refactor(custom-templates): return parse error

app/kubernetes/custom-templates/kube-create-custom-template-view/kube-create-custom-template-view.controller.js

@@ -83,7 +83,7 @@ class KubeCreateCustomTemplateViewController {
       return;
     }
 
-    const variables = getTemplateVariables(templateStr);
+    const [variables] = getTemplateVariables(templateStr);
 
     const isValid = !!variables;
 

app/kubernetes/custom-templates/kube-edit-custom-template-view/kube-edit-custom-template-view.controller.js

@@ -112,7 +112,7 @@ class KubeEditCustomTemplateViewController {
       return;
     }
 
-    const variables = getTemplateVariables(templateStr);
+    const [variables] = getTemplateVariables(templateStr);
 
     const isValid = !!variables;
 

app/portainer/views/custom-templates/create-custom-template-view/createCustomTemplateViewController.js

@@ -206,7 +206,7 @@ class CreateCustomTemplateViewController {
       return;
     }
 
-    const variables = getTemplateVariables(templateStr);
+    const [variables] = getTemplateVariables(templateStr);
 
     const isValid = !!variables;
 

app/portainer/views/custom-templates/edit-custom-template-view/editCustomTemplateViewController.js

@@ -178,7 +178,7 @@ class EditCustomTemplateViewController {
       return;
     }
 
-    const variables = getTemplateVariables(templateStr);
+    const [variables] = getTemplateVariables(templateStr);
 
     const isValid = !!variables;
 

app/react/portainer/custom-templates/components/utils.ts

@@ -4,31 +4,40 @@ import Mustache from 'mustache';
 import { VariableDefinition } from './CustomTemplatesVariablesDefinitionField/CustomTemplatesVariablesDefinitionField';
 
 export function getTemplateVariables(templateStr: string) {
-  const template = validateAndParse(templateStr);
+  const [template, error] = validateAndParse(templateStr);
 
   if (!template) {
-    return null;
+    return [null, error] as const;
   }
 
-  return template
+  return [
+    template
       .filter(([type, value]) => type === 'name' && value)
       .map(([, value]) => ({
         name: value,
         label: '',
         defaultValue: '',
         description: '',
-    }));
+      })),
+    null,
+  ] as const;
 }
-
+type TemplateSpans = ReturnType<typeof Mustache.parse>;
-function validateAndParse(templateStr: string) {
+function validateAndParse(
+  templateStr: string
+): readonly [TemplateSpans, null] | readonly [null, string] {
   if (!templateStr) {
-    return [];
+    return [[] as TemplateSpans, null] as const;
   }
 
   try {
-    return Mustache.parse(templateStr);
+    return [Mustache.parse(templateStr), null] as const;
   } catch (e) {
-    return null;
+    if (!(e instanceof Error)) {
+      return [null, 'Parse error'] as const;
+    }
+
+    return [null, e.message] as const;
   }
 }