GridVariable: Check mesh->get return

Not strictly necessary because variables are checked
before creating a GridVariable, but doesn't hurt.

Author: bendudson

src/field/fieldgenerators.hxx

@@ -311,7 +311,7 @@ public:
   // Constructor
   FieldTanhHat(FieldGeneratorPtr xin, FieldGeneratorPtr widthin,
                FieldGeneratorPtr centerin, FieldGeneratorPtr steepnessin)
-      : X(xin), width(widthin), center(centerin), steepness(steepnessin){};
+      : X(xin), width(widthin), center(centerin), steepness(steepnessin) {};
   // Clone containing the list of arguments
   FieldGeneratorPtr clone(const std::list<FieldGeneratorPtr> args) override;
   BoutReal generate(const bout::generator::Context& pos) override;
@@ -326,7 +326,7 @@ private:
 class FieldWhere : public FieldGenerator {
 public:
   FieldWhere(FieldGeneratorPtr test, FieldGeneratorPtr gt0, FieldGeneratorPtr lt0)
-      : test(test), gt0(gt0), lt0(lt0){};
+      : test(test), gt0(gt0), lt0(lt0) {};
 
   FieldGeneratorPtr clone(const std::list<FieldGeneratorPtr> args) override {
     if (args.size() != 3) {
@@ -368,23 +368,26 @@ private:
 
     Field3D get() {
       if (!var.isAllocated()) {
-        this->mesh->get(this->var, this->name);
+        // Read variable from mesh
+        if (this->mesh->get(this->var, this->name) != 0) {
+          throw BoutException("Couldn't read GridVariable '{}'", this->name);
+        }
       }
       return this->var;
     }
 
     Mesh* mesh;
     std::string name;
-    T var {};
+    T var{};
   };
 
   std::shared_ptr<LazyLoaded> variable;
+
 public:
   GridVariable(Mesh* mesh, std::string name)
-    : variable(std::make_shared<LazyLoaded>(mesh, std::move(name))) {}
+      : variable(std::make_shared<LazyLoaded>(mesh, std::move(name))) {}
 
-  GridVariable(std::shared_ptr<LazyLoaded> variable)
-    : variable(std::move(variable)) {}
+  GridVariable(std::shared_ptr<LazyLoaded> variable) : variable(std::move(variable)) {}
 
   double generate(const bout::generator::Context& ctx) override {
     return variable->get()(ctx.ix(), ctx.jy(), ctx.kz());
@@ -398,7 +401,6 @@ public:
   }
 
   std::string str() const override { return variable->name; }
-
 };
 
 #endif // BOUT_FIELDGENERATORS_H