Improve error messaging when only warnings issued #4465

src/pipeline.cc

@@ -1278,7 +1278,12 @@ class PipelineWorker : public Napi::AsyncWorker {
       if (what && what[0]) {
         (baton->err).append(what);
       } else {
-        (baton->err).append("Unknown error");
+        if (baton->input->failOn == VIPS_FAIL_ON_WARNING) {
+          (baton->err).append("Warning treated as error due to failOn setting");
+          baton->errUseWarning = true;
+        } else {
+          (baton->err).append("Unknown error");
+        }
       }
     }
     // Clean up libvips' per-request data and threads
@@ -1293,7 +1298,11 @@ class PipelineWorker : public Napi::AsyncWorker {
     // Handle warnings
     std::string warning = sharp::VipsWarningPop();
     while (!warning.empty()) {
-      debuglog.Call(Receiver().Value(), { Napi::String::New(env, warning) });
+      if (baton->errUseWarning) {
+        (baton->err).append("\n").append(warning);
+      } else {
+        debuglog.Call(Receiver().Value(), { Napi::String::New(env, warning) });
+      }
       warning = sharp::VipsWarningPop();
     }
 

src/pipeline.h

@@ -198,6 +198,7 @@ struct PipelineBaton {
   bool jxlLossless;
   VipsBandFormat rawDepth;
   std::string err;
+  bool errUseWarning;
   int keepMetadata;
   int withMetadataOrientation;
   double withMetadataDensity;
@@ -373,6 +374,7 @@ struct PipelineBaton {
     jxlEffort(7),
     jxlLossless(false),
     rawDepth(VIPS_FORMAT_UCHAR),
+    errUseWarning(false),
     keepMetadata(0),
     withMetadataOrientation(-1),
     withMetadataDensity(0.0),