Improve error messages in Darwin DNS-SD implementation. (project-chip…

…#33930)

We shouldn't claim a canceled browse that found things is a failure.

src/platform/Darwin/DnssdContexts.cpp

@@ -350,7 +350,17 @@ BrowseContext::BrowseContext(void * cbContext, DnssdBrowseCallback cb, DnssdServ
 
 void BrowseContext::DispatchFailure(const char * errorStr, CHIP_ERROR err)
 {
- ChipLogError(Discovery, "Mdns: Browse failure (%s)", errorStr);
+ if (err == CHIP_ERROR_CANCELLED && dispatchedSuccessOnce)
+ {
+ // We've been canceled after finding some devices. Treat this as a
+ // success, because maybe (common case, in fact) those were the devices
+ // our consumer was looking for.
+ ChipLogProgress(Discovery, "Mdns: Browse canceled");
+ }
+ else
+ {
+ ChipLogError(Discovery, "Mdns: Browse failure (%s)", errorStr);
+ }
  callback(context, nullptr, 0, true, err);
  MdnsContexts::GetInstance().Remove(this);
 }
@@ -376,6 +386,8 @@ void BrowseContext::DispatchPartialSuccess()
  sDispatchedServices = nullptr;
  sContextDispatchingSuccess = nullptr;
  services.clear();
+
+ dispatchedSuccessOnce = true;
 }
 
 void BrowseContext::OnBrowse(DNSServiceFlags flags, const char * name, const char * type, const char * domain, uint32_t interfaceId)

src/platform/Darwin/DnssdImpl.h

@@ -169,6 +169,7 @@ struct BrowseContext : public BrowseHandler
 {
  DnssdBrowseCallback callback;
  std::vector<std::pair<DnssdService, std::string>> services;
+ bool dispatchedSuccessOnce = false;
 
  BrowseContext(void * cbContext, DnssdBrowseCallback cb, DnssdServiceProtocol cbContextProtocol);