30 +151,31 @@
       (t/is (false? (errors/is-ignorable-exception? cause))))))
 
 ;; ---------------------------------------------------------------------------
-;; network-failure? tests
+;; network-failure->error tests
 ;; ---------------------------------------------------------------------------
 
-(t/deftest test-network-failure-browser-messages
-  (t/testing "The TypeError each browser gives a failed fetch is a network failure"
-    (doseq [message ["Failed to fetch"
-                     "Failed to fetch (design.penpot.app)"
-                     "NetworkError when attempting to fetch resource."
-                     "Load failed"
-                     "network error"]]
-      (t/is (true? (errors/network-failure? (make-error "TypeError" message)))
-            message))))
-
-(t/deftest test-network-failure-needs-type-error
-  (t/testing "Other errors with the same message are not network failures"
-    (t/is (false? (errors/network-failure? (make-error "Error" "Failed to fetch")))))
-  (t/testing "Other TypeErrors are not network failures"
-    (t/is (false? (errors/network-failure? (make-error "TypeError" "x is not a function"))))))
+(defn- with-online
+  "Call `f` while `navigator.onLine` reads `online?`."
+  [online? f]
+  (js/Object.defineProperty g/navigator "onLine"
+                            #js {:value online? :configurable true})
+  (try
+    (f)
+    (finally
+      (js-delete g/navigator "onLine"))))
 
 (t/deftest test-network-failure-becomes-environment-error
   (t/testing "A raw fetch failure is wrapped as an environment error"
     (let [cause (make-error "TypeError" "Failed to fetch")
           error (errors/network-failure->error cause)]
-      (t/is (contains? #{:network :offline} (:type (ex-data error))))
       (t/is (true? (errors/environment-error? error)))
       (t/is (= "Failed to fetch" (ex-message error)))
       (t/is (identical? cause (ex-cause error))))))
+
+(t/deftest test-network-failure-type-follows-connection
+  (let [cause (make-error "TypeError" "Failed to fetch")
+        type  #(:type (ex-data (errors/network-failure->error cause)))]
+    (t/testing "Offline browsers report :offline"
+      (t/is (= :offline (with-online false type))))
+    (t/testing "Online browsers report :network"
+      (t/is (= :network (with-online true type))))))

frontend/test/frontend_tests/util_http_test.cljs

@@ -7,8 +7,8 @@
 (ns frontend-tests.util-http-test
   (:require
    [app.util.http :as http]
-   [beicon.v2.core :as rx]
-   [cljs.test :as t :include-macros true]))
+   [cljs.test :as t :include-macros true]
+   [frontend-tests.helpers.async :as async]))
 
 (def ^:private uri "https://example.com/assets/file.json")
 
@@ -20,14 +20,14 @@
    :headers {}
    ::http/response #js {:text (fn [] (js/Promise.reject cause))}})
 
-(defn- read-error
+(defn- ^:async read-error
   "Read the body of `response` as text and resolve with the error raised."
   [response]
-  (js/Promise.
-   (fn [resolve]
-     (rx/subs! (fn [_] (resolve nil))
-               resolve
-               (http/process-response-type :text response)))))
+  (try
+    (await (async/->promise (http/process-response-type :text response)))
+    nil
+    (catch :default cause
+      cause)))
 
 (t/deftest ^:async body-read-network-failure-is-a-network-error
   (let [cause (js/TypeError. "network error")
@@ -41,3 +41,35 @@
   (let [cause (js/SyntaxError. "Unexpected token < in JSON")
         error (await (read-error (failing-response cause)))]
     (t/is (identical? cause error))))
+
+(t/deftest ^:async body-read-programming-error-passes-unchanged
+  (let [cause (js/TypeError. "body stream already read")
+        error (await (read-error (failing-response cause)))]
+    (t/is (identical? cause error))))
+
+;; ---------------------------------------------------------------------------
+;; network-failure? tests
+;; ---------------------------------------------------------------------------
+
+(defn- make-error
+  [error-name message]
+  (let [err (js/Error. message)]
+    (set! (.-name err) error-name)
+    err))
+
+(t/deftest test-network-failure-browser-messages
+  (t/testing "The TypeError each browser gives a failed fetch is a network failure"
+    (doseq [message ["Failed to fetch"
+                     "Failed to fetch (design.penpot.app)"
+                     "NetworkError when attempting to fetch resource."
+                     "Load failed"
+                     "network error"
+                     "Error in body stream"]]
+      (t/is (true? (http/network-failure? (make-error "TypeError" message)))
+            message))))
+
+(t/deftest test-network-failure-needs-type-error
+  (t/testing "Other errors with the same message are not network failures"
+    (t/is (false? (http/network-failure? (make-error "Error" "Failed to fetch")))))
+  (t/testing "Other TypeErrors are not network failures"
+    (t/is (false? (http/network-failure? (make-error "TypeError" "x is not a function"))))))