Clarify error message on undefined component instances, Closes #108

Author: rubensworks

lib/preprocess/parameterproperty/ParameterPropertyHandlerRange.ts

@@ -480,7 +480,8 @@ export class ParameterPropertyHandlerRange implements IParameterPropertyHandler
     const withTypes = value && value.properties.types.length > 0 ? ` with types "${value.properties.types.map(resource => resource.value)}"` : '';
     // eslint-disable-next-line @typescript-eslint/no-extra-parens
     const valueString = value ? (value.list ? `[${value.list.map(subValue => subValue.value).join(', ')}]` : value.value) : 'undefined';
-    throw new ErrorResourcesContext(`The value "${valueString}"${withTypes} for parameter "${parameter.value}" is not of required range type "${ParameterPropertyHandlerRange.rangeToDisplayString(parameter.property.range, genericsContext)}"`, {
+    const undefinedComponent = value && value.term.termType === 'NamedNode' && value.properties.types.length === 0 ? `. "${valueString}" seems to refer to a component instance that is not defined yet. Did you forget an import?` : '';
+    throw new ErrorResourcesContext(`The value "${valueString}"${withTypes} for parameter "${parameter.value}" is not of required range type "${ParameterPropertyHandlerRange.rangeToDisplayString(parameter.property.range, genericsContext)}"${undefinedComponent}`, {
       cause: conflict,
       value: value || 'undefined',
       ...Object.keys(genericsContext.bindings).length > 0 ?

test/unit/preprocess/parameterproperty/ParameterPropertyHandlerRange-test.ts

@@ -2790,7 +2790,7 @@ describe('ParameterPropertyHandlerRange', () => {
         objectLoader.createCompactedResource('ex:param'),
         genericsContext,
         conflict,
-      )).toThrow('The value "ex:value" for parameter "ex:param" is not of required range type "any"');
+      )).toThrow(`The value "ex:value" for parameter "ex:param" is not of required range type "any". "ex:value" seems to refer to a component instance that is not defined yet. Did you forget an import?`);
     });
 
     it('handles a defined value with types', () => {