throw detailed error message instead of npe

Author: simonljus

src/visitor.ts

@@ -42,8 +42,12 @@ export class Visitor extends TsVisitor {
   public getScalarType(scalarName: string): string | null {
     if (this.scalarDirection === 'both')
       return null;
-
-    return this.scalars[scalarName][this.scalarDirection];
+    }
+    const scalar = this.scalars[scalarName];
+    if (!scalar) {
+      throw new Error(`Unknown scalar ${scalarName}`);
+    }
+    return scalar[this.scalarDirection];
   }
 
   public shouldEmitAsNotAllowEmptyString(name: string): boolean {