Merge pull request #3306 from boutproject/more-debug

Improve saveParallel

Author: ZedThree

src/sys/options.cxx

@@ -364,10 +364,18 @@ void saveParallel(Options& opt, const std::string& name, const Field3D& tosave)
       Field3D tmp;
       tmp.allocate();
       const auto& fpar = tosave.ynext(i);
-      for (auto j : fpar.getValidRegionWithDefault("RGN_NO_BOUNDARY")) {
-        tmp[j.yp(-i)] = fpar[j];
+      if (fpar.isAllocated()) {
+        for (auto j : tmp.getRegion("RGN_NOY")) {
+          tmp[j] = fpar[j.yp(i)];
+        }
+        opt[fmt::format("{}_y{:+d}", name, i)] = tmp;
+      } else {
+        if (tosave.isFci()) { // likely an error
+          throw BoutException(
+              "Tried to save parallel fields - but parallel field {} is not allocated",
+              i);
+        }
       }
-      opt[fmt::format("{}_y{:+d}", name, i)] = tmp;
     }
   }
 }