fix(fetch): body.blob() sets Blob.type from Content-Type header

builtins/web/blob.cpp

@@ -26,9 +26,56 @@ template <typename T> bool validate_type(T *chars, size_t strlen) {
   return true;
 }
 
+
+// https://w3c.github.io/FileAPI/#convert-line-endings-to-native
+std::string convert_line_endings_to_native(std::string_view s) {
+  std::string native_line_ending = "\n";
+#ifdef _WIN32
+  native_line_ending = "\r\n";
+#endif
+
+  std::string result;
+  result.reserve(s.size());
+
+  size_t i = 0;
+  while (i < s.size()) {
+    switch (s[i]) {
+    case '\r': {
+      if (i + 1 < s.size() && s[i + 1] == '\n') {
+        result.append(native_line_ending);
+        i += 2;
+      } else {
+        result.append(native_line_ending);
+        i += 1;
+      }
+      break;
+    }
+    case '\n': {
+      result.append(native_line_ending);
+      i += 1;
+      break;
+    }
+    default: {
+      result.push_back(s[i]);
+      i += 1;
+      break;
+    }
+    }
+  }
+
+  return result;
+}
+
+} // anonymous namespace
+
+
+
+namespace builtins::web::blob {
+
+// https://w3c.github.io/FileAPI/#dfn-type
 // 1. If type contains any characters outside the range U+0020 to U+007E, then set t to the empty string.
 // 2. Convert every character in type to ASCII lowercase.
-JSString *normalize_type(JSContext *cx, HandleValue value) {
+JSString *Blob::normalize_type(JSContext *cx, JS::HandleValue value) {
   JS::RootedString value_str(cx);
 
   if (value.isObject() || value.isString()) {
@@ -60,15 +107,13 @@ JSString *normalize_type(JSContext *cx, HandleValue value) {
     if (!validate_type(chars, strlen)) {
       return JS_GetEmptyString(cx);
     }
-
     normalized = std::string(reinterpret_cast<const char *>(chars), strlen);
   } else {
     JS::AutoCheckCannotGC nogc(cx);
-    const auto *chars = (JS::GetTwoByteLinearStringChars(nogc, str));
+    const auto *chars = JS::GetTwoByteLinearStringChars(nogc, str);
     if (!validate_type(chars, strlen)) {
       return JS_GetEmptyString(cx);
     }
-
     normalized.reserve(strlen);
     for (size_t i = 0; i < strlen; ++i) {
       normalized += static_cast<unsigned char>(chars[i]);
@@ -81,51 +126,6 @@ JSString *normalize_type(JSContext *cx, HandleValue value) {
   return JS_NewStringCopyN(cx, normalized.c_str(), normalized.length());
 }
 
-// https://w3c.github.io/FileAPI/#convert-line-endings-to-native
-std::string convert_line_endings_to_native(std::string_view s) {
-  std::string native_line_ending = "\n";
-#ifdef _WIN32
-  native_line_ending = "\r\n";
-#endif
-
-  std::string result;
-  result.reserve(s.size());
-
-  size_t i = 0;
-  while (i < s.size()) {
-    switch (s[i]) {
-    case '\r': {
-      if (i + 1 < s.size() && s[i + 1] == '\n') {
-        result.append(native_line_ending);
-        i += 2;
-      } else {
-        result.append(native_line_ending);
-        i += 1;
-      }
-      break;
-    }
-    case '\n': {
-      result.append(native_line_ending);
-      i += 1;
-      break;
-    }
-    default: {
-      result.push_back(s[i]);
-      i += 1;
-      break;
-    }
-    }
-  }
-
-  return result;
-}
-
-} // anonymous namespace
-
-
-
-namespace builtins::web::blob {
-
 using js::Vector;
 using streams::BufReader;
 using streams::NativeStreamSource;
@@ -285,7 +285,7 @@ bool Blob::slice(JSContext *cx, HandleObject self, const CallArgs &args, Mutable
 
   if (args.hasDefined(2)) {
     HandleValue contentType_val = args.get(2);
-    if ((contentType = normalize_type(cx, contentType_val)) == nullptr) {
+    if ((contentType = Blob::normalize_type(cx, contentType_val)) == nullptr) {
       return false;
     }
   }
@@ -547,7 +547,7 @@ bool Blob::init_options(JSContext *cx, HandleObject self, HandleValue initv) {
       return false;
     }
 
-    auto *type_str = normalize_type(cx, type);
+    auto *type_str = Blob::normalize_type(cx, type);
     if (!type_str) {
       return false;
     }

builtins/web/blob.h

@@ -54,6 +54,7 @@ class Blob : public BuiltinImpl<Blob, FinalizableClassPolicy> {
   static bool read_blob_slice(JSContext *cx, HandleObject self, std::span<uint8_t> buf,
                               size_t start, size_t *read, bool *done);
 
+  static JSString *normalize_type(JSContext *cx, JS::HandleValue value);
   static JSObject *create(JSContext *cx, UniqueChars data, size_t data_len, HandleString type);
 
   static bool init_class(JSContext *cx, HandleObject global);

builtins/web/fetch/request-response.cpp

@@ -611,8 +611,32 @@ bool RequestOrResponse::parse_body(JSContext *cx, JS::HandleObject self, JS::Uni
     result.setObject(*array_buffer);
   } else if constexpr (result_type == RequestOrResponse::BodyReadResult::Blob) {
     JS::RootedString contentType(cx, JS_GetEmptyString(cx));
-    JS::RootedObject blob(cx, blob::Blob::create(cx, std::move(buf), len, contentType));
 
+    RootedObject headers(cx, RequestOrResponse::headers(cx, self));
+    if (!headers) {
+      return RejectPromiseWithPendingError(cx, result_promise);
+    }
+    auto content_type_key = host_api::HostString("Content-Type");
+    auto idx = Headers::lookup(cx, headers, content_type_key);
+    if (idx) {
+      auto *values = Headers::get_index(cx, headers, idx.value());
+      auto maybe_mime = extract_mime_type(std::get<1>(*values));
+      if (!maybe_mime.isErr()) {
+        auto mime_str = maybe_mime.unwrap().to_string();
+        JS::RootedString mime_js_str(cx, JS_NewStringCopyN(cx, mime_str.c_str(), mime_str.size()));
+        if (!mime_js_str) {
+          return RejectPromiseWithPendingError(cx, result_promise);
+        }
+        JS::RootedValue mime_val(cx, JS::StringValue(mime_js_str));
+        auto *normalized = blob::Blob::normalize_type(cx, mime_val);
+        if (!normalized) {
+          return RejectPromiseWithPendingError(cx, result_promise);
+        }
+        contentType = normalized;
+      }
+    }
+
+    JS::RootedObject blob(cx, blob::Blob::create(cx, std::move(buf), len, contentType));
     if (!blob) {
       return RejectPromiseWithPendingError(cx, result_promise);
     }

tests/wpt-harness/expectations/fetch/api/body/formdata.any.js.json

@@ -6,6 +6,6 @@
     "status": "PASS"
   },
   "Consume multipart/form-data headers case-insensitively": {
-    "status": "FAIL"
+    "status": "PASS"
   }
 }